diff options
| author | Vincent Whitchurch | 2018-11-09 10:12:30 +0100 |
|---|---|---|
| committer | Russell King | 2018-11-12 10:52:04 +0000 |
| commit | 344eb5539abf3e0b6ce22568c03e86450073e097 (patch) | |
| tree | 7ed1b8d9e68977e903e738c518e64cecb5936b8a /arch/arm/lib/getuser.S | |
| parent | f441882a5229ffaef61a47bccd4518f7e2749cbc (diff) | |
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/lib/getuser.S')
| -rw-r--r-- | arch/arm/lib/getuser.S | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/arm/lib/getuser.S b/arch/arm/lib/getuser.S index 746e7801dcdf..b2e4bc3a635e 100644 --- a/arch/arm/lib/getuser.S +++ b/arch/arm/lib/getuser.S @@ -42,6 +42,12 @@ _ASM_NOKPROBE(__get_user_1) ENTRY(__get_user_2) check_uaccess r0, 2, r1, r2, __get_user_bad +#if __LINUX_ARM_ARCH__ >= 6 + +2: TUSER(ldrh) r2, [r0] + +#else + #ifdef CONFIG_CPU_USE_DOMAINS rb .req ip 2: ldrbt r2, [r0], #1 @@ -56,6 +62,9 @@ rb .req r0 #else orr r2, rb, r2, lsl #8 #endif + +#endif /* __LINUX_ARM_ARCH__ >= 6 */ + mov r0, #0 ret lr ENDPROC(__get_user_2) @@ -145,7 +154,9 @@ _ASM_NOKPROBE(__get_user_bad8) .pushsection __ex_table, "a" .long 1b, __get_user_bad .long 2b, __get_user_bad +#if __LINUX_ARM_ARCH__ < 6 .long 3b, __get_user_bad +#endif .long 4b, __get_user_bad .long 5b, __get_user_bad8 .long 6b, __get_user_bad8 |