Alexander Potapenko
2012-Nov-30 00:46 UTC
[LLVMdev] radr://12777299, "potential pthread/eh bug exposed by libsanitizer"
Looks like this happens on x86_64 because the position of __cxa_throw
is too far from the allocated branch island (should be <2G). This can
be solved by allocating the branch islands somewhere near the text
segment (look for kIslandEnd in asan_mac.cc, this is currently
0x7fffffdf0000) or by patching the function with a longer instruction
sequence that stores the jump target in a register and jumps to that
target (which is a bit more complex to implement).
Once this problem is fixed, another one is going to arise. This is how
the first bytes of __cxa_throw look like:
0x0020c49ba5d916e0 <__cxa_throw+0>: lea 0xb4f01(%rip),%rax #
0x20c49ba5e465e8 <_ZN10__cxxabiv120__unexpected_handlerE>
0x0020c49ba5d916e7 <__cxa_throw+7>: push %rbx
0x0020c49ba5d916e8 <__cxa_throw+8>: lea -0x20(%rdi),%rbx
If we move the relative LEA instruction somewhere, we must fix the
constant in order to keep it pointing to the same address.
mach_override already does this for relative CALL and JMP
instructions, but not for LEA. This should be fairly simple to fix.
Note that the 32-bit variant crashes on another invalid address:
ASAN:SIGSEGV
==================================================================89768== ERROR:
AddressSanitizer: SEGV on unknown address 0xcccccccc
(pc 0x00061f8c sp 0xbffa8bd0 bp 0xbffa8cc8 T0)
AddressSanitizer can not provide additional info.
#0 0x61f8b
(/Users/glider/src/gcc-asan/inst/lib/i386/libstdc++.6.dylib+0x3f8b)
#1 0x91391724 (/usr/lib/system/libdyld.dylib+0x2724)
#2 0x0
Stats: 0M malloced (0M for red zones) by 3 calls
Stats: 0M realloced by 0 calls
Stats: 0M freed by 0 calls
Stats: 0M really freed by 0 calls
Stats: 1M (256 full pages) mmaped in 2 calls
mmaps by size class: 7:4095; 8:2047;
mallocs by size class: 7:1; 8:2;
frees by size class:
rfrees by size class:
Stats: malloc large: 0 small slow: 2
==89768== ABORTING
My guess is that this is caused by the following code being moved to a
branch island:
Dump of assembler code for function __cxa_throw:
0x00008f60 <__cxa_throw+0>: push %esi
0x00008f61 <__cxa_throw+1>: push %ebx
0x00008f62 <__cxa_throw+2>: call 0x7a60 <__x86.get_pc_thunk.bx>
Perhaps this makes __x86.get_pc_thunk.bx return an incorrect value.
Since libstdc++-v3 is built together with gcc, the two issues related
to instructions being moved to another place can be solved by padding
__cxa_throw() with five NOP instructions (enough to hold a JMP). I
believe this should be acceptable, because the performance penalty for
additional NOPs is negligible, and __cxa_throw() isn't a hot point.
On Thu, Nov 29, 2012 at 1:01 PM, Nick Kledzik <kledzik at apple.com>
wrote:> I debugged this a bit and it seems the mach_override patching of
__cxa_throw is bogus. The start of that function is patched to jump to garbage.
>
> Breakpoint 1, 0x0000000100001c19 in main ()
> (gdb) display/i $pc
> 2: x/i $pc 0x100001c19 <main+318>: callq 0x100016386
<dyld_stub___cxa_throw>
> (gdb) si
> 0x0000000100016386 in dyld_stub___cxa_throw ()
> 2: x/i $pc 0x100016386 <dyld_stub___cxa_throw>: jmpq
*0xae1c(%rip) # 0x1000211a8
> (gdb)
> 0x0000000102244870 in __cxa_throw ()
> 2: x/i $pc 0x102244870 <__cxa_throw>: jmpq 0xffd27000
> (gdb) # the above its __cxa_throw in gcc's libstdc++.6.dylib. The
first instruction has been patch to jump to a garbage address.
>
> (gdb) x/8i 0x102244870-8
> 0x102244868
<_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+56>:
std
> 0x102244869
<_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+57>:
(bad)
> 0x10224486a
<_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+58>:
decl (%rdi)
> 0x10224486c
<_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+60>:
(bad)
> 0x10224486d
<_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+61>:
add %r8b,(%rax)
> 0x102244870 <__cxa_throw>: jmpq 0xffd27000
> 0x102244875 <__cxa_throw+5>: or (%rax),%eax
> 0x102244877 <__cxa_throw+7>: push %rbx
> (gdb)
> (gdb) watch *0x102244870
> Hardware watchpoint 2: *4330899568
> (gdb) r
>
> Old value = -788165304
> New value = -1373139991
> 0x0000000100016203 in __asan_mach_override_ptr_custom ()
> (gdb) bt
> #0 0x0000000100016203 in __asan_mach_override_ptr_custom ()
> #1 0x0000000100015a9e in __interception::OverrideFunction ()
> #2 0x00007fff5fc13378 in ImageLoaderMachO::doModInitFunctions ()
> #3 0x00007fff5fc13762 in ImageLoaderMachO::doInitialization ()
> #4 0x00007fff5fc1006e in ImageLoader::recursiveInitialization ()
> #5 0x00007fff5fc0feba in ImageLoader::runInitializers ()
> #6 0x00007fff5fc01fc0 in dyld::initializeMainExecutable ()
> #7 0x00007fff5fc05b04 in dyld::_main ()
> #8 0x00007fff5fc01397 in dyldbootstrap::start ()
> #9 0x00007fff5fc0105e in _dyld_start ()
> (gdb) x/8i 0x102244870
> 0x102244870 <__cxa_throw>: jmpq 0xffd27000
> 0x102244875 <__cxa_throw+5>: or (%rax),%eax
> 0x102244877 <__cxa_throw+7>: push %rbx
> 0x102244878 <__cxa_throw+8>: lea -0x20(%rdi),%rbx
> 0x10224487c <__cxa_throw+12>: mov %rsi,-0x70(%rdi)
> # Here is where the patching is being done
>
> -Nick
>
> On Nov 29, 2012, at 11:07 AM, Alexander Potapenko wrote:
>>> On Thu, Nov 29, 2012 at 9:55 PM, Jack Howarth <howarth at
bromo.med.uc.edu>
>>> wrote:
>>>>
>>>> Nick,
>>>> Can you take a quick look at the asan_eh_bug.tar.bz testcase
>>>> I uploaded into the newly opened radr://12777299,
"potential
>>>> pthread/eh bug exposed by libsanitizer". The FSF gcc
developers
>>>> have ported llvm.org's asan code into FSF gcc (and are
keeping
>>>> it synced to the upstream llvm.org code). I have been helping
>>>> with the darwin build and testing -fsanitize=address against
the
>>>> complete FSF gcc testsuite. This seems to have exposed a
potential
>>>> bug in pthread or eh on darwin under libasan. Hundreds of test
cases
>>>> in the g++ and libstdc++ testsuites fail under
-fsanitize=address
>>>> in the following manner...
