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authorJames Morse <james.morse@arm.com>2016-02-05 14:58:48 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2016-02-18 17:27:04 +0000
commit57f4959bad0a154aeca125b7d38d1d9471a12422 (patch)
tree6d75f86840bb0bd2d3f4928993f696c44e2033c0 /arch/arm64/include/asm/uaccess.h
parentarm64: add ARMv8.2 id_aa64mmfr2 boiler plate (diff)
downloadlinux-dev-57f4959bad0a154aeca125b7d38d1d9471a12422.tar.xz
linux-dev-57f4959bad0a154aeca125b7d38d1d9471a12422.zip
arm64: kernel: Add support for User Access Override
'User Access Override' is a new ARMv8.2 feature which allows the unprivileged load and store instructions to be overridden to behave in the normal way. This patch converts {get,put}_user() and friends to use ldtr*/sttr* instructions - so that they can only access EL0 memory, then enables UAO when fs==KERNEL_DS so that these functions can access kernel memory. This allows user space's read/write permissions to be checked against the page tables, instead of testing addr<USER_DS, then using the kernel's read/write permissions. Signed-off-by: James Morse <james.morse@arm.com> [catalin.marinas@arm.com: move uao_thread_switch() above dsb()] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to '')
-rw-r--r--arch/arm64/include/asm/uaccess.h44
1 files changed, 32 insertions, 12 deletions
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index b2ede967fe7d..f973bdce8410 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -64,6 +64,16 @@ extern int fixup_exception(struct pt_regs *regs);
static inline void set_fs(mm_segment_t fs)
{
current_thread_info()->addr_limit = fs;
+
+ /*
+ * Enable/disable UAO so that copy_to_user() etc can access
+ * kernel memory with the unprivileged instructions.
+ */
+ if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
+ asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
+ else
+ asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
+ CONFIG_ARM64_UAO));
}
#define segment_eq(a, b) ((a) == (b))
@@ -113,9 +123,10 @@ static inline void set_fs(mm_segment_t fs)
* The "__xxx_error" versions set the third argument to -EFAULT if an error
* occurs, and leave it unchanged on success.
*/
-#define __get_user_asm(instr, reg, x, addr, err) \
+#define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
asm volatile( \
- "1: " instr " " reg "1, [%2]\n" \
+ "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
+ alt_instr " " reg "1, [%2]\n", feature) \
"2:\n" \
" .section .fixup, \"ax\"\n" \
" .align 2\n" \
@@ -138,16 +149,20 @@ do { \
CONFIG_ARM64_PAN)); \
switch (sizeof(*(ptr))) { \
case 1: \
- __get_user_asm("ldrb", "%w", __gu_val, (ptr), (err)); \
+ __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
case 2: \
- __get_user_asm("ldrh", "%w", __gu_val, (ptr), (err)); \
+ __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
case 4: \
- __get_user_asm("ldr", "%w", __gu_val, (ptr), (err)); \
+ __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
case 8: \
- __get_user_asm("ldr", "%", __gu_val, (ptr), (err)); \
+ __get_user_asm("ldr", "ldtr", "%", __gu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
default: \
BUILD_BUG(); \
@@ -181,9 +196,10 @@ do { \
((x) = 0, -EFAULT); \
})
-#define __put_user_asm(instr, reg, x, addr, err) \
+#define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
asm volatile( \
- "1: " instr " " reg "1, [%2]\n" \
+ "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
+ alt_instr " " reg "1, [%2]\n", feature) \
"2:\n" \
" .section .fixup,\"ax\"\n" \
" .align 2\n" \
@@ -205,16 +221,20 @@ do { \
CONFIG_ARM64_PAN)); \
switch (sizeof(*(ptr))) { \
case 1: \
- __put_user_asm("strb", "%w", __pu_val, (ptr), (err)); \
+ __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
case 2: \
- __put_user_asm("strh", "%w", __pu_val, (ptr), (err)); \
+ __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
case 4: \
- __put_user_asm("str", "%w", __pu_val, (ptr), (err)); \
+ __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
case 8: \
- __put_user_asm("str", "%", __pu_val, (ptr), (err)); \
+ __put_user_asm("str", "sttr", "%", __pu_val, (ptr), \
+ (err), ARM64_HAS_UAO); \
break; \
default: \
BUILD_BUG(); \