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Date: Tue, 10 Jul 2018 15:26:39 -0700
From: Yu-cheng Yu <yu-cheng.yu@...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@...capital.net>,
Balbir Singh <bsingharora@...il.com>,
Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.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@...omiun.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>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [RFC PATCH v2 27/27] x86/cet: Add arch_prctl functions for CET
arch_prctl(ARCH_CET_STATUS, unsigned long *addr)
Return CET feature status.
The parameter 'addr' is a pointer to a user buffer.
On returning to the caller, the kernel fills the following
information:
*addr = SHSTK/IBT status
*(addr + 1) = SHSTK base address
*(addr + 2) = SHSTK size
arch_prctl(ARCH_CET_DISABLE, unsigned long features)
Disable SHSTK and/or IBT specified in 'features'. Return -EPERM
if CET is locked out.
arch_prctl(ARCH_CET_LOCK)
Lock out CET feature.
arch_prctl(ARCH_CET_ALLOC_SHSTK, unsigned long *addr)
Allocate a new SHSTK.
The parameter 'addr' is a pointer to a user buffer and indicates
the desired SHSTK size to allocate. On returning to the caller
the buffer contains the address of the new SHSTK.
arch_prctl(ARCH_CET_LEGACY_BITMAP, unsigned long *addr)
Allocate an IBT legacy code bitmap if the current task does not
have one.
The parameter 'addr' is a pointer to a user buffer.
On returning to the caller, the kernel fills the following
information:
*addr = IBT bitmap base address
*(addr + 1) = IBT bitmap size
Signed-off-by: H.J. Lu <hjl.tools@...il.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
---
arch/x86/include/asm/cet.h | 5 ++
arch/x86/include/uapi/asm/prctl.h | 6 ++
arch/x86/kernel/Makefile | 2 +-
arch/x86/kernel/cet.c | 26 ++++++
arch/x86/kernel/cet_prctl.c | 141 ++++++++++++++++++++++++++++++
arch/x86/kernel/elf.c | 4 +
arch/x86/kernel/process.c | 6 ++
7 files changed, 189 insertions(+), 1 deletion(-)
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 d5737f3346f2..50b5284c6667 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -16,11 +16,14 @@ struct cet_status {
unsigned long ibt_bitmap_size;
unsigned int shstk_enabled:1;
unsigned int ibt_enabled:1;
+ unsigned int locked:1;
};
#ifdef CONFIG_X86_INTEL_CET
+int prctl_cet(int option, unsigned long 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_shstk(void);
void cet_disable_free_shstk(struct task_struct *p);
int cet_restore_signal(unsigned long ssp);
@@ -29,8 +32,10 @@ int cet_setup_ibt(void);
int cet_setup_ibt_bitmap(void);
void cet_disable_ibt(void);
#else
+static inline int prctl_cet(int option, unsigned long arg2) { return 0; }
static inline int cet_setup_shstk(void) { return 0; }
static inline int cet_setup_thread_shstk(struct task_struct *p) { return 0; }
+static inline int cet_alloc_shstk(unsigned long *arg) { return -EINVAL; }
static inline void cet_disable_shstk(void) {}
static inline void cet_disable_free_shstk(struct task_struct *p) {}
static inline int cet_restore_signal(unsigned long ssp) { return 0; }
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 5a6aac9fa41f..52ec04e443c5 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -14,4 +14,10 @@
#define ARCH_MAP_VDSO_32 0x2002
#define ARCH_MAP_VDSO_64 0x2003
+#define ARCH_CET_STATUS 0x3001
+#define ARCH_CET_DISABLE 0x3002
+#define ARCH_CET_LOCK 0x3003
+#define ARCH_CET_LEGACY_BITMAP 0x3004
+#define ARCH_CET_ALLOC_SHSTK 0x3005
+
#endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 36b14ef410c8..b9e6cdc6b4f7 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -139,7 +139,7 @@ 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-$(CONFIG_X86_INTEL_CET) += cet.o cet_prctl.o
obj-$(CONFIG_ARCH_HAS_PROGRAM_PROPERTIES) += elf.o
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index 2a366a5ccf20..20ce9ac8a0df 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -132,6 +132,32 @@ static unsigned long shstk_mmap(unsigned long addr, unsigned long len)
return addr;
}
+int cet_alloc_shstk(unsigned long *arg)
+{
+ unsigned long len = *arg;
+ unsigned long addr;
+ unsigned long token;
+ unsigned long ssp;
+
+ addr = shstk_mmap(0, len);
+ if (addr >= TASK_SIZE_MAX)
+ return -ENOMEM;
+
+ /* Restore token is 8 bytes and aligned to 8 bytes */
+ ssp = addr + len;
+ token = ssp;
+
+ if (!in_ia32_syscall())
+ token |= 1;
+ ssp -=8;
+
+ if (write_user_shstk_64(ssp, token))
+ 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..86bb78ae656d
