linux-kernel - Re: [PATCH 0/3] Fix kallsyms with CONFIG_LTO

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Message-ID: <CAPhsuW6fXrgL-r+XRs_pVg-3XSv21pbSPcZ8djYRjcs2sHDj7g@mail.gmail.com>
Date: Mon, 29 Jul 2024 22:36:50 -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 0/3] Fix kallsyms with CONFIG_LTO_CLANG

On Mon, Jul 29, 2024 at 5:54 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; while other users, such as kprobe, would match symbols
> without the suffix.
>
> Address this by sorting full symbols (with .llvm.<hash>) at build time, and
> split kallsyms APIs to explicitly match full symbols or without suffix.
> Specifically, exiting APIs will match symbols exactly. Two new APIs are
> added to match symbols with suffix. Use the new APIs in tracing/kprobes.

Forgot to mention: This is to follow up the discussions in this thread:

https://lore.kernel.org/live-patching/20240605032120.3179157-1-song@kernel.org/T/#u

Thanks,
Song