llvm dev - Jan 2019 - [llvm-pdbutil] : merge not working properly

(Yes you are right this is my fault)
Considering the string table, it only seems to contains file relative
informations in every pdb I am using, and it looks correct but I will check
it.
I looked at the pdb.cpp code about checksums and tables, I copied some
stuff and got things wrong according to cvdump, then I simplified the
process of copying the table and it worked (in cvdump it finds the file
matching line etc...) so I suspect this is also correct.

All the streams look good, but I will check deeper !

It seems right what you say about rva and modules, this is what I m afraid
of, doing all of this for nothing or almost..

Your idea looks good concerning the .text section in a separated dll, but
will it be executable memory ? .text is where static strings go right ?
When you say putting my jit in there, do you mean writing it when the
jitted_code.dll is loaded in memory or on the .dll file directly before
loading it ? In the first scenario I wonder if the section will be
executable, in the second scenario I can’t do it because it would require
perfect linking with the other code my jit points to..

Le mer. 23 janv. 2019 à 20:57, Zachary Turner <zturner at google.com> a
écrit :
> (BTW, I'm adding llvm-dev back to the list, I didn't notice it got
taken
> off.  In general I try to keep the list on all emails, even if it's
> extremely technical and specific, because someday someone else will try to
> do this, and it'll be nice if they can read the whole thread).
>
> I can think of a couple of things that might be wrong:
>
> 1) If the string table is in a different order, then anything that refers
> to the string table need to be changed to refer to the new offset.  If the
> string "foo" is at offset 12 in the old PDB, but offset 15 in the
new PDB,
> then somewhere there is a record which is going to look at offset 12 and
> expect to find something, and that will mess up.  The main place this is
> important is in the File Checksums table, there is an entry that says which
> file it is a checksum for, and that refers to the string table.  However,
> it's possible for certain symbol records to refer to the string table
too.
> See lld/COFF/PDB.cpp and Ctrl+F for "PDBStrTab" and you will find
some
> information about this.
>
> 2) When you run `llvm-pdbutil dump -streams` on the copied PDB, do all of
> them show a reasonable description?  Are there any streams that say (???)?
> If so, that's a problem.
>
> > does visual studio will consider a symbol file broken if the address
> goes beyond the official module address range (the compiled one), because
> my JIT code is allocated after the end of the module with VirtualAlloc
> That is a good question, and part of why my job is so difficult, because I
> can't look at their code.  But I think the answer is
"probably".  The
> debugger has to have some way to convert an address in your running process
> into a symbol and offset, because that's how all debug info is
represented
> in the PDB.  So if there is no module, then there is no RVA (because the R
> in RVA means relative, and what would it be relative to?).
>
> One idea to test this would be to create a DLL called jitted_code.dll,
> give it a huuuuuge .text section (probably just a .asm file and use some
> assembly directives to allocate a very large series of null bytes), and
> then write your jit code into that area.  This way you would not need to
> modify the existing PDB you would only need to make a new PDB called
> jitted_code.pdb with 1 module, and those symbols could have meaningful
> RVAs.  And you might not even need to detach the debugger if you do things
> this way, because you could just right click the jitted_code.dll module in
> the modules window and choose Load Symbols.
>
>
>
> On Wed, Jan 23, 2019 at 11:13 AM Vivien Millet <vivien.millet at
gmail.com>
> wrote:
>
>> Yes this is it, I just make a copy from a pdb generated by link.exe
(the
>> microsoft one).
>> Using llvm-pdbutil to compare is what I do, except I do it with
"-all"
>> And I get almost everything the same : same number of streams, section
>> map looks good,string table looks good (even if not the same order),
same
>> number of modules with the symbols and subsection practically the same,
and
>> this is why I get stuck, I miss something but I can't see what
because I
>> don't know where to look for. Visual studio works with it, I can
debug my
>> original exe, but probably without the globals...
>> And the other problem is that the difference between the dumps is not
>> necessarily a bug because the builder may generate new hashes values,
>> reorder streams, modules, etc ...
>>
>> Right now I gave up to have publics and globals streams and attacked
the
>> real goal : insert my jit codeview into the pdb. I have again done «
>> something » but as I don’t understand how the format work I don’t have
it
>> working in visual studio.. except once, a single time it worked and the
>> breakpoint turned on in the UI (even if the rva was broken for the
>> instructions) but it happened a single time .. then I get depressed the
>> next times..... cvdump displays it all « correct », no corrupt stuff
>> apparently. But what I do is probably wrong somewhere. What I do is I
take
>> .debug$S and .debug$T as is without relocations just to see, but what I
>> don’t know really is : does visual studio will consider a symbol file
>> broken if the address goes beyond the official module address range
(the
>> compiled one), because my JIT code is allocated after the end of the
module
>> with VirtualAlloc.
>> Another thing I don’t get is the section contribution, what is it
exactly
>> ? I inserted section contrib for all sections except the debug$ ones
but I
>> don’t know what i’m really doing and it’s my average problem
implementing
>> this JIT feature...
>> I also don’t know what are relocations inside the codeview format, what
>> is the difference between RVA and relocation, is there anything to do
with
>> this related to the codeview part I need to insert in the pdb ? I don’t
see
>> why visual studio needs more than just RVA<->Line mapping..
>> This is really making me crazy being so ignorant and trying to guess
what
>> visual studio does...
>>
>> Le lun. 21 janv. 2019 à 19:50, Zachary Turner <zturner at
google.com> a
>> écrit :
>>
>>> So if i understand correctly, you're basically just trying to
implement
>>> something like a pdb *copy*, just as a test to see if you can get
it to
>>> work.  So you generate a PDB with cl/link or clang-cl/lld-link,
then try to
>>> copy it using your tool, then see if it still works.
>>>
>>> If this is correct, and it's not working, then there is
probably just
>>> something you didn't copy.  Neither Publics nor globals
actually contain
>>> their own data, instead they just refer to records from the
corresponding
>>> module stream.  So an S_PROCREF for the function "main"
might have fields
>>> that say "the name of the function is main, and it's at
offset 20 of module
>>> 1".  So, if there is no module 1, or if offset 20 of module is
not actually
>>> an S_GPROC32 for the function main, then it will be broken.
>>>
>>> Did you also go through each module in the source PDB, add a new
module
>>> in the target PDB, then copy all of the symbols for each one?
>>>
>>> the best way to find differences is by using llvm-pdbutil on the
source
>>> and target PDBs and looking for things that look different.  For
example,
>>> I'd start with llvm-pdbutil dump -streams and then seeing if
they even have
>>> all the same streams.  If one of them is missing streams,
that's a good
>>> place to start.  If they have the same streams, then look for ones
where
>>> the size is different.  Then drill into those to see why the size
is
>>> different.
>>>
>>> LMK if that helps.
>>>
>>> On Mon, Jan 21, 2019 at 10:03 AM Vivien Millet <vivien.millet at
gmail.com>
>>> wrote:
>>>
>>>> For now I'm not merging my JIT CodeView section, I only try
to build a
>>>> pure copy of an existing PDB using the XxxBuilder classes
(PDBFileBuilder &
>>>> Co / reading a PDBFile) and check if visual studio wants to eat
it..
>>>> For Publics and Globals, what I do is naive, I use the
GsiStreamBuilder
>>>> and prey :)
>>>>
>>>>
>>>>
>>>>   if (File.hasPDBGlobalsStream() &&
File.getPDBGlobalsStream()) {
>>>>     GSIStreamBuilder &builder = this->getGsiBuilder();
>>>>     GlobalsStream &stream = *File.getPDBGlobalsStream();
>>>>     SymbolStream &SymbolRecords =
cantFail(File.getPDBSymbolStream());
>>>>
>>>>     for (uint32_t PubSymOff : stream.getGlobalsTable()) {
>>>>       CVSymbol Sym = SymbolRecords.readRecord(PubSymOff);
>>>>       builder.addGlobalSymbol(Sym);
>>>>     }
>>>>   }
>>>>   if (File.hasPDBPublicsStream() &&
File.getPDBPublicsStream()) {
>>>>     GSIStreamBuilder &builder = this->getGsiBuilder();
>>>>     PublicsStream &stream = *File.getPDBPublicsStream();
>>>>     SymbolStream &SymbolRecords =
cantFail(File.getPDBSymbolStream());
>>>>
>>>> 	std::vector<PublicSym32> Publics;
>>>>
>>>>     for (uint32_t PubSymOff : stream.getPublicsTable()) {
>>>>       PublicSym32 Pub = cantFail(
>>>>          
llvm::codeview::SymbolDeserializer::deserializeAs<PublicSym32>(
>>>>               SymbolRecords.readRecord(PubSymOff)));
>>>>       Publics.push_back(Pub);
>>>>     }
>>>>
>>>>     if (!Publics.empty()) {
>>>>       // Sort the public symbols and add them to the stream.
>>>>       std::sort(Publics.begin(), Publics.end(),
>>>>            [](const PublicSym32 &L, const PublicSym32
&R) {
>>>>              return L.Name < R.Name;
>>>>            });
>>>>       for (const PublicSym32 &Pub : Publics)
>>>>         builder.addPublicSymbol(Pub);
>>>>     }
>>>>
>>>>   }
>>>>
>>>> Is it what you meant ?
>>>>
>>>>
>>>>
>>>>
>>>> Le lun. 21 janv. 2019 à 18:50, Zachary Turner <zturner at
google.com> a
>>>> écrit :
>>>>
>>>>> Also, even if symbolGoesInGlobalsStream returns true, you
can’t just
>>>>> copy it. Functions, for example, which are S_GPROC32 or
S_LPROC32 in the
>>>>> module stream, are S_PROCREF in the globals stream.
Similarly, *everything*
>>>>> in the publics stream is S_PUB32. So you need to convert
each symbol to the
>>>>> proper type for the stream it’s going to go in
>>>>> On Mon, Jan 21, 2019 at 9:46 AM Zachary Turner <zturner
at google.com>
>>>>> wrote:
>>>>>
>>>>>> Publics are basically a list of everything that has a
mangled name.
>>>>>> To be honest, I don’t know what the debugger uses this
for.
>>>>>>
>>>>>> Globals is essentially every symbol in the pdb in one
large table.
>>>>>> The reason this is important is because if you type
“foo” in the watch
>>>>>> window, the debugger doesn’t necessarily know what
compiland foo comes
>>>>>> from. So it has to have a way to find everything in the
entire program no
>>>>>> matter what compiland it came from. That’s what the
globals are.
>>>>>>
>>>>>> Both publics and globals are hash tables, so one
possible reason
>>>>>> there might be a problem is that you need to rehash the
entire table. When
>>>>>> you build your modified pdb, I would suggest starting
with an empty publics
>>>>>> / globals stream, adding all items from the first pdb
by iterating over
>>>>>> those records and using a GlobalsStreamBuilder, then
adding all your jitted
>>>>>> items separately, then writing it out. That should make
sure it gets hashed
>>>>>> correctly.
>>>>>>
>>>>>> Are you doing that?
>>>>>>
>>>>>> Btw, not all symbols belong in the globals / publics
stream. Check
>>>>>> the code in lld and search for
symbolGoesInGlobalsStream and
>>>>>> symbolGoesInPublicsStream to see the logic it uses
>>>>>> On Mon, Jan 21, 2019 at 8:36 AM Vivien Millet <
>>>>>> vivien.millet at gmail.com> wrote:
>>>>>>
>>>>>>> Hi Zachary, sorry for disturbing again..
>>>>>>>
>>>>>>> I've fixed some problems (StringTable,
SectionMap and few things
>>>>>>> here and there..) and my converted PDB seems now to
work inside visual
>>>>>>> studio..
>>>>>>> But I'm not sure if I have full debug features
because I don't
>>>>>>> succeed to translate Publics and Globals correctly.
CVDump says PDB is
>>>>>>> corrupted whereas PDBUTIL -dump correctly displays
them.
>>>>>>> I don't really understand what Publics and
Globals stream really
>>>>>>> are, if the symbols are really in the corresponding
streams or if they are
>>>>>>> just references to somewhere else.
>>>>>>> The LLVM documentation is not complete about these
two Publics and
>>>>>>> Globals stream so I'm a bit lost on how to
handle them or find what is
>>>>>>> "corrupted" according to CVDump.
>>>>>>> I took example on LLD and yaml2pdb to help me to do
some tough
>>>>>>> conversions but I noticed that in yaml2pdb there is
no GsiStream exported
>>>>>>> (no GsiBuidler use and no reference to Publics or
Globals anywhere), is it
>>>>>>> wanted/correct ?
>>>>>>> Thanks and sorry If I'm a bit spaming, it's
my 99% time task right
>>>>>>> now and being stuck without any clue is difficult
:) But I guess you
>>>>>>> experienced even more suffering when documentation
didn't exist at all !
>>>>>>> Have a good day !
>>>>>>>
>>>>>>> Le dim. 20 janv. 2019 à 22:27, Vivien Millet <
>>>>>>> vivien.millet at gmail.com> a écrit :
>>>>>>>
>>>>>>>> ERRATUM, my bad, the pdb I tested is also
corrupted according to
>>>>>>>> cvdump.exe, I on't know why, I regenerated
again and now I have a working
>>>>>>>> dump. You don't need to fix anything.
