From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (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 6ABC7448D0F; Tue, 4 Aug 2026 10:36:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785839815; cv=none; b=VpHrFNPmhTf1Iu4HHPubrWCNSvZFogmo8keEMex5WFwolfc6ED1loMEG8pzcTz7OaThVICiCAKbI5AbsVTk1l7pB4CFzjI1sh1xAcD0tPl0GJZYXT+ucSByWi8J+d51LmcYMTPNWENdyewPheddybF2cn/JsA/ADgMDmHw8ERkA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785839815; c=relaxed/simple; bh=8gUFQfhcKCWl+SQPGfcUr9oaqzBY5sgciJASbO4/7I0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rC0CxoSLkwZLm4LZEyxDRJuU0/DjIdIHn/Gc5vzsRTBY57k/jb/cb02wldgDD+84JG75uE47HQ3y11x9dJ9pgqDdrjWOxTmg7Eq8uDBvtRKHPIr2K9/ZDcd3q6yHO8TdCppvO8cIJyhwS1AnD6lqOWxKrBeWuuflvAkwfPgrLu8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=HNgYoSzi; arc=none smtp.client-ip=115.124.30.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="HNgYoSzi" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1785839807; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=m8pnWfAyIRGdD3GPjP0E4M3+tZYcgxHxMKpoX0zv1+E=; b=HNgYoSzihfGlq6wTdD/gizC8bZc3oz/xHFF7IyAm/aS3OFsQNWNoS90rBFmq9ej4xmLwQ7QLn89hpGqPJon/99H/uIzH00BsP2i5W14+YSGosRPS3TbdHJqifNbFTRM8T7AiCPL1jD7h7atynDgrZamoewATN5+ox0WyIl/ruU0= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R211e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037026112;MF=wanghan@linux.alibaba.com;NM=1;PH=DS;RN=34;SR=0;TI=SMTPD_---0X8NlqYy_1785839800; Received: from wanghan-Workstation..(mailfrom:wanghan@linux.alibaba.com fp:SMTPD_---0X8NlqYy_1785839800 cluster:ay36) by smtp.aliyun-inc.com; Tue, 04 Aug 2026 18:36:45 +0800 From: Wang Han To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Alexandre Ghiti , linux-riscv@lists.infradead.org, Oleg Nesterov , Steven Rostedt , Masami Hiramatsu , Mark Rutland , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , oliver.yang@linux.alibaba.com, xueshuai@linux.alibaba.com, zhuo.song@linux.alibaba.com, jkchen@linux.alibaba.com, Marcos Paulo de Souza , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, live-patching@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v5 2/7] riscv: stacktrace: disable KASAN and KCOV instrumentation for stacktrace.o Date: Tue, 4 Aug 2026 18:36:21 +0800 Message-ID: <20260804103626.2803112-3-wanghan@linux.alibaba.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260804103626.2803112-1-wanghan@linux.alibaba.com> References: <20260804103626.2803112-1-wanghan@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit KASAN records stack traces for every alloc/free, which means it walks the unwinder very frequently. Instrumenting the stack trace collection code itself adds substantial overhead and makes the traces themselves noisier. KCOV instruments every basic-block edge. The unwinder is a hot path, especially with KASAN enabled, so KCOV instrumentation has the same kind of cost and noise problem here. Mark stacktrace.o as not KASAN- or KCOV-instrumented, matching the x86 treatment of its stack unwinding code. RISC-V keeps the relevant unwinder code in stacktrace.o, so a single translation-unit annotation covers the equivalent scope. This is a prerequisite preference for the upcoming reliable unwinder, but the change is valid on its own. Signed-off-by: Wang Han --- arch/riscv/kernel/Makefile | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index cabb99cadfb6..c565a72a36f3 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -44,6 +44,12 @@ CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_sbi_ecall.o = $(CC_FLAGS_FTRACE) endif +# When KASAN is enabled, a stack trace is recorded for every alloc/free, which +# can significantly impact performance. Avoid instrumenting the stack trace +# collection code to minimize this impact. +KASAN_SANITIZE_stacktrace.o := n +KCOV_INSTRUMENT_stacktrace.o := n + always-$(KBUILD_BUILTIN) += vmlinux.lds obj-y += head.o -- 2.43.0