arm64: entry: convert SError handlers to C

For various reasons we'd like to convert the bulk of arm64's exception
triage logic to C. As a step towards that, this patch converts the EL1
and EL0 SError triage logic to C.

Separate C functions are added for the native and compat cases so that
in subsequent patches we can handle native/compat differences in C.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-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/20210607094624.34689-4-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/exception.h

@@ -32,8 +32,11 @@ static inline u32 disr_to_esr(u64 disr)
 }
 
 asmlinkage void el1_sync_handler(struct pt_regs *regs);
+asmlinkage void el1_error_handler(struct pt_regs *regs);
 asmlinkage void el0_sync_handler(struct pt_regs *regs);
+asmlinkage void el0_error_handler(struct pt_regs *regs);
 asmlinkage void el0_sync_compat_handler(struct pt_regs *regs);
+asmlinkage void el0_error_compat_handler(struct pt_regs *regs);
 
 asmlinkage void noinstr enter_el1_irq_or_nmi(struct pt_regs *regs);
 asmlinkage void noinstr exit_el1_irq_or_nmi(struct pt_regs *regs);
@@ -57,4 +60,5 @@ void do_cp15instr(unsigned int esr, struct pt_regs *regs);
 void do_el0_svc(struct pt_regs *regs);
 void do_el0_svc_compat(struct pt_regs *regs);
 void do_ptrauth_fault(struct pt_regs *regs, unsigned int esr);
+void do_serror(struct pt_regs *regs, unsigned int esr);
 #endif	/* __ASM_EXCEPTION_H */

arch/arm64/kernel/entry-common.c

@@ -279,6 +279,16 @@ asmlinkage void noinstr el1_sync_handler(struct pt_regs *regs)
 	}
 }
 
+asmlinkage void noinstr el1_error_handler(struct pt_regs *regs)
+{
+	unsigned long esr = read_sysreg(esr_el1);
+
+	local_daif_restore(DAIF_ERRCTX);
+	arm64_enter_nmi(regs);
+	do_serror(regs, esr);
+	arm64_exit_nmi(regs);
+}
+
 asmlinkage void noinstr enter_from_user_mode(void)
 {
 	lockdep_hardirqs_off(CALLER_ADDR0);
@@ -468,6 +478,23 @@ asmlinkage void noinstr el0_sync_handler(struct pt_regs *regs)
 	}
 }
 
+static void __el0_error_handler_common(struct pt_regs *regs)
+{
+	unsigned long esr = read_sysreg(esr_el1);
+
+	enter_from_user_mode();
+	local_daif_restore(DAIF_ERRCTX);
+	arm64_enter_nmi(regs);
+	do_serror(regs, esr);
+	arm64_exit_nmi(regs);
+	local_daif_restore(DAIF_PROCCTX);
+}
+
+asmlinkage void noinstr el0_error_handler(struct pt_regs *regs)
+{
+	__el0_error_handler_common(regs);
+}
+
 #ifdef CONFIG_COMPAT
 static void noinstr el0_cp15(struct pt_regs *regs, unsigned long esr)
 {
@@ -526,4 +553,9 @@ asmlinkage void noinstr el0_sync_compat_handler(struct pt_regs *regs)
 		el0_inv(regs, esr);
 	}
 }
+
+asmlinkage void noinstr el0_error_compat_handler(struct pt_regs *regs)
+{
+	__el0_error_handler_common(regs);
+}
 #endif /* CONFIG_COMPAT */

arch/arm64/kernel/entry.S

@@ -757,7 +757,9 @@ SYM_CODE_END(el0_fiq_compat)
 
 SYM_CODE_START_LOCAL_NOALIGN(el0_error_compat)
 	kernel_entry 0, 32
-	b	el0_error_naked
+	mov	x0, sp
+	bl	el0_error_compat_handler
+	b	ret_to_user
 SYM_CODE_END(el0_error_compat)
 #endif
 
@@ -778,23 +780,15 @@ SYM_CODE_END(el0_fiq)
 
 SYM_CODE_START_LOCAL(el1_error)
 	kernel_entry 1
-	mrs	x1, esr_el1
-	enable_dbg
 	mov	x0, sp
-	bl	do_serror
+	bl	el1_error_handler
 	kernel_exit 1
 SYM_CODE_END(el1_error)
 
 SYM_CODE_START_LOCAL(el0_error)
 	kernel_entry 0
-el0_error_naked:
-	mrs	x25, esr_el1
-	user_exit_irqoff
-	enable_dbg
 	mov	x0, sp
-	mov	x1, x25
-	bl	do_serror
-	enable_daif
+	bl	el0_error_handler
 	b	ret_to_user
 SYM_CODE_END(el0_error)
 

arch/arm64/kernel/traps.c

@@ -869,15 +869,11 @@ bool arm64_is_fatal_ras_serror(struct pt_regs *regs, unsigned int esr)
 	}
 }
 
-asmlinkage void noinstr do_serror(struct pt_regs *regs, unsigned int esr)
+void do_serror(struct pt_regs *regs, unsigned int esr)
 {
-	arm64_enter_nmi(regs);
-
 	/* non-RAS errors are not containable */
 	if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(regs, esr))
 		arm64_serror_panic(regs, esr);
-
-	arm64_exit_nmi(regs);
 }
 
 /* GENERIC_BUG traps */