>>>>>>>>
>>>>>>>> Le dim. 20 janv. 2019 à 20:26, Vivien Millet
<
>>>>>>>> vivien.millet at gmail.com> a écrit :
>>>>>>>>
>>>>>>>>> Hi Zachary,
>>>>>>>>> I've done a first step to rewrite 
existing PDBFile with
>>>>>>>>> PDBFileBuilder, I get mostly of the work
done but I don't get as much
>>>>>>>>> output as input (some streams are not
mirrored for unknown reasons and some
>>>>>>>>> data must be missing here and there...).
>>>>>>>>> When I try to replace the original by the
rebuilt one for
>>>>>>>>> debugging, the pdb loads well but
breakpoints failed to activate with a
>>>>>>>>> "unexpected symbol reader error while
processing foobar.exe". You probably
>>>>>>>>> know what it means or already encountered
this error I guess.
>>>>>>>>> I also tried to create a minimal program to
simplify comparisons
>>>>>>>>> between original and new PDB but I get an
error dumping the original  pdb
>>>>>>>>> exported by visual studio  with -all
(PublicsStream.cpp|98). I think it is
>>>>>>>>> a bug.
>>>>>>>>> I've attached the related main.cpp and
PDB to this email if you
>>>>>>>>> want to check what is the error exactly
(vs2017, x86 and x64 have same
>>>>>>>>> issues).
>>>>>>>>> I've attached also my code (git diff).
I added an « identity »
>>>>>>>>> feature to pdbutil which uses the code I
wrote to regenerate the input pdb.
>>>>>>>>> You can use it to see what I get so far..
>>>>>>>>> I’ve seen you added recently a fix related
to FPO but you say it’s
>>>>>>>>> only for x86 so I don’t think it would
change something but who knows..
>>>>>>>>> Anyway, if you have a moment to check my
work so far and give me
>>>>>>>>> feedbacks it’s welcome because I get out of
ideas about what goes wrong..
>>>>>>>>> Thanks, I go back digging into the pdb
mysteries !
>>>>>>>>>
>>>>>>>>> Le ven. 18 janv. 2019 à 12:31, Vivien
Millet <
>>>>>>>>> vivien.millet at gmail.com> a écrit :
>>>>>>>>>
>>>>>>>>>> Ok ! It was just to be sure I
understood well.
>>>>>>>>>> Sorry for not replying directly, I
wanted to try first to emit
>>>>>>>>>> CodeView before continuing the
discussion and it was time for me to go to
>>>>>>>>>> bed here..
>>>>>>>>>> I just tried it now and it is very easy
to switch to CodeView.
>>>>>>>>>> For the ones interested : you just have
to give your TargetTriple to your
>>>>>>>>>> llvm::Module used for JIT and then call
>>>>>>>>>>
module->addModuleFlag(llvm::Module::Warning, "CodeView", 1) to tell
the
>>>>>>>>>> AsmPrinter this module prefer CodeView
instead of Dwarf.
>>>>>>>>>> I've checked the content of my .obj
file, and there is valid
>>>>>>>>>> .debug$T and  .debug$S sections, so
everything goes well until now.
>>>>>>>>>> Now as a parallel task I will try to
read the EXE PDB and
>>>>>>>>>> re-export it "as it" to see
if I break something in visual studio.
>>>>>>>>>> If I succeed to do that, that might be
added as a feature to
>>>>>>>>>> PDBFile or PDBFileBuilder to simplify
the process for other users.
>>>>>>>>>> I keep you in touch.
>>>>>>>>>> Thanks
>>>>>>>>>>
>>>>>>>>>> Le jeu. 17 janv. 2019 à 20:50, Zachary
Turner <zturner at google.com>
>>>>>>>>>> a écrit :
>>>>>>>>>>
>>>>>>>>>>> When I say "nothing to
do" I just mean that you won't have to do
>>>>>>>>>>> anything to convert the record from
one format (DWARF) to another format
>>>>>>>>>>> (CodeView).  You will have a COFF
object file either on disk (probably
>>>>>>>>>>> named foo.obj or something) or in
memory.  And this object file will have a
>>>>>>>>>>> .debug$S section with CodeView
symbols and a .debug$T section with CodeView
>>>>>>>>>>> types.  Then you will still need to
use the PDBFileBuilder to add these
>>>>>>>>>>> records to the final PDB, but they
will already be in the correct format
>>>>>>>>>>> that PDBFileBuilder expects, you
won't need to convert them from DWARF
>>>>>>>>>>> (which is not trivial).
>>>>>>>>>>>
>>>>>>>>>>> On Thu, Jan 17, 2019 at 11:26 AM
Vivien Millet <
>>>>>>>>>>> vivien.millet at gmail.com>
wrote:
>>>>>>>>>>>
>>>>>>>>>>>> That’s a good question, by
default when emitting the object
>>>>>>>>>>>> file I choose COFF but it
embeds dwarf and not codeview in the end.. there
>>>>>>>>>>>> probably is a way to do it or
at least it must be implemented if not yet..
>>>>>>>>>>>> Lets imagine I manage to do
that.. when you say there is
>>>>>>>>>>>> nothing to do, I still must
have a PDBFileBuilder to copy the codeview data
>>>>>>>>>>>> inside the EXE PDB right ? I
cannot insert them easily in the EXE PDB with
>>>>>>>>>>>> another way ?
>>>>>>>>>>>>
>>>>>>>>>>>> Le jeu. 17 janv. 2019 à 20:01,
Zachary Turner <
>>>>>>>>>>>> zturner at google.com> a
écrit :
>>>>>>>>>>>>
>>>>>>>>>>>>> Well, is it possible to
just hook up the CodeView debug info
>>>>>>>>>>>>> generator to MCJIT?  If
you're not jitting, and you just compile something,
>>>>>>>>>>>>> we translate all of the
LLVM metadata into CodeView in the file
>>>>>>>>>>>>> CodeViewDebug.cpp.  Then,
the object file just already has CodeView in it.
>>>>>>>>>>>>> If it's not hard to do,
this would probably be a better solution, because
>>>>>>>>>>>>> you don't have to worry
about *how* to translate DWARF into CodeView, which
>>>>>>>>>>>>> is not always trivial.
>>>>>>>>>>>>>
>>>>>>>>>>>>> If you can configure this
in MCJIT, you won't even need to do
>>>>>>>>>>>>> anything, you can just open
the ObjectFile, look for the .debug$T and
>>>>>>>>>>>>> .debug$S sections, iterate
over each one and re-write their TypeIndices
>>>>>>>>>>>>> while copying them to the
output PDB file.
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, Jan 17, 2019 at
10:52 AM Vivien Millet <
>>>>>>>>>>>>> vivien.millet at
gmail.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Ok I understand more
what you meant. In fact I don’t care
>>>>>>>>>>>>>> about the pdb size, at
least as a first step, so it won’t be a problem for
>>>>>>>>>>>>>> me to have duplicated
symbols. Concerning TypeIndices my plan if possible
>>>>>>>>>>>>>> is not to generate a
pdb for my jit and merge it, but instead directly
>>>>>>>>>>>>>> extract debug info from
a DwarfContext just after llvm::object::ObjectFile
>>>>>>>>>>>>>> is emitted by the JIT
engine and complete the EXE PDB I had rebuilt with
>>>>>>>>>>>>>> PDBFileBuilder. Does it
sounds a good bet to you ? If I succeed doing that
>>>>>>>>>>>>>> I think that could be a
good extension to the debugging possibilities of
>>>>>>>>>>>>>> MCJit if not being an
extension to pdbutil.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Le jeu. 17 janv. 2019 à
19:37, Zachary Turner <
>>>>>>>>>>>>>> zturner at
google.com> a écrit :
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Well, for example
the TPI stream is just one big collection
>>>>>>>>>>>>>>> of types. 
Presumably your JIT code will reuse some of the same types
>>>>>>>>>>>>>>> (perhaps,
std::string for example) as your non-jitted code.  Your jitted
>>>>>>>>>>>>>>> symbol records in
the object file (for example, a local variable of type
>>>>>>>>>>>>>>> std::string in your
jitted code) will refer to the type for std;:string by
>>>>>>>>>>>>>>> a TypeIndex, and
your original PDB will also refer to std::string by a
>>>>>>>>>>>>>>> different
TypeIndex.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> In LLD, when we
merge in types and symbols from each object
>>>>>>>>>>>>>>> file, we keep a
hash table of which types have already been seen, so that
>>>>>>>>>>>>>>> if we see the same
type again, we can just use the TypeIndex that we wrote
>>>>>>>>>>>>>>> on a previous
object file.  Then, when we add symbol records, we have to
>>>>>>>>>>>>>>> update its fields
that used the old TypeIndex to use the new TypeIndex
>>>>>>>>>>>>>>> instead.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> De-duplicating
though, I suppose, is not strictly necessary,
>>>>>>>>>>>>>>> it will just keep
your PDB size down.  But you *will* need to at least
>>>>>>>>>>>>>>> re-write the
TypeIndexes from the jitted code.  For example, you may decide
>>>>>>>>>>>>>>> that instead of
de-duplicating, you just append them all to the end of the
>>>>>>>>>>>>>>> TPI stream (where
all the types go in PDB) to keep things simple.  Since
>>>>>>>>>>>>>>> they were in a
different position before, they now have different
>>>>>>>>>>>>>>> TypeIndices.  So
you will need to re-write all TypeIndices so that they are
>>>>>>>>>>>>>>> correct after the
merge.   Both types and symbols can refer to types, so
>>>>>>>>>>>>>>> you will need to do
this both for the types of the jitted code as well as
>>>>>>>>>>>>>>> the symbols of the
jitted code.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Let me know if that
makes sense.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Thu, Jan 17,
2019 at 10:24 AM Vivien Millet <
>>>>>>>>>>>>>>> vivien.millet at
gmail.com> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Ok I see..
>>>>>>>>>>>>>>>> what do you
mean by “making sure to de-duplicate records as
>>>>>>>>>>>>>>>> necessary” ?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Le jeu. 17
janv. 2019 à 19:09, Zachary Turner <
>>>>>>>>>>>>>>>> zturner at
google.com> a écrit :
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> It's
possible in theory to support incremental updates to
>>>>>>>>>>>>>>>>> a PDB (the
file format is designed specifically with that in mind).  But
>>>>>>>>>>>>>>>>> this
functionality was never added to the PDB library since lld doesn't
>>>>>>>>>>>>>>>>> support
incremental linking, we never really needed it.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The
"dumb" way would be to just create a new PDB file,
>>>>>>>>>>>>>>>>> build it
using the old contents and the new contents (making sure to
>>>>>>>>>>>>>>>>>
de-duplicate records as necessary).
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Supporting
incremental updates should be possible, but
>>>>>>>>>>>>>>>>> most of
LLVM's File I/O abstractions are based around mmapping a file and
>>>>>>>>>>>>>>>>> writing to
it, which doesn't work when you don't know the file size in
>>>>>>>>>>>>>>>>> advance. 
So there would be some interesting problems to solve here.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Thu, Jan
17, 2019 at 10:03 AM Vivien Millet <
>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Hi
Zachary !
>>>>>>>>>>>>>>>>>> If
there a way to easily create a new PDBFileBuilder from
>>>>>>>>>>>>>>>>>> an
existing PDBFile or can/should I do the translation myself ?
>>>>>>>>>>>>>>>>>> I would
like to start from a builder filled with the EXE
>>>>>>>>>>>>>>>>>> PDB
data and then complete its DBI stream with the JIT module/symbols.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks
!
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Le mer.
16 janv. 2019 à 23:41, Vivien Millet <
>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> a écrit :
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
Thank you Zachary !
>>>>>>>>>>>>>>>>>>> I
will have some soon I think ..
>>>>>>>>>>>>>>>>>>> I
first need to explore the llvmpdb-util code more
>>>>>>>>>>>>>>>>>>>
because I don't even know where to start with the PDB api..
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Le
mer. 16 janv. 2019 à 22:51, Zachary Turner <
>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
Sure. Along the way I’m happy to answer any specific
>>>>>>>>>>>>>>>>>>>>
questions you might have too even if it’s for your downstream project
>>>>>>>>>>>>>>>>>>>>
On Wed, Jan 16, 2019 at 1:38 PM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
I would be up to improve pdbutil but I doubt I have
>>>>>>>>>>>>>>>>>>>>>
enough knowledge or time to provide the complete merge feature, it would
>>>>>>>>>>>>>>>>>>>>>
still be a very specific kind of merge as you describe it. Anyway I could
>>>>>>>>>>>>>>>>>>>>>
start trying to do it in my jit compiler and then, once I get something
>>>>>>>>>>>>>>>>>>>>>
working (if that happens :)), i can come back to you with the piece of code
>>>>>>>>>>>>>>>>>>>>>
and see if it is worth integrating it to pdbutil and how ?
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
Le mer. 16 janv. 2019 à 22:12, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
Well, that’s certainly possible, but improving
>>>>>>>>>>>>>>>>>>>>>>
llvm-pdbutil is another possibility. Doing it directly in your jit compiler
>>>>>>>>>>>>>>>>>>>>>>
will probably save you time though, since you won’t have to worry about
>>>>>>>>>>>>>>>>>>>>>>
writing tests and going through code review
>>>>>>>>>>>>>>>>>>>>>>
On Wed, Jan 16, 2019 at 1:01 PM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
Thanks for the tips !
>>>>>>>>>>>>>>>>>>>>>>>
When you talk about doing all of this I suppose you
>>>>>>>>>>>>>>>>>>>>>>>
think about using llvm/debuginfo/pdb, pick code here and there to generate
>>>>>>>>>>>>>>>>>>>>>>>
the pdb in memory, read the executable one and perform the merge directly
>>>>>>>>>>>>>>>>>>>>>>>
in my jit compiler, right ? Not using pdbutil ?
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
Le mar. 15 janv. 2019 à 22:49, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
On Tue, Jan 15, 2019 at 2:50 AM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
Hello Zachary !
>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks for your time !
>>>>>>>>>>>>>>>>>>>>>>>>>
So you are one of the happy guys who suffered from
>>>>>>>>>>>>>>>>>>>>>>>>>
the lack of PDB format information :)
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
Yes, that would be me :)
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
To be honest I'm really a beginner in the PDB
>>>>>>>>>>>>>>>>>>>>>>>>>
stuff, I just read some llvm documentation to understand what went wrong
>>>>>>>>>>>>>>>>>>>>>>>>>
when merging my PDBs.
>>>>>>>>>>>>>>>>>>>>>>>>>
In my case, what I do with my team and try to
>>>>>>>>>>>>>>>>>>>>>>>>>
achieve is this :
>>>>>>>>>>>>>>>>>>>>>>>>>
- Run our application under a visual studio
>>>>>>>>>>>>>>>>>>>>>>>>>
debugger
>>>>>>>>>>>>>>>>>>>>>>>>>
- Generate JIT code ( using llvm MCJIT  )
>>>>>>>>>>>>>>>>>>>>>>>>>
- Then, either :
>>>>>>>>>>>>>>>>>>>>>>>>>
- export as COFF obj file with dwarf
>>>>>>>>>>>>>>>>>>>>>>>>>
information and then convert it with cv2pdb to obtain a pdb of my JIT
>>>>>>>>>>>>>>>>>>>>>>>>>
symbols (what I do now)
>>>>>>>>>>>>>>>>>>>>>>>>>
- export directly to PDB my JIT debug info
>>>>>>>>>>>>>>>>>>>>>>>>>
(what i would like to do, if you have an idea how..)
>>>>>>>>>>>>>>>>>>>>>>>>>
- Detach the visual studio debugger
>>>>>>>>>>>>>>>>>>>>>>>>>
- Merge my JIT pdb into a copy of the executable
>>>>>>>>>>>>>>>>>>>>>>>>>
pdb (where things start to go bad..)
>>>>>>>>>>>>>>>>>>>>>>>>>
- Replace original executable by the copy
>>>>>>>>>>>>>>>>>>>>>>>>>
(creating a backup of original)
>>>>>>>>>>>>>>>>>>>>>>>>>
- Reattach  the visual studio debugger to my
>>>>>>>>>>>>>>>>>>>>>>>>>
executable (loading the new pdb version)
>>>>>>>>>>>>>>>>>>>>>>>>>
- Debug JIT code with visual studio.
>>>>>>>>>>>>>>>>>>>>>>>>>
- On each JIT rebuild, restart these steps from
>>>>>>>>>>>>>>>>>>>>>>>>>
the original native executable PDB to avoid merge conflict between the
>>>>>>>>>>>>>>>>>>>>>>>>>
multiple JIT iterations
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
Yea, it's an interesting use case.  It makes me
>>>>>>>>>>>>>>>>>>>>>>>>
think it would be nice if the PDB format supported some way of having a
>>>>>>>>>>>>>>>>>>>>>>>>
symbol which simply refers to another PDB file, that way you could re-write
>>>>>>>>>>>>>>>>>>>>>>>>
that PDB file at runtime once all your code is jitted, and when the
>>>>>>>>>>>>>>>>>>>>>>>>
debugger tries to look up that symbol, it finds a record that tells it to
>>>>>>>>>>>>>>>>>>>>>>>>
go check the other PDB file.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
So, here are the things I think you would need to
>>>>>>>>>>>>>>>>>>>>>>>>
do:
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
1) Create a JIT module in the module list with a
>>>>>>>>>>>>>>>>>>>>>>>>
unique name.  All symbols will go here.  llvm-pdbutil dump -modules shows
>>>>>>>>>>>>>>>>>>>>>>>>
you the list.  Be careful about putting it at the end though, because
>>>>>>>>>>>>>>>>>>>>>>>>
there's already one at the end called * LINKER * that is kind of special.
>>>>>>>>>>>>>>>>>>>>>>>>
On the other hand, you don't want to put it first because it means you will
>>>>>>>>>>>>>>>>>>>>>>>>
have to do lots of fixups on the EXE PDB.  It's probably best to add it
>>>>>>>>>>>>>>>>>>>>>>>>
right before the linker module, this has the least chance of breaking
>>>>>>>>>>>>>>>>>>>>>>>>
anything.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
2) In the debug stream for this module, add all
>>>>>>>>>>>>>>>>>>>>>>>>
symbols.  You will need to fix up their type indices.  As you noticed,
>>>>>>>>>>>>>>>>>>>>>>>>
llvm-pdbutil already merges type information from the JIT PDB, so after
>>>>>>>>>>>>>>>>>>>>>>>>
merging the type indices in the EXE PDB will be different than they were in
>>>>>>>>>>>>>>>>>>>>>>>>
the JIT PDB, but the symbol records will refer to the JIT PDB type
>>>>>>>>>>>>>>>>>>>>>>>>
indices.  So these need to be fixed up.  LLD already has code to do this,
>>>>>>>>>>>>>>>>>>>>>>>>
you can probably borrow a similar algorithm with some slight modifications
>>>>>>>>>>>>>>>>>>>>>>>>
(lldb/COFF/PDB.cpp, search for mergeSymbolRecords)
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
3) Merge in the new section contributions and
>>>>>>>>>>>>>>>>>>>>>>>>
section map.  See LLD again for how to modify these.  Hopefully the object
>>>>>>>>>>>>>>>>>>>>>>>>
file you exported contains relocated symbol addresses so you don't have to
>>>>>>>>>>>>>>>>>>>>>>>>
do any fixups here.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
4) Merge in the publics and globals.  This
>>>>>>>>>>>>>>>>>>>>>>>>
shouldn't be too hard, I think you can just iterate over them in the JIT
>>>>>>>>>>>>>>>>>>>>>>>>
PDB and add them to the new EXE PDB.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
You're kind of in uncharted territory here, so this
>>>>>>>>>>>>>>>>>>>>>>>>
is just a rough idea of what needs to be done.  There may be other issues
>>>>>>>>>>>>>>>>>>>>>>>>
that you don't encounter until you actually try it out.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
Unfortunately I don't personally have the time to
>>>>>>>>>>>>>>>>>>>>>>>>
work on this, but it sounds neat, and I'm happy to help if you run into
>>>>>>>>>>>>>>>>>>>>>>>>
questions or problems along the way.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
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.text is where code goes, I don't know why it's called .text, it's
just
been that way for many decades and the name stuck around.  But actually you
can call the section whatever you want.  Maybe it's even better to call it
something other than .text, because .text is where your DllMain and other
stuff will be.  You could call it .jit if you wanted to.  You should be
able to create the section with whatever flags you want to.  You'll need to
produce a jit_code.obj probably compiled from assembly that makes a section
named .jit and sets the flags to be executable (you can just copy the flags
from a normal .text section of some other program).  Then link this file
together along with a jitted_code_main.obj which you compiled from a simple
source file with a DllMain function that does nothing.  This would make
jitted_code.dll, then have your program link against jitted_code.lib.

Right now you jit the code into some buffer that you created with
VirtualAlloc.  If you do the above, it will load jitted_code.dll into
memory and the OS loader will allocate some memory for each section.  So
this would be like your VirtualAlloc, you can just find the address of the
.jit section and use that buffer instead of the VirtualAlloc buffer as the
target address of your jit operations.

Again, this is just an idea, no promises it will work, but unfortunately
that's kind of the best you can do when dealing with closed source things,
just make guesses and hope for the best.



On Wed, Jan 23, 2019 at 12:42 PM Vivien Millet <vivien.millet at
gmail.com>
wrote:
> (Yes you are right this is my fault)
> Considering the string table, it only seems to contains file relative
> informations in every pdb I am using, and it looks correct but I will check
> it.
> I looked at the pdb.cpp code about checksums and tables, I copied some
> stuff and got things wrong according to cvdump, then I simplified the
> process of copying the table and it worked (in cvdump it finds the file
> matching line etc...) so I suspect this is also correct.
>
> All the streams look good, but I will check deeper !
>
> It seems right what you say about rva and modules, this is what I m afraid
> of, doing all of this for nothing or almost..
>
> Your idea looks good concerning the .text section in a separated dll, but
> will it be executable memory ? .text is where static strings go right ?
> When you say putting my jit in there, do you mean writing it when the
> jitted_code.dll is loaded in memory or on the .dll file directly before
> loading it ? In the first scenario I wonder if the section will be
> executable, in the second scenario I can’t do it because it would require
> perfect linking with the other code my jit points to..
>
> Le mer. 23 janv. 2019 à 20:57, Zachary Turner <zturner at google.com>
a
> écrit :
>
>> (BTW, I'm adding llvm-dev back to the list, I didn't notice it
got taken
>> off.  In general I try to keep the list on all emails, even if it's
>> extremely technical and specific, because someday someone else will try
to
>> do this, and it'll be nice if they can read the whole thread).
>>
>> I can think of a couple of things that might be wrong:
>>
>> 1) If the string table is in a different order, then anything that
refers
>> to the string table need to be changed to refer to the new offset.  If
the
>> string "foo" is at offset 12 in the old PDB, but offset 15 in
the new PDB,
>> then somewhere there is a record which is going to look at offset 12
and
>> expect to find something, and that will mess up.  The main place this
is
>> important is in the File Checksums table, there is an entry that says
which
>> file it is a checksum for, and that refers to the string table. 
However,
>> it's possible for certain symbol records to refer to the string
table too.
>> See lld/COFF/PDB.cpp and Ctrl+F for "PDBStrTab" and you will
find some
>> information about this.
>>
>> 2) When you run `llvm-pdbutil dump -streams` on the copied PDB, do all
of
>> them show a reasonable description?  Are there any streams that say
(???)?
>> If so, that's a problem.
>>
>> > does visual studio will consider a symbol file broken if the
address
>> goes beyond the official module address range (the compiled one),
because
>> my JIT code is allocated after the end of the module with VirtualAlloc
>> That is a good question, and part of why my job is so difficult,
because
>> I can't look at their code.  But I think the answer is
"probably".  The
>> debugger has to have some way to convert an address in your running
process
>> into a symbol and offset, because that's how all debug info is
represented
>> in the PDB.  So if there is no module, then there is no RVA (because
the R
>> in RVA means relative, and what would it be relative to?).
>>
>> One idea to test this would be to create a DLL called jitted_code.dll,
>> give it a huuuuuge .text section (probably just a .asm file and use
some
>> assembly directives to allocate a very large series of null bytes), and
>> then write your jit code into that area.  This way you would not need
to
>> modify the existing PDB you would only need to make a new PDB called
>> jitted_code.pdb with 1 module, and those symbols could have meaningful
>> RVAs.  And you might not even need to detach the debugger if you do
things
>> this way, because you could just right click the jitted_code.dll module
in
>> the modules window and choose Load Symbols.
>>
>>
>>
>> On Wed, Jan 23, 2019 at 11:13 AM Vivien Millet <vivien.millet at
gmail.com>
>> wrote:
>>
>>> Yes this is it, I just make a copy from a pdb generated by link.exe
(the
>>> microsoft one).
>>> Using llvm-pdbutil to compare is what I do, except I do it with
"-all"
>>> And I get almost everything the same : same number of streams,
section
>>> map looks good,string table looks good (even if not the same
order), same
>>> number of modules with the symbols and subsection practically the
same, and
>>> this is why I get stuck, I miss something but I can't see what
because I
>>> don't know where to look for. Visual studio works with it, I
can debug my
>>> original exe, but probably without the globals...
>>> And the other problem is that the difference between the dumps is
not
>>> necessarily a bug because the builder may generate new hashes
values,
>>> reorder streams, modules, etc ...
>>>
>>> Right now I gave up to have publics and globals streams and
attacked the
>>> real goal : insert my jit codeview into the pdb. I have again done
«
>>> something » but as I don’t understand how the format work I don’t
have it
>>> working in visual studio.. except once, a single time it worked and
the
>>> breakpoint turned on in the UI (even if the rva was broken for the
>>> instructions) but it happened a single time .. then I get depressed
the
>>> next times..... cvdump displays it all « correct », no corrupt
stuff
>>> apparently. But what I do is probably wrong somewhere. What I do is
I take
>>> .debug$S and .debug$T as is without relocations just to see, but
what I
>>> don’t know really is : does visual studio will consider a symbol
file
>>> broken if the address goes beyond the official module address range
(the
>>> compiled one), because my JIT code is allocated after the end of
the module
>>> with VirtualAlloc.
>>> Another thing I don’t get is the section contribution, what is it
>>> exactly ? I inserted section contrib for all sections except the
debug$
>>> ones but I don’t know what i’m really doing and it’s my average
problem
>>> implementing this JIT feature...
>>> I also don’t know what are relocations inside the codeview format,
what
>>> is the difference between RVA and relocation, is there anything to
do with
>>> this related to the codeview part I need to insert in the pdb ? I
don’t see
>>> why visual studio needs more than just RVA<->Line mapping..
>>> This is really making me crazy being so ignorant and trying to
guess
>>> what visual studio does...
