From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) (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 2571C449EB2; Tue, 4 Aug 2026 10:36:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.98 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785839818; cv=none; b=Q5UfS4Tk6BopciyV/vvINxAX9O5oe2IboF7/LUn3FrNEyPeC93Wq5YFy1CNdQk4AuGiFCe03GxFBH8n7XUeWIaZ2W93ifGNi9ZRMclL1jy/jVc1XPeSSkzOlGUtmIMgqVgW3sVRHyQ3fBQpD1gMDl62Ke3flFKDRFm9VuJNn6AM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785839818; c=relaxed/simple; bh=S9PPBd03nshTXdebHu0IRlNHz4qa/HrTIvMxXIyLevQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tuz6Ywhru8WhNGBW0+FmeyAqgvm4dn5FbpVaYVD8I5XGjbDr9XUQAwDkxb/cADWS0l2jJSAl+mUzNnyjV71HPmLrxXDSXQxMxLUnl4/klOnqBzFE/1m/9+pdy5vUHkL51pfGcvFm1HnPyP/6t4WJ1h5zZaQc6/L6X+6S2e0YIZ0= 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=oKtJhQAt; arc=none smtp.client-ip=115.124.30.98 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="oKtJhQAt" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1785839810; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=cs5txbx9bpKaRI7bmx5ga6+SdBKGKPqwgmoXTwT+GtE=; b=oKtJhQAtmA+R8nrXmu143oKEEuBbtU+NRbzwqXPiNkJUfd8+0EdGIQu4/hUJ2EtH7Fo/mKEpuOcMS6pTG1jELEKtTj9dFF71KEPeWH/lFxXQd6Fg9SWP2Mcw/X1+ITSxIYRuDsiEuAUD0n5k8Fn1lhya7tdckWXPYqoIolcaFDc= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R471e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam011083073210;MF=wanghan@linux.alibaba.com;NM=1;PH=DS;RN=34;SR=0;TI=SMTPD_---0X8NlqaR_1785839806; Received: from wanghan-Workstation..(mailfrom:wanghan@linux.alibaba.com fp:SMTPD_---0X8NlqaR_1785839806 cluster:ay36) by smtp.aliyun-inc.com; Tue, 04 Aug 2026 18:36:48 +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 3/7] riscv: ftrace: always preserve s0 in dynamic ftrace register frame Date: Tue, 4 Aug 2026 18:36:22 +0800 Message-ID: <20260804103626.2803112-4-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 struct __arch_ftrace_regs declares s0 unconditionally, and both ftrace_regs_get_frame_pointer() and ftrace_partial_regs() read it unconditionally. But the SAVE_ABI_REGS / RESTORE_ABI_REGS macros in mcount-dyn.S only stored s0 under HAVE_FUNCTION_GRAPH_FP_TEST (CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_FRAME_POINTER). With CONFIG_FRAME_POINTER=n the slot held whatever was on the stack before, so any callback going through ftrace_partial_regs() saw a garbage regs->s0. RISC-V kernels default to FRAME_POINTER=y, which is why this has not bitten in practice. Save and restore s0 unconditionally in the dynamic ftrace ABI register frame. This fixes the latent garbage-s0 case, brings the dynamic ftrace path in line with the static _mcount path (mcount.S SAVE_ABI_STATE already saves s0 unconditionally), and matches the frame layout already documented in the comment above SAVE_ABI_REGS. It is also a prerequisite for the upcoming reliable unwinder, which reads ftrace_regs_get_frame_pointer(fregs) directly. The cost is one extra REG_S/REG_L pair per traced call, negligible compared to the overall ftrace cost; the existing FREGS_SIZE_ON_STACK already reserved the slot, so no extra stack space is used. Reviewed-by: Shuai Xue Signed-off-by: Wang Han --- arch/riscv/kernel/mcount-dyn.S | 4 ---- 1 file changed, 4 deletions(-) diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S index 082fe0b0e3c0..26c55fba8fec 100644 --- a/arch/riscv/kernel/mcount-dyn.S +++ b/arch/riscv/kernel/mcount-dyn.S @@ -85,9 +85,7 @@ addi sp, sp, -FREGS_SIZE_ON_STACK REG_S t0, FREGS_EPC(sp) REG_S x1, FREGS_RA(sp) -#ifdef HAVE_FUNCTION_GRAPH_FP_TEST REG_S x8, FREGS_S0(sp) -#endif REG_S x6, FREGS_T1(sp) #ifdef CONFIG_CC_IS_CLANG REG_S x7, FREGS_T2(sp) @@ -113,9 +111,7 @@ .macro RESTORE_ABI_REGS REG_L t0, FREGS_EPC(sp) REG_L x1, FREGS_RA(sp) -#ifdef HAVE_FUNCTION_GRAPH_FP_TEST REG_L x8, FREGS_S0(sp) -#endif REG_L x6, FREGS_T1(sp) #ifdef CONFIG_CC_IS_CLANG REG_L x7, FREGS_T2(sp) -- 2.43.0