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From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Borislav Petkov <bp@alien8.de>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
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	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v10 26/26] x86/cet/shstk: Add arch_prctl functions for shadow stack
Date: Wed, 29 Apr 2020 15:07:32 -0700
Message-ID: <20200429220732.31602-27-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20200429220732.31602-1-yu-cheng.yu@intel.com>

arch_prctl(ARCH_X86_CET_STATUS, u64 *args)
    Get CET feature status.

    The parameter 'args' is a pointer to a user buffer.  The kernel returns
    the following information:

    *args = shadow stack/IBT status
    *(args + 1) = shadow stack base address
    *(args + 2) = shadow stack size

arch_prctl(ARCH_X86_CET_DISABLE, u64 features)
    Disable CET features specified in 'features'.  Return -EPERM if CET is
    locked.

arch_prctl(ARCH_X86_CET_LOCK)
    Lock in CET features.

arch_prctl(ARCH_X86_CET_ALLOC_SHSTK, u64 *args)
    Allocate a new shadow stack.

    The parameter 'args' is a pointer to a user buffer containing the
    desired size to allocate.  The kernel returns the allocated shadow
    stack address in *args.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
v10:
- Verify CET is enabled before handling arch_prctl.
- Change input parameters from unsigned long to u64, to make it clear they
  are 64-bit.

 arch/x86/include/asm/cet.h        |  4 ++
 arch/x86/include/uapi/asm/prctl.h |  5 ++
 arch/x86/kernel/Makefile          |  2 +-
 arch/x86/kernel/cet.c             | 29 +++++++++++
 arch/x86/kernel/cet_prctl.c       | 87 +++++++++++++++++++++++++++++++
 arch/x86/kernel/process.c         |  4 +-
 6 files changed, 128 insertions(+), 3 deletions(-)
 create mode 100644 arch/x86/kernel/cet_prctl.c

diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index 71dc92acd2f2..99e6e741d28c 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -14,16 +14,20 @@ struct sc_ext;
 struct cet_status {
 	unsigned long	shstk_base;
 	unsigned long	shstk_size;
+	unsigned int	locked:1;
 };
 
 #ifdef CONFIG_X86_INTEL_CET
+int prctl_cet(int option, u64 arg2);
 int cet_setup_shstk(void);
 int cet_setup_thread_shstk(struct task_struct *p);
+int cet_alloc_shstk(unsigned long *arg);
 void cet_disable_free_shstk(struct task_struct *p);
 int cet_verify_rstor_token(bool ia32, unsigned long ssp, unsigned long *new_ssp);
 void cet_restore_signal(struct sc_ext *sc);
 int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc);
 #else
+static inline int prctl_cet(int option, u64 arg2) { return -EINVAL; }
 static inline int cet_setup_thread_shstk(struct task_struct *p) { return 0; }
 static inline void cet_disable_free_shstk(struct task_struct *p) {}
 static inline void cet_restore_signal(struct sc_ext *sc) { return; }
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 5a6aac9fa41f..d962f0ec9ccf 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -14,4 +14,9 @@
 #define ARCH_MAP_VDSO_32	0x2002
 #define ARCH_MAP_VDSO_64	0x2003
 
+#define ARCH_X86_CET_STATUS		0x3001
+#define ARCH_X86_CET_DISABLE		0x3002
+#define ARCH_X86_CET_LOCK		0x3003
+#define ARCH_X86_CET_ALLOC_SHSTK	0x3004
+
 #endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index e9cc2551573b..0b621e2afbdc 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -144,7 +144,7 @@ obj-$(CONFIG_UNWINDER_ORC)		+= unwind_orc.o
 obj-$(CONFIG_UNWINDER_FRAME_POINTER)	+= unwind_frame.o
 obj-$(CONFIG_UNWINDER_GUESS)		+= unwind_guess.o
 
-obj-$(CONFIG_X86_INTEL_CET)		+= cet.o
+obj-$(CONFIG_X86_INTEL_CET)		+= cet.o cet_prctl.o
 
 ###
 # 64 bit specific files
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index 121552047b86..c1b9b540c03e 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -145,6 +145,35 @@ static int create_rstor_token(bool ia32, unsigned long ssp,
 	return 0;
 }
 
