From nobody Sun Feb 8 18:32:36 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 82A27C6FD1D for ; Mon, 20 Mar 2023 16:46:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231560AbjCTQqs (ORCPT ); Mon, 20 Mar 2023 12:46:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231365AbjCTQpd (ORCPT ); Mon, 20 Mar 2023 12:45:33 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 519002F061; Mon, 20 Mar 2023 09:40:26 -0700 (PDT) Date: Mon, 20 Mar 2023 16:39:23 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679330364; 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=oKiFxBEw1yS5DJivCNsyd0fXE6HM+bfuo7/jVCU8d5c=; b=zFGG29d/DB0E0dmVraZSAib4/yAZWf9W7UPZDzWUL3s9E+qhIDJOiuNaGgFqy+bBDtE+y2 +obu5tsZrWR8Gm4ot4nPgcVmk/T+TiEq3VVCC+Voya5TXJ3t4P8xOY/TXyI/XminLEz9Ol s8bUm1vEoh2v5V0u0vFUoPutzEtH50XT27nb77aClfm/IMNC6LbReKk/vLm9UXD/MtESoO uFZIbhpFy7esbhkCXB/iLW/xN5tVXPW0zety5+nilnnvQndj7DPppHggghpR8gBFEFf87q XDhqaBHafNrx9yr4QOon1RQzRAndV+OW7QFyq75gRmkfh/vT3zuzIwuxwQhzeg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679330364; 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=oKiFxBEw1yS5DJivCNsyd0fXE6HM+bfuo7/jVCU8d5c=; b=k18qUEUT1j7Fx205waQbzyleKMeW0D2q99YK03Ys015xJvR2Y5UqDJS2Re861Dycht5BwN ImQ3/c5HBAB2i/Bg== 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: <167933036373.5837.16141492830702089407.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: c40a7569ad82fb4714a6b40ddf79b9fd27443438 Gitweb: https://git.kernel.org/tip/c40a7569ad82fb4714a6b40ddf79b9fd2= 7443438 Author: Rick Edgecombe AuthorDate: Sat, 18 Mar 2023 17:15:23 -07:00 Committer: Dave Hansen CommitterDate: Mon, 20 Mar 2023 09:01:11 -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/20230319001535.23210-29-rick.p.edgecombe%= 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 | 7 ++++- arch/x86/kernel/shstk.c | 44 ++++++++++++++++++++++++++++++- 6 files changed, 85 insertions(+), 1 deletion(-) 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 8d73004..bd16e01 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 500b96e..b2b3b72 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -20,4 +20,10 @@ #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 =20 +/* Don't use 0x3001-0x3004 because of old glibcs */ + +#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 92446f1..b366641 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -146,6 +146,8 @@ 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 bb65a68..9bbad17 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -514,6 +514,8 @@ 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); @@ -830,7 +832,10 @@ long do_arch_prctl_64(struct task_struct *task, int op= tion, unsigned long arg2) case ARCH_MAP_VDSO_64: return prctl_map_vdso(&vdso_image_64, 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; +}