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| /* SPDX-License-Identifier: GPL-2.0-only */
| /*
| * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org>
| */
|
| #include <linux/linkage.h>
| #include <asm/assembler.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]
|
| ldr_l x16, efi_rt_stack_top
| mov sp, x16
| #ifdef CONFIG_SHADOW_CALL_STACK
| str x18, [sp, #-16]!
| #endif
|
| /*
| * 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
|
| mov sp, x29
| 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.
| */
| #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)
|
|
