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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>,
	Nadav Amit <nadav.amit@gmail.com>,
	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>,
	Pengfei Xu <pengfei.xu@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v14 25/26] x86/cet/shstk: Add arch_prctl functions for shadow stack
Date: Mon, 12 Oct 2020 08:38:49 -0700
Message-ID: <20201012153850.26996-26-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20201012153850.26996-1-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, unsigned int features)
    Disable CET features specified in 'features'.  Return -EPERM if CET is
    locked.

arch_prctl(ARCH_X86_CET_LOCK)
    Lock in CET features.

Also change do_arch_prctl_common()'s parameter 'cpuid_enabled' to
'arg2', as it is now also passed to prctl_cet().

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
 arch/x86/include/asm/cet.h              |  3 ++
 arch/x86/include/uapi/asm/prctl.h       |  4 ++
 arch/x86/kernel/Makefile                |  2 +-
 arch/x86/kernel/cet_prctl.c             | 68 +++++++++++++++++++++++++
 arch/x86/kernel/process.c               |  6 +--
 tools/arch/x86/include/uapi/asm/prctl.h |  4 ++
 6 files changed, 83 insertions(+), 4 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 ec4b5e62d0ce..16870e5bc8eb 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -14,9 +14,11 @@ struct sc_ext;
 struct cet_status {
 	unsigned long	shstk_base;
 	unsigned long	shstk_size;
+	unsigned int	locked:1;
 };
 
 #ifdef CONFIG_X86_CET
+int prctl_cet(int option, u64 arg2);
 int cet_setup_shstk(void);
 int cet_setup_thread_shstk(struct task_struct *p, unsigned long clone_flags);
 void cet_disable_shstk(void);
@@ -25,6 +27,7 @@ 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,
 					 unsigned long clone_flags) { return 0; }
 static inline void cet_disable_shstk(void) {}
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 5a6aac9fa41f..9245bf629120 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -14,4 +14,8 @@
 #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
+
 #endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 1fb85595afa7..321ef52e4470 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -145,7 +145,7 @@ obj-$(CONFIG_UNWINDER_ORC)		+= unwind_orc.o
 obj-$(CONFIG_UNWINDER_FRAME_POINTER)	+= unwind_frame.o
 obj-$(CONFIG_UNWINDER_GUESS)		+= unwind_guess.o
 
-obj-$(CONFIG_X86_CET)			+= cet.o
+obj-$(CONFIG_X86_CET)			+= cet.o cet_prctl.o
 
 ###
 # 64 bit specific files
diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c
new file mode 100644
index 000000000000..bd5ad11763e4
--- /dev/null
+++ b/arch/x86/kernel/cet_prctl.c
@@ -0,0 +1,68 @@
+// 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 copy_status_to_user(struct cet_status *cet, u64 arg2)
+{
+	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));
+}
+
+int prctl_cet(int option, u64 arg2)
+{
+	struct cet_status *cet;
+	unsigned int features;
+
+	/*
+	 * GLIBC's ENOTSUPP == EOPNOTSUPP == 95, and it does not recognize
+	 * the kernel's ENOTSUPP (524).  So return EOPNOTSUPP here.
+	 */
+	if (!IS_ENABLED(CONFIG_X86_CET))
+		return -EOPNOTSUPP;
+
+	cet = &current->thread.cet;
+
+	if (option == ARCH_X86_CET_STATUS)
+		return copy_status_to_user(cet, arg2);
+
+	if (!static_cpu_has(X86_FEATURE_SHSTK))
+		return -EOPNOTSUPP;
+
+	switch (option) {
+	case ARCH_X86_CET_DISABLE:
+		if (cet->locked)
+			return -EPERM;
+
+		features = (unsigned int)arg2;
+
+		if (features & GNU_PROPERTY_X86_FEATURE_1_INVAL)
+			return -EINVAL;
+		if (features & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+			cet_disable_shstk();
+		return 0;
+
+	case ARCH_X86_CET_LOCK:
+		cet->locked = 1;
+		return 0;
+
+	default:
+		return -ENOSYS;
+	}
+}
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 67632ba893b7..33cb6da22ef0 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -977,14 +977,14 @@ unsigned long get_wchan(struct task_struct *p)
 }
 
 long do_arch_prctl_common(struct task_struct *task, int option,
-			  unsigned long cpuid_enabled)
+			  unsigned long arg2)
 {
 	switch (option) {
 	case ARCH_GET_CPUID:
 		return get_cpuid_mode();
 	case ARCH_SET_CPUID:
-		return set_cpuid_mode(task, cpuid_enabled);
+		return set_cpuid_mode(task, arg2);
 	}
 
-	return -EINVAL;
+	return prctl_cet(option, arg2);
 }
diff --git a/tools/arch/x86/include/uapi/asm/prctl.h b/tools/arch/x86/include/uapi/asm/prctl.h
index 5a6aac9fa41f..9245bf629120 100644
--- a/tools/arch/x86/include/uapi/asm/prctl.h
+++ b/tools/arch/x86/include/uapi/asm/prctl.h
@@ -14,4 +14,8 @@
 #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
+
 #endif /* _ASM_X86_PRCTL_H */
-- 
2.21.0


  parent reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 15:38 [PATCH v14 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 01/26] Documentation/x86: Add CET description Yu-cheng Yu
2020-11-06 17:34   ` Borislav Petkov
2020-11-06 18:16     ` Yu, Yu-cheng
2020-11-06 18:28       ` Borislav Petkov
2020-11-06 18:32         ` Yu, Yu-cheng
2020-10-12 15:38 ` [PATCH v14 02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-11-06 18:49   ` Borislav Petkov
2020-11-06 19:48     ` Yu, Yu-cheng
2020-11-06 20:11       ` Borislav Petkov
2020-11-06 20:14         ` Yu, Yu-cheng
2020-10-12 15:38 ` [PATCH v14 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-10-12 19:58   ` Cyrill Gorcunov
2020-10-12 20:48     ` Yu, Yu-cheng
2020-10-12 15:38 ` [PATCH v14 04/26] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 08/26] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 09/26] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 10/26] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 12/26] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 13/26] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 14/26] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 15/26] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 16/26] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 17/26] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 18/26] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 19/26] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 20/26] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 21/26] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 22/26] binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND properties Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 23/26] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 24/26] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2020-10-12 15:38 ` Yu-cheng Yu [this message]
2020-10-12 15:38 ` [PATCH v14 26/26] mm: Introduce PROT_SHSTK for " Yu-cheng Yu

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