>>>>
>>>> ASAN:SIGSEGV
>>>>
================================================================>>>>
==2738== ERROR: AddressSanitizer: SEGV on unknown address 0x0000ffd27000
>>>> (pc 0x0000ffd27000 sp 0x7fff55e40828 bp 0x7fff55e408f0 T0)
>>>> AddressSanitizer can not provide additional info.
>>>> #0 0xffd26fff
(/Users/howarth/asan_eh_bug/./cond1_asan.exe+0xf5f67fff)
>>>> #1 0x7fff8bd827e0 (/usr/lib/system/libdyld.dylib+0x27e0)
>>>> #2 0x0
>>>> Stats: 0M malloced (0M for red zones) by 3 calls
>>>> Stats: 0M realloced by 0 calls
>>>> Stats: 0M freed by 0 calls
>>>> Stats: 0M really freed by 0 calls
>>>> Stats: 1M (384 full pages) mmaped in 3 calls
>>>> mmaps by size class: 7:4095; 8:2047; 9:1023;
>>>> mallocs by size class: 7:1; 8:1; 9:1;
>>>> frees by size class:
>>>> rfrees by size class:
>>>> Stats: malloc large: 0 small slow: 3
>>>> ==2738== ABORTING
>>>>
>>>> The failure of...
>>>>
>>>> FAIL: g++.dg/eh/cond1.C -std=c++98 execution test
>>>>
>>>> was used as the test case for the radar report and compiled
with...
>>>>
>>>> g++-fsf-4.8 -static-libasan -fsanitize=address -std=c++98
cond1.C -g -O0
>>>> -o cond1_asan.exe
>>>>
>>>> to produce the above failure. When compiled without libasan
as...
>>>>
>>>> g++-fsf-4.8 -std=c++98 cond1.C -g -O0 -o cond1_no_asan.exe
>>>>
>>>> the resulting executable runs fine. Debugging this in gdb seems
to show
>>>> that the failure
>>>> is occuring in the final call to dyld_stub_pthread_once (). The
same test
>>>> case
>>>> compiles fine with -fsanitize=address under llvm 3.2 clang++
and produces
>>>> no runtime errors
>>>> but the code execution path is very different in that case
(because of the
>>>> different
>>>> libstdc++).
>>>> Can you take a quick peek at this and determine if this is a
darwin
>>>> pthread or unwinder
>>>> bug or an issue with libasan that FSF gcc's compiler is
exposing? Thanks
>>>> in advance for
>>>> any help on this.
>>>> Jack
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>
>>>
>>
>>
>>
>> --
>> Alexander Potapenko
>> Software Engineer
>> Google Moscow
>
--
Alexander Potapenko
Software Engineer
Google Moscow
Kostya Serebryany
2012-Nov-30 09:41 UTC
[LLVMdev] radr://12777299, "potential pthread/eh bug exposed by libsanitizer"
Just want to remind everyone that we plan to stop using mach_override in asanin favor of OSX's native function interposition. So, we probably don't want to spend too much effort fixing mach_override. --kcc On Fri, Nov 30, 2012 at 4:46 AM, Alexander Potapenko <glider at google.com>wrote:> Looks like this happens on x86_64 because the position of __cxa_throw > is too far from the allocated branch island (should be <2G). This can > be solved by allocating the branch islands somewhere near the text > segment (look for kIslandEnd in asan_mac.cc, this is currently > 0x7fffffdf0000) or by patching the function with a longer instruction > sequence that stores the jump target in a register and jumps to that > target (which is a bit more complex to implement). > > Once this problem is fixed, another one is going to arise. This is how > the first bytes of __cxa_throw look like: > > 0x0020c49ba5d916e0 <__cxa_throw+0>: lea 0xb4f01(%rip),%rax # > 0x20c49ba5e465e8 <_ZN10__cxxabiv120__unexpected_handlerE> > 0x0020c49ba5d916e7 <__cxa_throw+7>: push %rbx > 0x0020c49ba5d916e8 <__cxa_throw+8>: lea -0x20(%rdi),%rbx > > If we move the relative LEA instruction somewhere, we must fix the > constant in order to keep it pointing to the same address. > mach_override already does this for relative CALL and JMP > instructions, but not for LEA. This should be fairly simple to fix. > > Note that the 32-bit variant crashes on another invalid address: > > ASAN:SIGSEGV > ================================================================> ==89768== ERROR: AddressSanitizer: SEGV on unknown address 0xcccccccc > (pc 0x00061f8c sp 0xbffa8bd0 bp 0xbffa8cc8 T0) > AddressSanitizer can not provide additional info. > #0 0x61f8b > (/Users/glider/src/gcc-asan/inst/lib/i386/libstdc++.6.dylib+0x3f8b) > #1 0x91391724 (/usr/lib/system/libdyld.dylib+0x2724) > #2 0x0 > Stats: 0M malloced (0M for red zones) by 3 calls > Stats: 0M realloced by 0 calls > Stats: 0M freed by 0 calls > Stats: 0M really freed by 0 calls > Stats: 1M (256 full pages) mmaped in 2 calls > mmaps by size class: 7:4095; 8:2047; > mallocs by size class: 7:1; 8:2; > frees by size class: > rfrees by size class: > Stats: malloc large: 0 small slow: 2 > ==89768== ABORTING > > My guess is that this is caused by the following code being moved to a > branch island: > > Dump of assembler code for function __cxa_throw: > 0x00008f60 <__cxa_throw+0>: push %esi > 0x00008f61 <__cxa_throw+1>: push %ebx > 0x00008f62 <__cxa_throw+2>: call 0x7a60 <__x86.get_pc_thunk.bx> > > Perhaps this makes __x86.get_pc_thunk.bx return an incorrect value. > > Since libstdc++-v3 is built together with gcc, the two issues related > to instructions being moved to another