Messages in this thread | | | Subject | Re: [RFC PATCH 1/3] arm64: entry: Remove unnecessary calculation for S_SP in EL1h | From | Jungseok Lee <> | Date | Tue, 8 Sep 2015 00:51:04 +0900 |
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On Sep 7, 2015, at 11:56 PM, Mark Rutland wrote:
Hi Mark,
> 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@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 >> .endif >> 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.
Best Regards Jungseok Lee
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