arm64: entry: fold el1_inv() into el1h_64_sync_handler()

An unexpected synchronous exception from EL1h could happen at any time,
and for robustness we should treat this as an NMI, making minimal
assumptions about the context the exception was taken from.

Currently el1_inv() assumes we can use enter_from_kernel_mode(), and
also assumes that we should inherit the original DAIF value. Neither of
these are desireable when we take an unexpected exception. Further,
after el1_inv() calls __panic_unhandled(), the remainder of the function
is unreachable, and therefore superfluous.

Let's address this and simplify things by having el1h_64_sync_handler()
call __panic_unhandled() directly, without any of the redundant logic.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Reported-by: Joey Gouly <joey.gouly@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210607094624.34689-16-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: mrutland-arm

arch/arm64/kernel/entry-common.c

@@ -264,15 +264,6 @@ static void noinstr el1_undef(struct pt_regs *regs)
 	exit_to_kernel_mode(regs);
 }
 
-static void noinstr el1_inv(struct pt_regs *regs, unsigned long esr)
-{
-	enter_from_kernel_mode(regs);
-	local_daif_inherit(regs);
-	__panic_unhandled(regs, "64-bit el1h sync", esr);
-	local_daif_mask();
-	exit_to_kernel_mode(regs);
-}
-
 static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
 {
 	regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
@@ -346,7 +337,7 @@ asmlinkage void noinstr el1h_64_sync_handler(struct pt_regs *regs)
 		el1_fpac(regs, esr);
 		break;
 	default:
-		el1_inv(regs, esr);
+		__panic_unhandled(regs, "64-bit el1h sync", esr);
 	}
 }