place can be solved by padding > __cxa_throw() with five NOP instructions (enough to hold a JMP). I > believe this should be acceptable, because the performance penalty for > additional NOPs is negligible, and __cxa_throw() isn't a hot point. > > On Thu, Nov 29, 2012 at 1:01 PM, Nick Kledzik <kledzik at apple.com> wrote: > > I debugged this a bit and it seems the mach_override patching of > __cxa_throw is bogus. The start of that function is patched to jump to > garbage. > > > > Breakpoint 1, 0x0000000100001c19 in main () > > (gdb) display/i $pc > > 2: x/i $pc 0x100001c19 <main+318>: callq 0x100016386 > <dyld_stub___cxa_throw> > > (gdb) si > > 0x0000000100016386 in dyld_stub___cxa_throw () > > 2: x/i $pc 0x100016386 <dyld_stub___cxa_throw>: jmpq > *0xae1c(%rip) # 0x1000211a8 > > (gdb) > > 0x0000000102244870 in __cxa_throw () > > 2: x/i $pc 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > (gdb) # the above its __cxa_throw in gcc's libstdc++.6.dylib. The > first instruction has been patch to jump to a garbage address. > > > > (gdb) x/8i 0x102244870-8 > > 0x102244868 > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+56>: > std > > 0x102244869 > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+57>: > (bad) > > 0x10224486a > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+58>: > decl (%rdi) > > 0x10224486c > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+60>: > (bad) > > 0x10224486d > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+61>: > add %r8b,(%rax) > > 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > 0x102244875 <__cxa_throw+5>: or (%rax),%eax > > 0x102244877 <__cxa_throw+7>: push %rbx > > (gdb) > > (gdb) watch *0x102244870 > > Hardware watchpoint 2: *4330899568 > > (gdb) r > > > > Old value = -788165304 > > New value = -1373139991 > > 0x0000000100016203 in __asan_mach_override_ptr_custom () > > (gdb) bt > > #0 0x0000000100016203 in __asan_mach_override_ptr_custom () > > #1 0x0000000100015a9e in __interception::OverrideFunction () > > #2 0x00007fff5fc13378 in ImageLoaderMachO::doModInitFunctions () > > #3 0x00007fff5fc13762 in ImageLoaderMachO::doInitialization () > > #4 0x00007fff5fc1006e in ImageLoader::recursiveInitialization () > > #5 0x00007fff5fc0feba in ImageLoader::runInitializers () > > #6 0x00007fff5fc01fc0 in dyld::initializeMainExecutable () > > #7 0x00007fff5fc05b04 in dyld::_main () > > #8 0x00007fff5fc01397 in dyldbootstrap::start () > > #9 0x00007fff5fc0105e in _dyld_start () > > (gdb) x/8i 0x102244870 > > 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > 0x102244875 <__cxa_throw+5>: or (%rax),%eax > > 0x102244877 <__cxa_throw+7>: push %rbx > > 0x102244878 <__cxa_throw+8>: lea -0x20(%rdi),%rbx > > 0x10224487c <__cxa_throw+12>: mov %rsi,-0x70(%rdi) > > # Here is where the patching is being done > > > > -Nick > > > > On Nov 29, 2012, at 11:07 AM, Alexander Potapenko wrote: > >>> On Thu, Nov 29, 2012 at 9:55 PM, Jack Howarth < > howarth at bromo.med.uc.edu> > >>> wrote: > >>>> > >>>> Nick, > >>>> Can you take a quick look at the asan_eh_bug.tar.bz testcase > >>>> I uploaded into the newly opened radr://12777299, "potential > >>>> pthread/eh bug exposed by libsanitizer". The FSF gcc developers > >>>> have ported llvm.org's asan code into FSF gcc (and are keeping > >>>> it synced to the upstream llvm.org code). I have been helping > >>>> with the darwin build and testing -fsanitize=address against the > >>>> complete FSF gcc testsuite. This seems to have exposed a potential > >>>> bug in pthread or eh on darwin under libasan. Hundreds of test cases > >>>> in the g++ and libstdc++ testsuites fail under -fsanitize=address > >>>> in the following manner... > >>>> > >>>> ASAN:SIGSEGV > >>>> ================================================================> >>>> ==2738== ERROR: AddressSanitizer: SEGV on unknown address > 0x0000ffd27000 > >>>> (pc 0x0000ffd27000 sp 0x7fff55e40828 bp 0x7fff55e408f0 T0) > >>>> AddressSanitizer can not provide additional info. > >>>> #0 0xffd26fff > (/Users/howarth/asan_eh_bug/./cond1_asan.exe+0xf5f67fff) > >>>> #1 0x7fff8bd827e0 (/usr/lib/system/libdyld.dylib+0x27e0) > >>>> #2 0x0 > >>>> Stats: 0M malloced (0M for red zones) by 3 calls > >>>> Stats: 0M realloced by 0 calls > >>>> Stats: 0M freed by 0 calls > >>>> Stats: 0M really freed by 0 calls > >>>> Stats: 1M (384 full pages) mmaped in 3 calls > >>>> mmaps by size class: 7:4095; 8:2047; 9:1023; > >>>> mallocs by size class: 7:1; 8:1; 9:1; > >>>> frees by size class: > >>>> rfrees by size class: > >>>> Stats: malloc large: 0 small slow: 3 > >>>> ==2738== ABORTING > >>>> > >>>> The failure of... > >>>> > >>>> FAIL: g++.dg/eh/cond1.C -std=c++98 execution test > >>>> > >>>> was used as the test case for the radar report and compiled with... > >>>> > >>>> g++-fsf-4.8 -static-libasan -fsanitize=address -std=c++98 cond1.C -g > -O0 > >>>> -o cond1_asan.exe > >>>> > >>>> to produce the above failure. When