On Fri, May 15, 2020 at 06:27:53PM +0100, Will Deacon wrote: > x18 holds the SCS stack pointer value, so introduce a register alias to > make this easier to read in assembly code. > > Signed-off-by: Will Deacon <w...@kernel.org>
I scanned through arm64 for all instances of x18, and it looks like you've covered all the relevant uses here. In kvm we save/restore x18 a bunch becasue it might be a platform register, but we do that unconditionally and without knowledge of what it contains, so I think that's fine to leave as-is. Therefore: Reviewed-by: Mark Rutland <mark.rutl...@arm.com> As an aside, the comment in entry-ftrace.S is now stale where it says that x18 is safe to clobber. I can send a patch to clean that up, unless you want to do that yourself. Mark. > --- > arch/arm64/include/asm/scs.h | 6 ++++-- > arch/arm64/kernel/entry.S | 10 +++++----- > arch/arm64/kernel/head.S | 2 +- > 3 files changed, 10 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h > index 6b8cf4352fe3..d46efdd2060a 100644 > --- a/arch/arm64/include/asm/scs.h > +++ b/arch/arm64/include/asm/scs.h > @@ -7,12 +7,14 @@ > #include <asm/asm-offsets.h> > > #ifdef CONFIG_SHADOW_CALL_STACK > + scs_sp .req x18 > + > .macro scs_load tsk, tmp > - ldr x18, [\tsk, #TSK_TI_SCS_SP] > + ldr scs_sp, [\tsk, #TSK_TI_SCS_SP] > .endm > > .macro scs_save tsk, tmp > - str x18, [\tsk, #TSK_TI_SCS_SP] > + str scs_sp, [\tsk, #TSK_TI_SCS_SP] > .endm > #else > .macro scs_load tsk, tmp > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index cb0516e6f963..741faf0706f1 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -394,7 +394,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 > .macro irq_stack_entry > mov x19, sp // preserve the original sp > #ifdef CONFIG_SHADOW_CALL_STACK > - mov x24, x18 // preserve the original shadow stack > + mov x24, scs_sp // preserve the original shadow stack > #endif > > /* > @@ -416,7 +416,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 > > #ifdef CONFIG_SHADOW_CALL_STACK > /* also switch to the irq shadow stack */ > - adr_this_cpu x18, irq_shadow_call_stack, x26 > + adr_this_cpu scs_sp, irq_shadow_call_stack, x26 > #endif > > 9998: > @@ -430,7 +430,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 > .macro irq_stack_exit > mov sp, x19 > #ifdef CONFIG_SHADOW_CALL_STACK > - mov x18, x24 > + mov scs_sp, x24 > #endif > .endm > > @@ -1071,9 +1071,9 @@ SYM_CODE_START(__sdei_asm_handler) > #ifdef CONFIG_SHADOW_CALL_STACK > /* Use a separate shadow call stack for normal and critical events */ > cbnz w4, 3f > - adr_this_cpu dst=x18, sym=sdei_shadow_call_stack_normal, tmp=x6 > + adr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_normal, tmp=x6 > b 4f > -3: adr_this_cpu dst=x18, sym=sdei_shadow_call_stack_critical, tmp=x6 > +3: adr_this_cpu dst=scs_sp, sym=sdei_shadow_call_stack_critical, tmp=x6 > 4: > #endif > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 2b01c19c5483..1293baddfd20 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -426,7 +426,7 @@ SYM_FUNC_START_LOCAL(__primary_switched) > mov x29, sp > > #ifdef CONFIG_SHADOW_CALL_STACK > - adr_l x18, init_shadow_call_stack // Set shadow call stack > + adr_l scs_sp, init_shadow_call_stack // Set shadow call stack > #endif > > str_l x21, __fdt_pointer, x5 // Save FDT pointer > -- > 2.26.2.761.g0e0b3e54be-goog >
