linux-kernel - Re: [PATCH v3 0/2] Fix kallsyms with CONFIG_LTO

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Message-ID: <CAPhsuW64RyYhHsFeJSj7=+4uHBo7LucWtWY5xOxN20aujxadGg@mail.gmail.com>
Date: Mon, 12 Aug 2024 09:21:02 -0700
From: Song Liu <song@...nel.org>
To: live-patching@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Cc: jpoimboe@...nel.org, jikos@...nel.org, mbenes@...e.cz, pmladek@...e.com, 
	joe.lawrence@...hat.com, nathan@...nel.org, morbo@...gle.com, 
	justinstitt@...gle.com, mcgrof@...nel.org, thunder.leizhen@...wei.com, 
	kees@...nel.org, kernel-team@...a.com, mmaurer@...gle.com, 
	samitolvanen@...gle.com, mhiramat@...nel.org, rostedt@...dmis.org
Subject: Re: [PATCH v3 0/2] Fix kallsyms with CONFIG_LTO_CLANG

Hi folks,

Do we have more concerns and/or suggestions with this set? If not,
what would be the next step for it?

Thanks,
Song

On Wed, Aug 7, 2024 at 3:05 PM Song Liu <song@...nel.org> wrote:
>
> With CONFIG_LTO_CLANG, the compiler/linker adds .llvm.<hash> suffix to
> local symbols to avoid duplications. Existing scripts/kallsyms sorts
> symbols without .llvm.<hash> suffix. However, this causes quite some
> issues later on. Some users of kallsyms, such as livepatch, have to match
> symbols exactly.
>
> Address this by sorting full symbols at build time, and let kallsyms
> lookup APIs to match the symbols exactly.
>
> Changes v2 => v3:
> 1. Remove the _without_suffix APIs, as kprobe will not use them.
>    (Masami Hiramatsu)
>
> v2: https://lore.kernel.org/live-patching/20240802210836.2210140-1-song@kernel.org/T/#u
>
> Changes v1 => v2:
> 1. Update the APIs to remove all .XXX suffixes (v1 only removes .llvm.*).
> 2. Rename the APIs as *_without_suffix. (Masami Hiramatsu)
> 3. Fix another user from kprobe. (Masami Hiramatsu)
> 4. Add tests for the new APIs in kallsyms_selftests.
>
> v1: https://lore.kernel.org/live-patching/20240730005433.3559731-1-song@kernel.org/T/#u
>
> Song Liu (2):
>   kallsyms: Do not cleanup .llvm.<hash> suffix before sorting symbols
>   kallsyms: Match symbols exactly with CONFIG_LTO_CLANG
>
>  kernel/kallsyms.c          | 55 +++++---------------------------------
>  kernel/kallsyms_selftest.c | 22 +--------------
>  scripts/kallsyms.c         | 31 ++-------------------
>  scripts/link-vmlinux.sh    |  4 ---
>  4 files changed, 9 insertions(+), 103 deletions(-)
>
> --
> 2.43.5