arm64: scs: Use 'scs_sp' register alias for x18

x18 holds the SCS stack pointer value, so introduce a register alias to
make this easier to read in assembly code.

Tested-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h
index 6b8cf43..d46efdd 100644 (file)
--- 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 cb0516e..741faf0 100644 (file)
--- 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 2b01c19..1293bad 100644 (file)
--- 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