compiled without libasan as... > >>>> > >>>> g++-fsf-4.8 -std=c++98 cond1.C -g -O0 -o cond1_no_asan.exe > >>>> > >>>> the resulting executable runs fine. Debugging this in gdb seems to > show > >>>> that the failure > >>>> is occuring in the final call to dyld_stub_pthread_once (). The same > test > >>>> case > >>>> compiles fine with -fsanitize=address under llvm 3.2 clang++ and > produces > >>>> no runtime errors > >>>> but the code execution path is very different in that case (because > of the > >>>> different > >>>> libstdc++). > >>>> Can you take a quick peek at this and determine if this is a darwin > >>>> pthread or unwinder > >>>> bug or an issue with libasan that FSF gcc's compiler is exposing? > Thanks > >>>> in advance for > >>>> any help on this. > >>>> Jack > >>>> _______________________________________________ > >>>> LLVM Developers mailing list > >>>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > >>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > >>> > >>> > >> > >> > >> > >> -- > >> Alexander Potapenko > >> Software Engineer > >> Google Moscow > > > > > > -- > Alexander Potapenko > Software Engineer > Google Moscow >-------------- next part -------------- An HTML attachment was scrubbed... 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Jack Howarth
2012-Nov-30 14:56 UTC
[LLVMdev] radr://12777299, "potential pthread/eh bug exposed by libsanitizer"
On Fri, Nov 30, 2012 at 01:41:05PM +0400, Kostya Serebryany wrote:> Just want to remind everyone that we plan to stop using mach_override in > asanin favor of OSX's native function interposition. > So, we probably don't want to spend too much effort fixing mach_override. > > --kccKostya, Is the native function interposition that is being adopted based on... https://github.com/rentzsch/mach_inject ? I assume that any method used will be transparent to the user and not require manually setting DYLD_INSERT_LIBRARIES, correct? Jack> > On Fri, Nov 30, 2012 at 4:46 AM, Alexander Potapenko <glider at google.com>wrote: > > > Looks like this happens on x86_64 because the position of __cxa_throw > > is too far from the allocated branch island (should be <2G). This can > > be solved by allocating the branch islands somewhere near the text > > segment (look for kIslandEnd in asan_mac.cc, this is currently > > 0x7fffffdf0000) or by patching the function with a longer instruction > > sequence that stores the jump target in a register and jumps to that > > target (which is a bit more complex to implement). > > > > Once this problem is fixed, another one is going to arise. This is how > > the first bytes of __cxa_throw look like: > > > > 0x0020c49ba5d916e0 <__cxa_throw+0>: lea 0xb4f01(%rip),%rax # > > 0x20c49ba5e465e8 <_ZN10__cxxabiv120__unexpected_handlerE> > > 0x0020c49ba5d916e7 <__cxa_throw+7>: push %rbx > > 0x0020c49ba5d916e8 <__cxa_throw+8>: lea -0x20(%rdi),%rbx > > > > If we move the relative LEA instruction somewhere, we must fix the > > constant in order to keep it pointing to the same address. > > mach_override already does this for relative CALL and JMP > > instructions, but not for LEA. This should be fairly simple to fix. > > > > Note that the 32-bit variant crashes on another invalid address: > > > > ASAN:SIGSEGV > > ================================================================> > ==89768== ERROR: AddressSanitizer: SEGV on unknown address 0xcccccccc > > (pc 0x00061f8c sp 0xbffa8bd0 bp 0xbffa8cc8 T0) > > AddressSanitizer can not provide additional info. > > #0 0x61f8b > > (/Users/glider/src/gcc-asan/inst/lib/i386/libstdc++.6.dylib+0x3f8b) > > #1 0x91391724 (/usr/lib/system/libdyld.dylib+0x2724) > > #2 0x0 > > Stats: 0M malloced (0M for red zones) by 3 calls > > Stats: 0M realloced by 0 calls > > Stats: 0M freed by 0 calls > > Stats: 0M really freed by 0 calls > > Stats: 1M (256 full pages) mmaped in 2 calls > > mmaps by size class: 7:4095; 8:2047; > > mallocs by size class: 7:1; 8:2; > > frees by size class: > > rfrees by size class: > > Stats: malloc large: 0 small slow: 2 > > ==89768== ABORTING > > > > My guess is that this is caused by the following code being moved to a > > branch island: > > > > Dump of assembler code for function __cxa_throw: > > 0x00008f60 <__cxa_throw+0>: push %esi > > 0x00008f61 <__cxa_throw+1>: push %ebx > > 0x00008f62 <__cxa_throw+2>: call 0x7a60 <__x86.get_pc_thunk.bx> > > > > Perhaps this makes __x86.get_pc_thunk.bx return an incorrect value. > > > > Since libstdc++-v3 is built together with gcc, the two issues related > > to instructions being moved to another place can be solved by padding > > __cxa_throw() with five NOP instructions (enough to hold a JMP). I > > believe this should be acceptable, because the performance penalty for > > additional NOPs is negligible, and __cxa_throw() isn't a hot point. > > > > On Thu, Nov 29, 2012 at 1:01 PM, Nick Kledzik <kledzik at apple.com> wrote: > > > I debugged this a bit and it seems