From 3425d934fc0312f62024163736a7afe4de20c10f Mon Sep 17 00:00:00 2001 From: Sai Praneeth Date: Tue, 11 Sep 2018 12:15:22 -0700 Subject: efi/x86: Handle page faults occurring while running EFI runtime services Memory accesses performed by UEFI runtime services should be limited to: - reading/executing from EFI_RUNTIME_SERVICES_CODE memory regions - reading/writing from/to EFI_RUNTIME_SERVICES_DATA memory regions - reading/writing by-ref arguments - reading/writing from/to the stack. Accesses outside these regions may cause the kernel to hang because the memory region requested by the firmware isn't mapped in efi_pgd, which causes a page fault in ring 0 and the kernel fails to handle it, leading to die(). To save kernel from hanging, add an EFI specific page fault handler which recovers from such faults by 1. If the efi runtime service is efi_reset_system(), reboot the machine through BIOS. 2. If the efi runtime service is _not_ efi_reset_system(), then freeze efi_rts_wq and schedule a new process. The EFI page fault handler offers us two advantages: 1. Avoid potential hangs caused by buggy firmware. 2. Shout loud that the firmware is buggy and hence is not a kernel bug. Tested-by: Bhupesh Sharma Suggested-by: Matt Fleming Based-on-code-from: Ricardo Neri Signed-off-by: Sai Praneeth Prakhya Reviewed-by: Thomas Gleixner [ardb: clarify commit log] Signed-off-by: Ard Biesheuvel --- arch/x86/include/asm/efi.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/include/asm/efi.h') diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index cec5fae23eb3..eea40d52ca78 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -140,6 +140,7 @@ extern void __init efi_apply_memmap_quirks(void); extern int __init efi_reuse_config(u64 tables, int nr_tables); extern void efi_delete_dummy_variable(void); extern void efi_switch_mm(struct mm_struct *mm); +extern void efi_recover_from_page_fault(unsigned long phys_addr); struct efi_setup_data { u64 fw_vendor; -- cgit v1.2.3