1 files changed, 49 insertions, 0 deletions
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index a908a37f0367..fab05de2e12d 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -144,3 +144,52 @@ asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
 	pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
 	return s;
 }
+
+DEFINE_SPINLOCK(efi_rt_lock);
+
+asmlinkage u64 *efi_rt_stack_top __ro_after_init;
+
+asmlinkage efi_status_t __efi_rt_asm_recover(void);
+
+bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
+{
+	 /* Check whether the exception occurred while running the firmware */
+	if (current_work() != &efi_rts_work.work || regs->pc >= TASK_SIZE_64)
+		return false;
+
+	pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
+	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+	clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+
+	regs->regs[0]	= EFI_ABORTED;
+	regs->regs[30]	= efi_rt_stack_top[-1];
+	regs->pc	= (u64)__efi_rt_asm_recover;
+
+	if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK))
+		regs->regs[18] = efi_rt_stack_top[-2];
+
+	return true;
+}
+
+/* EFI requires 8 KiB of stack space for runtime services */
+static_assert(THREAD_SIZE >= SZ_8K);
+
+static int __init arm64_efi_rt_init(void)
+{
+	void *p;
+
+	if (!efi_enabled(EFI_RUNTIME_SERVICES))
+		return 0;
+
+	p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL,
+			   NUMA_NO_NODE, &&l);
+l:	if (!p) {
+		pr_warn("Failed to allocate EFI runtime stack\n");
+		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+		return -ENOMEM;
+	}
+
+	efi_rt_stack_top = p + THREAD_SIZE;
+	return 0;
+}
+core_initcall(arm64_efi_rt_init);