[+ Mark R. since we looked at this together a little at ELC]
Catalin Marinas <[email protected]> writes:
> On Sun, Apr 27, 2014 at 08:44:12PM +0100, Larry Bassel wrote:
>> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
>> index 39ac630..eda7755 100644
>> --- a/arch/arm64/kernel/entry.S
>> +++ b/arch/arm64/kernel/entry.S
> [...]
>> @@ -421,28 +421,30 @@ el0_da:
>> /*
>> * Data abort handling
>> */
>> - mrs x0, far_el1
>> - bic x0, x0, #(0xff << 56)
>> disable_step x1
>> isb
>> enable_dbg
>> // enable interrupts before calling the main handler
>> enable_irq
>> + mrs x0, far_el1
>> + bic x0, x0, #(0xff << 56)
>> mov x1, x25
>> mov x2, sp
>> b do_mem_abort
>
> Reading the far_el1 after enable_dbg and enable_irq is racy, we can no
> longer guarantee its value in the original data abort context.
Catalin, can you confirm x26 would be a safe place to stash far_el1 and
then restore it after ct_user_exit. Something like this (which seems to
work for me):
el0_da:
/*
*
Data abort handling
*/
mrs x26, far_el1
disable_step x1
isb
enable_dbg
// enable interrupts before calling the main handler
enable_irq
ct_user_exit
mov x0, x26
bic x0, x0, #(0xff << 56)
mov x1, x25
mov x2, sp
adr lr, ret_from_exception
b do_mem_abort
Kevin
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