arm64: kprobe: disable probe of fault prone ptrauth instruction

With the addition of ARMv8.3-FPAC feature, the probe of authenticate
ptrauth instructions (AUT*) may cause ptrauth fault exception in case of
authenticate failure so they cannot be safely single stepped.

Hence the probe of authenticate instructions is disallowed but the
corresponding pac ptrauth instruction (PAC*) is not affected and they can
still be probed. Also AUTH* instructions do not make sense at function
entry points so most realistic probes would be unaffected by this change.
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Link: https://lore.kernel.org/r/20200914083656.21428-6-amit.kachhap@arm.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/insn.c

@@ -60,16 +60,10 @@ bool __kprobes aarch64_insn_is_steppable_hint(u32 insn)
 	case AARCH64_INSN_HINT_XPACLRI:
 	case AARCH64_INSN_HINT_PACIA_1716:
 	case AARCH64_INSN_HINT_PACIB_1716:
-	case AARCH64_INSN_HINT_AUTIA_1716:
-	case AARCH64_INSN_HINT_AUTIB_1716:
 	case AARCH64_INSN_HINT_PACIAZ:
 	case AARCH64_INSN_HINT_PACIASP:
 	case AARCH64_INSN_HINT_PACIBZ:
 	case AARCH64_INSN_HINT_PACIBSP:
-	case AARCH64_INSN_HINT_AUTIAZ:
-	case AARCH64_INSN_HINT_AUTIASP:
-	case AARCH64_INSN_HINT_AUTIBZ:
-	case AARCH64_INSN_HINT_AUTIBSP:
 	case AARCH64_INSN_HINT_BTI:
 	case AARCH64_INSN_HINT_BTIC:
 	case AARCH64_INSN_HINT_BTIJ: