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Re: [PATCH] x86-64/memset: Mark the debugger symbol as hidden
On 07/05/2018 15:31, H.J. Lu wrote:
> On Mon, May 7, 2018 at 11:22 AM, Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>> On 07/05/2018 14:59, H.J. Lu wrote:
>>> On Sat, May 5, 2018 at 8:46 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>>>> When MEMSET_SYMBOL (__memset, erms) is provided for debugger, mark it
>>>> as hidden so that it will be local to the library.
>>>>
>>>> Any comments?
>>>>
>>>> H.J.
>>>> ---
>>>> * sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
>>>> (MEMSET_SYMBOL (__memset, erms)): Mark the debugger symbol as
>>>> hidden.
>>>> ---
>>>> sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
>>>> index d0fe79c9f1..a0560cd5c8 100644
>>>> --- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
>>>> +++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
>>>> @@ -131,7 +131,8 @@ END (__memset_chk_erms)
>>>> /* Only used to measure performance of REP STOSB. */
>>>> ENTRY (__memset_erms)
>>>> # else
>>>> -/* Provide a symbol to debugger. */
>>>> +/* Provide a hidden symbol to debugger. */
>>>> + .hidden MEMSET_SYMBOL (__memset, erms)
>>>> ENTRY (MEMSET_SYMBOL (__memset, erms))
>>>> # endif
>>>> L(stosb):
>>>> --
>>>> 2.17.0
>>>>
>>>
>>> I am checking it in.
>>>
>>
>> Why is this need only for this symbol in particular and not for all other
>> ifunc variations? What debugger is missing and does it potentially might
>> affect other architectures as well?
>
> This is specific to memset-vec-unaligned-erms.S. The code looks like
>
> function 1 entry:
> ..
> ret
>
> local label:
> ...
> ret
>
> function 2 entry:
> ...
> jump to local label
>
> If "local label" isn't in the symbol table, gdb will think you jump to
> "function 1"
> when single-stepping over "jump to local label".
>
Right, thanks for the explanation.