>>>
>>> Le lun. 21 janv. 2019 à 19:50, Zachary Turner <zturner at
google.com> a
>>> écrit :
>>>
>>>> So if i understand correctly, you're basically just trying
to implement
>>>> something like a pdb *copy*, just as a test to see if you can
get it to
>>>> work.  So you generate a PDB with cl/link or clang-cl/lld-link,
then try to
>>>> copy it using your tool, then see if it still works.
>>>>
>>>> If this is correct, and it's not working, then there is
probably just
>>>> something you didn't copy.  Neither Publics nor globals
actually contain
>>>> their own data, instead they just refer to records from the
corresponding
>>>> module stream.  So an S_PROCREF for the function
"main" might have fields
>>>> that say "the name of the function is main, and it's
at offset 20 of module
>>>> 1".  So, if there is no module 1, or if offset 20 of
module is not actually
>>>> an S_GPROC32 for the function main, then it will be broken.
>>>>
>>>> Did you also go through each module in the source PDB, add a
new module
>>>> in the target PDB, then copy all of the symbols for each one?
>>>>
>>>> the best way to find differences is by using llvm-pdbutil on
the source
>>>> and target PDBs and looking for things that look different. 
For example,
>>>> I'd start with llvm-pdbutil dump -streams and then seeing
if they even have
>>>> all the same streams.  If one of them is missing streams,
that's a good
>>>> place to start.  If they have the same streams, then look for
ones where
>>>> the size is different.  Then drill into those to see why the
size is
>>>> different.
>>>>
>>>> LMK if that helps.
>>>>
>>>> On Mon, Jan 21, 2019 at 10:03 AM Vivien Millet
<vivien.millet at gmail.com>
>>>> wrote:
>>>>
>>>>> For now I'm not merging my JIT CodeView section, I only
try to build a
>>>>> pure copy of an existing PDB using the XxxBuilder classes
(PDBFileBuilder &
>>>>> Co / reading a PDBFile) and check if visual studio wants to
eat it..
>>>>> For Publics and Globals, what I do is naive, I use the
>>>>> GsiStreamBuilder and prey :)
>>>>>
>>>>>
>>>>>
>>>>>   if (File.hasPDBGlobalsStream() &&
File.getPDBGlobalsStream()) {
>>>>>     GSIStreamBuilder &builder =
this->getGsiBuilder();
>>>>>     GlobalsStream &stream =
*File.getPDBGlobalsStream();
>>>>>     SymbolStream &SymbolRecords =
cantFail(File.getPDBSymbolStream());
>>>>>
>>>>>     for (uint32_t PubSymOff : stream.getGlobalsTable()) {
>>>>>       CVSymbol Sym = SymbolRecords.readRecord(PubSymOff);
>>>>>       builder.addGlobalSymbol(Sym);
>>>>>     }
>>>>>   }
>>>>>   if (File.hasPDBPublicsStream() &&
File.getPDBPublicsStream()) {
>>>>>     GSIStreamBuilder &builder =
this->getGsiBuilder();
>>>>>     PublicsStream &stream =
*File.getPDBPublicsStream();
>>>>>     SymbolStream &SymbolRecords =
cantFail(File.getPDBSymbolStream());
>>>>>
>>>>> 	std::vector<PublicSym32> Publics;
>>>>>
>>>>>     for (uint32_t PubSymOff : stream.getPublicsTable()) {
>>>>>       PublicSym32 Pub = cantFail(
>>>>>          
llvm::codeview::SymbolDeserializer::deserializeAs<PublicSym32>(
>>>>>               SymbolRecords.readRecord(PubSymOff)));
>>>>>       Publics.push_back(Pub);
>>>>>     }
>>>>>
>>>>>     if (!Publics.empty()) {
>>>>>       // Sort the public symbols and add them to the
stream.
>>>>>       std::sort(Publics.begin(), Publics.end(),
>>>>>            [](const PublicSym32 &L, const PublicSym32
&R) {
>>>>>              return L.Name < R.Name;
>>>>>            });
>>>>>       for (const PublicSym32 &Pub : Publics)
>>>>>         builder.addPublicSymbol(Pub);
>>>>>     }
>>>>>
>>>>>   }
>>>>>
>>>>> Is it what you meant ?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Le lun. 21 janv. 2019 à 18:50, Zachary Turner <zturner
at google.com> a
>>>>> écrit :
>>>>>
>>>>>> Also, even if symbolGoesInGlobalsStream returns true,
you can’t just
>>>>>> copy it. Functions, for example, which are S_GPROC32 or
S_LPROC32 in the
>>>>>> module stream, are S_PROCREF in the globals stream.
Similarly, *everything*
>>>>>> in the publics stream is S_PUB32. So you need to
convert each symbol to the
>>>>>> proper type for the stream it’s going to go in
>>>>>> On Mon, Jan 21, 2019 at 9:46 AM Zachary Turner
<zturner at google.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Publics are basically a list of everything that has
a mangled name.
>>>>>>> To be honest, I don’t know what the debugger uses
this for.
>>>>>>>
>>>>>>> Globals is essentially every symbol in the pdb in
one large table.
>>>>>>> The reason this is important is because if you type
“foo” in the watch
>>>>>>> window, the debugger doesn’t necessarily know what
compiland foo comes
>>>>>>> from. So it has to have a way to find everything in
the entire program no
>>>>>>> matter what compiland it came from. That’s what the
globals are.
>>>>>>>
>>>>>>> Both publics and globals are hash tables, so one
possible reason
>>>>>>> there might be a problem is that you need to rehash
the entire table. When
>>>>>>> you build your modified pdb, I would suggest
starting with an empty publics
>>>>>>> / globals stream, adding all items from the first
pdb by iterating over
>>>>>>> those records and using a GlobalsStreamBuilder,
then adding all your jitted
>>>>>>> items separately, then writing it out. That should
make sure it gets hashed
>>>>>>> correctly.
>>>>>>>
>>>>>>> Are you doing that?
>>>>>>>
>>>>>>> Btw, not all symbols belong in the globals /
publics stream. Check
>>>>>>> the code in lld and search for
symbolGoesInGlobalsStream and
>>>>>>> symbolGoesInPublicsStream to see the logic it uses
>>>>>>> On Mon, Jan 21, 2019 at 8:36 AM Vivien Millet <
>>>>>>> vivien.millet at gmail.com> wrote:
>>>>>>>
>>>>>>>> Hi Zachary, sorry for disturbing again..
>>>>>>>>
>>>>>>>> I've fixed some problems (StringTable,
SectionMap and few things
>>>>>>>> here and there..) and my converted PDB seems
now to work inside visual
>>>>>>>> studio..
>>>>>>>> But I'm not sure if I have full debug
features because I don't
>>>>>>>> succeed to translate Publics and Globals
correctly. CVDump says PDB is
>>>>>>>> corrupted whereas PDBUTIL -dump correctly
displays them.
>>>>>>>> I don't really understand what Publics and
Globals stream really
>>>>>>>> are, if the symbols are really in the
corresponding streams or if they are
>>>>>>>> just references to somewhere else.
>>>>>>>> The LLVM documentation is not complete about
these two Publics and
>>>>>>>> Globals stream so I'm a bit lost on how to
handle them or find what is
>>>>>>>> "corrupted" according to CVDump.
>>>>>>>> I took example on LLD and yaml2pdb to help me
to do some tough
>>>>>>>> conversions but I noticed that in yaml2pdb
there is no GsiStream exported
>>>>>>>> (no GsiBuidler use and no reference to Publics
or Globals anywhere), is it
>>>>>>>> wanted/correct ?
>>>>>>>> Thanks and sorry If I'm a bit spaming,
it's my 99% time task right
>>>>>>>> now and being stuck without any clue is
difficult :) But I guess you
>>>>>>>> experienced even more suffering when
documentation didn't exist at all !
>>>>>>>> Have a good day !
>>>>>>>>
>>>>>>>> Le dim. 20 janv. 2019 à 22:27, Vivien Millet
<
>>>>>>>> vivien.millet at gmail.com> a écrit :
>>>>>>>>
>>>>>>>>> ERRATUM, my bad, the pdb I tested is also
corrupted according to
>>>>>>>>> cvdump.exe, I on't know why, I
regenerated again and now I have a working
>>>>>>>>> dump. You don't need to fix anything.
>>>>>>>>>
>>>>>>>>> Le dim. 20 janv. 2019 à 20:26, Vivien
Millet <
>>>>>>>>> vivien.millet at gmail.com> a écrit :
>>>>>>>>>
>>>>>>>>>> Hi Zachary,
>>>>>>>>>> I've done a first step to rewrite 
existing PDBFile with
>>>>>>>>>> PDBFileBuilder, I get mostly of the
work done but I don't get as much
>>>>>>>>>> output as input (some streams are not
mirrored for unknown reasons and some
>>>>>>>>>> data must be missing here and
there...).
>>>>>>>>>> When I try to replace the original by
the rebuilt one for
>>>>>>>>>> debugging, the pdb loads well but
breakpoints failed to activate with a
>>>>>>>>>> "unexpected symbol reader error
while processing foobar.exe". You probably
>>>>>>>>>> know what it means or already
encountered this error I guess.
>>>>>>>>>> I also tried to create a minimal
program to simplify comparisons
>>>>>>>>>> between original and new PDB but I get
an error dumping the original  pdb
>>>>>>>>>> exported by visual studio  with -all
(PublicsStream.cpp|98). I think it is
>>>>>>>>>> a bug.
>>>>>>>>>> I've attached the related main.cpp
and PDB to this email if you
>>>>>>>>>> want to check what is the error exactly
(vs2017, x86 and x64 have same
>>>>>>>>>> issues).
>>>>>>>>>> I've attached also my code (git
diff). I added an « identity »
>>>>>>>>>> feature to pdbutil which uses the code
I wrote to regenerate the input pdb.
>>>>>>>>>> You can use it to see what I get so
far..
>>>>>>>>>> I’ve seen you added recently a fix
related to FPO but you say
>>>>>>>>>> it’s only for x86 so I don’t think it
would change something but who knows..
>>>>>>>>>> Anyway, if you have a moment to check
my work so far and give me
>>>>>>>>>> feedbacks it’s welcome because I get
out of ideas about what goes wrong..
>>>>>>>>>> Thanks, I go back digging into the pdb
mysteries !
>>>>>>>>>>
>>>>>>>>>> Le ven. 18 janv. 2019 à 12:31, Vivien
Millet <
>>>>>>>>>> vivien.millet at gmail.com> a écrit
:
>>>>>>>>>>
>>>>>>>>>>> Ok ! It was just to be sure I
understood well.
>>>>>>>>>>> Sorry for not replying directly, I
wanted to try first to emit
>>>>>>>>>>> CodeView before continuing the
discussion and it was time for me to go to
>>>>>>>>>>> bed here..
>>>>>>>>>>> I just tried it now and it is very
easy to switch to CodeView.
>>>>>>>>>>> For the ones interested : you just
have to give your TargetTriple to your
>>>>>>>>>>> llvm::Module used for JIT and then
call
>>>>>>>>>>>
module->addModuleFlag(llvm::Module::Warning, "CodeView", 1) to tell
the
>>>>>>>>>>> AsmPrinter this module prefer
CodeView instead of Dwarf.
>>>>>>>>>>> I've checked the content of my
.obj file, and there is valid
>>>>>>>>>>> .debug$T and  .debug$S sections, so
everything goes well until now.
>>>>>>>>>>> Now as a parallel task I will try
to read the EXE PDB and
>>>>>>>>>>> re-export it "as it" to
see if I break something in visual studio.
>>>>>>>>>>> If I succeed to do that, that might
be added as a feature to
>>>>>>>>>>> PDBFile or PDBFileBuilder to
simplify the process for other users.
>>>>>>>>>>> I keep you in touch.
>>>>>>>>>>> Thanks
>>>>>>>>>>>
>>>>>>>>>>> Le jeu. 17 janv. 2019 à 20:50,
Zachary Turner <
>>>>>>>>>>> zturner at google.com> a écrit :
>>>>>>>>>>>
>>>>>>>>>>>> When I say "nothing to
do" I just mean that you won't have to
>>>>>>>>>>>> do anything to convert the
record from one format (DWARF) to another format
>>>>>>>>>>>> (CodeView).  You will have a
COFF object file either on disk (probably
>>>>>>>>>>>> named foo.obj or something) or
in memory.  And this object file will have a
>>>>>>>>>>>> .debug$S section with CodeView
symbols and a .debug$T section with CodeView
>>>>>>>>>>>> types.  Then you will still
need to use the PDBFileBuilder to add these
>>>>>>>>>>>> records to the final PDB, but
they will already be in the correct format
>>>>>>>>>>>> that PDBFileBuilder expects,
you won't need to convert them from DWARF
>>>>>>>>>>>> (which is not trivial).
>>>>>>>>>>>>
>>>>>>>>>>>> On Thu, Jan 17, 2019 at 11:26
AM Vivien Millet <
>>>>>>>>>>>> vivien.millet at gmail.com>
wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> That’s a good question, by
default when emitting the object
>>>>>>>>>>>>> file I choose COFF but it
embeds dwarf and not codeview in the end.. there
>>>>>>>>>>>>> probably is a way to do it
or at least it must be implemented if not yet..
