From nobody Sun Feb 8 13:39:25 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77F12EB64DA for ; Fri, 16 Jun 2023 19:17:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345421AbjFPTRy (ORCPT ); Fri, 16 Jun 2023 15:17:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345881AbjFPTRB (ORCPT ); Fri, 16 Jun 2023 15:17:01 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44DCA35B0; Fri, 16 Jun 2023 12:16:59 -0700 (PDT) Date: Fri, 16 Jun 2023 19:16:57 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686943018; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=8XuJ6YuRqUzwOTlhaknw+WawfU0LUst7NDEOUNRMRjQ=; b=QX1jU4I4q0ubCgR1EEFwJZiv6sn/FAHXRSuPdnlmhJL/QeAb0EJCCKwqCk+fWNkiGugpJG hC5JrUj7St6/Mt1LgbbBKY3+wCmFYnI6MHtQb0hiw/WyjBcf8bLuaEJgVCaorLYX7sJI8w dZQNBvpbVhn0p3qSbMYny1aoeST1D3vN3oKca9EkHQfxYekzjivPTusKmfxYJpDaLvpvX3 uK1Sx3bonAJquD0nX/56YLhxQ5F0faXDJ5S2+TyDuOS/7YpFWN7pDsJDTjsHM6HRzWK6vZ 2dqxLCymXnCE0GVvbCB7OGAh/N3NooOkYwVDCgcQMkw0jxNTYrmQ3S4mawrO5g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686943018; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=8XuJ6YuRqUzwOTlhaknw+WawfU0LUst7NDEOUNRMRjQ=; b=2BcVps5In8mF16QXWn7ZxVOWatpdwxi+AQC1P3zdD4xG6JACQ1ClgWm09omlsDUAkQo7Yo mKQr/Rpqqmwg/hBQ== From: "tip-bot2 for Rick Edgecombe" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/shstk] x86: Introduce userspace API for shadow stack Cc: "Kirill A. Shutemov" , Rick Edgecombe , Dave Hansen , "Borislav Petkov (AMD)" , Kees Cook , "Mike Rapoport (IBM)" , Pengfei Xu , John Allen , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <168694301742.404.5197173232109177026.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/shstk branch of tip: Commit-ID: c4610d713f17879a2f3d70a72f793557489fa2d4 Gitweb: https://git.kernel.org/tip/c4610d713f17879a2f3d70a72f7935574= 89fa2d4 Author: Rick Edgecombe AuthorDate: Mon, 12 Jun 2023 17:10:52 -07:00 Committer: Dave Hansen CommitterDate: Thu, 15 Jun 2023 16:31:34 -07:00 x86: Introduce userspace API for shadow stack Add three new arch_prctl() handles: - ARCH_SHSTK_ENABLE/DISABLE enables or disables the specified feature. Returns 0 on success or a negative value on error. - ARCH_SHSTK_LOCK prevents future disabling or enabling of the specified feature. Returns 0 on success or a negative value on error. The features are handled per-thread and inherited over fork(2)/clone(2), but reset on exec(). Co-developed-by: Kirill A. Shutemov Signed-off-by: Kirill A. Shutemov Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Kees Cook Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook Link: https://lore.kernel.org/all/20230613001108.3040476-27-rick.p.edgecomb= e%40intel.com --- arch/x86/include/asm/processor.h | 6 ++++- arch/x86/include/asm/shstk.h | 21 ++++++++++++++- arch/x86/include/uapi/asm/prctl.h | 6 ++++- arch/x86/kernel/Makefile | 2 +- arch/x86/kernel/process_64.c | 6 ++++- arch/x86/kernel/shstk.c | 44 ++++++++++++++++++++++++++++++- 6 files changed, 85 insertions(+) create mode 100644 arch/x86/include/asm/shstk.h create mode 100644 arch/x86/kernel/shstk.c diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/proces= sor.h index a1e4fa5..407d555 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -28,6 +28,7 @@ struct vm86; #include #include #include +#include =20 #include #include @@ -475,6 +476,11 @@ struct thread_struct { */ u32 pkru; =20 +#ifdef CONFIG_X86_USER_SHADOW_STACK + unsigned long features; + unsigned long features_locked; +#endif + /* Floating point and extended processor state */ struct fpu fpu; /* diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h new file mode 100644 index 0000000..ec75380 --- /dev/null +++ b/arch/x86/include/asm/shstk.