--- /dev/null
+++ b/arch/x86/kernel/cet_prctl.c
@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/errno.h>
+#include <linux/uaccess.h>
+#include <linux/prctl.h>
+#include <linux/compat.h>
+#include <asm/processor.h>
+#include <asm/prctl.h>
+#include <asm/elf.h>
+#include <asm/elf_property.h>
+#include <asm/cet.h>
+
+/* See Documentation/x86/intel_cet.txt. */
+
+static int handle_get_status(unsigned long arg2)
+{
+ unsigned int features = 0;
+ unsigned long shstk_base, shstk_size;
+
+ if (current->thread.cet.shstk_enabled)
+ features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+ if (current->thread.cet.ibt_enabled)
+ features |= GNU_PROPERTY_X86_FEATURE_1_IBT;
+
+ shstk_base = current->thread.cet.shstk_base;
+ shstk_size = current->thread.cet.shstk_size;
+
+ if (in_ia32_syscall()) {
+ unsigned int buf[3];
+
+ buf[0] = features;
+ buf[1] = (unsigned int)shstk_base;
+ buf[2] = (unsigned int)shstk_size;
+ return copy_to_user((unsigned int __user *)arg2, buf,
+ sizeof(buf));
+ } else {
+ unsigned long buf[3];
+
+ buf[0] = (unsigned long)features;
+ buf[1] = shstk_base;
+ buf[2] = shstk_size;
+ return copy_to_user((unsigned long __user *)arg2, buf,
+ sizeof(buf));
+ }
+}
+
+static int handle_alloc_shstk(unsigned long arg2)
+{
+ int err = 0;
+ unsigned long shstk_size = 0;
+
+ if (in_ia32_syscall()) {
+ unsigned int size;
+
+ err = get_user(size, (unsigned int __user *)arg2);
+ if (!err)
+ shstk_size = size;
+ } else {
+ err = get_user(shstk_size, (unsigned long __user *)arg2);
+ }
+
+ if (err)
+ return -EFAULT;
+
+ err = cet_alloc_shstk(&shstk_size);
+ if (err)
+ return -err;
+
+ if (in_ia32_syscall()) {
+ if (put_user(shstk_size, (unsigned int __user *)arg2))
+ return -EFAULT;
+ } else {
+ if (put_user(shstk_size, (unsigned long __user *)arg2))
+ return -EFAULT;
+ }
+ return 0;
+}
+
+static int handle_bitmap(unsigned long arg2)
+{
+ unsigned long addr, size;
+
+ if (current->thread.cet.ibt_enabled) {
+ if (!current->thread.cet.ibt_bitmap_addr)
+ cet_setup_ibt_bitmap();
+ addr = current->thread.cet.ibt_bitmap_addr;
+ size = current->thread.cet.ibt_bitmap_size;
+ } else {
+ addr = 0;
+ size = 0;
+ }
+
+ if (in_compat_syscall()) {
+ if (put_user(addr, (unsigned int __user *)arg2) ||
+ put_user(size, (unsigned int __user *)arg2 + 1))
+ return -EFAULT;
+ } else {
+ if (put_user(addr, (unsigned long __user *)arg2) ||
+ put_user(size, (unsigned long __user *)arg2 + 1))
+ return -EFAULT;
+ }
+ return 0;
+}
+
+int prctl_cet(int option, unsigned long arg2)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_SHSTK) &&
+ !cpu_feature_enabled(X86_FEATURE_IBT))
+ return -EINVAL;
+
+ switch (option) {
+ case ARCH_CET_STATUS:
+ return handle_get_status(arg2);
+
+ case ARCH_CET_DISABLE:
+ if (current->thread.cet.locked)
+ return -EPERM;
+ if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+ cet_disable_free_shstk(current);
+ if (arg2 & GNU_PROPERTY_X86_FEATURE_1_IBT)
+ cet_disable_ibt();
+
+ return 0;
+
+ case ARCH_CET_LOCK:
+ current->thread.cet.locked = 1;
+ return 0;
+
+ case ARCH_CET_ALLOC_SHSTK:
+ return handle_alloc_shstk(arg2);
+
+ /*
+ * Allocate legacy bitmap and return address & size to user.
+ */
+ case ARCH_CET_LEGACY_BITMAP:
+ return handle_bitmap(arg2);
+
+ default:
+ return -EINVAL;
+ }
+}
diff --git a/arch/x86/kernel/elf.c b/arch/x86/kernel/elf.c
index 42e08d3b573e..3d4934fdac7f 100644
--- a/arch/x86/kernel/elf.c
+++ b/arch/x86/kernel/elf.c
@@ -8,7 +8,10 @@
#include <asm/cet.h>
#include <asm/elf_property.h>
+#include <asm/prctl.h>
+#include <asm/processor.h>
#include <uapi/linux/elf-em.h>
+#include <uapi/linux/prctl.h>
#include <linux/binfmts.h>
#include <linux/elf.h>
#include <linux/slab.h>
@@ -255,6 +258,7 @@ int arch_setup_features(void *ehdr_p, void *phdr_p,
current->thread.cet.ibt_enabled = 0;
current->thread.cet.ibt_bitmap_addr = 0;
current->thread.cet.ibt_bitmap_size = 0;
+ current->thread.cet.locked = 0;
if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
if (shstk) {
err = cet_setup_shstk();
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 43a57d284a22..259b92664981 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -795,6 +795,12 @@ 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);
+ case ARCH_CET_STATUS:
+ case ARCH_CET_DISABLE:
+ case ARCH_CET_LOCK:
+ case ARCH_CET_ALLOC_SHSTK:
+ case ARCH_CET_LEGACY_BITMAP:
+ return prctl_cet(option, cpuid_enabled);
}
return -EINVAL;
--
2.17.1
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