From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 45887524B0; Mon, 6 Jan 2025 22:42:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736203332; cv=none; b=CObfgEmWVk2RTgJK0lbURYxxqWCCta/WmAQdFG8nsHGP1uaInYY5jGSI1HBQEcawYXj99RBTxa2dm4DleagNIc8l3ulXKy8+WwvQyXZI7l8pt5puWkMyO7zrLziYHfZOBndIb/eXTyusM28Tr5yxa9mW40WEUyFTSwc4fb9jLjQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736203332; c=relaxed/simple; bh=T58Y1wysAHdymYcFdZzV+21Kmdl0+ykGjRQW2kpOB80=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=lksYQZyOmZ/kBo5nKf9TjshRFSkYRFPI6ROPVPCcQFjWOoCWWn04jThjwnE9HCXa7lKmf55lPVq3q1mTaK5Ke4D/00+VeEkq0PNR4WVHTpGLc2QUe0N5gONVAQMyntfk/2yVeMy3mkK5D+xGv60kZbQTpyhrUmH3bMyI5FmXcSg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZZF4ELhh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZZF4ELhh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70533C4CEDD; Mon, 6 Jan 2025 22:42:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736203331; bh=T58Y1wysAHdymYcFdZzV+21Kmdl0+ykGjRQW2kpOB80=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ZZF4ELhhJ3GiaeQgxVBOCi6nsGFivEBR4S6ATBK1hMnNb17EPgKLBz4grEv/xZn32 wuGgvrsEjOQrPYo9RzyfoGY69RSebs/gLMXSOOdx/5UBJOT6KPRzS5CgdQnkKevzqf jLlfimDqOXzDb0EPitv/QCDPRCQd7XoPgp16CQve9G4vOXTkliSEYJ2R+Y2Bv3WOOF SN+mSldEZ11zbSwz6TRWN+bQdLpHGHX5B//hS5ZmCyuZnAe3X1s9mD1cNPzB8U4PAg LzHyctQZfmPOJjJpqYWNAHEgHGG9tHSm0q4A+ICPA74NktR6TCkEyz5WZIxY/765ge 6tZ0J+47+06Fg== Date: Tue, 7 Jan 2025 07:42:05 +0900 From: Masami Hiramatsu (Google) To: Jiri Olsa Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Masami Hiramatsu Subject: Re: [PATCH bpf-next 1/2] bpf: Return error for missed kprobe multi bpf program execution Message-Id: <20250107074205.cb65bd26e29343c4a2f5084e@kernel.org> In-Reply-To: <20250106175048.1443905-1-jolsa@kernel.org> References: <20250106175048.1443905-1-jolsa@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 6 Jan 2025 18:50:47 +0100 Jiri Olsa wrote: > When kprobe multi bpf program can't be executed due to recursion check, > we currently return 0 (success) to fprobe layer where it's ignored for > standard kprobe multi probes. > > For kprobe session the success return value will make fprobe layer to > install return probe and try to execute it as well. > > But the return session probe should not get executed, because the entry > part did not run. FWIW the return probe bpf program most likely won't get > executed, because its recursion check will likely fail as well, but we > don't need to run it in the first place.. also we can make this clear > and obvious. Yeah, that's right. > > It also affects missed counts for kprobe session program execution, which > are now doubled (extra count for not executed return probe). > > Signed-off-by: Jiri Olsa Looks good to me. Acked-by: Masami Hiramatsu (Google) Thanks! > --- > kernel/trace/bpf_trace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index 48db147c6c7d..1f3d4b72a3f2 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -2797,7 +2797,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, > > if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) { > bpf_prog_inc_misses_counter(link->link.prog); > - err = 0; > + err = 1; > goto out; > } > > -- > 2.47.0 > -- Masami Hiramatsu (Google)