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Re: [PATCH v2 1/2] ppc64le: Store correct function entry address in symbol_table
- From: "Naveen N. Rao" <naveen dot n dot rao at linux dot vnet dot ibm dot com>
- To: Ravi Bangoria <ravi dot bangoria at linux dot vnet dot ibm dot com>
- Cc: systemtap at sourceware dot org, hemant at linux dot vnet dot ibm dot com, atrajeev at linux dot vnet dot ibm dot com, mjw at redhat dot com, fche at redhat dot com, dsmith at redhat dot com
- Date: Tue, 23 Aug 2016 16:34:54 +0530
- Subject: Re: [PATCH v2 1/2] ppc64le: Store correct function entry address in symbol_table
- Authentication-results: sourceware.org; auth=none
- References: <1471949084-17594-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com>
On 2016/08/23 05:44AM, Ravi Bangoria wrote:
> PPC64 ELF ABI v2 has a Global Entry Point and a Local Entry Point for
> the functions. Debuginfo of ELF contains GEP which is same as entrypc
> while symbol table contains GEP and offset, from which we can calculate
> LEP. LEP is used to call function within single CU, when TOC pointer
> update is not required. Placing a probe on LEP catches call from both
> the GEP and the LEP but, by default, systemtap probes on GEP.
>
> For ppc64le, Systemtap stores LEP in symbol table and prioritize symbol
> table over debuginfo. But, storing LEP in symbol table has couple of
> regression effect. As LEP is only required at a time of adding a probe,
> don't store it in symbol table.
>
> No need to prioritize symbol table as well because debuginfo and symbol
> table both will contain Global Entry Point.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
> ---
> Changes in v2:
> - Little bit change in patch description, no logical changes.
You should also mention that this reverts whatever commit that this
does...
- Naveen