>>>>>>>>>>>>> Lets imagine I manage to do
that.. when you say there is
>>>>>>>>>>>>> nothing to do, I still must
have a PDBFileBuilder to copy the codeview data
>>>>>>>>>>>>> inside the EXE PDB right ?
I cannot insert them easily in the EXE PDB with
>>>>>>>>>>>>> another way ?
>>>>>>>>>>>>>
>>>>>>>>>>>>> Le jeu. 17 janv. 2019 à
20:01, Zachary Turner <
>>>>>>>>>>>>> zturner at google.com> a
écrit :
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Well, is it possible to
just hook up the CodeView debug info
>>>>>>>>>>>>>> generator to MCJIT?  If
you're not jitting, and you just compile something,
>>>>>>>>>>>>>> we translate all of the
LLVM metadata into CodeView in the file
>>>>>>>>>>>>>> CodeViewDebug.cpp. 
Then, the object file just already has CodeView in it.
>>>>>>>>>>>>>> If it's not hard to
do, this would probably be a better solution, because
>>>>>>>>>>>>>> you don't have to
worry about *how* to translate DWARF into CodeView, which
>>>>>>>>>>>>>> is not always trivial.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> If you can configure
this in MCJIT, you won't even need to do
>>>>>>>>>>>>>> anything, you can just
open the ObjectFile, look for the .debug$T and
>>>>>>>>>>>>>> .debug$S sections,
iterate over each one and re-write their TypeIndices
>>>>>>>>>>>>>> while copying them to
the output PDB file.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Thu, Jan 17, 2019 at
10:52 AM Vivien Millet <
>>>>>>>>>>>>>> vivien.millet at
gmail.com> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Ok I understand
more what you meant. In fact I don’t care
>>>>>>>>>>>>>>> about the pdb size,
at least as a first step, so it won’t be a problem for
>>>>>>>>>>>>>>> me to have
duplicated symbols. Concerning TypeIndices my plan if possible
>>>>>>>>>>>>>>> is not to generate
a pdb for my jit and merge it, but instead directly
>>>>>>>>>>>>>>> extract debug info
from a DwarfContext just after llvm::object::ObjectFile
>>>>>>>>>>>>>>> is emitted by the
JIT engine and complete the EXE PDB I had rebuilt with
>>>>>>>>>>>>>>> PDBFileBuilder.
Does it sounds a good bet to you ? If I succeed doing that
>>>>>>>>>>>>>>> I think that could
be a good extension to the debugging possibilities of
>>>>>>>>>>>>>>> MCJit if not being
an extension to pdbutil.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Le jeu. 17 janv.
2019 à 19:37, Zachary Turner <
>>>>>>>>>>>>>>> zturner at
google.com> a écrit :
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Well, for
example the TPI stream is just one big collection
>>>>>>>>>>>>>>>> of types. 
Presumably your JIT code will reuse some of the same types
>>>>>>>>>>>>>>>> (perhaps,
std::string for example) as your non-jitted code.  Your jitted
>>>>>>>>>>>>>>>> symbol records
in the object file (for example, a local variable of type
>>>>>>>>>>>>>>>> std::string in
your jitted code) will refer to the type for std;:string by
>>>>>>>>>>>>>>>> a TypeIndex,
and your original PDB will also refer to std::string by a
>>>>>>>>>>>>>>>> different
TypeIndex.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> In LLD, when we
merge in types and symbols from each object
>>>>>>>>>>>>>>>> file, we keep a
hash table of which types have already been seen, so that
>>>>>>>>>>>>>>>> if we see the
same type again, we can just use the TypeIndex that we wrote
>>>>>>>>>>>>>>>> on a previous
object file.  Then, when we add symbol records, we have to
>>>>>>>>>>>>>>>> update its
fields that used the old TypeIndex to use the new TypeIndex
>>>>>>>>>>>>>>>> instead.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> De-duplicating
though, I suppose, is not strictly
>>>>>>>>>>>>>>>> necessary, it
will just keep your PDB size down.  But you *will* need to at
>>>>>>>>>>>>>>>> least re-write
the TypeIndexes from the jitted code.  For example, you may
>>>>>>>>>>>>>>>> decide that
instead of de-duplicating, you just append them all to the end
>>>>>>>>>>>>>>>> of the TPI
stream (where all the types go in PDB) to keep things simple.
>>>>>>>>>>>>>>>> Since they were
in a different position before, they now have different
>>>>>>>>>>>>>>>> TypeIndices. 
So you will need to re-write all TypeIndices so that they are
>>>>>>>>>>>>>>>> correct after
the merge.   Both types and symbols can refer to types, so
>>>>>>>>>>>>>>>> you will need
to do this both for the types of the jitted code as well as
>>>>>>>>>>>>>>>> the symbols of
the jitted code.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Let me know if
that makes sense.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On Thu, Jan 17,
2019 at 10:24 AM Vivien Millet <
>>>>>>>>>>>>>>>> vivien.millet
at gmail.com> wrote:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Ok I see..
>>>>>>>>>>>>>>>>> what do you
mean by “making sure to de-duplicate records
>>>>>>>>>>>>>>>>> as
necessary” ?
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Le jeu. 17
janv. 2019 à 19:09, Zachary Turner <
>>>>>>>>>>>>>>>>> zturner at
google.com> a écrit :
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
It's possible in theory to support incremental updates to
>>>>>>>>>>>>>>>>>> a PDB
(the file format is designed specifically with that in mind).  But
>>>>>>>>>>>>>>>>>> this
functionality was never added to the PDB library since lld doesn't
>>>>>>>>>>>>>>>>>> support
incremental linking, we never really needed it.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> The
"dumb" way would be to just create a new PDB file,
>>>>>>>>>>>>>>>>>> build
it using the old contents and the new contents (making sure to
>>>>>>>>>>>>>>>>>>
de-duplicate records as necessary).
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
Supporting incremental updates should be possible, but
>>>>>>>>>>>>>>>>>> most of
LLVM's File I/O abstractions are based around mmapping a file and
>>>>>>>>>>>>>>>>>> writing
to it, which doesn't work when you don't know the file size in
>>>>>>>>>>>>>>>>>>
advance.  So there would be some interesting problems to solve here.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> On Thu,
Jan 17, 2019 at 10:03 AM Vivien Millet <
>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Hi
Zachary !
>>>>>>>>>>>>>>>>>>> If
there a way to easily create a new PDBFileBuilder
>>>>>>>>>>>>>>>>>>>
from an existing PDBFile or can/should I do the translation myself ?
>>>>>>>>>>>>>>>>>>> I
would like to start from a builder filled with the EXE
>>>>>>>>>>>>>>>>>>> PDB
data and then complete its DBI stream with the JIT module/symbols.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
Thanks !
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Le
mer. 16 janv. 2019 à 23:41, Vivien Millet <
>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> a écrit :
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
Thank you Zachary !
>>>>>>>>>>>>>>>>>>>>
I will have some soon I think ..
>>>>>>>>>>>>>>>>>>>>
I first need to explore the llvmpdb-util code more
>>>>>>>>>>>>>>>>>>>>
because I don't even know where to start with the PDB api..
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
Le mer. 16 janv. 2019 à 22:51, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
Sure. Along the way I’m happy to answer any specific
>>>>>>>>>>>>>>>>>>>>>
questions you might have too even if it’s for your downstream project
>>>>>>>>>>>>>>>>>>>>>
On Wed, Jan 16, 2019 at 1:38 PM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
I would be up to improve pdbutil but I doubt I have
>>>>>>>>>>>>>>>>>>>>>>
enough knowledge or time to provide the complete merge feature, it would
>>>>>>>>>>>>>>>>>>>>>>
still be a very specific kind of merge as you describe it. Anyway I could
>>>>>>>>>>>>>>>>>>>>>>
start trying to do it in my jit compiler and then, once I get something
>>>>>>>>>>>>>>>>>>>>>>
working (if that happens :)), i can come back to you with the piece of code
>>>>>>>>>>>>>>>>>>>>>>
and see if it is worth integrating it to pdbutil and how ?
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
Le mer. 16 janv. 2019 à 22:12, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
Well, that’s certainly possible, but improving
>>>>>>>>>>>>>>>>>>>>>>>
llvm-pdbutil is another possibility. Doing it directly in your jit compiler
>>>>>>>>>>>>>>>>>>>>>>>
will probably save you time though, since you won’t have to worry about
>>>>>>>>>>>>>>>>>>>>>>>
writing tests and going through code review
>>>>>>>>>>>>>>>>>>>>>>>
On Wed, Jan 16, 2019 at 1:01 PM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
Thanks for the tips !
>>>>>>>>>>>>>>>>>>>>>>>>
When you talk about doing all of this I suppose you
>>>>>>>>>>>>>>>>>>>>>>>>
think about using llvm/debuginfo/pdb, pick code here and there to generate
>>>>>>>>>>>>>>>>>>>>>>>>
the pdb in memory, read the executable one and perform the merge directly
>>>>>>>>>>>>>>>>>>>>>>>>
in my jit compiler, right ? Not using pdbutil ?
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
Le mar. 15 janv. 2019 à 22:49, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
On Tue, Jan 15, 2019 at 2:50 AM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
Hello Zachary !
>>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks for your time !
>>>>>>>>>>>>>>>>>>>>>>>>>>
So you are one of the happy guys who suffered
>>>>>>>>>>>>>>>>>>>>>>>>>>
from the lack of PDB format information :)
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
Yes, that would be me :)
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
To be honest I'm really a beginner in the PDB
>>>>>>>>>>>>>>>>>>>>>>>>>>
stuff, I just read some llvm documentation to understand what went wrong
>>>>>>>>>>>>>>>>>>>>>>>>>>
when merging my PDBs.
>>>>>>>>>>>>>>>>>>>>>>>>>>
In my case, what I do with my team and try to
>>>>>>>>>>>>>>>>>>>>>>>>>>
achieve is this :
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Run our application under a visual studio
>>>>>>>>>>>>>>>>>>>>>>>>>>
debugger
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Generate JIT code ( using llvm MCJIT  )
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Then, either :
>>>>>>>>>>>>>>>>>>>>>>>>>>
- export as COFF obj file with dwarf
>>>>>>>>>>>>>>>>>>>>>>>>>>
information and then convert it with cv2pdb to obtain a pdb of my JIT
>>>>>>>>>>>>>>>>>>>>>>>>>>
symbols (what I do now)
>>>>>>>>>>>>>>>>>>>>>>>>>>
- export directly to PDB my JIT debug info
>>>>>>>>>>>>>>>>>>>>>>>>>>
(what i would like to do, if you have an idea how..)
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Detach the visual studio debugger
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Merge my JIT pdb into a copy of the executable
>>>>>>>>>>>>>>>>>>>>>>>>>>
pdb (where things start to go bad..)
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Replace original executable by the copy
>>>>>>>>>>>>>>>>>>>>>>>>>>
(creating a backup of original)
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Reattach  the visual studio debugger to my
>>>>>>>>>>>>>>>>>>>>>>>>>>
executable (loading the new pdb version)
>>>>>>>>>>>>>>>>>>>>>>>>>>
- Debug JIT code with visual studio.
>>>>>>>>>>>>>>>>>>>>>>>>>>
- On each JIT rebuild, restart these steps from
>>>>>>>>>>>>>>>>>>>>>>>>>>
the original native executable PDB to avoid merge conflict between the
>>>>>>>>>>>>>>>>>>>>>>>>>>
multiple JIT iterations
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
Yea, it's an interesting use case.  It makes me
>>>>>>>>>>>>>>>>>>>>>>>>>
think it would be nice if the PDB format supported some way of having a
>>>>>>>>>>>>>>>>>>>>>>>>>
symbol which simply refers to another PDB file, that way you could re-write
>>>>>>>>>>>>>>>>>>>>>>>>>
that PDB file at runtime once all your code is jitted, and when the
>>>>>>>>>>>>>>>>>>>>>>>>>
debugger tries to look up that symbol, it finds a record that tells it to
>>>>>>>>>>>>>>>>>>>>>>>>>
go check the other PDB file.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
So, here are the things I think you would need to
>>>>>>>>>>>>>>>>>>>>>>>>>
do:
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
1) Create a JIT module in the module list with a
>>>>>>>>>>>>>>>>>>>>>>>>>
unique name.  All symbols will go here.  llvm-pdbutil dump -modules shows
>>>>>>>>>>>>>>>>>>>>>>>>>
you the list.  Be careful about putting it at the end though, because
>>>>>>>>>>>>>>>>>>>>>>>>>
there's already one at the end called * LINKER * that is kind of special.