the mach_override patching of > > __cxa_throw is bogus. The start of that function is patched to jump to > > garbage. > > > > > > Breakpoint 1, 0x0000000100001c19 in main () > > > (gdb) display/i $pc > > > 2: x/i $pc 0x100001c19 <main+318>: callq 0x100016386 > > <dyld_stub___cxa_throw> > > > (gdb) si > > > 0x0000000100016386 in dyld_stub___cxa_throw () > > > 2: x/i $pc 0x100016386 <dyld_stub___cxa_throw>: jmpq > > *0xae1c(%rip) # 0x1000211a8 > > > (gdb) > > > 0x0000000102244870 in __cxa_throw () > > > 2: x/i $pc 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > > (gdb) # the above its __cxa_throw in gcc's libstdc++.6.dylib. The > > first instruction has been patch to jump to a garbage address. > > > > > > (gdb) x/8i 0x102244870-8 > > > 0x102244868 > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+56>: > > std > > > 0x102244869 > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+57>: > > (bad) > > > 0x10224486a > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+58>: > > decl (%rdi) > > > 0x10224486c > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+60>: > > (bad) > > > 0x10224486d > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+61>: > > add %r8b,(%rax) > > > 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > > 0x102244875 <__cxa_throw+5>: or (%rax),%eax > > > 0x102244877 <__cxa_throw+7>: push %rbx > > > (gdb) > > > (gdb) watch *0x102244870 > > > Hardware watchpoint 2: *4330899568 > > > (gdb) r > > > > > > Old value = -788165304 > > > New value = -1373139991 > > > 0x0000000100016203 in __asan_mach_override_ptr_custom () > > > (gdb) bt > > > #0 0x0000000100016203 in __asan_mach_override_ptr_custom () > > > #1 0x0000000100015a9e in __interception::OverrideFunction () > > > #2 0x00007fff5fc13378 in ImageLoaderMachO::doModInitFunctions () > > > #3 0x00007fff5fc13762 in ImageLoaderMachO::doInitialization () > > > #4 0x00007fff5fc1006e in ImageLoader::recursiveInitialization () > > > #5 0x00007fff5fc0feba in ImageLoader::runInitializers () > > > #6 0x00007fff5fc01fc0 in dyld::initializeMainExecutable () > > > #7 0x00007fff5fc05b04 in dyld::_main () > > > #8 0x00007fff5fc01397 in dyldbootstrap::start () > > > #9 0x00007fff5fc0105e in _dyld_start () > > > (gdb) x/8i 0x102244870 > > > 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > > 0x102244875 <__cxa_throw+5>: or (%rax),%eax > > > 0x102244877 <__cxa_throw+7>: push %rbx > > > 0x102244878 <__cxa_throw+8>: lea -0x20(%rdi),%rbx > > > 0x10224487c <__cxa_throw+12>: mov %rsi,-0x70(%rdi) > > > # Here is where the patching is being done > > > > > > -Nick > > > > > > On Nov 29, 2012, at 11:07 AM, Alexander Potapenko wrote: > > >>> On Thu, Nov 29, 2012 at 9:55 PM, Jack Howarth < > > howarth at bromo.med.uc.edu> > > >>> wrote: > > >>>> > > >>>> Nick, > > >>>> Can you take a quick look at the asan_eh_bug.tar.bz testcase > > >>>> I uploaded into the newly opened radr://12777299, "potential > > >>>> pthread/eh bug exposed by libsanitizer". The FSF gcc developers > > >>>> have ported llvm.org's asan code into FSF gcc (and are keeping > > >>>> it synced to the upstream llvm.org code). I have been helping > > >>>> with the darwin build and testing -fsanitize=address against the > > >>>> complete FSF gcc testsuite. This seems to have exposed a potential > > >>>> bug in pthread or eh on darwin under libasan. Hundreds of test cases > > >>>> in the g++ and libstdc++ testsuites fail under -fsanitize=address > > >>>> in the following manner... > > >>>> > > >>>> ASAN:SIGSEGV > > >>>> ================================================================> > >>>> ==2738== ERROR: AddressSanitizer: SEGV on unknown address > > 0x0000ffd27000 > > >>>> (pc 0x0000ffd27000 sp 0x7fff55e40828 bp 0x7fff55e408f0 T0) > > >>>> AddressSanitizer can not provide additional info. > > >>>> #0 0xffd26fff > > (/Users/howarth/asan_eh_bug/./cond1_asan.exe+0xf5f67fff) > > >>>> #1 0x7fff8bd827e0 (/usr/lib/system/libdyld.dylib+0x27e0) > > >>>> #2 0x0 > > >>>> Stats: 0M malloced (0M for red zones) by 3 calls > > >>>> Stats: 0M realloced by 0 calls > > >>>> Stats: 0M freed by 0 calls > > >>>> Stats: 0M really freed by 0 calls > > >>>> Stats: 1M (384 full pages) mmaped in 3 calls > > >>>> mmaps by size class: 7:4095; 8:2047; 9:1023; > > >>>> mallocs by size class: 7:1; 8:1; 9:1; > > >>>> frees by size class: > > >>>> rfrees by size class: > > >>>> Stats: malloc large: 0 small slow: 3 > > >>>> ==2738== ABORTING > > >>>> > > >>>> The failure of... > > >>>> > > >>>> FAIL: g++.dg/eh/cond1.C -std=c++98 execution test > > >>>> > > >>>> was used as the test case for the radar report and compiled with... > > >>>> > > >>>> g++-fsf-4.8 -static-libasan -fsanitize=address -std=c++98 cond1.C -g > > -O0 > > >>>> -o cond1_asan.exe > > >>>> > > >>>> to produce the above failure. When compiled without libasan as... > > >>>> > > >>>> g++-fsf-4.8 -std=c++98 cond1.C -g -O0 -o cond1_no_asan.exe > > >>>> > > >>>> the resulting