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8a9a1a1873
Comparing current_work() against efi_rts_work.work is sufficient to decide whether current is currently running EFI runtime services code at any level in its call stack. However, there are other potential users of the EFI runtime stack, such as the ACPI subsystem, which may invoke efi_call_virt_pointer() directly, and so any sync exceptions occurring in firmware during those calls are currently misidentified. So instead, let's check whether the stashed value of the thread stack pointer points into current's thread stack. This can only be the case if current was interrupted while running EFI runtime code. Note that this implies that we should clear the stashed value after switching back, to avoid false positives. Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
88 lines
2 KiB
ArmAsm
88 lines
2 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org>
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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SYM_FUNC_START(__efi_rt_asm_wrapper)
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stp x29, x30, [sp, #-112]!
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mov x29, sp
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/*
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* Register x18 is designated as the 'platform' register by the AAPCS,
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* which means firmware running at the same exception level as the OS
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* (such as UEFI) should never touch it.
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*/
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stp x1, x18, [sp, #16]
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/*
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* Preserve all callee saved registers and preserve the stack pointer
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* value at the base of the EFI runtime stack so we can recover from
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* synchronous exceptions occurring while executing the firmware
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* routines.
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*/
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stp x19, x20, [sp, #32]
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stp x21, x22, [sp, #48]
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stp x23, x24, [sp, #64]
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stp x25, x26, [sp, #80]
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stp x27, x28, [sp, #96]
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ldr_l x16, efi_rt_stack_top
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mov sp, x16
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stp x18, x29, [sp, #-16]!
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/*
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* We are lucky enough that no EFI runtime services take more than
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* 5 arguments, so all are passed in registers rather than via the
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* stack.
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*/
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mov x8, x0
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mov x0, x2
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mov x1, x3
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mov x2, x4
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mov x3, x5
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mov x4, x6
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blr x8
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mov x16, sp
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mov sp, x29
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str xzr, [x16, #8] // clear recorded task SP value
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ldp x1, x2, [sp, #16]
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cmp x2, x18
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ldp x29, x30, [sp], #112
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b.ne 0f
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ret
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0:
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/*
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* With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a
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* shadow stack pointer, which we need to restore before returning to
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* potentially instrumented code. This is safe because the wrapper is
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* called with preemption disabled and a separate shadow stack is used
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* for interrupts.
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*/
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#ifdef CONFIG_SHADOW_CALL_STACK
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ldr_l x18, efi_rt_stack_top
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ldr x18, [x18, #-16]
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#endif
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b efi_handle_corrupted_x18 // tail call
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SYM_FUNC_END(__efi_rt_asm_wrapper)
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SYM_CODE_START(__efi_rt_asm_recover)
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mov sp, x30
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ldr_l x16, efi_rt_stack_top // clear recorded task SP value
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str xzr, [x16, #-8]
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ldp x19, x20, [sp, #32]
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ldp x21, x22, [sp, #48]
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ldp x23, x24, [sp, #64]
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ldp x25, x26, [sp, #80]
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ldp x27, x28, [sp, #96]
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ldp x29, x30, [sp], #112
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ret
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SYM_CODE_END(__efi_rt_asm_recover)
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