>>>>>>>>>>>>>>>>>>>>>>>>>
On the other hand, you don't want to put it first because it means you will
>>>>>>>>>>>>>>>>>>>>>>>>>
have to do lots of fixups on the EXE PDB.  It's probably best to add it
>>>>>>>>>>>>>>>>>>>>>>>>>
right before the linker module, this has the least chance of breaking
>>>>>>>>>>>>>>>>>>>>>>>>>
anything.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
2) In the debug stream for this module, add all
>>>>>>>>>>>>>>>>>>>>>>>>>
symbols.  You will need to fix up their type indices.  As you noticed,
>>>>>>>>>>>>>>>>>>>>>>>>>
llvm-pdbutil already merges type information from the JIT PDB, so after
>>>>>>>>>>>>>>>>>>>>>>>>>
merging the type indices in the EXE PDB will be different than they were in
>>>>>>>>>>>>>>>>>>>>>>>>>
the JIT PDB, but the symbol records will refer to the JIT PDB type
>>>>>>>>>>>>>>>>>>>>>>>>>
indices.  So these need to be fixed up.  LLD already has code to do this,
>>>>>>>>>>>>>>>>>>>>>>>>>
you can probably borrow a similar algorithm with some slight modifications
>>>>>>>>>>>>>>>>>>>>>>>>>
(lldb/COFF/PDB.cpp, search for mergeSymbolRecords)
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
3) Merge in the new section contributions and
>>>>>>>>>>>>>>>>>>>>>>>>>
section map.  See LLD again for how to modify these.  Hopefully the object
>>>>>>>>>>>>>>>>>>>>>>>>>
file you exported contains relocated symbol addresses so you don't have to
>>>>>>>>>>>>>>>>>>>>>>>>>
do any fixups here.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
4) Merge in the publics and globals.  This
>>>>>>>>>>>>>>>>>>>>>>>>>
shouldn't be too hard, I think you can just iterate over them in the JIT
>>>>>>>>>>>>>>>>>>>>>>>>>
PDB and add them to the new EXE PDB.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
You're kind of in uncharted territory here, so
>>>>>>>>>>>>>>>>>>>>>>>>>
this is just a rough idea of what needs to be done.  There may be other
>>>>>>>>>>>>>>>>>>>>>>>>>
issues that you don't encounter until you actually try it out.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
Unfortunately I don't personally have the time to
>>>>>>>>>>>>>>>>>>>>>>>>>
work on this, but it sounds neat, and I'm happy to help if you run into
>>>>>>>>>>>>>>>>>>>>>>>>>
questions or problems along the way.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
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Hello Zachary,
Sorry for replying so lately but It's been a week I'm thinking an
working
hard on your  "dll memory buffer"  idea to see if it works and give
you
feedbacks !
And it works pretty well until now :
I shared on the list what I did :
- create a .ASM file full of "int 3" instructions (to ensure that if
we
execute over the boundaries we instantly break.
- Compile this to a .DLL
- use hexadecimal editor to change ".text" section Characteristics
from
Read/Execute to Read/Write/Execute
- run my program which does JIT compilation
- get the start RVA of the .text section (which is always 0x1000 in my case)
- Load the .DLL and use the ModuleAddress+RVA as a memory buffer in a
custom DllMemMgr I give to MCJIT
- On NotifyObjectEmitted replace the dll pdb by a custom one I build myself
with your PDBFileBuilder
- On finalizing memory, reload first the dll to trigger visual studio pdb
reloading (not working don't know why yet), ensure it goes into the same
virtual space, protect memory using VirtualProtect.
- Place a breakpoint in my JIT file, it displays "loaded", execute
JIT, it
breaks
...and ....
* drums *
Visual Studio CRASHES when I open the Watch window or Locals/Auto/etc ...
and this, every time, I don't know why..
I noticed, when compiling C++ equivalent to my JIT program, that a simple
"int param" is written size=20 in C++ pdb and size=16 in my JIT pdb,
do you
know what this "size" attribute represent in the S_LOCAL Symbol
section ? I
suspect the symbol section to have program for the watch issue .. but I am
not sure, If you have an idea...
I also had an "illegal instruction" exception when stepping with F10
after
break, but when I'm not breaking the code it runs well..

A lot of mysteries there again...

Visual studio displays well the disassembly with the debug lines at the
right place, etc .. so I don't get why visual studio crashes..
Another issue I have is that I always have to remove/add my breakpoint so
that visual studio realy breaks, even if it says "I'm a good breakpoint
at
that good address". Does it have a relation with file checksums ? It seems
mine has a "none" checksum so I suspect this to be the problem.. but I
don't know how to fix it because I added the checksum with addChecksum with
the good file name and still I get "none" in the dump...
So right know I'm quite hopeful because I get something reacting in Visual
studio, but I have no idea why it crashes..

Have you already encountered this issue when testing your generated pdbs ?
Do you know the role of Section Contributions in the PDB/debugging session
?
Any tip for checking Symbol record validity in the dump ? looks good to me,
no ??? anywhere or Error ..

Thank you !





Le mer. 23 janv. 2019 à 22:29, Zachary Turner <zturner at google.com> a
écrit :
> .text is where code goes, I don't know why it's called .text,
it's just
> been that way for many decades and the name stuck around.  But actually you
> can call the section whatever you want.  Maybe it's even better to call
it
> something other than .text, because .text is where your DllMain and other
> stuff will be.  You could call it .jit if you wanted to.  You should be
> able to create the section with whatever flags you want to.  You'll
need to
> produce a jit_code.obj probably compiled from assembly that makes a section
> named .jit and sets the flags to be executable (you can just copy the flags
> from a normal .text section of some other program).  Then link this file
> together along with a jitted_code_main.obj which you compiled from a simple
> source file with a DllMain function that does nothing.  This would make
> jitted_code.dll, then have your program link against jitted_code.lib.
>
> Right now you jit the code into some buffer that you created with
> VirtualAlloc.  If you do the above, it will load jitted_code.dll into
> memory and the OS loader will allocate some memory for each section.  So
> this would be like your VirtualAlloc, you can just find the address of the
> .jit section and use that buffer instead of the VirtualAlloc buffer as the
> target address of your jit operations.
>
> Again, this is just an idea, no promises it will work, but unfortunately
> that's kind of the best you can do when dealing with closed source
things,
> just make guesses and hope for the best.
>
>
>
> On Wed, Jan 23, 2019 at 12:42 PM Vivien Millet <vivien.millet at
gmail.com>
> wrote:
>
>> (Yes you are right this is my fault)
>> Considering the string table, it only seems to contains file relative
>> informations in every pdb I am using, and it looks correct but I will
check
>> it.
>> I looked at the pdb.cpp code about checksums and tables, I copied some
>> stuff and got things wrong according to cvdump, then I simplified the
>> process of copying the table and it worked (in cvdump it finds the file
>> matching line etc...) so I suspect this is also correct.
>>
>> All the streams look good, but I will check deeper !
>>
>> It seems right what you say about rva and modules, this is what I m
>> afraid of, doing all of this for nothing or almost..
>>
>> Your idea looks good concerning the .text section in a separated dll,
but
>> will it be executable memory ? .text is where static strings go right ?
>> When you say putting my jit in there, do you mean writing it when the
>> jitted_code.dll is loaded in memory or on the .dll file directly before
>> loading it ? In the first scenario I wonder if the section will be
>> executable, in the second scenario I can’t do it because it would
require
>> perfect linking with the other code my jit points to..
>>
>> Le mer. 23 janv. 2019 à 20:57, Zachary Turner <zturner at
google.com> a
>> écrit :
>>
>>> (BTW, I'm adding llvm-dev back to the list, I didn't notice
it got taken
>>> off.  In general I try to keep the list on all emails, even if
it's
>>> extremely technical and specific, because someday someone else will
try to
>>> do this, and it'll be nice if they can read the whole thread).
>>>
>>> I can think of a couple of things that might be wrong:
>>>
>>> 1) If the string table is in a different order, then anything that
>>> refers to the string table need to be changed to refer to the new
offset.
>>> If the string "foo" is at offset 12 in the old PDB, but
offset 15 in the
>>> new PDB, then somewhere there is a record which is going to look at
offset
>>> 12 and expect to find something, and that will mess up.  The main
place
>>> this is important is in the File Checksums table, there is an entry
that
>>> says which file it is a checksum for, and that refers to the string
table.
>>> However, it's possible for certain symbol records to refer to
the string
>>> table too.  See lld/COFF/PDB.cpp and Ctrl+F for
"PDBStrTab" and you will
>>> find some information about this.
>>>
>>> 2) When you run `llvm-pdbutil dump -streams` on the copied PDB, do
all
>>> of them show a reasonable description?  Are there any streams that
say
>>> (???)?  If so, that's a problem.
>>>
>>> > does visual studio will consider a symbol file broken if the
address
>>> goes beyond the official module address range (the compiled one),
because
>>> my JIT code is allocated after the end of the module with
VirtualAlloc
>>> That is a good question, and part of why my job is so difficult,
because
>>> I can't look at their code.  But I think the answer is
"probably".  The
>>> debugger has to have some way to convert an address in your running
process
>>> into a symbol and offset, because that's how all debug info is
represented
>>> in the PDB.  So if there is no module, then there is no RVA
(because the R
>>> in RVA means relative, and what would it be relative to?).
>>>
>>> One idea to test this would be to create a DLL called
jitted_code.dll,
>>> give it a huuuuuge .text section (probably just a .asm file and use
some
>>> assembly directives to allocate a very large series of null bytes),
and
>>> then write your jit code into that area.  This way you would not
need to
>>> modify the existing PDB you would only need to make a new PDB
called
>>> jitted_code.pdb with 1 module, and those symbols could have
meaningful
>>> RVAs.  And you might not even need to detach the debugger if you do
things
>>> this way, because you could just right click the jitted_code.dll
module in
>>> the modules window and choose Load Symbols.
>>>
>>>
>>>
>>> On Wed, Jan 23, 2019 at 11:13 AM Vivien Millet <vivien.millet at
gmail.com>
>>> wrote:
>>>
>>>> Yes this is it, I just make a copy from a pdb generated by
link.exe
>>>> (the microsoft one).
>>>> Using llvm-pdbutil to compare is what I do, except I do it with
"-all"
>>>> And I get almost everything the same : same number of streams,
section
>>>> map looks good,string table looks good (even if not the same
order), same
>>>> number of modules with the symbols and subsection practically
the same, and
>>>> this is why I get stuck, I miss something but I can't see
what because I
>>>> don't know where to look for. Visual studio works with it,
I can debug my
>>>> original exe, but probably without the globals...
>>>> And the other problem is that the difference between the dumps
is not
>>>> necessarily a bug because the builder may generate new hashes
values,
>>>> reorder streams, modules, etc ...
>>>>
>>>> Right now I gave up to have publics and globals streams and
attacked
>>>> the real goal : insert my jit codeview into the pdb. I have
again done «
>>>> something » but as I don’t understand how the format work I
don’t have it
>>>> working in visual studio.. except once, a single time it worked
and the
>>>> breakpoint turned on in the UI (even if the rva was broken for
the
>>>> instructions) but it happened a single time .. then I get
depressed the
>>>> next times..... cvdump displays it all « correct », no corrupt
stuff
>>>> apparently. But what I do is probably wrong somewhere. What I
do is I take
>>>> .debug$S and .debug$T as is without relocations just to see,
but what I
>>>> don’t know really is : does visual studio will consider a
symbol file
>>>> broken if the address goes beyond the official module address
range (the
>>>> compiled one), because my JIT code is allocated after the end
of the module
>>>> with VirtualAlloc.
>>>> Another thing I don’t get is the section contribution, what is
it
>>>> exactly ? I inserted section contrib for all sections except
the debug$
>>>> ones but I don’t know what i’m really doing and it’s my average
problem
>>>> implementing this JIT feature...
>>>> I also don’t know what are relocations inside the codeview
format, what
>>>> is the difference between RVA and relocation, is there anything
to do with
>>>> this related to the codeview part I need to insert in the pdb ?
I don’t see
>>>> why visual studio needs more than just RVA<->Line
mapping..
>>>> This is really making me crazy being so ignorant and trying to
guess
>>>> what visual studio does...
>>>>
>>>> Le lun. 21 janv. 2019 à 19:50, Zachary Turner <zturner at
google.com> a
>>>> écrit :
>>>>
>>>>> So if i understand correctly, you're basically just
trying to
>>>>> implement something like a pdb *copy*, just as a test to
see if you can get
>>>>> it to work.  So you generate a PDB with cl/link or
clang-cl/lld-link, then
>>>>> try to copy it using your tool, then see if it still works.
>>>>>
>>>>> If this is correct, and it's not working, then there is
probably just
>>>>> something you didn't copy.  Neither Publics nor globals
actually contain
>>>>> their own data, instead they just refer to records from the
corresponding
>>>>> module stream.  So an S_PROCREF for the function
"main" might have fields
>>>>> that say "the name of the function is main, and
it's at offset 20 of module
>>>>> 1".  So, if there is no module 1, or if offset 20 of
module is not actually
>>>>> an S_GPROC32 for the function main, then it will be broken.
>>>>>
>>>>> Did you also go through each module in the source PDB, add
a new
>>>>> module in the target PDB, then copy all of the symbols for
each one?
>>>>>
>>>>> the best way to find differences is by using llvm-pdbutil
on the
>>>>> source and target PDBs and looking for things that look
different.  For
>>>>> example, I'd start with llvm-pdbutil dump -streams and
then seeing if they
>>>>> even have all the same streams.  If one of them is missing
streams, that's
>>>>> a good place to start.  If they have the same streams, then
look for ones
>>>>> where the size is different.  Then drill into those to see
why the size is
>>>>> different.
>>>>>
>>>>> LMK if that helps.
>>>>>
>>>>> On Mon, Jan 21, 2019 at 10:03 AM Vivien Millet <
>>>>> vivien.millet at gmail.com> wrote:
>>>>>
>>>>>> For now I'm not merging my JIT CodeView section, I
only try to build
>>>>>> a pure copy of an existing PDB using the XxxBuilder
classes (PDBFileBuilder
>>>>>> & Co / reading a PDBFile) and check if visual
studio wants to eat it..
