[PATCH v4 3/3] Fix: Priotirize symbol table lookup for ppc64le

[Hemant Kumar]

On 04/22/2015 07:18 PM, Mark Wielaard wrote:
> On Mon, 2015-04-20 at 15:59 +0530, Hemant Kumar wrote:
>> PPC64 ELF ABI v2 has a Global entry point and a local entry point
>> for the functions. We need the Local entry point in order to probe
>> these functions. However, the DIE for these functions in debuginfo
>> return the function.entrypc which is same as the global entry point.
>> The local entry point is not encoded in the debuginfo of the ELFs. The
>> offset to local entry point is however encoded in the st_other field
>> of these symbols in the symbol table.
>> We need to use this field to adjust the sym.st_value to actually point
>> to the local entry point instead of the global entry point.
>>
>> This patch is in relation to this bug :
>> https://sourceware.org/bugzilla/show_bug.cgi?id=17638
>>
>> So, while adding symbols to the sym_table, we add an offset of
>> PPC64_LOCAL_ENTRY_OFFSET(sym.st_other) to st_value.
>> And when the function address is queried in query_dwarf_func(), we give
>> priority to the cached sym_table, where we can retrieve the adjusted
>> entry address of the function. If we don't get any address from the
>> symbol table, then we proceed to get from the debuginfo.
>>
>> Macro definition PPC64_LOCAL_ENTRY_OFFSET has been picked up from glibc.
>> It won't be defined if we are building systemtap on a machine having
>> older elf.h and hence, won't recognize PPC64_LOCAL_ENTRY_OFFSET.
> Looks good. Pushed with one tiny change (in the commit message):
> s/Priotirize/Prioritize/

Thanks a lot Mark.

-- 
Thanks,
Hemant Kumar