diff options
| -rw-r--r-- | arch/x86/include/asm/efi.h | 1 | ||||
| -rw-r--r-- | arch/x86/mm/fault.c | 9 | ||||
| -rw-r--r-- | arch/x86/platform/efi/quirks.c | 78 | ||||
| -rw-r--r-- | drivers/firmware/efi/runtime-wrappers.c | 8 | ||||
| -rw-r--r-- | include/linux/efi.h | 8 |
5 files changed, 103 insertions, 1 deletions
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; diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 47bebfe6efa7..a5b9ddb0f1fe 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -16,6 +16,7 @@ #include <linux/prefetch.h> /* prefetchw */ #include <linux/context_tracking.h> /* exception_enter(), ... */ #include <linux/uaccess.h> /* faulthandler_disabled() */ +#include <linux/efi.h> /* efi_recover_from_page_fault()*/ #include <linux/mm_types.h> #include <asm/cpufeature.h> /* boot_cpu_has, ... */ @@ -25,6 +26,7 @@ #include <asm/vsyscall.h> /* emulate_vsyscall */ #include <asm/vm86.h> /* struct vm86 */ #include <asm/mmu_context.h> /* vma_pkey() */ +#include <asm/efi.h> /* efi_recover_from_page_fault()*/ #define CREATE_TRACE_POINTS #include <asm/trace/exceptions.h> @@ -789,6 +791,13 @@ no_context(struct pt_regs *regs, unsigned long error_code, return; /* + * Buggy firmware could access regions which might page fault, try to + * recover from such faults. + */ + if (IS_ENABLED(CONFIG_EFI)) + efi_recover_from_page_fault(address); + + /* * Oops. The kernel tried to access some bad page. We'll have to * terminate things with extreme prejudice: */ diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c index 844d31cb8a0c..669babcaf245 100644 --- a/arch/x86/platform/efi/quirks.c +++ b/arch/x86/platform/efi/quirks.c @@ -16,6 +16,7 @@ #include <asm/efi.h> #include <asm/uv/uv.h> #include <asm/cpu_device_id.h> +#include <asm/reboot.h> #define EFI_MIN_RESERVE 5120 @@ -654,3 +655,80 @@ int efi_capsule_setup_info(struct capsule_info *cap_info, void *kbuff, } #endif + +/* + * If any access by any efi runtime service causes a page fault, then, + * 1. If it's efi_reset_system(), reboot through BIOS. + * 2. If any other efi runtime service, then + * a. Return error status to the efi caller process. + * b. Disable EFI Runtime Services forever and + * c. Freeze efi_rts_wq and schedule new process. + * + * @return: Returns, if the page fault is not handled. This function + * will never return if the page fault is handled successfully. + */ +void efi_recover_from_page_fault(unsigned long phys_addr) +{ + if (!IS_ENABLED(CONFIG_X86_64)) + return; + + /* + * Make sure that an efi runtime service caused the page fault. + * "efi_mm" cannot be used to check if the page fault had occurred + * in the firmware context because efi=old_map doesn't use efi_pgd. + */ + if (efi_rts_work.efi_rts_id == NONE) + return; + + /* + * Address range 0x0000 - 0x0fff is always mapped in the efi_pgd, so + * page faulting on these addresses isn't expected. + */ + if (phys_addr >= 0x0000 && phys_addr <= 0x0fff) + return; + + /* + * Print stack trace as it might be useful to know which EFI Runtime + * Service is buggy. + */ + WARN(1, FW_BUG "Page fault caused by firmware at PA: 0x%lx\n", + phys_addr); + + /* + * Buggy efi_reset_system() is handled differently from other EFI + * Runtime Services as it doesn't use efi_rts_wq. Although, + * native_machine_emergency_restart() says that machine_real_restart() + * could fail, it's better not to compilcate this fault handler + * because this case occurs *very* rarely and hence could be improved + * on a need by basis. + */ + if (efi_rts_work.efi_rts_id == RESET_SYSTEM) { + pr_info("efi_reset_system() buggy! Reboot through BIOS\n"); + machine_real_restart(MRR_BIOS); + return; + } + + /* + * Before calling EFI Runtime Service, the kernel has switched the + * calling process to efi_mm. Hence, switch back to task_mm. + */ + arch_efi_call_virt_teardown(); + + /* Signal error status to the efi caller process */ + efi_rts_work.status = EFI_ABORTED; + complete(&efi_rts_work.efi_rts_comp); + + clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); + pr_info("Froze efi_rts_wq and disabled EFI Runtime Services\n"); + + /* + * Call schedule() in an infinite loop, so that any spurious wake ups + * will never run efi_rts_wq again. + */ + for (;;) { + set_current_state(TASK_IDLE); + schedule(); + } + + return; +} diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c index b18b2d864c2c..a19d845bdb06 100644 --- a/drivers/firmware/efi/runtime-wrappers.c +++ b/drivers/firmware/efi/runtime-wrappers.c @@ -61,6 +61,11 @@ struct efi_runtime_work efi_rts_work; ({ \ efi_rts_work.status = EFI_ABORTED; \ \ + if (!efi_enabled(EFI_RUNTIME_SERVICES)) { \ + pr_warn_once("EFI Runtime Services are disabled!\n"); \ + goto exit; \ + } \ + \ init_completion(&efi_rts_work.efi_rts_comp); \ INIT_WORK_ONSTACK(&efi_rts_work.work, efi_call_rts); \ efi_rts_work.arg1 = _arg1; \ @@ -79,6 +84,8 @@ struct efi_runtime_work efi_rts_work; else \ pr_err("Failed to queue work to efi_rts_wq.\n"); \ \ +exit: \ + efi_rts_work.efi_rts_id = NONE; \ efi_rts_work.status; \ }) @@ -393,6 +400,7 @@ static void virt_efi_reset_system(int reset_type, "could not get exclusive access to the firmware\n"); return; } + efi_rts_work.efi_rts_id = RESET_SYSTEM; __efi_call_virt(reset_system, reset_type, status, data_size, data); up(&efi_runtime_lock); } diff --git a/include/linux/efi.h b/include/linux/efi.h index a929d2bf41fa..845174e113ce 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1662,8 +1662,13 @@ struct linux_efi_tpm_eventlog { extern int efi_tpm_eventlog_init(void); -/* efi_runtime_service() function identifiers */ +/* + * efi_runtime_service() function identifiers. + * "NONE" is used by efi_recover_from_page_fault() to check if the page + * fault happened while executing an efi runtime service. + */ enum efi_rts_ids { + NONE, GET_TIME, SET_TIME, GET_WAKEUP_TIME, @@ -1673,6 +1678,7 @@ enum efi_rts_ids { SET_VARIABLE, QUERY_VARIABLE_INFO, GET_NEXT_HIGH_MONO_COUNT, + RESET_SYSTEM, UPDATE_CAPSULE, QUERY_CAPSULE_CAPS, }; |