>>>>>> For Publics and Globals, what I do is naive, I use the
>>>>>> GsiStreamBuilder and prey :)
>>>>>>
>>>>>>
>>>>>>
>>>>>>   if (File.hasPDBGlobalsStream() &&
File.getPDBGlobalsStream()) {
>>>>>>     GSIStreamBuilder &builder =
this->getGsiBuilder();
>>>>>>     GlobalsStream &stream =
*File.getPDBGlobalsStream();
>>>>>>     SymbolStream &SymbolRecords =
cantFail(File.getPDBSymbolStream());
>>>>>>
>>>>>>     for (uint32_t PubSymOff : stream.getGlobalsTable())
{
>>>>>>       CVSymbol Sym =
SymbolRecords.readRecord(PubSymOff);
>>>>>>       builder.addGlobalSymbol(Sym);
>>>>>>     }
>>>>>>   }
>>>>>>   if (File.hasPDBPublicsStream() &&
File.getPDBPublicsStream()) {
>>>>>>     GSIStreamBuilder &builder =
this->getGsiBuilder();
>>>>>>     PublicsStream &stream =
*File.getPDBPublicsStream();
>>>>>>     SymbolStream &SymbolRecords =
cantFail(File.getPDBSymbolStream());
>>>>>>
>>>>>> 	std::vector<PublicSym32> Publics;
>>>>>>
>>>>>>     for (uint32_t PubSymOff : stream.getPublicsTable())
{
>>>>>>       PublicSym32 Pub = cantFail(
>>>>>>          
llvm::codeview::SymbolDeserializer::deserializeAs<PublicSym32>(
>>>>>>               SymbolRecords.readRecord(PubSymOff)));
>>>>>>       Publics.push_back(Pub);
>>>>>>     }
>>>>>>
>>>>>>     if (!Publics.empty()) {
>>>>>>       // Sort the public symbols and add them to the
stream.
>>>>>>       std::sort(Publics.begin(), Publics.end(),
>>>>>>            [](const PublicSym32 &L, const
PublicSym32 &R) {
>>>>>>              return L.Name < R.Name;
>>>>>>            });
>>>>>>       for (const PublicSym32 &Pub : Publics)
>>>>>>         builder.addPublicSymbol(Pub);
>>>>>>     }
>>>>>>
>>>>>>   }
>>>>>>
>>>>>> Is it what you meant ?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Le lun. 21 janv. 2019 à 18:50, Zachary Turner
<zturner at google.com> a
>>>>>> écrit :
>>>>>>
>>>>>>> Also, even if symbolGoesInGlobalsStream returns
true, you can’t just
>>>>>>> copy it. Functions, for example, which are
S_GPROC32 or S_LPROC32 in the
>>>>>>> module stream, are S_PROCREF in the globals stream.
Similarly, *everything*
>>>>>>> in the publics stream is S_PUB32. So you need to
convert each symbol to the
>>>>>>> proper type for the stream it’s going to go in
>>>>>>> On Mon, Jan 21, 2019 at 9:46 AM Zachary Turner
<zturner at google.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Publics are basically a list of everything that
has a mangled name.
>>>>>>>> To be honest, I don’t know what the debugger
uses this for.
>>>>>>>>
>>>>>>>> Globals is essentially every symbol in the pdb
in one large table.
>>>>>>>> The reason this is important is because if you
type “foo” in the watch
>>>>>>>> window, the debugger doesn’t necessarily know
what compiland foo comes
>>>>>>>> from. So it has to have a way to find
everything in the entire program no
>>>>>>>> matter what compiland it came from. That’s what
the globals are.
>>>>>>>>
>>>>>>>> Both publics and globals are hash tables, so
one possible reason
>>>>>>>> there might be a problem is that you need to
rehash the entire table. When
>>>>>>>> you build your modified pdb, I would suggest
starting with an empty publics
>>>>>>>> / globals stream, adding all items from the
first pdb by iterating over
>>>>>>>> those records and using a GlobalsStreamBuilder,
then adding all your jitted
>>>>>>>> items separately, then writing it out. That
should make sure it gets hashed
>>>>>>>> correctly.
>>>>>>>>
>>>>>>>> Are you doing that?
>>>>>>>>
>>>>>>>> Btw, not all symbols belong in the globals /
publics stream. Check
>>>>>>>> the code in lld and search for
symbolGoesInGlobalsStream and
>>>>>>>> symbolGoesInPublicsStream to see the logic it
uses
>>>>>>>> On Mon, Jan 21, 2019 at 8:36 AM Vivien Millet
<
>>>>>>>> vivien.millet at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Hi Zachary, sorry for disturbing again..
>>>>>>>>>
>>>>>>>>> I've fixed some problems (StringTable,
SectionMap and few things
>>>>>>>>> here and there..) and my converted PDB
seems now to work inside visual
>>>>>>>>> studio..
>>>>>>>>> But I'm not sure if I have full debug
features because I don't
>>>>>>>>> succeed to translate Publics and Globals
correctly. CVDump says PDB is
>>>>>>>>> corrupted whereas PDBUTIL -dump correctly
displays them.
>>>>>>>>> I don't really understand what Publics
and Globals stream really
>>>>>>>>> are, if the symbols are really in the
corresponding streams or if they are
>>>>>>>>> just references to somewhere else.
>>>>>>>>> The LLVM documentation is not complete
about these two Publics and
>>>>>>>>> Globals stream so I'm a bit lost on how
to handle them or find what is
>>>>>>>>> "corrupted" according to CVDump.
>>>>>>>>> I took example on LLD and yaml2pdb to help
me to do some tough
>>>>>>>>> conversions but I noticed that in yaml2pdb
there is no GsiStream exported
>>>>>>>>> (no GsiBuidler use and no reference to
Publics or Globals anywhere), is it
>>>>>>>>> wanted/correct ?
>>>>>>>>> Thanks and sorry If I'm a bit spaming,
it's my 99% time task right
>>>>>>>>> now and being stuck without any clue is
difficult :) But I guess you
>>>>>>>>> experienced even more suffering when
documentation didn't exist at all !
>>>>>>>>> Have a good day !
>>>>>>>>>
>>>>>>>>> Le dim. 20 janv. 2019 à 22:27, Vivien
Millet <
>>>>>>>>> vivien.millet at gmail.com> a écrit :
>>>>>>>>>
>>>>>>>>>> ERRATUM, my bad, the pdb I tested is
also corrupted according to
>>>>>>>>>> cvdump.exe, I on't know why, I
regenerated again and now I have a working
>>>>>>>>>> dump. You don't need to fix
anything.
>>>>>>>>>>
>>>>>>>>>> Le dim. 20 janv. 2019 à 20:26, Vivien
Millet <
>>>>>>>>>> vivien.millet at gmail.com> a écrit
:
>>>>>>>>>>
>>>>>>>>>>> Hi Zachary,
>>>>>>>>>>> I've done a first step to
rewrite  existing PDBFile with
>>>>>>>>>>> PDBFileBuilder, I get mostly of the
work done but I don't get as much
>>>>>>>>>>> output as input (some streams are
not mirrored for unknown reasons and some
>>>>>>>>>>> data must be missing here and
there...).
>>>>>>>>>>> When I try to replace the original
by the rebuilt one for
>>>>>>>>>>> debugging, the pdb loads well but
breakpoints failed to activate with a
>>>>>>>>>>> "unexpected symbol reader
error while processing foobar.exe". You probably
>>>>>>>>>>> know what it means or already
encountered this error I guess.
>>>>>>>>>>> I also tried to create a minimal
program to simplify comparisons
>>>>>>>>>>> between original and new PDB but I
get an error dumping the original  pdb
>>>>>>>>>>> exported by visual studio  with
-all (PublicsStream.cpp|98). I think it is
>>>>>>>>>>> a bug.
>>>>>>>>>>> I've attached the related
main.cpp and PDB to this email if you
>>>>>>>>>>> want to check what is the error
exactly (vs2017, x86 and x64 have same
>>>>>>>>>>> issues).
>>>>>>>>>>> I've attached also my code (git
diff). I added an « identity »
>>>>>>>>>>> feature to pdbutil which uses the
code I wrote to regenerate the input pdb.
>>>>>>>>>>> You can use it to see what I get so
far..
>>>>>>>>>>> I’ve seen you added recently a fix
related to FPO but you say
>>>>>>>>>>> it’s only for x86 so I don’t think
it would change something but who knows..
>>>>>>>>>>> Anyway, if you have a moment to
check my work so far and give me
>>>>>>>>>>> feedbacks it’s welcome because I
get out of ideas about what goes wrong..
>>>>>>>>>>> Thanks, I go back digging into the
pdb mysteries !
>>>>>>>>>>>
>>>>>>>>>>> Le ven. 18 janv. 2019 à 12:31,
Vivien Millet <
>>>>>>>>>>> vivien.millet at gmail.com> a
écrit :
>>>>>>>>>>>
>>>>>>>>>>>> Ok ! It was just to be sure I
understood well.
>>>>>>>>>>>> Sorry for not replying
directly, I wanted to try first to emit
>>>>>>>>>>>> CodeView before continuing the
discussion and it was time for me to go to
>>>>>>>>>>>> bed here..
>>>>>>>>>>>> I just tried it now and it is
very easy to switch to CodeView.
>>>>>>>>>>>> For the ones interested : you
just have to give your TargetTriple to your
>>>>>>>>>>>> llvm::Module used for JIT and
then call
>>>>>>>>>>>>
module->addModuleFlag(llvm::Module::Warning, "CodeView", 1) to tell
the
>>>>>>>>>>>> AsmPrinter this module prefer
CodeView instead of Dwarf.
>>>>>>>>>>>> I've checked the content of
my .obj file, and there is valid
>>>>>>>>>>>> .debug$T and  .debug$S
sections, so everything goes well until now.
>>>>>>>>>>>> Now as a parallel task I will
try to read the EXE PDB and
>>>>>>>>>>>> re-export it "as it"
to see if I break something in visual studio.
>>>>>>>>>>>> If I succeed to do that, that
might be added as a feature to
>>>>>>>>>>>> PDBFile or PDBFileBuilder to
simplify the process for other users.
>>>>>>>>>>>> I keep you in touch.
>>>>>>>>>>>> Thanks
>>>>>>>>>>>>
>>>>>>>>>>>> Le jeu. 17 janv. 2019 à 20:50,
Zachary Turner <
>>>>>>>>>>>> zturner at google.com> a
écrit :
>>>>>>>>>>>>
>>>>>>>>>>>>> When I say "nothing to
do" I just mean that you won't have to
>>>>>>>>>>>>> do anything to convert the
record from one format (DWARF) to another format
>>>>>>>>>>>>> (CodeView).  You will have
a COFF object file either on disk (probably
>>>>>>>>>>>>> named foo.obj or something)
or in memory.  And this object file will have a
>>>>>>>>>>>>> .debug$S section with
CodeView symbols and a .debug$T section with CodeView
>>>>>>>>>>>>> types.  Then you will still
need to use the PDBFileBuilder to add these
>>>>>>>>>>>>> records to the final PDB,
but they will already be in the correct format
>>>>>>>>>>>>> that PDBFileBuilder
expects, you won't need to convert them from DWARF
>>>>>>>>>>>>> (which is not trivial).
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, Jan 17, 2019 at
11:26 AM Vivien Millet <
>>>>>>>>>>>>> vivien.millet at
gmail.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> That’s a good question,
by default when emitting the object
>>>>>>>>>>>>>> file I choose COFF but
it embeds dwarf and not codeview in the end.. there
>>>>>>>>>>>>>> probably is a way to do
it or at least it must be implemented if not yet..
>>>>>>>>>>>>>> Lets imagine I manage
to do that.. when you say there is
>>>>>>>>>>>>>> nothing to do, I still
must have a PDBFileBuilder to copy the codeview data
>>>>>>>>>>>>>> inside the EXE PDB
right ? I cannot insert them easily in the EXE PDB with
>>>>>>>>>>>>>> another way ?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Le jeu. 17 janv. 2019 à
20:01, Zachary Turner <
>>>>>>>>>>>>>> zturner at
google.com> a écrit :
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Well, is it
possible to just hook up the CodeView debug info
>>>>>>>>>>>>>>> generator to MCJIT?
If you're not jitting, and you just compile something,
>>>>>>>>>>>>>>> we translate all of
the LLVM metadata into CodeView in the file
>>>>>>>>>>>>>>> CodeViewDebug.cpp. 
Then, the object file just already has CodeView in it.
>>>>>>>>>>>>>>> If it's not
hard to do, this would probably be a better solution, because
>>>>>>>>>>>>>>> you don't have
to worry about *how* to translate DWARF into CodeView, which
>>>>>>>>>>>>>>> is not always
trivial.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> If you can
configure this in MCJIT, you won't even need to
>>>>>>>>>>>>>>> do anything, you
can just open the ObjectFile, look for the .debug$T and
>>>>>>>>>>>>>>> .debug$S sections,
iterate over each one and re-write their TypeIndices
>>>>>>>>>>>>>>> while copying them
to the output PDB file.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Thu, Jan 17,
2019 at 10:52 AM Vivien Millet <
>>>>>>>>>>>>>>> vivien.millet at
gmail.com> wrote:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Ok I understand
more what you meant. In fact I don’t care
>>>>>>>>>>>>>>>> about the pdb
size, at least as a first step, so it won’t be a problem for
>>>>>>>>>>>>>>>> me to have
duplicated symbols. Concerning TypeIndices my plan if possible
>>>>>>>>>>>>>>>> is not to
generate a pdb for my jit and merge it, but instead directly
>>>>>>>>>>>>>>>> extract debug
info from a DwarfContext just after llvm::object::ObjectFile
>>>>>>>>>>>>>>>> is emitted by
the JIT engine and complete the EXE PDB I had rebuilt with
>>>>>>>>>>>>>>>> PDBFileBuilder.
