Messages in this thread | | | Date | Mon, 07 Sep 2015 15:48:49 +0100 | From | James Morse <> | Subject | Re: [RFC PATCH 1/3] arm64: entry: Remove unnecessary calculation for S_SP in EL1h |
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On 04/09/15 15:23, 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. > > Signed-off-by: Jungseok Lee <jungseoklee85@gmail.com> > 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 >
This sp value gets written to the struct pt_regs that is built on the stack, and passed to the fault handlers, see 'el1_sp_pc' in kernel/entry.S, which goes on to call do_sp_pc_abort() which prints this value out. (Other fault handlers may make decisions based on this value). It should be present and correct.
Thanks,
James
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