arm64: Introduce esr_brk_comment, esr_is_cfi_brk

As it is already used in two places, move esr_comment() to a header for
re-use, with a clearer name.

Introduce esr_is_cfi_brk() to detect kCFI BRK syndromes, currently used
by early_brk64() but soon to also be used by hypervisor code.
Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240610063244.2828978-7-ptosi@google.comSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/include/asm/esr.h

@@ -379,6 +379,11 @@
 #ifndef __ASSEMBLY__
 #include <asm/types.h>
 
+static inline unsigned long esr_brk_comment(unsigned long esr)
+{
+	return esr & ESR_ELx_BRK64_ISS_COMMENT_MASK;
+}
+
 static inline bool esr_is_data_abort(unsigned long esr)
 {
 	const unsigned long ec = ESR_ELx_EC(esr);
@@ -386,6 +391,12 @@ static inline bool esr_is_data_abort(unsigned long esr)
 	return ec == ESR_ELx_EC_DABT_LOW || ec == ESR_ELx_EC_DABT_CUR;
 }
 
+static inline bool esr_is_cfi_brk(unsigned long esr)
+{
+	return ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
+	       (esr_brk_comment(esr) & ~CFI_BRK_IMM_MASK) == CFI_BRK_IMM_BASE;
+}
+
 static inline bool esr_fsc_is_translation_fault(unsigned long esr)
 {
 	/* Translation fault, level -1 */

arch/arm64/kernel/debug-monitors.c

@@ -312,9 +312,7 @@ static int call_break_hook(struct pt_regs *regs, unsigned long esr)
 	 * entirely not preemptible, and we can use rcu list safely here.
 	 */
 	list_for_each_entry_rcu(hook, list, node) {
-		unsigned long comment = esr & ESR_ELx_BRK64_ISS_COMMENT_MASK;
-
-		if ((comment & ~hook->mask) == hook->imm)
+		if ((esr_brk_comment(esr) & ~hook->mask) == hook->imm)
 			fn = hook->fn;
 	}
 

arch/arm64/kernel/traps.c

@@ -1105,8 +1105,6 @@ static struct break_hook ubsan_break_hook = {
 };
 #endif
 
-#define esr_comment(esr) ((esr) & ESR_ELx_BRK64_ISS_COMMENT_MASK)
-
 /*
  * Initial handler for AArch64 BRK exceptions
  * This handler only used until debug_traps_init().
@@ -1115,15 +1113,15 @@ int __init early_brk64(unsigned long addr, unsigned long esr,
 		struct pt_regs *regs)
 {
 #ifdef CONFIG_CFI_CLANG
-	if ((esr_comment(esr) & ~CFI_BRK_IMM_MASK) == CFI_BRK_IMM_BASE)
+	if (esr_is_cfi_brk(esr))
 		return cfi_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
 #ifdef CONFIG_KASAN_SW_TAGS
-	if ((esr_comment(esr) & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
+	if ((esr_brk_comment(esr) & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
 		return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
 #ifdef CONFIG_UBSAN_TRAP
-	if ((esr_comment(esr) & ~UBSAN_BRK_MASK) == UBSAN_BRK_IMM)
+	if ((esr_brk_comment(esr) & ~UBSAN_BRK_MASK) == UBSAN_BRK_IMM)
 		return ubsan_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
 	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;

arch/arm64/kvm/handle_exit.c

@@ -423,7 +423,7 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
 	if (mode != PSR_MODE_EL2t && mode != PSR_MODE_EL2h) {
 		kvm_err("Invalid host exception to nVHE hyp!\n");
 	} else if (ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
-		   (esr & ESR_ELx_BRK64_ISS_COMMENT_MASK) == BUG_BRK_IMM) {
+		   esr_brk_comment(esr) == BUG_BRK_IMM) {
 		const char *file = NULL;
 		unsigned int line = 0;