From 8a9a1a18731eb123e35f48176380a18b9782845e Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 28 Oct 2022 16:39:14 +0200 Subject: arm64: efi: Avoid workqueue to check whether EFI runtime is live 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 Signed-off-by: Ard Biesheuvel --- arch/arm64/kernel/efi-rt-wrapper.S | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/arm64/kernel/efi-rt-wrapper.S') diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S index d872d18101d8..e8ae803662cf 100644 --- a/arch/arm64/kernel/efi-rt-wrapper.S +++ b/arch/arm64/kernel/efi-rt-wrapper.S @@ -46,7 +46,10 @@ SYM_FUNC_START(__efi_rt_asm_wrapper) 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 @@ -71,6 +74,9 @@ 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] -- cgit v1.2.3