Does it sounds a good bet to you ? If I succeed doing that
>>>>>>>>>>>>>>>> I think that
could be a good extension to the debugging possibilities of
>>>>>>>>>>>>>>>> MCJit if not
being an extension to pdbutil.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Le jeu. 17
janv. 2019 à 19:37, Zachary Turner <
>>>>>>>>>>>>>>>> zturner at
google.com> a écrit :
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Well, for
example the TPI stream is just one big
>>>>>>>>>>>>>>>>> collection
of types.  Presumably your JIT code will reuse some of the same
>>>>>>>>>>>>>>>>> types
(perhaps, std::string for example) as your non-jitted code.  Your
>>>>>>>>>>>>>>>>> jitted
symbol records in the object file (for example, a local variable of
>>>>>>>>>>>>>>>>> type
std::string in your jitted code) will refer to the type for
>>>>>>>>>>>>>>>>> std;:string
by a TypeIndex, and your original PDB will also refer to
>>>>>>>>>>>>>>>>> std::string
by a different TypeIndex.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> In LLD,
when we merge in types and symbols from each
>>>>>>>>>>>>>>>>> object
file, we keep a hash table of which types have already been seen, so
>>>>>>>>>>>>>>>>> that if we
see the same type again, we can just use the TypeIndex that we
>>>>>>>>>>>>>>>>> wrote on a
previous object file.  Then, when we add symbol records, we have
>>>>>>>>>>>>>>>>> to update
its fields that used the old TypeIndex to use the new TypeIndex
>>>>>>>>>>>>>>>>> instead.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
De-duplicating though, I suppose, is not strictly
>>>>>>>>>>>>>>>>> necessary,
it will just keep your PDB size down.  But you *will* need to at
>>>>>>>>>>>>>>>>> least
re-write the TypeIndexes from the jitted code.  For example, you may
>>>>>>>>>>>>>>>>> decide that
instead of de-duplicating, you just append them all to the end
>>>>>>>>>>>>>>>>> of the TPI
stream (where all the types go in PDB) to keep things simple.
>>>>>>>>>>>>>>>>> Since they
were in a different position before, they now have different
>>>>>>>>>>>>>>>>>
TypeIndices.  So you will need to re-write all TypeIndices so that they are
>>>>>>>>>>>>>>>>> correct
after the merge.   Both types and symbols can refer to types, so
>>>>>>>>>>>>>>>>> you will
need to do this both for the types of the jitted code as well as
>>>>>>>>>>>>>>>>> the symbols
of the jitted code.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Let me know
if that makes sense.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Thu, Jan
17, 2019 at 10:24 AM Vivien Millet <
>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Ok I
see..
>>>>>>>>>>>>>>>>>> what do
you mean by “making sure to de-duplicate records
>>>>>>>>>>>>>>>>>> as
necessary” ?
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Le jeu.
17 janv. 2019 à 19:09, Zachary Turner <
>>>>>>>>>>>>>>>>>> zturner
at google.com> a écrit :
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
It's possible in theory to support incremental updates
>>>>>>>>>>>>>>>>>>> to
a PDB (the file format is designed specifically with that in mind).  But
>>>>>>>>>>>>>>>>>>>
this functionality was never added to the PDB library since lld doesn't
>>>>>>>>>>>>>>>>>>>
support incremental linking, we never really needed it.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> The
"dumb" way would be to just create a new PDB file,
>>>>>>>>>>>>>>>>>>>
build it using the old contents and the new contents (making sure to
>>>>>>>>>>>>>>>>>>>
de-duplicate records as necessary).
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
Supporting incremental updates should be possible, but
>>>>>>>>>>>>>>>>>>>
most of LLVM's File I/O abstractions are based around mmapping a file and
>>>>>>>>>>>>>>>>>>>
writing to it, which doesn't work when you don't know the file size in
>>>>>>>>>>>>>>>>>>>
advance.  So there would be some interesting problems to solve here.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On
Thu, Jan 17, 2019 at 10:03 AM Vivien Millet <
>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
Hi Zachary !
>>>>>>>>>>>>>>>>>>>>
If there a way to easily create a new PDBFileBuilder
>>>>>>>>>>>>>>>>>>>>
from an existing PDBFile or can/should I do the translation myself ?
>>>>>>>>>>>>>>>>>>>>
I would like to start from a builder filled with the
>>>>>>>>>>>>>>>>>>>>
EXE PDB data and then complete its DBI stream with the JIT module/symbols.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
Thanks !
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
Le mer. 16 janv. 2019 à 23:41, Vivien Millet <
>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> a écrit :
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
Thank you Zachary !
>>>>>>>>>>>>>>>>>>>>>
I will have some soon I think ..
>>>>>>>>>>>>>>>>>>>>>
I first need to explore the llvmpdb-util code more
>>>>>>>>>>>>>>>>>>>>>
because I don't even know where to start with the PDB api..
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
Le mer. 16 janv. 2019 à 22:51, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
Sure. Along the way I’m happy to answer any specific
>>>>>>>>>>>>>>>>>>>>>>
questions you might have too even if it’s for your downstream project
>>>>>>>>>>>>>>>>>>>>>>
On Wed, Jan 16, 2019 at 1:38 PM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
I would be up to improve pdbutil but I doubt I have
>>>>>>>>>>>>>>>>>>>>>>>
enough knowledge or time to provide the complete merge feature, it would
>>>>>>>>>>>>>>>>>>>>>>>
still be a very specific kind of merge as you describe it. Anyway I could
>>>>>>>>>>>>>>>>>>>>>>>
start trying to do it in my jit compiler and then, once I get something
>>>>>>>>>>>>>>>>>>>>>>>
working (if that happens :)), i can come back to you with the piece of code
>>>>>>>>>>>>>>>>>>>>>>>
and see if it is worth integrating it to pdbutil and how ?
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>
Le mer. 16 janv. 2019 à 22:12, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
Well, that’s certainly possible, but improving
>>>>>>>>>>>>>>>>>>>>>>>>
llvm-pdbutil is another possibility. Doing it directly in your jit compiler
>>>>>>>>>>>>>>>>>>>>>>>>
will probably save you time though, since you won’t have to worry about
>>>>>>>>>>>>>>>>>>>>>>>>
writing tests and going through code review
>>>>>>>>>>>>>>>>>>>>>>>>
On Wed, Jan 16, 2019 at 1:01 PM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks for the tips !
>>>>>>>>>>>>>>>>>>>>>>>>>
When you talk about doing all of this I suppose
>>>>>>>>>>>>>>>>>>>>>>>>>
you think about using llvm/debuginfo/pdb, pick code here and there to
>>>>>>>>>>>>>>>>>>>>>>>>>
generate the pdb in memory, read the executable one and perform the merge
>>>>>>>>>>>>>>>>>>>>>>>>>
directly in my jit compiler, right ? Not using pdbutil ?
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>
Le mar. 15 janv. 2019 à 22:49, Zachary Turner <
>>>>>>>>>>>>>>>>>>>>>>>>>
zturner at google.com> a écrit :
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
On Tue, Jan 15, 2019 at 2:50 AM Vivien Millet <
>>>>>>>>>>>>>>>>>>>>>>>>>>
vivien.millet at gmail.com> wrote:
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>
Hello Zachary !
>>>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks for your time !
>>>>>>>>>>>>>>>>>>>>>>>>>>>
So you are one of the happy guys who suffered
>>>>>>>>>>>>>>>>>>>>>>>>>>>
from the lack of PDB format information :)
>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
Yes, that would be me :)
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>
To be honest I'm really a beginner in the PDB
>>>>>>>>>>>>>>>>>>>>>>>>>>>
stuff, I just read some llvm documentation to understand what went wrong
>>>>>>>>>>>>>>>>>>>>>>>>>>>
when merging my PDBs.
>>>>>>>>>>>>>>>>>>>>>>>>>>>
In my case, what I do with my team and try to
>>>>>>>>>>>>>>>>>>>>>>>>>>>
achieve is this :
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Run our application under a visual studio
>>>>>>>>>>>>>>>>>>>>>>>>>>>
debugger
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Generate JIT code ( using llvm MCJIT  )
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Then, either :
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- export as COFF obj file with dwarf
>>>>>>>>>>>>>>>>>>>>>>>>>>>
information and then convert it with cv2pdb to obtain a pdb of my JIT
>>>>>>>>>>>>>>>>>>>>>>>>>>>
symbols (what I do now)
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- export directly to PDB my JIT debug info
>>>>>>>>>>>>>>>>>>>>>>>>>>>
(what i would like to do, if you have an idea how..)
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Detach the visual studio debugger
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Merge my JIT pdb into a copy of the executable
>>>>>>>>>>>>>>>>>>>>>>>>>>>
pdb (where things start to go bad..)
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Replace original executable by the copy
>>>>>>>>>>>>>>>>>>>>>>>>>>>
(creating a backup of original)
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Reattach  the visual studio debugger to my
>>>>>>>>>>>>>>>>>>>>>>>>>>>
executable (loading the new pdb version)
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- Debug JIT code with visual studio.
>>>>>>>>>>>>>>>>>>>>>>>>>>>
- On each JIT rebuild, restart these steps from
>>>>>>>>>>>>>>>>>>>>>>>>>>>
the original native executable PDB to avoid merge conflict between the
>>>>>>>>>>>>>>>>>>>>>>>>>>>
multiple JIT iterations
>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
Yea, it's an interesting use case.  It makes me
>>>>>>>>>>>>>>>>>>>>>>>>>>
think it would be nice if the PDB format supported some way of having a
>>>>>>>>>>>>>>>>>>>>>>>>>>
symbol which simply refers to another PDB file, that way you could re-write
>>>>>>>>>>>>>>>>>>>>>>>>>>
that PDB file at runtime once all your code is jitted, and when the
>>>>>>>>>>>>>>>>>>>>>>>>>>
debugger tries to look up that symbol, it finds a record that tells it to
>>>>>>>>>>>>>>>>>>>>>>>>>>
go check the other PDB file.
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
So, here are the things I think you would need to
>>>>>>>>>>>>>>>>>>>>>>>>>>
do:
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
1) Create a JIT module in the module list with a
>>>>>>>>>>>>>>>>>>>>>>>>>>
unique name.  All symbols will go here.  llvm-pdbutil dump -modules shows
>>>>>>>>>>>>>>>>>>>>>>>>>>
you the list.  Be careful about putting it at the end though, because
>>>>>>>>>>>>>>>>>>>>>>>>>>
there's already one at the end called * LINKER * that is kind of special.
>>>>>>>>>>>>>>>>>>>>>>>>>>
On the other hand, you don't want to put it first because it means you will
>>>>>>>>>>>>>>>>>>>>>>>>>>
have to do lots of fixups on the EXE PDB.  It's probably best to add it
>>>>>>>>>>>>>>>>>>>>>>>>>>
right before the linker module, this has the least chance of breaking
>>>>>>>>>>>>>>>>>>>>>>>>>>
anything.
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
2) In the debug stream for this module, add all
>>>>>>>>>>>>>>>>>>>>>>>>>>
symbols.  You will need to fix up their type indices.  As you noticed,
>>>>>>>>>>>>>>>>>>>>>>>>>>
llvm-pdbutil already merges type information from the JIT PDB, so after
>>>>>>>>>>>>>>>>>>>>>>>>>>
merging the type indices in the EXE PDB will be different than they were in
>>>>>>>>>>>>>>>>>>>>>>>>>>
the JIT PDB, but the symbol records will refer to the JIT PDB type
>>>>>>>>>>>>>>>>>>>>>>>>>>
indices.  So these need to be fixed up.  LLD already has code to do this,
>>>>>>>>>>>>>>>>>>>>>>>>>>
you can probably borrow a similar algorithm with some slight modifications
>>>>>>>>>>>>>>>>>>>>>>>>>>
(lldb/COFF/PDB.cpp, search for mergeSymbolRecords)
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
3) Merge in the new section contributions and
>>>>>>>>>>>>>>>>>>>>>>>>>>
section map.  See LLD again for how to modify these.  Hopefully the object
>>>>>>>>>>>>>>>>>>>>>>>>>>
file you exported contains relocated symbol addresses so you don't have to
>>>>>>>>>>>>>>>>>>>>>>>>>>
do any fixups here.
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
4) Merge in the publics and globals.  This
>>>>>>>>>>>>>>>>>>>>>>>>>>
shouldn't be too hard, I think you can just iterate over them in the JIT
>>>>>>>>>>>>>>>>>>>>>>>>>>
PDB and add them to the new EXE PDB.
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
You're kind of in uncharted territory here, so
>>>>>>>>>>>>>>>>>>>>>>>>>>
this is just a rough idea of what needs to be done.  There may be other
>>>>>>>>>>>>>>>>>>>>>>>>>>
issues that you don't encounter until you actually try it out.
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
Unfortunately I don't personally have the time to
>>>>>>>>>>>>>>>>>>>>>>>>>>
work on this, but it sounds neat, and I'm happy to help if you run into
>>>>>>>>>>>>>>>>>>>>>>>>>>
questions or problems along the way.
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>
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