Merge tag 'efi-fixes-for-v6.2-2' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi

Pull EFI fixes from Ard Biesheuvel:
 "Another couple of EFI fixes, of which the first two were already in
  -next when I sent out the previous PR, but they caused some issues on
  non-EFI boots so I let them simmer for a bit longer.

   - ensure the EFI ResetSystem and ACPI PRM calls are recognized as
     users of the EFI runtime, and therefore protected against
     exceptions

   - account for the EFI runtime stack in the stacktrace code

   - remove Matthew Garrett's MAINTAINERS entry for efivarfs"

* tag 'efi-fixes-for-v6.2-2' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
  efi: Remove Matthew Garrett as efivarfs maintainer
  arm64: efi: Account for the EFI runtime stack in stack unwinder
  arm64: efi: Avoid workqueue to check whether EFI runtime is live

6 files changed, 44 insertions, 2 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index f781f936ae35..468f39a37b33 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7615,7 +7615,6 @@ S:	Maintained
 F:	drivers/firmware/efi/test/
 
 EFI VARIABLE FILESYSTEM
-M:	Matthew Garrett <matthew.garrett@nebula.com>
 M:	Jeremy Kerr <jk@ozlabs.org>
 M:	Ard Biesheuvel <ardb@kernel.org>
 L:	linux-efi@vger.kernel.org
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 31d13a6001df..de4ff90785b2 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -48,8 +48,17 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
 })
 
 extern spinlock_t efi_rt_lock;
+extern u64 *efi_rt_stack_top;
 efi_status_t __efi_rt_asm_wrapper(void *, const char *, ...);
 
+/*
+ * efi_rt_stack_top[-1] contains the value the stack pointer had before
+ * switching to the EFI runtime stack.
+ */
+#define current_in_efi()						\
+	(!preemptible() && efi_rt_stack_top != NULL &&			\
+	 on_task_stack(current, READ_ONCE(efi_rt_stack_top[-1]), 1))
+
 #define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
 
 /*
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 4e5354beafb0..66ec8caa6ac0 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -106,4 +106,19 @@ static inline struct stack_info stackinfo_get_sdei_critical(void)
 #define stackinfo_get_sdei_critical()	stackinfo_get_unknown()
 #endif
 
+#ifdef CONFIG_EFI
+extern u64 *efi_rt_stack_top;
+
+static inline struct stack_info stackinfo_get_efi(void)
+{
+	unsigned long high = (u64)efi_rt_stack_top;
+	unsigned long low = high - THREAD_SIZE;
+
+	return (struct stack_info) {
+		.low = low,
+		.high = high,
+	};
+}
+#endif
+
 #endif	/* __ASM_STACKTRACE_H */
diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S
index d872d18101d8..e8ae803662cf 100644
--- a/arch/arm64/kernel/efi-rt-wrapper.S
+++ b/arch/arm64/kernel/efi-rt-wrapper.S
@@ -46,7 +46,10 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
 	mov	x4, x6
 	blr	x8
 
+	mov	x16, sp
 	mov	sp, x29
+	str	xzr, [x16, #8]			// clear recorded task SP value
+
 	ldp	x1, x2, [sp, #16]
 	cmp	x2, x18
 	ldp	x29, x30, [sp], #112
@@ -71,6 +74,9 @@ SYM_FUNC_END(__efi_rt_asm_wrapper)
 SYM_CODE_START(__efi_rt_asm_recover)
 	mov	sp, x30
 
+	ldr_l	x16, efi_rt_stack_top		// clear recorded task SP value
+	str	xzr, [x16, #-8]
+
 	ldp	x19, x20, [sp, #32]
 	ldp	x21, x22, [sp, #48]
 	ldp	x23, x24, [sp, #64]
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index fab05de2e12d..b273900f4566 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -11,6 +11,7 @@
 #include <linux/init.h>
 
 #include <asm/efi.h>
+#include <asm/stacktrace.h>
 
 static bool region_is_misaligned(const efi_memory_desc_t *md)
 {
@@ -154,7 +155,7 @@ 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)
+	if (!current_in_efi() || regs->pc >= TASK_SIZE_64)
 		return false;
 
 	pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 117e2c180f3c..83154303e682 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2012 ARM Ltd.
  */
 #include <linux/kernel.h>
+#include <linux/efi.h>
 #include <linux/export.h>
 #include <linux/ftrace.h>
 #include <linux/sched.h>
@@ -12,6 +13,7 @@
 #include <linux/sched/task_stack.h>
 #include <linux/stacktrace.h>
 
+#include <asm/efi.h>
 #include <asm/irq.h>
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
@@ -186,6 +188,13 @@ void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
 			: stackinfo_get_unknown();		\
 	})
 
+#define STACKINFO_EFI						\
+	({							\
+		((task == current) && current_in_efi())		\
+			? stackinfo_get_efi()			\
+			: stackinfo_get_unknown();		\
+	})
+
 noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
 			      void *cookie, struct task_struct *task,
 			      struct pt_regs *regs)
@@ -200,6 +209,9 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
 		STACKINFO_SDEI(normal),
 		STACKINFO_SDEI(critical),
 #endif
+#ifdef CONFIG_EFI
+		STACKINFO_EFI,
+#endif
 	};
 	struct unwind_state state = {
 		.stacks = stacks,