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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, #-112]!
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]
/*
* 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.
*/
mov x8, x0
mov x0, x2
mov x1, x3
mov x2, x4
mov x3, x5
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], #112
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)
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)
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