RFR(L): 8049716: PPC64: Implement SA on Linux/PPC64

[Maynard Johnson]

On 12/04/2014 01:15 PM, Alexander Smundak wrote:
> The changes for agent/src/os/linux/symtab.c
> b/agent/src/os/linux/symtab.c in
> http://cr.openjdk.java.net/~simonis/webrevs/8049716 will break
> Linux/PPC64 little-endian:
> it uses ABIv2, which dropped function descriptors. So the preprocessor
> brackets in it should
> read
> #if defined(ppc64) && !defined(ABI_ELFv2)
> instead of just
> #if defined(ppc64)
Hi, Alexander,
I think this is actually fine everywhere except one place. The 'opd' variable will be
set to something other than NULL at line 379 only if running on ppc64 BE. So in
the rest of that function, opd is checked for non-null before using it.  The only
place where I think there may be a problem is at line 455:

--------------------------
#if defined(ppc64)
  // On Linux/PPC64 the debuginfo files contain an empty file descriptor
  // section (i.e. '.opd' section) which makes the resolution of symbols
  // with the above algorithm impossible (we would need the have both, the
  // .opd section from the library and the symbol table from the debuginfo
  // file which doesn't match with the current workflow.)
  if (false) {
#else
  // Look for a separate debuginfo file.
  if (try_debuginfo) {
#endif
--------------------------

Here I think we should do as you suggest:
   #if defined(ppc64) && !defined(ABI_ELFv2)

-Maynard
> 
> Sorry for the late notice.
> Sasha
> 
> On Thu, Dec 4, 2014 at 9:50 AM, Volker Simonis <volker.simonis at gmail.com> wrote:
>> Hi,
>>
>> I'd like to submit this webrev which adds support for the SA agent on
>> Linux/PPC64 on behalf of Maynard Johnson who is the main author of the
>> change:
>>
>> http://cr.openjdk.java.net/~simonis/webrevs/8049716
>> https://bugs.openjdk.java.net/browse/JDK-8049716
>>
>> I have already reviewed and tested the change and from my side
>> everything looks fine.
>>
>> The change touches quite some shared code but all of these changes are
>> trivial and straight-forward (i.e. they just add Linux/PPC64 support
>> with the help of '#ifdef's in C or yet another 'elseif' clause in
>> Java).
>>
>> We need a second reviewer and a sponsor who can push this to the
>> hotspot repository once the review is completed.
>>
>> Thank you and best regards,
>> Volker
>