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Message-Id: <20230613001108.3040476-27-rick.p.edgecombe@intel.com>
Date: Mon, 12 Jun 2023 17:10:52 -0700
From: Rick Edgecombe <rick.p.edgecombe@...el.com>
To: x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-mm@...ck.org,
linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Andy Lutomirski <luto@...nel.org>,
Balbir Singh <bsingharora@...il.com>,
Borislav Petkov <bp@...en8.de>,
Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Eugene Syromiatnikov <esyr@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
"H . J . Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Nadav Amit <nadav.amit@...il.com>,
Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
Peter Zijlstra <peterz@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
Weijiang Yang <weijiang.yang@...el.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
John Allen <john.allen@....com>, kcc@...gle.com,
eranian@...gle.com, rppt@...nel.org, jamorris@...ux.microsoft.com,
dethoma@...rosoft.com, akpm@...ux-foundation.org,
Andrew.Cooper3@...rix.com, christina.schimpe@...el.com,
david@...hat.com, debug@...osinc.com, szabolcs.nagy@....com,
torvalds@...ux-foundation.org, broonie@...nel.org
Cc: rick.p.edgecombe@...el.com, Pengfei Xu <pengfei.xu@...el.com>
Subject: [PATCH v9 26/42] 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 <kirill.shutemov@...ux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Kees Cook <keescook@...omium.org>
Acked-by: Mike Rapoport (IBM) <rppt@...nel.org>
Tested-by: Pengfei Xu <pengfei.xu@...el.com>
Tested-by: John Allen <john.allen@....com>
Tested-by: Kees Cook <keescook@...omium.org>
---
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/processor.h
index a1e4fa58b357..407d5551b6a7 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -28,6 +28,7 @@ struct vm86;
#include <asm/unwind_hints.h>
#include <asm/vmxfeatures.h>
#include <asm/vdso/processor.h>
+#include <asm/shstk.h>
#include <linux/personality.h>
#include <linux/cache.h>
@@ -475,6 +476,11 @@ struct thread_struct {
*/
u32 pkru;
+#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 000000000000..ec753809f074
--- /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 <linux/types.h>
+
+struct task_struct;
+
+#ifdef CONFIG_X86_USER_SHADOW_STACK
+long shstk_prctl(struct task_struct *task, int option, unsigned long features);
+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 e8d7ebbca1a4..1cd44ecc9ce0 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
+/* 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
+#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 abee0564b750..6b6bf47652ee 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -147,6 +147,8 @@ obj-$(CONFIG_CALL_THUNKS) += callthunks.o
obj-$(CONFIG_X86_CET) += cet.o
+obj-$(CONFIG_X86_USER_SHADOW_STACK) += shstk.o
+
###
# 64 bit specific files
ifeq ($(CONFIG_X86_64),y)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 3d181c16a2f6..0f89aa0186d1 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);
}
+ 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 option, 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 = -EINVAL;
break;
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
new file mode 100644
index 000000000000..41ed6552e0a5
--- /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 <yu-cheng.yu@...el.com>
+ */
+
+#include <linux/sched.h>
+#include <linux/bitops.h>
+#include <asm/prctl.h>
+
+void reset_thread_features(void)
+{
+ current->thread.features = 0;
+ current->thread.features_locked = 0;
+}
+
+long shstk_prctl(struct task_struct *task, int option, unsigned long features)
+{
+ if (option == ARCH_SHSTK_LOCK) {
+ task->thread.features_locked |= features;
+ return 0;
+ }
+
+ /* Don't allow via ptrace */
+ if (task != 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 == ARCH_SHSTK_DISABLE) {
+ return -EINVAL;
+ }
+
+ /* Handle ARCH_SHSTK_ENABLE */
+ return -EINVAL;
+}
--
2.34.1
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