+int cet_alloc_shstk(unsigned long *arg)
+{
+	unsigned long len = *arg;
+	unsigned long addr;
+	unsigned long token;
+	unsigned long ssp;
+
+	addr = alloc_shstk(round_up(len, PAGE_SIZE));
+
+	if (IS_ERR((void *)addr))
+		return PTR_ERR((void *)addr);
+
+	/* Restore token is 8 bytes and aligned to 8 bytes */
+	ssp = addr + len;
+	token = ssp;
+
+	if (!in_ia32_syscall())
+		token |= TOKEN_MODE_64;
+	ssp -= 8;
+
+	if (write_user_shstk_64(ssp, token)) {
+		vm_munmap(addr, len);
+		return -EINVAL;
+	}
+
+	*arg = addr;
+	return 0;
+}
+
 int cet_setup_shstk(void)
 {
 	unsigned long addr, size;
diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c
new file mode 100644
index 000000000000..0139c48f2215
--- /dev/null
+++ b/arch/x86/kernel/cet_prctl.c
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/errno.h>
+#include <linux/uaccess.h>
+#include <linux/prctl.h>
+#include <linux/compat.h>
+#include <linux/mman.h>
+#include <linux/elfcore.h>
+#include <asm/processor.h>
+#include <asm/prctl.h>
+#include <asm/cet.h>
+
+/* See Documentation/x86/intel_cet.rst. */
+
+static int handle_get_status(u64 arg2)
+{
+	struct cet_status *cet = &current->thread.cet;
+	u64 buf[3] = {0, 0, 0};
+
+	if (cet->shstk_size) {
+		buf[0] |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+		buf[1] = (u64)cet->shstk_base;
+		buf[2] = (u64)cet->shstk_size;
+	}
+
+	return copy_to_user((u64 __user *)arg2, buf, sizeof(buf));
+}
+
+static int handle_alloc_shstk(u64 arg2)
+{
+	int err = 0;
+	unsigned long arg;
+	unsigned long addr = 0;
+	unsigned long size = 0;
+
+	if (get_user(arg, (unsigned long __user *)arg2))
+		return -EFAULT;
+
+	size = arg;
+	err = cet_alloc_shstk(&arg);
+	if (err)
+		return err;
+
+	addr = arg;
+	if (put_user((u64)addr, (u64 __user *)arg2)) {
+		vm_munmap(addr, size);
+		return -EFAULT;
+	}
+
+	return 0;
+}
+
+int prctl_cet(int option, u64 arg2)
+{
+	struct cet_status *cet;
+
+	if (!IS_ENABLED(CONFIG_X86_INTEL_CET))
+		return -EINVAL;
+
+	if (option == ARCH_X86_CET_STATUS)
+		return handle_get_status(arg2);
+
+	if (!static_cpu_has(X86_FEATURE_SHSTK))
+		return -EINVAL;
+
+	cet = &current->thread.cet;
+
+	switch (option) {
+	case ARCH_X86_CET_DISABLE:
+		if (cet->locked)
+			return -EPERM;
+		if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+			cet_disable_free_shstk(current);
+
+		return 0;
+
+	case ARCH_X86_CET_LOCK:
+		cet->locked = 1;
+		return 0;
+
+	case ARCH_X86_CET_ALLOC_SHSTK:
+		return handle_alloc_shstk(arg2);
+
+	default:
+		return -EINVAL;
+	}
+}
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ef1c2b8086a2..de6773dd6a16 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -996,7 +996,7 @@ long do_arch_prctl_common(struct task_struct *task, int option,
 		return get_cpuid_mode();
 	case ARCH_SET_CPUID:
 		return set_cpuid_mode(task, cpuid_enabled);
+	default:
+		return prctl_cet(option, cpuid_enabled);
 	}
-
-	return -EINVAL;
 }
-- 
2.21.0


  parent reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-29 22:07 [PATCH v10 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 01/26] Documentation/x86: Add CET description Yu-cheng Yu
2020-04-29 22:53   ` Dave Hansen
2020-04-29 23:02     ` Yu-cheng Yu
2020-05-12 23:20       ` Yu-cheng Yu
2020-05-15 18:39         ` Dave Hansen
2020-05-15 21:33           ` Yu-cheng Yu
2020-05-15 22:43             ` Dave Hansen
2020-05-15 23:29               ` Yu-cheng Yu
2020-05-15 23:56                 ` Dave Hansen
2020-05-16  2:51                   ` H.J. Lu
2020-05-17 23:09                     ` Dave Hansen
2020-05-16  2:53                   ` Yu-cheng Yu
2020-05-18 13:41                     ` Dave Hansen
2020-05-18 14:01                       ` H.J. Lu
2020-05-18 14:26                         ` Dave Hansen
2020-05-18 14:21                       ` Yu-cheng Yu
2020-05-18 23:47                     ` Yu-cheng Yu
2020-05-19  0:38                       ` Dave Hansen
2020-05-19  1:35                         ` Andy Lutomirski
2020-05-20  1:04                           ` Andy Lutomirski
2020-05-29  2:08                             ` Yu-cheng Yu
2020-05-16  0:13               ` Andrew Cooper
2020-05-16  2:37                 ` H.J. Lu
2020-05-16 14:09                   ` Andrew Cooper
2020-05-22 16:49                     ` Peter Zijlstra
2020-05-22 17:48                       ` Andrew Cooper
2020-04-29 22:07 ` [PATCH v10 02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 04/26] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-05-07 15:55   ` Dave Hansen
2020-05-07 16:59     ` Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 08/26] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 09/26] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 10/26] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 12/26] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 13/26] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 14/26] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 15/26] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 16/26] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 17/26] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 18/26] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 19/26] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 20/26] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 21/26] ELF: UAPI and Kconfig additions for ELF program properties Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 22/26] ELF: Add ELF program property parsing support Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 23/26] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 24/26] x86/cet/shstk: ELF header parsing for shadow stack Yu-cheng Yu
2020-04-29 22:07 ` [PATCH v10 25/26] x86/cet/shstk: Handle thread " Yu-cheng Yu
2020-04-29 22:07 ` Yu-cheng Yu [this message]
2020-05-21 22:42   ` [PATCH v10 26/26] x86/cet/shstk: Add arch_prctl functions for " Kees Cook
2020-05-22 17:17     ` Yu-cheng Yu
2020-05-22 17:29       ` Eugene Syromiatnikov
2020-05-22 18:13         ` Yu-cheng Yu
2020-05-21 15:15 ` [PATCH v10 00/26] Control-flow Enforcement: Shadow Stack Josh Poimboeuf
2020-05-21 15:57   ` Yu-cheng Yu
2020-05-21 18:50     ` Josh Poimboeuf
2020-05-21 19:08       ` Yu-cheng Yu

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