From 3e3934176a4f9d479dea5cdd2fe6dd560f0ca0cf Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Thu, 16 Jan 2020 18:35:48 +0000 Subject: [PATCH] arm64: entry: cleanup sp_el0 manipulation The kernel stashes the current task struct in sp_el0 so that this can be acquired consistently/cheaply when required. When we take an exception from EL0 we have to: 1) stash the original sp_el0 value 2) find the current task 3) update sp_el0 with the current task pointer Currently steps #1 and #2 occur in one place, and step #3 a while later. As the value of sp_el0 is immaterial between these points, let's move them together to make the code clearer and minimize ifdeffery. This necessitates moving the comment for MDSCR_EL1.SS. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: James Morse Cc: Will Deacon Signed-off-by: Will Deacon --- arch/arm64/kernel/entry.S | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 7c6a0a4..3d7a9c0 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -167,9 +167,13 @@ alternative_cb_end .if \el == 0 clear_gp_regs mrs x21, sp_el0 - ldr_this_cpu tsk, __entry_task, x20 // Ensure MDSCR_EL1.SS is clear, - ldr x19, [tsk, #TSK_TI_FLAGS] // since we can unmask debug - disable_step_tsk x19, x20 // exceptions when scheduling. + ldr_this_cpu tsk, __entry_task, x20 + msr sp_el0, tsk + + // Ensure MDSCR_EL1.SS is clear, since we can unmask debug exceptions + // when scheduling. + ldr x19, [tsk, #TSK_TI_FLAGS] + disable_step_tsk x19, x20 apply_ssbd 1, x22, x23 @@ -232,13 +236,6 @@ alternative_else_nop_endif str w21, [sp, #S_SYSCALLNO] .endif - /* - * Set sp_el0 to current thread_info. - */ - .if \el == 0 - msr sp_el0, tsk - .endif - /* Save pmr */ alternative_if ARM64_HAS_IRQ_PRIO_MASKING mrs_s x20, SYS_ICC_PMR_EL1 -- 2.7.4