Re: [PATCH] kallsyms: let kallsyms_on_each_match_symbol match symbols exactly

["Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>]

On 2023/6/16 13:01, Song Liu wrote:
> 
> 
>> On Jun 15, 2023, at 7:19 PM, Leizhen (ThunderTown) <thunder.leizhen@huawei.com> wrote:
>>
>> On 2023/6/16 1:00, Song Liu wrote:
>>> With CONFIG_LTO_CLANG, kallsyms.c:cleanup_symbol_name() removes symbols
>>> suffixes during comparison. This is problematic for livepatch, as
>>> kallsyms_on_each_match_symbol may find multiple matches for the same
>>> symbol, and fail with:
>>>
>>>  livepatch: unresolvable ambiguity for symbol 'xxx' in object 'yyy'
>>
>> Did you forget to specify 'old_sympos'? When there are multiple symbols with
>> the same name, we need to specify the sequence number of the symbols to be
>> matched.
> 
> 
> old_sympos is indeed 0 here. However, the issue with CONFIG_LTO_CLANG 
> is different. Here is an example:
> 
> $ grep bpf_verifier_vlog /proc/kallsyms
> ffffffff81549f60 t bpf_verifier_vlog
> ffffffff8268b430 d bpf_verifier_vlog._entry
> ffffffff8282a958 d bpf_verifier_vlog._entry_ptr
> ffffffff82e12a1f d bpf_verifier_vlog.__already_done
> 
> kallsyms_on_each_match_symbol matches "bpf_verifier_vlog" to all of 
> these because of cleanup_symbol_name(). IOW, we only have one 
> function called bpf_verifier_vlog, but kallsyms_on_each_match_symbol() 
> matches it to bpf_verifier_vlog.*. 
> 
> Does this make sense?

Sorry. I mistakenly thought you were operating a static function.

These suffixes are not mentioned in the comments in the function
cleanup_symbol_name(). So I didn't notice it.

> 
> Thanks,
> Song
> 
> 
> .
> 

-- 
Regards,
  Zhen Lei