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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 B3453C433E1 for ; Fri, 15 May 2020 17:28:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 942BD20758 for ; Fri, 15 May 2020 17:28:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589563692; bh=fLJmnHjaGKDfs+Gb3LVnn2aRUVteAb4UfTr5WAVaLiE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=h5zQ38rcWrKGMuMQN5WuqSsWE5Atv+byS5NpHmAqhFuYzXIBM/LytUKk7A6Nf1Axd T0XZDNho3ygvFuEwHfR0gBUMsz0YK5j/Kn3OsDkUEEQL7XBb2Td3TOYB7ww0ME47/f QVfOkaBNJQJM25RZpkBHs5s0s6l1QNrv8ohIfk9A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726639AbgEOR2L (ORCPT ); Fri, 15 May 2020 13:28:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:53088 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726023AbgEOR2J (ORCPT ); Fri, 15 May 2020 13:28:09 -0400 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 DF3E92073E; Fri, 15 May 2020 17:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589563688; bh=fLJmnHjaGKDfs+Gb3LVnn2aRUVteAb4UfTr5WAVaLiE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YUMdl8UVD1wbfLieayUNpca2emxYYKWi0iAXuBeyCak2VV0iNSLbcfw5GtTRdwo5l vzd4LIUFQNWi7JUqr2nb9ZCq8mQr0a/00VVMJBzmRtFd855hECkL4C6lSwGbEWPuqv K8AHLB7hqv4S5/iEUVX+vGGvRZhblP19B/Kx21II= From: Will Deacon To: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, Will Deacon , Sami Tolvanen , Kees Cook , Catalin Marinas , Mark Rutland , Jann Horn , Ard Biesheuvel , Peter Zijlstra , kernel-team@android.com Subject: [PATCH 1/6] arm64: scs: Store absolute SCS stack pointer value in thread_info Date: Fri, 15 May 2020 18:27:51 +0100 Message-Id: <20200515172756.27185-2-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200515172756.27185-1-will@kernel.org> References: <20200515172756.27185-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Storing the SCS information in thread_info as a {base,offset} pair introduces an additional load instruction on the ret-to-user path, since the SCS stack pointer in x18 has to be converted back to an offset by subtracting the base. Replace the offset with the absolute SCS stack pointer value instead and avoid the redundant load. Signed-off-by: Will Deacon --- arch/arm64/include/asm/scs.h | 9 ++++----- arch/arm64/include/asm/thread_info.h | 4 ++-- arch/arm64/kernel/asm-offsets.c | 2 +- include/linux/scs.h | 8 ++++---- kernel/scs.c | 3 +-- 5 files changed, 12 insertions(+), 14 deletions(-) diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h index 96549353b0cb..6b8cf4352fe3 100644 --- a/arch/arm64/include/asm/scs.h +++ b/arch/arm64/include/asm/scs.h @@ -4,16 +4,15 @@ #ifdef __ASSEMBLY__ +#include + #ifdef CONFIG_SHADOW_CALL_STACK .macro scs_load tsk, tmp - ldp x18, \tmp, [\tsk, #TSK_TI_SCS_BASE] - add x18, x18, \tmp + ldr x18, [\tsk, #TSK_TI_SCS_SP] .endm .macro scs_save tsk, tmp - ldr \tmp, [\tsk, #TSK_TI_SCS_BASE] - sub \tmp, x18, \tmp - str \tmp, [\tsk, #TSK_TI_SCS_OFFSET] + str x18, [\tsk, #TSK_TI_SCS_SP] .endm #else .macro scs_load tsk, tmp diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 9df79c0a4c43..6ea8b6a26ae9 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -43,7 +43,7 @@ struct thread_info { }; #ifdef CONFIG_SHADOW_CALL_STACK void *scs_base; - unsigned long scs_offset; + void *scs_sp; #endif }; @@ -107,7 +107,7 @@ void arch_release_task_struct(struct task_struct *tsk); #ifdef CONFIG_SHADOW_CALL_STACK #define INIT_SCS \ .scs_base = init_shadow_call_stack, \ - .scs_offset = 0, + .scs_sp = init_shadow_call_stack, #else #define INIT_SCS #endif diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index d7934250b68c..a098a45f63d8 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -36,7 +36,7 @@ int main(void) #endif #ifdef CONFIG_SHADOW_CALL_STACK DEFINE(TSK_TI_SCS_BASE, offsetof(struct task_struct, thread_info.scs_base)); - DEFINE(TSK_TI_SCS_OFFSET, offsetof(struct task_struct, thread_info.scs_offset)); + DEFINE(TSK_TI_SCS_SP, offsetof(struct task_struct, thread_info.scs_sp)); #endif DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); #ifdef CONFIG_STACKPROTECTOR diff --git a/include/linux/scs.h b/include/linux/scs.h index 3f3662621a27..0eb2485ef832 100644 --- a/include/linux/scs.h +++ b/include/linux/scs.h @@ -27,7 +27,7 @@ #define SCS_END_MAGIC (0x5f6UL + POISON_POINTER_DELTA) #define task_scs(tsk) (task_thread_info(tsk)->scs_base) -#define task_scs_offset(tsk) (task_thread_info(tsk)->scs_offset) +#define task_scs_sp(tsk) (task_thread_info(tsk)->scs_sp) void scs_init(void); int scs_prepare(struct task_struct *tsk, int node); @@ -39,7 +39,7 @@ static inline void scs_task_reset(struct task_struct *tsk) * Reset the shadow stack to the base address in case the task * is reused. */ - task_scs_offset(tsk) = 0; + task_scs_sp(tsk) = task_scs(tsk); } static inline unsigned long *__scs_magic(void *s) @@ -50,9 +50,9 @@ static inline unsigned long *__scs_magic(void *s) static inline bool scs_corrupted(struct task_struct *tsk) { unsigned long *magic = __scs_magic(task_scs(tsk)); + unsigned long sz = task_scs_sp(tsk) - task_scs(tsk); - return (task_scs_offset(tsk) >= SCS_SIZE - 1 || - READ_ONCE_NOCHECK(*magic) != SCS_END_MAGIC); + return sz >= SCS_SIZE - 1 || READ_ONCE_NOCHECK(*magic) != SCS_END_MAGIC; } #else /* CONFIG_SHADOW_CALL_STACK */ diff --git a/kernel/scs.c b/kernel/scs.c index 9389c28f0853..5ff8663e4a67 100644 --- a/kernel/scs.c +++ b/kernel/scs.c @@ -60,8 +60,7 @@ int scs_prepare(struct task_struct *tsk, int node) if (!s) return -ENOMEM; - task_scs(tsk) = s; - task_scs_offset(tsk) = 0; + task_scs(tsk) = task_scs_sp(tsk) = s; scs_account(tsk, 1); return 0; } -- 2.26.2.761.g0e0b3e54be-goog