From patchwork Wed Nov 17 14:07:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 12692901 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29FB9C433EF for ; Wed, 17 Nov 2021 14:10:21 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id EA48960FF2 for ; Wed, 17 Nov 2021 14:10:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org EA48960FF2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org 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:MIME-Version:List-Subscribe:List-Help: List-Post:List-Archive:List-Unsubscribe:List-Id: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=mGle3ptGp8ebQi28ogJ9+b5sAw9PjpCaAJymy+AK+Pg=; b=aTULAyDmPKZGOE 70jE2D6+IGMx+Ibtq/7Txt8Yjq44TUva5I65DGhhKmb6cxoL3yswV6IWbEU8Qpu3RGH86J0LC0/XC TvwP+X538oBW2d/wg2fXZ6xSZGFg88qJjUK9CNz5/OGzVQURflDDcJ0jPPz2ogQNCOSx0t4Bl67Cw RaIKYKV8cQ55ZoU+EJGwx39tCq8IrpnkaMS9RRCySiCp6LPwQ2Zr+4Oeg38B2ZugmI7ExRXZtliWF RHClgSh1FoJpUD2QLUo4lOc8uQZSukEz8KZkaXRiEn5P5eDbQjuiYpiIxYsh/kwd5zwed1HcP1X8Z 959L6E5RfVWlYPlg/Y1Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mnLcK-0051gu-Oe; Wed, 17 Nov 2021 14:08:52 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mnLbY-0051Ny-8E for linux-arm-kernel@lists.infradead.org; Wed, 17 Nov 2021 14:08:05 +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 3C0C61396; Wed, 17 Nov 2021 06:08:03 -0800 (PST) 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 AD6FD3F70D; Wed, 17 Nov 2021 06:08:00 -0800 (PST) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: aou@eecs.berkeley.edu, borntraeger@de.ibm.com, bp@alien8.de, broonie@kernel.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, gor@linux.ibm.com, hca@linux.ibm.com, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com, mark.rutland@arm.com, mhiramat@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, palmer@dabbelt.com, paul.walmsley@sifive.com, peterz@infradead.org, rostedt@goodmis.org, tglx@linutronix.de, will@kernel.org Subject: [PATCH 4/9] arm64: Make perf_callchain_kernel() use arch_stack_walk() Date: Wed, 17 Nov 2021 14:07:32 +0000 Message-Id: <20211117140737.44420-5-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20211117140737.44420-1-mark.rutland@arm.com> References: <20211117140737.44420-1-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211117_060804_419930_278A4898 X-CRM114-Status: GOOD ( 12.52 ) 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: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: "Madhavan T. Venkataraman" To enable RELIABLE_STACKTRACE and LIVEPATCH on arm64, we need to substantially rework arm64's unwinding code. As part of this, we want to minimize the set of unwind interfaces we expose, and avoid open-coding of unwind logic outside of stacktrace.c. Currently perf_callchain_kernel() walks the stack of an interrupted context by calling start_backtrace() with the context's PC and FP, and iterating unwind steps using walk_stackframe(). This is functionally equivalent to calling arch_stack_walk() with the interrupted context's pt_regs, which will start with the PC and FP from the regs. Make perf_callchain_kernel() use arch_stack_walk(). This simplifies perf_callchain_kernel(), and in future will alow us to make walk_stackframe() private to stacktrace.c. At the same time, we update the callchain_trace() callback to check the return value of perf_callchain_store(), which indicates whether there is space for any further entries. When a non-zero value is returned, further calls will be ignored, and are redundant, so we can stop the unwind at this point. We also remove the stale and confusing comment for callchain_trace. There should be no functional change as a result of this patch. Signed-off-by: Madhavan T. Venkataraman Tested-by: Mark Rutland Reviewed-by: Mark Brown Reviewed-by: Mark Rutland [Mark: elaborate commit message, remove comment] Signed-off-by: Mark Rutland --- arch/arm64/kernel/perf_callchain.c | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c index 4a72c2727309..2160a53272b7 100644 --- a/arch/arm64/kernel/perf_callchain.c +++ b/arch/arm64/kernel/perf_callchain.c @@ -132,30 +132,21 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry, } } -/* - * Gets called by walk_stackframe() for every stackframe. This will be called - * whist unwinding the stackframe and is like a subroutine return so we use - * the PC. - */ static bool callchain_trace(void *data, unsigned long pc) { struct perf_callchain_entry_ctx *entry = data; - perf_callchain_store(entry, pc); - return true; + return perf_callchain_store(entry, pc) == 0; } void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs) { - struct stackframe frame; - if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) { /* We don't support guest os callchain now */ return; } - start_backtrace(&frame, regs->regs[29], regs->pc); - walk_stackframe(current, &frame, callchain_trace, entry); + arch_stack_walk(callchain_trace, entry, current, regs); } unsigned long perf_instruction_pointer(struct pt_regs *regs)