diff options
Diffstat (limited to 'arch/arm64/kernel/efi-rt-wrapper.S')
| -rw-r--r-- | arch/arm64/kernel/efi-rt-wrapper.S | 59 |
1 files changed, 54 insertions, 5 deletions
diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S index 3fc71106cb2b..e8ae803662cf 100644 --- a/arch/arm64/kernel/efi-rt-wrapper.S +++ b/arch/arm64/kernel/efi-rt-wrapper.S @@ -4,9 +4,10 @@ */ #include <linux/linkage.h> +#include <asm/assembler.h> -ENTRY(__efi_rt_asm_wrapper) - stp x29, x30, [sp, #-32]! +SYM_FUNC_START(__efi_rt_asm_wrapper) + stp x29, x30, [sp, #-112]! mov x29, sp /* @@ -17,6 +18,22 @@ ENTRY(__efi_rt_asm_wrapper) stp x1, x18, [sp, #16] /* + * Preserve all callee saved registers and preserve the stack pointer + * value at the base of the EFI runtime stack so we can recover from + * synchronous exceptions occurring while executing the firmware + * routines. + */ + stp x19, x20, [sp, #32] + stp x21, x22, [sp, #48] + stp x23, x24, [sp, #64] + stp x25, x26, [sp, #80] + stp x27, x28, [sp, #96] + + ldr_l x16, efi_rt_stack_top + mov sp, x16 + stp x18, x29, [sp, #-16]! + + /* * We are lucky enough that no EFI runtime services take more than * 5 arguments, so all are passed in registers rather than via the * stack. @@ -29,10 +46,42 @@ ENTRY(__efi_rt_asm_wrapper) mov x4, x6 blr x8 + mov x16, sp + mov sp, x29 + str xzr, [x16, #8] // clear recorded task SP value + ldp x1, x2, [sp, #16] cmp x2, x18 - ldp x29, x30, [sp], #32 + ldp x29, x30, [sp], #112 b.ne 0f ret -0: b efi_handle_corrupted_x18 // tail call -ENDPROC(__efi_rt_asm_wrapper) +0: + /* + * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a + * shadow stack pointer, which we need to restore before returning to + * potentially instrumented code. This is safe because the wrapper is + * called with preemption disabled and a separate shadow stack is used + * for interrupts. + */ +#ifdef CONFIG_SHADOW_CALL_STACK + ldr_l x18, efi_rt_stack_top + ldr x18, [x18, #-16] +#endif + + b efi_handle_corrupted_x18 // tail call +SYM_FUNC_END(__efi_rt_asm_wrapper) + +SYM_CODE_START(__efi_rt_asm_recover) + mov sp, x30 + + ldr_l x16, efi_rt_stack_top // clear recorded task SP value + str xzr, [x16, #-8] + + ldp x19, x20, [sp, #32] + ldp x21, x22, [sp, #48] + ldp x23, x24, [sp, #64] + ldp x25, x26, [sp, #80] + ldp x27, x28, [sp, #96] + ldp x29, x30, [sp], #112 + ret +SYM_CODE_END(__efi_rt_asm_recover) |