[RFC PATCH 1/3] arm64: entry: Remove unnecessary calculation for S_SP in EL1h
jungseoklee85 at gmail.com
Mon Sep 7 08:51:04 PDT 2015
On Sep 7, 2015, at 11:56 PM, Mark Rutland wrote:
> On Fri, Sep 04, 2015 at 03:23:05PM +0100, Jungseok Lee wrote:
>> Under EL1h, S_SP data is not seen in kernel_exit. Thus, x21 calculation
>> is not needed in kernel_entry. Currently, S_SP information is vaild only
>> when sp_el0 is used.
> I don't think this is true. The generic BUG implementation will grab the
> saved SP from the pt_regs, and with this change we'll report whatever
> happened to be in x21 instead.
>> Signed-off-by: Jungseok Lee <jungseoklee85 at gmail.com>
>> arch/arm64/kernel/entry.S | 2 --
>> 1 file changed, 2 deletions(-)
>> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
>> index e163518..d23ca0d 100644
>> --- a/arch/arm64/kernel/entry.S
>> +++ b/arch/arm64/kernel/entry.S
>> @@ -91,8 +91,6 @@
>> get_thread_info tsk // Ensure MDSCR_EL1.SS is clear,
>> ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug
>> disable_step_tsk x19, x20 // exceptions when scheduling.
>> - .else
>> - add x21, sp, #S_FRAME_SIZE
>> mrs x22, elr_el1
>> mrs x23, spsr_el1
> Immediately after this we do:
> stp lr, x21, [sp, #S_LR]
> To store the LR and SP to the pt_regs which bug_handler would use.
> Am I missing smoething?
No, You're right. As James mentioned, x21 is used in do_sp_pc_abort.
Thanks for the comment.
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