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 E5CA2C433F5 for ; Wed, 13 Oct 2021 12:18:01 +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 A627460F23 for ; Wed, 13 Oct 2021 12:18:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A627460F23 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=B6VQ8hQiowsfk3F8mIEta305td4W83cDfNtuwao/Q4Y=; b=e1V4IpX5SHehgr KZPhGVQ1r3UjgZrJByEc9Ui1iTrcUT2RebbdBOfAXVdsL1sNBeBNdcpmYv4voZYN6qUFncCh745SV fPYN0fgcKRN/BfwVq4GEXZnPUmodI3qAsYl7EQOzBE4NAbJfzlIklV0M2LNPgkD6BDC1ZBRz6dZoM y+j0METmR3rLzGN3zg1n2cM0y0sVmqRAW6yJIyP8wo8sPkiXZxw2TCePnOFdACKZR/ncRJnS0DSBF wsqszCuu6d5iE3zLjCzLx4afRvlxMPS2QsyzdtliCopuFb2cz9YsNy8CjjjesVeidhZpRp2XUQMcV bS8XErGizXOW4rBseT8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1madAD-00GUfZ-Qt; Wed, 13 Oct 2021 12:15:18 +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 1mac0h-00G9v6-In 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 A037013D5; Wed, 13 Oct 2021 04:01:22 -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 6FA5C3F70D; Wed, 13 Oct 2021 04:01:20 -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 02/13] arm64: lib: __arch_copy_from_user(): fold fixups into body Date: Wed, 13 Oct 2021 12:00:48 +0100 Message-Id: <20211013110059.10324-3-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_040123_796855_28380838 X-CRM114-Status: GOOD ( 11.47 ) 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_copy_from_user() places its exception fixups in the `.fixup` section without any clear association with __arch_copy_from_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_copy_from_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_copy_from_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/copy_from_user.S | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S index 2cf999e41d30..f50ba67a73b4 100644 --- a/arch/arm64/lib/copy_from_user.S +++ b/arch/arm64/lib/copy_from_user.S @@ -60,11 +60,7 @@ SYM_FUNC_START(__arch_copy_from_user) #include "copy_template.S" mov x0, #0 // Nothing to copy ret -SYM_FUNC_END(__arch_copy_from_user) -EXPORT_SYMBOL(__arch_copy_from_user) - .section .fixup,"ax" - .align 2 9997: cmp dst, dstin b.ne 9998f // Before being absolutely sure we couldn't copy anything, try harder @@ -72,4 +68,5 @@ USER(9998f, ldtrb tmp1w, [srcin]) strb tmp1w, [dst], #1 9998: sub x0, end, dst // bytes not copied ret - .previous +SYM_FUNC_END(__arch_copy_from_user) +EXPORT_SYMBOL(__arch_copy_from_user) -- 2.11.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel