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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8840C433F5 for ; Wed, 13 Oct 2021 12:15:52 +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 AF63C610EA for ; Wed, 13 Oct 2021 12:15:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org AF63C610EA 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=xRRjn+PBnOrr09V9VW9AIeXMx3Q4D/r4mMrgNokuFN8=; b=AtsqA3r0lGyFr6 nHCxMMIOFO/zWjS/hP6oFadkJHajKojFPJzwfIVEd4FK3KuKPGOqpwJfTn6//x6jven/hYCtikhSZ Q55FGyux0oylkweZCelAMOKW+InrB7qzlT0rEa2GWnsIWtiHEfn9zEqILMKjKtS3R0aa5KDwX87x/ Aeqb2qy5sb7A2ZnnqJ8mjdkEM6sivJwP9gMCGaZJxMyiOdjis9sCgywrFfW5EI/WCaTj5r3a0jQY+ +/ma00LG2zfFh/G29RfkQK4sTiRRHVqpf40Sm7sw4Vy+gtdRvOG9Kj2rP62Ql4t0kvSR+1owFNL8E fTP4igNS3s57YfX7o6ow==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mad8N-00GU9Q-E8; Wed, 13 Oct 2021 12:13:24 +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 1mac0g-00G9uO-4B for linux-arm-kernel@lists.infradead.org; Wed, 13 Oct 2021 11:01:26 +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 974991063; Wed, 13 Oct 2021 04:01:19 -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 61EB23F70D; Wed, 13 Oct 2021 04:01:17 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: alexandru.elisei@arm.com, andrii@kernel.org, ardb@kernel.org, ast@kernel.org, broonie@kernel.org, catalin.marinas@arm.com, daniel@iogearbox.net, dvyukov@google.com, james.morse@arm.com, jean-philippe@linaro.org, jpoimboe@redhat.com, mark.rutland@arm.com, maz@kernel.org, peterz@infradead.org, robin.murphy@arm.com, suzuki.poulose@arm.com, will@kernel.org Subject: [PATCH 01/13] arm64: lib: __arch_clear_user(): fold fixups into body Date: Wed, 13 Oct 2021 12:00:47 +0100 Message-Id: <20211013110059.10324-2-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20211013110059.10324-1-mark.rutland@arm.com> References: <20211013110059.10324-1-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211013_040122_330503_77DF5CF5 X-CRM114-Status: GOOD ( 12.01 ) 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Like other functions, __arch_clear_user() places its exception fixups in the `.fixup` section without any clear association with __arch_clear_user() itself. If we backtrace the fixup code, it will be symbolized as an offset from the nearest prior symbol, which happens to be `__entry_tramp_text_end`. Further, since the PC adjustment for the fixup is akin to a direct branch rather than a function call, __arch_clear_user() itself will be missing from the backtrace. This is confusing and hinders debugging. In general this pattern will also be problematic for CONFIG_LIVEPATCH, since fixups often return to their associated function, but this isn't accurately captured in the stacktrace. To solve these issues for assembly functions, we must move fixups into the body of the functions themselves, after the usual fast-path returns. This patch does so for __arch_clear_user(). Inline assembly will be dealt with in subsequent patches. Other than the improved backtracing, there should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: James Morse Cc: Mark Brown Cc: Robin Murphy Cc: Will Deacon --- arch/arm64/lib/clear_user.S | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S index a7efb2ad2a1c..dac13df4a1ed 100644 --- a/arch/arm64/lib/clear_user.S +++ b/arch/arm64/lib/clear_user.S @@ -45,13 +45,10 @@ USER(9f, sttrh wzr, [x0]) USER(7f, sttrb wzr, [x2, #-1]) 5: mov x0, #0 ret -SYM_FUNC_END(__arch_clear_user) -EXPORT_SYMBOL(__arch_clear_user) - .section .fixup,"ax" - .align 2 7: sub x0, x2, #5 // Adjust for faulting on the final byte... 8: add x0, x0, #4 // ...or the second word of the 4-7 byte case 9: sub x0, x2, x0 ret - .previous +SYM_FUNC_END(__arch_clear_user) +EXPORT_SYMBOL(__arch_clear_user) -- 2.11.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel