| /* SPDX-License-Identifier: GPL-2.0-only */ |
| /* |
| * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org> |
| */ |
| |
| #include <linux/linkage.h> |
| |
| SYM_FUNC_START(__efi_rt_asm_wrapper) |
| stp x29, x30, [sp, #-32]! |
| mov x29, sp |
| |
| /* |
| * Register x18 is designated as the 'platform' register by the AAPCS, |
| * which means firmware running at the same exception level as the OS |
| * (such as UEFI) should never touch it. |
| */ |
| stp x1, x18, [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. |
| */ |
| mov x8, x0 |
| mov x0, x2 |
| mov x1, x3 |
| mov x2, x4 |
| mov x3, x5 |
| mov x4, x6 |
| blr x8 |
| |
| ldp x1, x2, [sp, #16] |
| cmp x2, x18 |
| ldp x29, x30, [sp], #32 |
| b.ne 0f |
| ret |
| 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. |
| */ |
| mov x18, x2 |
| b efi_handle_corrupted_x18 // tail call |
| SYM_FUNC_END(__efi_rt_asm_wrapper) |
