From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A0ED5C88E64 for ; Mon, 14 Sep 2026 09:27:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=UymK0l+wXKT8ZvqD5sSeBb2oMu8VqqgRu9qfNF5SylI=; b=Ma7UFH0Z3BQmNu J2k43zBOo8/2yG5M31Ttn09V5G0golF8oHs+E2APHQypXqYOzhivGqqUVud8rm0omOyKHFOALFQdi G6Bmf3Waq9TK/Z+Q+XQxLvNrLrU0MNS4siSJE1kMM6KpSVIjpzYxMSA0L9lOP3c2ToYmOdBlbl9iv 6jtBrT2tBPjJsGxp0TrkTMcBrHTLj+bheGwSt0W79SeMxDb4nGJdEPTc9Qqov06W3suZec9hxUTmU r6p6y8ni/WGPFp2ct8VrHk7alt4A/IRzo121wbj3yDP0cpkd31wOd2D2CnsHL1ntTOP7TdYqEr9Z0 2xUvRs4w96sSO1beh4gg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x62xt-00000002wsP-3JwD; Mon, 14 Sep 2026 09:27:06 +0000 Received: from out30-113.freemail.mail.aliyun.com ([115.124.30.113]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x62xr-00000002wpA-05Aw for linux-riscv@lists.infradead.org; Mon, 14 Sep 2026 09:27:04 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1789378021; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=jYjFQWHS7zv+XprgIgV3x6FJiEuRmhHyfb5LEr80eCs=; b=i8r8UpHA7n83OVKbEGQW69I7yiO3HbNaB53aua/mFu9SXmjZEEVo4DoHzvTomW+Tz6tW/irMUFLiaDCro+aKZVPhpHBa56Bm6WLXtPc1G51ffLoS83cWx81hVb+L6TForVLerHfCdN/jMytBzln1m7kTiP/NbQ6RjTIGGv0oHyM= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=xueshuai@linux.alibaba.com;NM=1;PH=DS;RN=34;SR=0;TI=SMTPD_---0XAuO-nk_1789378017; Received: from localhost.localdomain(mailfrom:xueshuai@linux.alibaba.com fp:SMTPD_---0XAuO-nk_1789378017 cluster:ay36) by smtp.aliyun-inc.com; Mon, 14 Sep 2026 17:26:58 +0800 From: Shuai Xue To: palmer@dabbelt.com, pjw@kernel.org, aou@eecs.berkeley.edu Cc: alex@ghiti.fr, linux-riscv@lists.infradead.org, oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, mark.rutland@arm.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, james.clark@linaro.org, jpoimboe@kernel.org, jikos@kernel.org, mbenes@suse.cz, pmladek@suse.com, joe.lawrence@redhat.com, shuah@kernel.org, mpdesouza@suse.com, oliver.yang@linux.alibaba.com, zhuo.song@linux.alibaba.com, xueshuai@linux.alibaba.com, jkchen@linux.alibaba.com, 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 v6 3/7] riscv: ftrace: always preserve s0 in dynamic ftrace register frame Date: Mon, 14 Sep 2026 17:26:44 +0800 Message-Id: <20260914092648.51254-4-xueshuai@linux.alibaba.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260914092648.51254-1-xueshuai@linux.alibaba.com> References: <20260914092648.51254-1-xueshuai@linux.alibaba.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260914_022703_368733_351ED8F3 X-CRM114-Status: UNSURE ( 7.47 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Wang Han 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 Assisted-by: Qoder:Qwen-3.8-MAX-Preview Signed-off-by: Wang Han Signed-off-by: Shuai Xue --- 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 082fe0b0e3c08..26c55fba8fec7 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) -- 2.39.3 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv