Re: [PATCH 2/3] kallsyms: Add APIs to match symbol without .llmv. suffix.

Leizhen (ThunderTown)
2024-08-02T06:53:58Z

On 2024/8/2 11:45, Song Liu wrote:
>
>
>> On Aug 1, 2024, at 6:18 PM, Leizhen (ThunderTown) <thunder.leizhen@huaweicloud.com> wrote:
>>
>> On 2024/7/31 9:00, Song Liu wrote:
>>> Hi Masami,
>>>
>>>> On Jul 30, 2024, at 6:03 AM, Masami Hiramatsu <mhiramat@kernel.org> wrote:
>>>>
>>>> On Mon, 29 Jul 2024 17:54:32 -0700
>>>> Song Liu <song@kernel.org> wrote:
>>>>
>>>>> With CONFIG_LTO_CLANG=y, the compiler may add suffix to function names
>>>>> to avoid duplication. This causes confusion with users of kallsyms.
>>>>> On one hand, users like livepatch are required to match the symbols
>>>>> exactly. On the other hand, users like kprobe would like to match to
>>>>> original function names.
>>>>>
>>>>> Solve this by splitting kallsyms APIs. Specifically, existing APIs now
>>>>> should match the symbols exactly. Add two APIs that matches the full
>>>>> symbol, or only the part without .llvm.suffix. Specifically, the following
>>>>> two APIs are added:
>>>>>
>>>>> 1. kallsyms_lookup_name_or_prefix()
>>>>> 2. kallsyms_on_each_match_symbol_or_prefix()
>>>>
>>>> Since this API only removes the suffix, "match prefix" is a bit confusing.
>>>> (this sounds like matching "foo" with "foo" and "foo_bar", but in reality,
>>>> it only matches "foo" and "foo.llvm.*")
>>>> What about the name below?
>>>>
>>>> kallsyms_lookup_name_without_suffix()
>>>> kallsyms_on_each_match_symbol_without_suffix()
>>>
>>> I am open to name suggestions. I named it as xx or prefix to highlight
>>> that these two APIs will try match full name first, and they only match
>>> the symbol without suffix when there is no full name match.
>>>
>>> Maybe we can call them:
>>> - kallsyms_lookup_name_or_without_suffix()
>>> - kallsyms_on_each_match_symbol_or_without_suffix()
>>>
>>> Again, I am open to any name selections here.
>>
>> Only static functions have suffixes. In my opinion, explicitly marking static
>> might be a little clearer.
>> kallsyms_lookup_static_name()
>> kallsyms_on_each_match_static_symbol()
>
> While these names are shorter, I think they are more confusing. Not all
> folks know that only static functions can have suffixes.
>
> Maybe we should not hide the "try match full name first first" in the
> API, and let the users handle it. Then, we can safely call the new APIs
> *_without_suffix(), as Masami suggested.

Yes, that would be clearer.

>
> If there is no objections, I will send v2 based on this direction.
>
> Thanks,
> Song
>

--
Regards,
Zhen Lei