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arm64: kernel: do not need to reset UAO on exception entry 

Commit e19a6ee246 ("arm64: kernel: Save and restore UAO and
addr_limit on exception entry") states that exception handler inherits
the original PSTATE.UAO value, so UAO needes to be reset
explicitly. However, ARM 8.2 Extension documentation says:

PSTATE.UAO is copied to SPSR_ELx.UAO and is then set to 0 on an
exception taken from AArch64 to AArch64

so hardware already does the right thing.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Acked-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Vladimir Murzin 2016-09-01 14:35:59 +01:00 committed by Will Deacon
parent e937dd5782
commit 563cada03d
1 changed files with 1 additions and 1 deletions
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2
arch/arm64/kernel/entry.S
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@ -104,7 +104,7 @@
str x20, [sp, #S_ORIG_ADDR_LIMIT]
mov x20, #TASK_SIZE_64
str x20, [tsk, #TI_ADDR_LIMIT]
ALTERNATIVE(nop, SET_PSTATE_UAO(0), ARM64_HAS_UAO, CONFIG_ARM64_UAO)
/* No need to reset PSTATE.UAO, hardware's already set it to 0 for us */
.endif /* \el == 0 */
mrs x22, elr_el1
mrs x23, spsr_el1