executable runs fine. Debugging this in gdb seems to > > show > > >>>> that the failure > > >>>> is occuring in the final call to dyld_stub_pthread_once (). The same > > test > > >>>> case > > >>>> compiles fine with -fsanitize=address under llvm 3.2 clang++ and > > produces > > >>>> no runtime errors > > >>>> but the code execution path is very different in that case (because > > of the > > >>>> different > > >>>> libstdc++). > > >>>> Can you take a quick peek at this and determine if this is a darwin > > >>>> pthread or unwinder > > >>>> bug or an issue with libasan that FSF gcc's compiler is exposing? > > Thanks > > >>>> in advance for > > >>>> any help on this. > > >>>> Jack > > >>>> _______________________________________________ > > >>>> LLVM Developers mailing list > > >>>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > > >>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > >>> > > >>> > > >> > > >> > > >> > > >> -- > > >> Alexander Potapenko > > >> Software Engineer > > >> Google Moscow > > > > > > > > > > > -- > > Alexander Potapenko > > Software Engineer > > Google Moscow > >
Jack Howarth
2012-Dec-01 00:33 UTC
[LLVMdev] radr://12777299, "potential pthread/eh bug exposed by libsanitizer"
On Fri, Nov 30, 2012 at 01:41:05PM +0400, Kostya Serebryany wrote:> Just want to remind everyone that we plan to stop using mach_override in > asanin favor of OSX's native function interposition. > So, we probably don't want to spend too much effort fixing mach_override. > > --kccKostya, Unless I am misunderstanding the code in asan/asan_intercepted_functions.h, using MAC_INTERPOSE_FUNCTIONS on FSF gcc will require the missing blocks support to be implemented. I did a quick and dirty attempt to build libasan using libsanitizer/asan/dynamic/asan_interceptors_dynamic.cc imported from llvm svn. The bootstrap chokes on... /bin/sh ../libtool --tag=CXX --mode=compile /sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/./gcc/xg++ -B/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/./gcc/ -nostdinc++ -nostdinc++ -I/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/include/x86_64-apple-darwin12.2.0 -I/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/include -I/sw/src/fink.build/gcc48-4.8.0-1000/gcc-4.8-20121130/libstdc++-v3/libsupc++ -I/sw/src/fink.build/gcc48-4.8.0-1000/gcc-4.8-20121130/libstdc++-v3/include/backward -I/sw/src/fink.build/gcc48-4.8.0-1000/gcc-4.8-20121130/libstdc++-v3/testsuite/util -L/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/src -L/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/src/.libs -B/sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/bin/ -B/sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/lib/ -isystem /sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/include -isystem /sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/sys-include -D_GNU_SOURCE -D_DEBUG -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -DASAN_HAS_EXCEPTIONS=1 -DASAN_FLEXIBLE_MAPPING_AND_OFFSET=0 -DASAN_NEEDS_SEGV=1 -DMAC_INTERPOSE_FUNCTIONS -I. -I../../../../gcc-4.8-20121130/libsanitizer/asan -I ../../../../gcc-4.8-20121130/libsanitizer/include -I ../../../../gcc-4.8-20121130/libsanitizer -Wall -W -Wno-unused-parameter -Wwrite-strings -pedantic -Wno-long-long -fPIC -fno-builtin -fno-exceptions -fomit-frame-pointer -funwind-tables -fvisibility=hidden -Wno-variadic-macros -Wno-c99-extensions -g -O2 -MT asan_interceptors.lo -MD -MP -MF .deps/asan_interceptors.Tpo -c -o asan_interceptors.lo ../../../../gcc-4.8-20121130/libsanitizer/asan/asan_interceptors.cc libtool: compile: /sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/./gcc/xg++ -B/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/./gcc/ -nostdinc++ -nostdinc++ -I/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/include/x86_64-apple-darwin12.2.0 -I/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/include -I/sw/src/fink.build/gcc48-4.8.0-1000/gcc-4.8-20121130/libstdc++-v3/libsupc++ -I/sw/src/fink.build/gcc48-4.8.0-1000/gcc-4.8-20121130/libstdc++-v3/include/backward -I/sw/src/fink.build/gcc48-4.8.0-1000/gcc-4.8-20121130/libstdc++-v3/testsuite/util -L/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/src -L/sw/src/fink.build/gcc48-4.8.0-1000/darwin_objdir/x86_64-apple-darwin12.2.0/libstdc++-v3/src/.libs -B/sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/bin/ -B/sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/lib/ -isystem /sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/include -isystem /sw/lib/gcc4.8/x86_64-apple-darwin12.2.0/sys-include -D_GNU_SOURCE -D_DEBUG -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -DASAN_HAS_EXCEPTIONS=1 -DASAN_FLEXIBLE_MAPPING_AND_OFFSET=0 -DASAN_NEEDS_SEGV=1 -DMAC_INTERPOSE_FUNCTIONS -I. -I../../../../gcc-4.8-20121130/libsanitizer/asan -I ../../../../gcc-4.8-20121130/libsanitizer/include -I ../../../../gcc-4.8-20121130/libsanitizer -Wall -W -Wno-unused-parameter -Wwrite-strings -pedantic -Wno-long-long -fPIC -fno-builtin -fno-exceptions -fomit-frame-pointer -funwind-tables -fvisibility=hidden -Wno-variadic-macros -Wno-c99-extensions -g -O2 -MT asan_interceptors.lo -MD -MP -MF .deps/asan_interceptors.Tpo -c ../../../../gcc-4.8-20121130/libsanitizer/asan/asan_interceptors.cc -fno-common -DPIC -o .libs/asan_interceptors.o In file included from ../../../../gcc-4.8-20121130/libsanitizer/asan/asan_interceptors.cc:15:0: ../../../../gcc-4.8-20121130/libsanitizer/asan/asan_intercepted_functions.h:209:57: error: expected ‘)’ before ‘^’ token dispatch_queue_t dq, void (^work)(void)); ^ etc. So we may be stuck with mach_override until someone steps up to implement the missing blocks support for darwin in FSF gcc. Jack> > On Fri, Nov 30, 2012 at 4:46 AM, Alexander Potapenko <glider at google.com>wrote: > > > Looks like this happens on x86_64 because the position of __cxa_throw > > is too far from the allocated branch island (should be <2G). This can > > be solved by allocating the branch islands somewhere near the text > > segment (look for kIslandEnd in asan_mac.cc, this is currently > > 0x7fffffdf0000) or by patching the function with a longer instruction > > sequence that stores the jump target in a register and jumps to that > > target (which is a bit more complex to implement). > > > > Once this problem is fixed, another one is going to arise. This is how > > the first bytes of __cxa_throw look like: > > > > 0x0020c49ba5d916e0 <__cxa_throw+0>: lea 0xb4f01(%rip),%rax # > > 0x20c49ba5e465e8 <_ZN10__cxxabiv120__unexpected_handlerE> > > 0x0020c49ba5d916e7 <__cxa_throw+7>: push %rbx > > 0x0020c49ba5d916e8 <__cxa_throw+8>: lea -0x20(%rdi),%rbx > > > > If we move the relative LEA instruction somewhere, we must fix the > > constant in order to keep it pointing to the same address. > > mach_override already does this for relative CALL and JMP > > instructions, but not for LEA. This should be fairly simple to fix. > > > > Note that the 32-bit variant crashes on another invalid address: > > > > ASAN:SIGSEGV > > ================================================================> > ==89768== ERROR: AddressSanitizer: SEGV on unknown address 0xcccccccc > > (pc 0x00061f8c sp 0xbffa8bd0 bp 0xbffa8cc8 T0) > > AddressSanitizer can not provide additional info. > > #0 0x61f8b > > (/Users/glider/src/gcc-asan/inst/lib/i386/libstdc++.6.dylib+0x3f8b) > > #1 0x91391724 (/usr/lib/system/libdyld.dylib+0x2724) > > #2 0x0 > > Stats: 0M malloced (0M for red zones) by 3 calls > > Stats: 0M realloced by 0 calls > > Stats: 0M freed by 0 calls > > Stats: 0M really freed by 0 calls > > Stats: 1M (256 full pages) mmaped in 2 calls > > mmaps by size class: 7:4095; 8:2047; > > mallocs by size class: 7:1; 8:2; > > frees by size class: > > rfrees by size class: > > Stats: malloc large: 0 small slow: 2 > > ==89768== ABORTING > > > > My guess is that this is caused by the following code being moved to a > > branch island: > > > > Dump of assembler code for function __cxa_throw: > > 0x00008f60 <__cxa_throw+0>: push %esi > > 0x00008f61 <__cxa_throw+1>: push %ebx > > 0x00008f62 <__cxa_throw+2>: call 0x7a60 <__x86.get_pc_thunk.bx> > > > > Perhaps this makes __x86.get_pc_thunk.bx return an incorrect value. > > > > Since libstdc++-v3 is built together with gcc, the two issues related > > to instructions being moved to another place can be solved by padding > > __cxa_throw() with five NOP instructions (enough to hold a JMP). I > > believe this should be acceptable, because the performance penalty for > > additional NOPs is negligible, and __cxa_throw() isn't a hot point. > > > > On Thu, Nov 29, 2012 at 1:01 PM, Nick Kledzik <kledzik at apple.com> wrote: > > > I debugged this a bit and it seems the mach_override patching of > > __cxa_throw is bogus. The start of that function is patched to jump to > > garbage. > > > > > > Breakpoint 1, 0x0000000100001c19 in main () > > > (gdb) display/i $pc > > > 2: x/i $pc 0x100001c19 <main+318>: callq 0x100016386 > > <dyld_stub___cxa_throw> > > > (gdb) si > > > 0x0000000100016386 in dyld_stub___cxa_throw () > > > 2: x/i $pc 0x100016386 <dyld_stub___cxa_throw>: jmpq > > *0xae1c(%rip) # 0x1000211a8 > > > (gdb) > > > 0x0000000102244870 in __cxa_throw () > > > 2: x/i $pc 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > > (gdb) # the above its __cxa_throw in gcc's libstdc++.6.dylib. The > > first instruction has been patch to jump to a garbage address. > > > > > > (gdb) x/8i 0x102244870-8 > > > 0x102244868 > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+56>: > > std > > > 0x102244869 > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+57>: > > (bad) > > > 0x10224486a > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+58>: > > decl (%rdi) > > > 0x10224486c > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+60>: > > (bad) > > > 0x10224486d > > <_ZL23__gxx_exception_cleanup19_Unwind_Reason_CodeP17_Unwind_Exception+61>: > > add %r8b,(%rax) > > > 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > > 0x102244875 <__cxa_throw+5>: or (%rax),%eax > > > 0x102244877 <__cxa_throw+7>: push %rbx > > > (gdb) > > > (gdb) watch *0x102244870 > > > Hardware watchpoint 2: *4330899568 > > > (gdb) r > > > > > > Old value = -788165304 > > > New value = -1373139991 > > > 0x0000000100016203 in __asan_mach_override_ptr_custom () > > > (gdb) bt > > > #0 0x0000000100016203 in __asan_mach_override_ptr_custom () > > > #1 0x0000000100015a9e in __interception::OverrideFunction () > > > #2 0x00007fff5fc13378 in ImageLoaderMachO::doModInitFunctions () > > > #3 0x00007fff5fc13762 in ImageLoaderMachO::doInitialization () > > > #4 0x00007fff5fc1006e in ImageLoader::recursiveInitialization () > > > #5 0x00007fff5fc0feba in ImageLoader::runInitializers () > > > #6 0x00007fff5fc01fc0 in dyld::initializeMainExecutable () > > > #7 0x00007fff5fc05b04 in dyld::_main () > > > #8 0x00007fff5fc01397 in dyldbootstrap::start () > > > #9 0x00007fff5fc0105e in _dyld_start () > > > (gdb) x/8i 0x102244870 > > > 0x102244870 <__cxa_throw>: jmpq 0xffd27000 > > > 0x102244875 <__cxa_throw+5>: or (%rax),%eax > > > 0x102244877 <__cxa_throw+7>: push %rbx > > > 0x102244878 <__cxa_throw+8>: lea -0x20(%rdi),%rbx > > > 0x10224487c <__cxa_throw+12>: mov %rsi,-0x70(%rdi) > > > # Here is where the patching is being done > > > > > > -Nick > > > > > > On Nov 29, 2012, at 11:07 AM, Alexander Potapenko wrote: > > >>> On Thu, Nov 29, 2012 at 9:55 PM, Jack Howarth < > > howarth at bromo.med.uc.edu> > > >>> wrote: > > >>>> > > >>>> Nick, > > >>>> Can you take a quick look at the asan_eh_bug.tar.bz testcase > > >>>> I uploaded into the newly opened radr://12777299, "potential > > >>>> pthread/eh bug exposed by libsanitizer". The FSF gcc developers > > >>>> have ported llvm.org's asan code into FSF gcc (and are keeping > > >>>> it synced to the upstream llvm.org code). I have been helping > > >>>> with the darwin build and testing -fsanitize=address against the > > >>>> complete FSF gcc testsuite. This seems to have exposed a potential > > >>>> bug in pthread or eh on darwin under libasan. Hundreds of test cases > > >>>> in the g++ and libstdc++ testsuites fail under -fsanitize=address > > >>>> in the following manner... > > >>>> > > >>>> ASAN:SIGSEGV > > >>>> ================================================================> > >>>> ==2738== ERROR: AddressSanitizer: SEGV on unknown address > > 0x0000ffd27000 > > >>>> (pc 0x0000ffd27000 sp 0x7fff55e40828 bp 0x7fff55e408f0 T0) > > >>>> AddressSanitizer can not provide additional info. > > >>>> #0 0xffd26fff > > (/Users/howarth/asan_eh_bug/./cond1_asan.exe+0xf5f67fff) > > >>>> #1 0x7fff8bd827e0 (/usr/lib/system/libdyld.dylib+0x27e0) > > >>>> #2 0x0 > > >>>> Stats: 0M malloced (0M for red zones) by 3 calls > > >>>> Stats: 0M realloced by 0 calls > > >>>> Stats: 0M freed by 0 calls > > >>>> Stats: 0M really freed by 0 calls > > >>>> Stats: 1M (384 full pages) mmaped in 3 calls > > >>>> mmaps by size class: 7:4095; 8:2047; 9:1023; > > >>>> mallocs by size class: 7:1; 8:1; 9:1; > > >>>> frees by size class: > > >>>> rfrees by size class: > > >>>> Stats: malloc large: 0 small slow: 3 > > >>>> ==2738== ABORTING > > >>>> > > >>>> The failure of... > > >>>> > > >>>> FAIL: g++.dg/eh/cond1.C -std=c++98 execution test > > >>>> > > >>>> was used as the test case for the radar report and compiled with... > > >>>> > > >>>> g++-fsf-4.8 -static-libasan -fsanitize=address -std=c++98 cond1.C -g > > -O0 > > >>>> -o cond1_asan.exe > > >>>> > > >>>> to produce the above failure. When compiled without libasan as... > > >>>> > > >>>> g++-fsf-4.8 -std=c++98 cond1.C -g -O0 -o cond1_no_asan.exe > > >>>> > > >>>> the resulting executable runs fine. Debugging this in gdb seems to > > show > > >>>> that the failure > > >>>> is occuring in the final call to dyld_stub_pthread_once (). The same > > test > > >>>> case > > >>>> compiles fine with -fsanitize=address under llvm 3.2 clang++ and > > produces > > >>>> no runtime errors > > >>>> but the code execution path is very different in that case (because > > of the > > >>>> different > > >>>> libstdc++). > > >>>> Can you take a quick peek at this and determine if this is a darwin > > >>>> pthread or unwinder > > >>>> bug or an issue with libasan that FSF gcc's compiler is exposing? > > Thanks > > >>>> in advance for > > >>>> any help on this. > > >>>> Jack > > >>>> _______________________________________________ > > >>>> LLVM Developers mailing list > > >>>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > > >>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > > >>> > > >>> > > >> > > >> > > >> > > >> -- > > >> Alexander Potapenko > > >> Software Engineer > > >> Google Moscow > > > > > > > > > > > -- > > Alexander Potapenko > > Software Engineer > > Google Moscow > >
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