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_SHSTK_H +#define _ASM_X86_SHSTK_H + +#ifndef __ASSEMBLY__ +#include + +struct task_struct; + +#ifdef CONFIG_X86_USER_SHADOW_STACK +long shstk_prctl(struct task_struct *task, int option, unsigned long featu= res); +void reset_thread_features(void); +#else +static inline long shstk_prctl(struct task_struct *task, int option, + unsigned long arg2) { return -EINVAL; } +static inline void reset_thread_features(void) {} +#endif /* CONFIG_X86_USER_SHADOW_STACK */ + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_X86_SHSTK_H */ diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/= prctl.h index e8d7ebb..1cd44ec 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -23,9 +23,15 @@ #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 =20 +/* Don't use 0x3001-0x3004 because of old glibcs */ + #define ARCH_GET_UNTAG_MASK 0x4001 #define ARCH_ENABLE_TAGGED_ADDR 0x4002 #define ARCH_GET_MAX_TAG_BITS 0x4003 #define ARCH_FORCE_TAGGED_SVA 0x4004 =20 +#define ARCH_SHSTK_ENABLE 0x5001 +#define ARCH_SHSTK_DISABLE 0x5002 +#define ARCH_SHSTK_LOCK 0x5003 + #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index abee056..6b6bf47 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -147,6 +147,8 @@ obj-$(CONFIG_CALL_THUNKS) +=3D callthunks.o =20 obj-$(CONFIG_X86_CET) +=3D cet.o =20 +obj-$(CONFIG_X86_USER_SHADOW_STACK) +=3D shstk.o + ### # 64 bit specific files ifeq ($(CONFIG_X86_64),y) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 3d181c1..0f89aa0 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -515,6 +515,8 @@ start_thread_common(struct pt_regs *regs, unsigned long= new_ip, load_gs_index(__USER_DS); } =20 + reset_thread_features(); + loadsegment(fs, 0); loadsegment(es, _ds); loadsegment(ds, _ds); @@ -894,6 +896,10 @@ long do_arch_prctl_64(struct task_struct *task, int op= tion, unsigned long arg2) else return put_user(LAM_U57_BITS, (unsigned long __user *)arg2); #endif + case ARCH_SHSTK_ENABLE: + case ARCH_SHSTK_DISABLE: + case ARCH_SHSTK_LOCK: + return shstk_prctl(task, option, arg2); default: ret =3D -EINVAL; break; diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c new file mode 100644 index 0000000..41ed655 --- /dev/null +++ b/arch/x86/kernel/shstk.c @@ -0,0 +1,44 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * shstk.c - Intel shadow stack support + * + * Copyright (c) 2021, Intel Corporation. + * Yu-cheng Yu + */ + +#include +#include +#include + +void reset_thread_features(void) +{ + current->thread.features =3D 0; + current->thread.features_locked =3D 0; +} + +long shstk_prctl(struct task_struct *task, int option, unsigned long featu= res) +{ + if (option =3D=3D ARCH_SHSTK_LOCK) { + task->thread.features_locked |=3D features; + return 0; + } + + /* Don't allow via ptrace */ + if (task !=3D current) + return -EINVAL; + + /* Do not allow to change locked features */ + if (features & task->thread.features_locked) + return -EPERM; + + /* Only support enabling/disabling one feature at a time. */ + if (hweight_long(features) > 1) + return -EINVAL; + + if (option =3D=3D ARCH_SHSTK_DISABLE) { + return -EINVAL; + } + + /* Handle ARCH_SHSTK_ENABLE */ + return -EINVAL; +}