@@ -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;
@@ -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>
@@ -788,6 +790,13 @@ no_context(struct pt_regs *regs, unsigned long error_code,
if (is_errata93(regs, address))
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:
@@ -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;
+}
@@ -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);
}
@@ -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,
};