From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out199-13.us.a.mail.aliyun.com (out199-13.us.a.mail.aliyun.com [47.90.199.13]) (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 D8EE33AE188; Mon, 29 Jun 2026 06:48:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=47.90.199.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782715706; cv=none; b=DYJRO4Gl8o9TkXNP6PvOiJ0ea4JDSWgFf/J8SoPHntOtJZNk9z0JGeVSDUBvjV0RKlam3tsB5XbiajwM6AeQhy0lPGR5A0/hrDHP68q9f+2Quep+xHDU7R2O78osymf8TLobh79QOaIzdoLisp9QBVy/Y5j9nEDM908knO3F6Xo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782715706; c=relaxed/simple; bh=S9PPBd03nshTXdebHu0IRlNHz4qa/HrTIvMxXIyLevQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=A0phZaABrFuQ2vyfkMFzFj5jj7RARkvACAPK7TnGpsWeHTZPkrXgskbT/JYvGg9Xut2NMv2Xvnn9jgTHjKFro9sZAJFVofjn2DKu2aTft2XYTmd+ETCDflBu6wf1P4S/tkq+RatFZYCnM01t1IbsQSor2f5yaSbkJ85O680QNzk= 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=RMnGm7bG; arc=none smtp.client-ip=47.90.199.13 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="RMnGm7bG" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1782715689; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=cs5txbx9bpKaRI7bmx5ga6+SdBKGKPqwgmoXTwT+GtE=; b=RMnGm7bGVVXeA52sHPH5YIYUBBBDtE6zrwfryltfVAt1PtVhGj0UefGc9IlY4gSyg3iQ2T1udaWTPKFqHDQxAe0EtD6Ic9nJfoJKeo6rAuJ8/ePC35kMOQL5QqsFeZdLKrZNHCfw+ANQZnnEpqtyfaIh4iVtImo5rksqyltPo+k= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037009110;MF=wanghan@linux.alibaba.com;NM=1;PH=DS;RN=34;SR=0;TI=SMTPD_---0X5nWtcO_1782715355; Received: from wanghan-Workstation..(mailfrom:wanghan@linux.alibaba.com fp:SMTPD_---0X5nWtcO_1782715355 cluster:ay36) by smtp.aliyun-inc.com; Mon, 29 Jun 2026 14:42:36 +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 v4 3/7] riscv: ftrace: always preserve s0 in dynamic ftrace register frame Date: Mon, 29 Jun 2026 14:42:24 +0800 Message-ID: <20260629064228.3195856-4-wanghan@linux.alibaba.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@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