[RFC PATCH 23/36] arm64/efi: Implement override for IRQ flags checks

[Vladimir Murzin]

Take advantage of the recent changes to the way arm64 represents IRQ
flags and implement an architecture-specific override for the EFI IRQ
flags check.

IRQ flags now carry both DAIF and PMR state. EFI is not expected to
modify either of them, so check both when verifying that IRQ state is
preserved across EFI runtime calls.

Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
 arch/arm64/include/asm/efi.h | 38 ++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index e8a9783235cb..479741d52c90 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -5,6 +5,7 @@
 #include <asm/boot.h>
 #include <asm/cpufeature.h>
 #include <asm/fpsimd.h>
+#include <asm/interrupts/common_flags.h>
 #include <asm/io.h>
 #include <asm/memory.h>
 #include <asm/mmu_context.h>
@@ -48,18 +49,43 @@ void arch_efi_call_virt_teardown(void);
 	(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)
-
 /*
  * Even when Linux uses IRQ priorities for IRQ disabling, EFI does not.
  * And EFI shouldn't really play around with priority masking as it is not aware
  * which priorities the OS has assigned to its interrupts.
  */
 #define arch_efi_save_flags(state_flags)		\
-	((void)((state_flags) = read_sysreg(daif)))
-
-#define arch_efi_restore_flags(state_flags)	write_sysreg(state_flags, daif)
-
+	((void)((state_flags) = arch_local_save_flags()))
+
+#define arch_efi_restore_flags(state_flags)			\
+do {								\
+	arm64_exc_hwstate_t __st = {.flags=state_flags};	\
+								\
+	arm64_update_exc_hwstate(__st, true, true);		\
+ } while(0)
+
+#define arch_efi_check_flags(state_flags, caller)									\
+do {															\
+	arm64_exc_hwstate_t __actual = {.flags =  arch_local_save_flags() };						\
+	arm64_exc_hwstate_t __expected = {.flags=state_flags};								\
+															\
+	if (__expected.flags == __actual.flags)										\
+		break;													\
+															\
+	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_NOW_UNRELIABLE);							\
+															\
+	if (system_uses_irq_prio_masking()) {										\
+		pr_err_ratelimited(FW_BUG "DAIF+PMR corrupted (0x%x + 0x%x=>0x%x + 0x%x) by EFI call from %pS\n",	\
+				   __expected.daif, __expected.pmr, __actual.daif, __actual.pmr,			\
+				   caller ?: __builtin_return_address(0));						\
+	} else {													\
+		pr_err_ratelimited(FW_BUG "DAIF corrupted (0x%x=>0x%x) by EFI call from %pS\n",				\
+				   __expected.daif, __actual.daif,							\
+				   caller ?: __builtin_return_address(0));						\
+	}														\
+															\
+	arch_efi_restore_flags(state_flags);										\
+} while(0)
 
 /* arch specific definitions used by the stub code */
 
-- 
2.34.1