From e8dfdf3162eb549d064b8c10b1564f7e8ee82591 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 28 Oct 2022 16:39:14 +0200 Subject: arm64: efi: Recover from synchronous exceptions occurring in firmware Unlike x86, which has machinery to deal with page faults that occur during the execution of EFI runtime services, arm64 has nothing like that, and a synchronous exception raised by firmware code brings down the whole system. With more EFI based systems appearing that were not built to run Linux (such as the Windows-on-ARM laptops based on Qualcomm SOCs), as well as the introduction of PRM (platform specific firmware routines that are callable just like EFI runtime services), we are more likely to run into issues of this sort, and it is much more likely that we can identify and work around such issues if they don't bring down the system entirely. Since we already use a EFI runtime services call wrapper in assembler, we can quite easily add some code that captures the execution state at the point where the call is made, allowing us to revert to this state and proceed execution if the call triggered a synchronous exception. Given that the kernel and the firmware don't share any data structures that could end up in an indeterminate state, we can happily continue running, as long as we mark the EFI runtime services as unavailable from that point on. Signed-off-by: Ard Biesheuvel Acked-by: Catalin Marinas --- drivers/firmware/efi/runtime-wrappers.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/firmware/efi/runtime-wrappers.c') diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c index f3e54f6616f0..7feee3d9c2bf 100644 --- a/drivers/firmware/efi/runtime-wrappers.c +++ b/drivers/firmware/efi/runtime-wrappers.c @@ -83,6 +83,7 @@ struct efi_runtime_work efi_rts_work; else \ pr_err("Failed to queue work to efi_rts_wq.\n"); \ \ + WARN_ON_ONCE(efi_rts_work.status == EFI_ABORTED); \ exit: \ efi_rts_work.efi_rts_id = EFI_NONE; \ efi_rts_work.status; \ -- cgit v1.2.3