1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org>
6 #include <linux/linkage.h>
8 SYM_FUNC_START(__efi_rt_asm_wrapper)
9 stp x29, x30, [sp, #-112]!
13 * Register x18 is designated as the 'platform' register by the AAPCS,
14 * which means firmware running at the same exception level as the OS
15 * (such as UEFI) should never touch it.
17 stp x1, x18, [sp, #16]
20 * Preserve all callee saved registers and preserve the stack pointer
21 * value at the base of the EFI runtime stack so we can recover from
22 * synchronous exceptions occurring while executing the firmware
25 stp x19, x20, [sp, #32]
26 stp x21, x22, [sp, #48]
27 stp x23, x24, [sp, #64]
28 stp x25, x26, [sp, #80]
29 stp x27, x28, [sp, #96]
31 ldr_l x16, efi_rt_stack_top
33 stp x18, x29, [sp, #-16]!
36 * We are lucky enough that no EFI runtime services take more than
37 * 5 arguments, so all are passed in registers rather than via the
51 ldp x29, x30, [sp], #112
56 * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a
57 * shadow stack pointer, which we need to restore before returning to
58 * potentially instrumented code. This is safe because the wrapper is
59 * called with preemption disabled and a separate shadow stack is used
62 #ifdef CONFIG_SHADOW_CALL_STACK
63 ldr_l x18, efi_rt_stack_top
67 b efi_handle_corrupted_x18 // tail call
68 SYM_FUNC_END(__efi_rt_asm_wrapper)
70 SYM_CODE_START(__efi_rt_asm_recover)
73 ldp x19, x20, [sp, #32]
74 ldp x21, x22, [sp, #48]
75 ldp x23, x24, [sp, #64]
76 ldp x25, x26, [sp, #80]
77 ldp x27, x28, [sp, #96]
78 ldp x29, x30, [sp], #112
80 SYM_CODE_END(__efi_rt_asm_recover)