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Subject[PATCH v2 2/2] arm64: uaccess: Implement unsafe accessors
Date
Current implementation of get/put_user_unsafe default to get/put_user
which toggle PAN before each access, despite having been told by the caller
that multiple accesses to user memory were about to happen.

Provide implementations for user_access_begin/end to turn PAN off/on and
implement unsafe accessors that assume PAN was already turned off.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
---
arch/arm64/include/asm/sysreg.h | 2 +
arch/arm64/include/asm/uaccess.h | 89 +++++++++++++++++++++++++++++++---------
2 files changed, 71 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 842fb95..4e6477b 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -108,6 +108,8 @@
#define SYS_DC_CSW sys_insn(1, 0, 7, 10, 2)
#define SYS_DC_CISW sys_insn(1, 0, 7, 14, 2)

+#define SYS_PSTATE_PAN sys_reg(3, 0, 4, 2, 3)
+
#define SYS_OSDTRRX_EL1 sys_reg(2, 0, 0, 0, 2)
#define SYS_MDCCINT_EL1 sys_reg(2, 0, 0, 2, 0)
#define SYS_MDSCR_EL1 sys_reg(2, 0, 0, 2, 2)
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 07c3408..cabfcae 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -233,6 +233,23 @@ static inline void uaccess_enable_not_uao(void)
__uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
}

+#define unsafe_user_region_active uaccess_region_active
+static inline bool uaccess_region_active(void)
+{
+ if (system_uses_ttbr0_pan()) {
+ u64 ttbr;
+
+ ttbr = read_sysreg(ttbr1_el1);
+ return ttbr & TTBR_ASID_MASK;
+ } else if (cpus_have_const_cap(ARM64_ALT_PAN_NOT_UAO)) {
+ return (read_sysreg(sctlr_el1) & SCTLR_EL1_SPAN) ?
+ false :
+ !read_sysreg_s(SYS_PSTATE_PAN);
+ }
+
+ return false;
+}
+
/*
* Sanitise a uaccess pointer such that it becomes NULL if above the
* current addr_limit.
@@ -276,11 +293,9 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
: "+r" (err), "=&r" (x) \
: "r" (addr), "i" (-EFAULT))

-#define __get_user_err(x, ptr, err) \
+#define __get_user_err_unsafe(x, ptr, err) \
do { \
unsigned long __gu_val; \
- __chk_user_ptr(ptr); \
- uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
__get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
@@ -301,17 +316,26 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
default: \
BUILD_BUG(); \
} \
- uaccess_disable_not_uao(); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
} while (0)

-#define __get_user_check(x, ptr, err) \
+#define __get_user_err_check(x, ptr, err) \
+do { \
+ __typeof__(x) __gu_dest; \
+ __chk_user_ptr(ptr); \
+ uaccess_enable_not_uao(); \
+ __get_user_err_unsafe((__gu_dest), (ptr), (err)); \
+ uaccess_disable_not_uao(); \
+ (x) = __gu_dest; \
+} while (0)
+
+#define __get_user_err(x, ptr, err, accessor) \
({ \
__typeof__(*(ptr)) __user *__p = (ptr); \
might_fault(); \
if (access_ok(VERIFY_READ, __p, sizeof(*__p))) { \
__p = uaccess_mask_ptr(__p); \
- __get_user_err((x), __p, (err)); \
+ accessor((x), __p, (err)); \
} else { \
(x) = 0; (err) = -EFAULT; \
} \
@@ -319,14 +343,14 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)

#define __get_user_error(x, ptr, err) \
({ \
- __get_user_check((x), (ptr), (err)); \
+ __get_user_err((x), (ptr), (err), __get_user_err_check); \
(void)0; \
})

#define __get_user(x, ptr) \
({ \
int __gu_err = 0; \
- __get_user_check((x), (ptr), __gu_err); \
+ __get_user_err((x), (ptr), __gu_err, __get_user_err_check); \
__gu_err; \
})

@@ -346,41 +370,46 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
: "+r" (err) \
: "r" (x), "r" (addr), "i" (-EFAULT))

-#define __put_user_err(x, ptr, err) \
+#define __put_user_err_unsafe(x, ptr, err) \
do { \
- __typeof__(*(ptr)) __pu_val = (x); \
- __chk_user_ptr(ptr); \
- uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
- __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
+ __put_user_asm("strb", "sttrb", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 2: \
- __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
+ __put_user_asm("strh", "sttrh", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 4: \
- __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
+ __put_user_asm("str", "sttr", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 8: \
- __put_user_asm("str", "sttr", "%x", __pu_val, (ptr), \
+ __put_user_asm("str", "sttr", "%x", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
default: \
BUILD_BUG(); \
} \
+} while (0)
+
+#define __put_user_err_check(x, ptr, err) \
+do { \
+ __typeof__(*(ptr)) __pu_val = (x); \
+ __chk_user_ptr(ptr); \
+ uaccess_enable_not_uao(); \
+ __put_user_err_unsafe(__pu_val, (ptr), (err)); \
uaccess_disable_not_uao(); \
} while (0)

-#define __put_user_check(x, ptr, err) \
+#define __put_user_err(x, ptr, err, accessor) \
({ \
__typeof__(*(ptr)) __user *__p = (ptr); \
might_fault(); \
if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) { \
__p = uaccess_mask_ptr(__p); \
- __put_user_err((x), __p, (err)); \
+ accessor((x), __p, (err)); \
} else { \
(err) = -EFAULT; \
} \
@@ -388,19 +417,39 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)

#define __put_user_error(x, ptr, err) \
({ \
- __put_user_check((x), (ptr), (err)); \
+ __put_user_err((x), (ptr), (err), __put_user_err_check); \
(void)0; \
})

#define __put_user(x, ptr) \
({ \
int __pu_err = 0; \
- __put_user_check((x), (ptr), __pu_err); \
+ __put_user_err((x), (ptr), __pu_err, __put_user_err_check); \
__pu_err; \
})

#define put_user __put_user

+
+#define user_access_begin() uaccess_enable_not_uao()
+#define user_access_end() uaccess_disable_not_uao()
+
+#define unsafe_get_user(x, ptr, err) \
+do { \
+ int __gu_err = 0; \
+ __get_user_err((x), (ptr), __gu_err, __get_user_err_unsafe); \
+ if (__gu_err != 0) \
+ goto err; \
+} while (0)
+
+#define unsafe_put_user(x, ptr, err) \
+do { \
+ int __pu_err = 0; \
+ __put_user_err((x), (ptr), __pu_err, __put_user_err_unsafe); \
+ if (__pu_err != 0) \
+ goto err; \
+} while (0)
+
extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
#define raw_copy_from_user(to, from, n) \
({ \
--
1.9.1
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