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 X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3BBE8C433E0 for ; Wed, 20 May 2020 17:56:30 +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 D01D8204EF for ; Wed, 20 May 2020 17:56:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="V3+oYevA"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="AHe4SmCv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D01D8204EF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Fw5qVV272vxBJE0L31osW31EuQ16SJ0oMeCClP5LWT4=; b=V3+oYevAR7Q9M1 c8Vq5iig9jloT39RvdqwwbYR1frEee6PKHZFDK9N4roqHBojaiDDOQvhFZNkTzBc2us9xomqbc9CF FdIidh1siQSRMFUpyjcwDs7nkEWr1ZWXVwDqWxC25WOLPX/lztENYA+rFJd9Fwj9YX46zWV6eRd7n bIoPf2lmRiMReu8xphFuEsWVYcIyo/sBIV+K+i6MNjHYl/zscXQUE8A2Kt5EVRX4hBZuzSF6wT+Zv LRT5d/D6s6gE1psLfk1VYileuG/Fu8sSJUh8dl/sORBYT/zPg2CHHgRyEtH7kLPi25Lk2HwYIB1ZJ jMH1enpeF9jtXB7Onefw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbSx9-0003cc-98; Wed, 20 May 2020 17:56:27 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbSwV-0003Bv-ND for linux-arm-kernel@lists.infradead.org; Wed, 20 May 2020 17:55:49 +0000 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AB203207D3; Wed, 20 May 2020 17:55:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589997347; bh=pE3MkVZY471XRFLCctHScbvRxFLwzWHgK4om4WNmEL4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AHe4SmCvguYRi366RAl6CyvVITaWmcBbOWbCL+gpABg99unQaQgA4g0nwFot5npTG Xyhxl2YzFVBqYSGHPncd91NrmfN0SZ3NttKF42wVKOk9tKs4yud3x9+OWqRmwVnRbI Qs3Nv8T23s9htbdD0sq6kbb8Sscec3DNxlV07fNo= From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v3 1/2] arm64: vdso: Don't prefix sigreturn trampoline with a BTI C instruction Date: Wed, 20 May 2020 18:55:38 +0100 Message-Id: <20200520175539.28464-2-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200520175539.28464-1-will@kernel.org> References: <20200520175539.28464-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200520_105547_800821_F285FB32 X-CRM114-Status: GOOD ( 11.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Will Deacon , Tamas Zsoldos , Mark Brown , kernel-team@android.com, Dave Martin , Daniel Kiss Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org For better or worse, GDB relies on the exact instruction sequence in the VDSO sigreturn trampoline in order to unwind from signals correctly. Commit c91db232da48 ("arm64: vdso: Convert to modern assembler annotations") unfortunately added a BTI C instruction to the start of __kernel_rt_sigreturn, which breaks this check. Thankfully, it's also not required, since the trampoline is called from a RET instruction when returning from the signal handler Remove the unnecessary BTI C instruction from __kernel_rt_sigreturn, and do the same for the 32-bit VDSO as well for good measure. Cc: Daniel Kiss Cc: Tamas Zsoldos Reviewed-by: Dave Martin Reviewed-by: Mark Brown Fixes: c91db232da48 ("arm64: vdso: Convert to modern assembler annotations") Signed-off-by: Will Deacon --- arch/arm64/include/asm/linkage.h | 6 +++--- arch/arm64/kernel/vdso/sigreturn.S | 11 +++++++++-- arch/arm64/kernel/vdso32/sigreturn.S | 16 ++++++++-------- 3 files changed, 20 insertions(+), 13 deletions(-) diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h index b5a7998a6b2a..81fefd2a1d02 100644 --- a/arch/arm64/include/asm/linkage.h +++ b/arch/arm64/include/asm/linkage.h @@ -15,9 +15,9 @@ #define BTI_J hint 36 ; /* - * When using in-kernel BTI we need to ensure that assembly functions - * have suitable annotations. Override SYM_FUNC_START to insert a BTI - * landing pad at the start of everything. + * When using in-kernel BTI we need to ensure that PCS-conformant assembly + * functions have suitable annotations. Override SYM_FUNC_START to insert + * a BTI landing pad at the start of everything. */ #define SYM_FUNC_START(name) \ SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN) \ diff --git a/arch/arm64/kernel/vdso/sigreturn.S b/arch/arm64/kernel/vdso/sigreturn.S index 3fb13b81f780..0c921130002a 100644 --- a/arch/arm64/kernel/vdso/sigreturn.S +++ b/arch/arm64/kernel/vdso/sigreturn.S @@ -15,7 +15,14 @@ .text nop -SYM_FUNC_START(__kernel_rt_sigreturn) +/* + * GDB relies on being able to identify the sigreturn instruction sequence to + * unwind from signal handlers. We cannot, therefore, use SYM_FUNC_START() + * here, as it will emit a BTI C instruction and break the unwinder. Thankfully, + * this function is only ever called from a RET and so omitting the landing pad + * is perfectly fine. + */ +SYM_CODE_START(__kernel_rt_sigreturn) .cfi_startproc .cfi_signal_frame .cfi_def_cfa x29, 0 @@ -24,6 +31,6 @@ SYM_FUNC_START(__kernel_rt_sigreturn) mov x8, #__NR_rt_sigreturn svc #0 .cfi_endproc -SYM_FUNC_END(__kernel_rt_sigreturn) +SYM_CODE_END(__kernel_rt_sigreturn) emit_aarch64_feature_1_and diff --git a/arch/arm64/kernel/vdso32/sigreturn.S b/arch/arm64/kernel/vdso32/sigreturn.S index 620524969696..b36d4e2267a3 100644 --- a/arch/arm64/kernel/vdso32/sigreturn.S +++ b/arch/arm64/kernel/vdso32/sigreturn.S @@ -17,39 +17,39 @@ .save {r0-r15} .pad #COMPAT_SIGFRAME_REGS_OFFSET nop -SYM_FUNC_START(__kernel_sigreturn_arm) +SYM_CODE_START(__kernel_sigreturn_arm) mov r7, #__NR_compat_sigreturn svc #0 .fnend -SYM_FUNC_END(__kernel_sigreturn_arm) +SYM_CODE_END(__kernel_sigreturn_arm) .fnstart .save {r0-r15} .pad #COMPAT_RT_SIGFRAME_REGS_OFFSET nop -SYM_FUNC_START(__kernel_rt_sigreturn_arm) +SYM_CODE_START(__kernel_rt_sigreturn_arm) mov r7, #__NR_compat_rt_sigreturn svc #0 .fnend -SYM_FUNC_END(__kernel_rt_sigreturn_arm) +SYM_CODE_END(__kernel_rt_sigreturn_arm) .thumb .fnstart .save {r0-r15} .pad #COMPAT_SIGFRAME_REGS_OFFSET nop -SYM_FUNC_START(__kernel_sigreturn_thumb) +SYM_CODE_START(__kernel_sigreturn_thumb) mov r7, #__NR_compat_sigreturn svc #0 .fnend -SYM_FUNC_END(__kernel_sigreturn_thumb) +SYM_CODE_END(__kernel_sigreturn_thumb) .fnstart .save {r0-r15} .pad #COMPAT_RT_SIGFRAME_REGS_OFFSET nop -SYM_FUNC_START(__kernel_rt_sigreturn_thumb) +SYM_CODE_START(__kernel_rt_sigreturn_thumb) mov r7, #__NR_compat_rt_sigreturn svc #0 .fnend -SYM_FUNC_END(__kernel_rt_sigreturn_thumb) +SYM_CODE_END(__kernel_rt_sigreturn_thumb) -- 2.26.2.761.g0e0b3e54be-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel