linux-kernel - Re: [PATCH] tracing: Disable branch profiling in noinstr code

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Message-ID: <871puq2uop.ffs@tglx>
Date: Fri, 21 Mar 2025 17:51:50 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>, Ingo
 Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] tracing: Disable branch profiling in noinstr code

On Thu, Mar 20 2025 at 23:05, Josh Poimboeuf wrote:

> CONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()
> for each use of likely() or unlikely().  If the caller is noinstr, that
> breaks the noinstr rules.
>
> Disable branch profiling for files which have noinstr functions.  Fixes
> many warnings like the following:
>
>   vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section
>   vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section
>   vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section
>   ...

Acked-by: Thomas Gleixner <tglx@...utronix.de>

Thanks for fixing this!

Though the real fix would be to rip out this likely/unlikely tracer
hackery all together.

        tglx