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| author | Vincent Whitchurch <vincent.whitchurch@axis.com> | 2018-11-09 10:12:30 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@armlinux.org.uk> | 2018-11-12 11:52:04 +0100 |
| commit | 344eb5539abf3e0b6ce22568c03e86450073e097 (patch) | |
| tree | 7ed1b8d9e68977e903e738c518e64cecb5936b8a /arch/arm/include/asm/uaccess.h | |
| parent | ARM: 8812/1: Optimise copy_{from/to}_user for !CPU_USE_DOMAINS (diff) | |
| download | linux-344eb5539abf3e0b6ce22568c03e86450073e097.tar.xz linux-344eb5539abf3e0b6ce22568c03e86450073e097.zip | |
ARM: 8813/1: Make aligned 2-byte getuser()/putuser() atomic on ARMv6+
getuser() and putuser() (and there underscored variants) use two
strb[t]/ldrb[t] instructions when they are asked to get/put 16-bits.
This means that the read/write is not atomic even when performed to a
16-bit-aligned address.
This leads to problems with vhost: vhost uses __getuser() to read the
vring's 16-bit avail.index field, and if it happens to observe a partial
update of the index, wrong descriptors will be used which will lead to a
breakdown of the virtio communication. A similar problem exists for
__putuser() which is used to write to the vring's used.index field.
The reason these functions use strb[t]/ldrb[t] is because strht/ldrht
instructions did not exist until ARMv6T2/ARMv7. So we should be easily
able to fix this on ARMv7. Also, since all ARMv6 processors also don't
actually use the unprivileged instructions anymore for uaccess (since
CONFIG_CPU_USE_DOMAINS is not used) we can easily fix them too.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/include/asm/uaccess.h')
| -rw-r--r-- | arch/arm/include/asm/uaccess.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index c136eef8f690..6390a40f16e7 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -349,6 +349,13 @@ do { \ #define __get_user_asm_byte(x, addr, err) \ __get_user_asm(x, addr, err, ldrb) +#if __LINUX_ARM_ARCH__ >= 6 + +#define __get_user_asm_half(x, addr, err) \ + __get_user_asm(x, addr, err, ldrh) + +#else + #ifndef __ARMEB__ #define __get_user_asm_half(x, __gu_addr, err) \ ({ \ @@ -367,6 +374,8 @@ do { \ }) #endif +#endif /* __LINUX_ARM_ARCH__ >= 6 */ + #define __get_user_asm_word(x, addr, err) \ __get_user_asm(x, addr, err, ldr) #endif @@ -442,6 +451,13 @@ do { \ #define __put_user_asm_byte(x, __pu_addr, err) \ __put_user_asm(x, __pu_addr, err, strb) +#if __LINUX_ARM_ARCH__ >= 6 + +#define __put_user_asm_half(x, __pu_addr, err) \ + __put_user_asm(x, __pu_addr, err, strh) + +#else + #ifndef __ARMEB__ #define __put_user_asm_half(x, __pu_addr, err) \ ({ \ @@ -458,6 +474,8 @@ do { \ }) #endif +#endif /* __LINUX_ARM_ARCH__ >= 6 */ + #define __put_user_asm_word(x, __pu_addr, err) \ __put_user_asm(x, __pu_addr, err, str) |