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 AEC09C433FE for ; Tue, 19 Oct 2021 16:04:29 +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 800B060EE3 for ; Tue, 19 Oct 2021 16:04:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 800B060EE3 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=1NhS+ku3uc5ep9g2+YOr7ZNl9+tOaaWe1NgHietzi+o=; b=ve2sbPnpCbCu8j HuA9ZYa/k++Jt+FLswGBX3DHuioyyXPv7Uf8iz8g8rUSUfh6NBZqOdzUd3j82qVveHSpOkTs6gxVn v74lNZs7OggkunnhZ2CiSZLw8yyrvPs6u+ksvcZN2I81eXLculibIZWwnzpXZm9uXptcQYGOFK2sX qhRGnN7oc7Y7nH6lSO9XzyEfTlOSMU2xQ7MOqVAOTqhbIIg3NUBVbNcg7csSyNU4AHXNqI/XddV3L 2Yp/yfk8pntJKXlpp2BL7SKCOvI2Vfy7wKwRVzgqm7x9RYg5fxcgXve2SJL0ADciL80zr3SFDhT9v W3CXkl3Dnry+Ai+Sa6KQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mcra0-001nSh-JK; Tue, 19 Oct 2021 16:03:08 +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 1mcrZW-001nIw-Vz for linux-arm-kernel@lists.infradead.org; Tue, 19 Oct 2021 16:02:41 +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 2A72311FB; Tue, 19 Oct 2021 09:02:38 -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 EC8BA3F694; Tue, 19 Oct 2021 09:02:35 -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 v2 03/13] arm64: lib: __arch_copy_to_user(): fold fixups into body Date: Tue, 19 Oct 2021 17:02:09 +0100 Message-Id: <20211019160219.5202-4-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20211019160219.5202-1-mark.rutland@arm.com> References: <20211019160219.5202-1-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211019_090239_096372_5A4635DA X-CRM114-Status: GOOD ( 11.81 ) 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_to_user() places its exception fixups in the `.fixup` section without any clear association with __arch_copy_to_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_to_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_to_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 Acked-by: Robin Murphy Reviewed-by: Ard Biesheuvel Cc: Catalin Marinas Cc: James Morse Cc: Mark Brown Cc: Will Deacon --- arch/arm64/lib/copy_to_user.S | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S index 9f380eecf653..802231772608 100644 --- a/arch/arm64/lib/copy_to_user.S +++ b/arch/arm64/lib/copy_to_user.S @@ -59,11 +59,8 @@ SYM_FUNC_START(__arch_copy_to_user) #include "copy_template.S" mov x0, #0 ret -SYM_FUNC_END(__arch_copy_to_user) -EXPORT_SYMBOL(__arch_copy_to_user) - .section .fixup,"ax" - .align 2 + // Exception fixups 9997: cmp dst, dstin b.ne 9998f // Before being absolutely sure we couldn't copy anything, try harder @@ -72,4 +69,5 @@ USER(9998f, sttrb tmp1w, [dst]) add dst, dst, #1 9998: sub x0, end, dst // bytes not copied ret - .previous +SYM_FUNC_END(__arch_copy_to_user) +EXPORT_SYMBOL(__arch_copy_to_user) -- 2.11.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel