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

Song Liu
2024-08-02T17:16:26Z

> On Jul 29, 2024, at 5:54 PM, 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()
>
> These APIs will be used by kprobe.
>
> Also cleanup some code and adjust kallsyms_selftests accordingly.
>
> Signed-off-by: Song Liu <song@kernel.org>

Actually, if we only remove .llvm.<hash> suffix, but keep other .XXX
suffix, the *_without_suffx APIs will have the same issue Yonghong
tried to fix in commit 33f0467fe06934d5e4ea6e24ce2b9c65ce618e26:
binary search with symbols - .llvm.<hash> suffix is not correct.
(Please see the commit log of 33f0467fe06934d5e4ea6e24ce2b9c65ce618e26
for more details.)

I am updating the code to remove all .XXX suffix. This design will
not have this issue.

Thanks,
Song