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Date: Mon, 22 Sep 2025 08:36:16 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Menglong Dong <menglong8.dong@gmail.com>, Jiri Olsa <jolsa@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, X86 ML <x86@kernel.org>,
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	Andrii Nakryiko <andrii@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH] x86/ibt: make is_endbr() notrace
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On Thu, Sep 18, 2025 at 10:53:51AM -0700, Alexei Starovoitov wrote:

> > notrace don't help with kprobes in general, only with __fentry__ sites.
> 
> Are you sure ? Last time I checked "notrace" prevents kprobing
> anywhere in that function.

#define notrace                 __attribute__((__no_instrument_function__))

AFAICT that only inhibits the compiler from generating __fentry__ calls.

There is NOKPROBE_SYMBOL() to explicitly exclude kprobes from a symbol.

And we have noinstr, which along with a gazillion code-gen attributes
puts things in a .noinstr.text section and that section is also excluded
from kprobe placement.