arm64: Introduce esr_is_ubsan_brk()

Soon, KVM is going to use this logic for hypervisor panics,
so add it in a wrapper that can be used by the hypervisor exit
handler to decode hyp panics.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250430162713.1997569-2-smostafa@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: misaleh

arch/arm64/include/asm/esr.h

@@ -440,6 +440,11 @@ static inline bool esr_is_cfi_brk(unsigned long esr)
 	       (esr_brk_comment(esr) & ~CFI_BRK_IMM_MASK) == CFI_BRK_IMM_BASE;
 }
 
+static inline bool esr_is_ubsan_brk(unsigned long esr)
+{
+	return (esr_brk_comment(esr) & ~UBSAN_BRK_MASK) == UBSAN_BRK_IMM;
+}
+
 static inline bool esr_fsc_is_translation_fault(unsigned long esr)
 {
 	esr = esr & ESR_ELx_FSC;

arch/arm64/kernel/traps.c

@@ -1145,7 +1145,7 @@ int __init early_brk64(unsigned long addr, unsigned long esr,
 		return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
 #ifdef CONFIG_UBSAN_TRAP
-	if ((esr_brk_comment(esr) & ~UBSAN_BRK_MASK) == UBSAN_BRK_IMM)
+	if (esr_is_ubsan_brk(esr))
 		return ubsan_handler(regs, esr) != DBG_HOOK_HANDLED;
 #endif
 	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;