From patchwork Thu Oct 17 09:25:36 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 13839716 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 752AED21269 for ; Thu, 17 Oct 2024 09:44:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=7LJ+YLf0BwqUkC0mTf7O5hNS0S8STTI1qDzjKylgYXg=; b=WofBh5rSq9hQ+azY4kpcSj6SSJ TNth0UOQpdV2w3qQe21n0eY++2bBAxZTI6ARdaTTHy9Ojft0prE3uvtxkzwbpYPC3lDGq647FJuWC GAEqk0rMATsnh6GL4DnePcNXy+BQ6SS3hg+EaJmXZxLF13XxNiOQG710N0CzVEbQx5k9SkEGUmKW3 ixGsBxhvLjG2i8LGDIolY0Q9mvfZW5tOd9FUgGa423z6r7r0ORc+F4Ptm+KjO5VacWKubEXxoDLXJ jTfKiVlmR+SimdQj5GjlBqVojHvxZOOHaRaKefm8O/XlDzL0TaTFJowHbxIVkkzbuFhWWM8ltud/D mzKa1c/Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t1N3k-0000000EOJy-2KtY; Thu, 17 Oct 2024 09:44:44 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t1Mlk-0000000EKjQ-03n4 for linux-arm-kernel@lists.infradead.org; Thu, 17 Oct 2024 09:26:10 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 40FB4FEC; Thu, 17 Oct 2024 02:26:37 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 901623F528; Thu, 17 Oct 2024 02:26:05 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: ardb@kernel.org, broonie@kernel.org, catalin.marinas@arm.com, jpoimboe@kernel.org, kaleshsingh@google.com, madvenka@linux.microsoft.com, mark.rutland@arm.com, maz@kernel.org, mbenes@suse.cz, puranjay12@gmail.com, will@kernel.org Subject: [PATCH v2 08/10] arm64: stacktrace: report recovered PCs Date: Thu, 17 Oct 2024 10:25:36 +0100 Message-Id: <20241017092538.1859841-9-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20241017092538.1859841-1-mark.rutland@arm.com> References: <20241017092538.1859841-1-mark.rutland@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241017_022608_162158_219BC4CF X-CRM114-Status: GOOD ( 16.26 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org When analysing a stacktrace it can be useful to know whether an unwound PC has been rewritten by fgraph or kretprobes, as in some situations these may be suspect or be known to be unreliable. This patch adds flags to track when an unwind entry has recovered the PC from fgraph and/or kretprobes, and updates dump_backtrace() to log when this is the case. The flags recorded are: "F" - the PC was recovered from fgraph "K" - the PC was recovered from kretprobes These flags are recorded and logged in addition to the original source of the unwound PC. For example, with the ftrace_graph profiler enabled globally, and kretprobes installed on generic_handle_domain_irq() and do_interrupt_handler(), a backtrace triggered by magic-sysrq + L reports: | Call trace: | show_stack+0x20/0x40 (CF) | dump_stack_lvl+0x60/0x80 (F) | dump_stack+0x18/0x28 | nmi_cpu_backtrace+0xfc/0x140 | nmi_trigger_cpumask_backtrace+0x1c8/0x200 | arch_trigger_cpumask_backtrace+0x20/0x40 | sysrq_handle_showallcpus+0x24/0x38 (F) | __handle_sysrq+0xa8/0x1b0 (F) | handle_sysrq+0x38/0x50 (F) | pl011_int+0x460/0x5a8 (F) | __handle_irq_event_percpu+0x60/0x220 (F) | handle_irq_event+0x54/0xc0 (F) | handle_fasteoi_irq+0xa8/0x1d0 (F) | generic_handle_domain_irq+0x34/0x58 (F) | gic_handle_irq+0x54/0x140 (FK) | call_on_irq_stack+0x24/0x58 (F) | do_interrupt_handler+0x88/0xa0 | el1_interrupt+0x34/0x68 (FK) | el1h_64_irq_handler+0x18/0x28 | el1h_64_irq+0x64/0x68 | default_idle_call+0x34/0x180 | do_idle+0x204/0x268 | cpu_startup_entry+0x40/0x50 (F) | rest_init+0xe4/0xf0 | start_kernel+0x744/0x750 | __primary_switched+0x80/0x90 Note that as these flags are reported next to the recovered PC value, they appear on the callers of instrumented functions. For example gic_handle_irq() has a "K" marker because generic_handle_domain_irq() was instrumented with kretprobes and had its return address rewritten. Signed-off-by: Mark Rutland Reviewed-by: Mark Brown Reviewed-by: Miroslav Benes Reviewed-by: Puranjay Mohan Cc: Ard Biesheuvel Cc: Josh Poimboeuf Cc: Kalesh Singh Cc: Madhavan T. Venkataraman Cc: Marc Zyngier Cc: Will Deacon --- arch/arm64/kernel/stacktrace.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 83ab37e13159e..f8e231683dad9 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -28,6 +28,14 @@ enum kunwind_source { KUNWIND_SOURCE_REGS_PC, }; +union unwind_flags { + unsigned long all; + struct { + unsigned long fgraph : 1, + kretprobe : 1; + }; +}; + /* * Kernel unwind state * @@ -46,6 +54,7 @@ struct kunwind_state { struct llist_node *kr_cur; #endif enum kunwind_source source; + union unwind_flags flags; }; static __always_inline void @@ -55,6 +64,7 @@ kunwind_init(struct kunwind_state *state, unwind_init_common(&state->common); state->task = task; state->source = KUNWIND_SOURCE_UNKNOWN; + state->flags.all = 0; } /* @@ -127,6 +137,7 @@ kunwind_recover_return_address(struct kunwind_state *state) if (WARN_ON_ONCE(state->common.pc == orig_pc)) return -EINVAL; state->common.pc = orig_pc; + state->flags.fgraph = 1; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ @@ -137,6 +148,7 @@ kunwind_recover_return_address(struct kunwind_state *state) (void *)state->common.fp, &state->kr_cur); state->common.pc = orig_pc; + state->flags.kretprobe = 1; } #endif /* CONFIG_KRETPROBES */ @@ -157,6 +169,8 @@ kunwind_next(struct kunwind_state *state) unsigned long fp = state->common.fp; int err; + state->flags.all = 0; + /* Final frame; nothing to unwind */ if (fp == (unsigned long)&task_pt_regs(tsk)->stackframe) return -ENOENT; @@ -331,12 +345,18 @@ static const char *state_source_string(const struct kunwind_state *state) static bool dump_backtrace_entry(const struct kunwind_state *state, void *arg) { const char *source = state_source_string(state); + union unwind_flags flags = state->flags; + bool has_info = source || flags.all; char *loglvl = arg; - printk("%s %pSb%s%s%s\n", loglvl, + + printk("%s %pSb%s%s%s%s%s\n", loglvl, (void *)state->common.pc, - source ? " (" : "", + has_info ? " (" : "", source ? source : "", - source ? ")" : ""); + flags.fgraph ? "F" : "", + flags.kretprobe ? "K" : "", + has_info ? ")" : ""); + return true; }