llvm dev - Sep 2016 - How to insert instructions before each function calls?

> On 5 Sep 2016, at 16:14, SHUCAI YAO <yaos4 at mcmaster.ca> wrote:
> 
> 
> Hi Dean,
> 
> Do you have any example for this?  I would like have a look at how you
handle this in XRay if it is possible.
> 
Yes, this is all upstream -- if you look in lib/CodeGen/XRayInstrument.cpp and
the associated lowering code for X86 in lib/Target/X86/X86MCInstLower.cpp and/or
search for PATCHABLE_RET in include/... and lib/... then that should give you a
better idea of how this works. :)

Cheers

-- Dean

Hi Dean,

Thank you very much.  I solved my problems by using the similar structure.

BTW, I saw there is a hacky way to do the relative jump in function
of LowerPATCHABLE_FUNCTION_ENTER. I think directional local symbol can
implement it too:

1. t = getDirectionalLocalSymbol  first;

2. jmp t

3. then emit  nops

4. createDirectionalLocalSymbol(t)

Hope it can help.

Thank you!
Shucai

On Mon, Sep 5, 2016 at 9:21 PM, Dean Michael Berris <dean.berris at
gmail.com>
wrote:
> > On 5 Sep 2016, at 16:14, SHUCAI YAO <yaos4 at mcmaster.ca>
wrote:
> >
> >
> > Hi Dean,
> >
> > Do you have any example for this?  I would like have a look at how you
> handle this in XRay if it is possible.
> >
>
> Yes, this is all upstream -- if you look in lib/CodeGen/XRayInstrument.cpp
> and the associated lowering code for X86 in
lib/Target/X86/X86MCInstLower.cpp
> and/or search for PATCHABLE_RET in include/... and lib/... then that should
> give you a better idea of how this works. :)
>
> Cheers
>
> -- Dean
>
>
>
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> On 20 Sep 2016, at 01:39, SHUCAI YAO <yaos4 at mcmaster.ca> wrote:
> 
> 
> Hi Dean,
> 
> Thank you very much.  I solved my problems by using the similar structure. 
Awesome -- happy to help!
> 
> BTW, I saw there is a hacky way to do the relative jump in function of
LowerPATCHABLE_FUNCTION_ENTER. I think directional local symbol can implement it
too:
> 1. t = getDirectionalLocalSymbol  first; 
> 2. jmp t
> 3. then emit  nops
> 4. createDirectionalLocalSymbol(t)
> 
> Hope it can help. 
> 
Interesting. Thanks, I'll try that next time in that part of the woods
again. :)

Cheers

-- Dean