arm64: probes: Disable kprobes/uprobes on MOPS instructions

FEAT_MOPS instructions require that all three instructions (prologue,
main and epilogue) appear consecutively in memory. Placing a
kprobe/uprobe on one of them doesn't work as only a single instruction
gets executed out-of-line or simulated. So don't allow placing a probe
on a MOPS instruction.

Fixes: b756412 ("arm64: mops: detect and enable FEAT_MOPS")
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20240930161051.3777828-2-kristina.martsenko@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: kristina-martsenko

arch/arm64/include/asm/insn.h

@@ -353,6 +353,7 @@ __AARCH64_INSN_FUNCS(ldrsw_lit,	0xFF000000, 0x98000000)
 __AARCH64_INSN_FUNCS(exclusive,	0x3F800000, 0x08000000)
 __AARCH64_INSN_FUNCS(load_ex,	0x3F400000, 0x08400000)
 __AARCH64_INSN_FUNCS(store_ex,	0x3F400000, 0x08000000)
+__AARCH64_INSN_FUNCS(mops,	0x3B200C00, 0x19000400)
 __AARCH64_INSN_FUNCS(stp,	0x7FC00000, 0x29000000)
 __AARCH64_INSN_FUNCS(ldp,	0x7FC00000, 0x29400000)
 __AARCH64_INSN_FUNCS(stp_post,	0x7FC00000, 0x28800000)

arch/arm64/kernel/probes/decode-insn.c

@@ -58,10 +58,13 @@ static bool __kprobes aarch64_insn_is_steppable(u32 insn)
 	 * Instructions which load PC relative literals are not going to work
 	 * when executed from an XOL slot. Instructions doing an exclusive
 	 * load/store are not going to complete successfully when single-step
-	 * exception handling happens in the middle of the sequence.
+	 * exception handling happens in the middle of the sequence. Memory
+	 * copy/set instructions require that all three instructions be placed
+	 * consecutively in memory.
 	 */
 	if (aarch64_insn_uses_literal(insn) ||
-	    aarch64_insn_is_exclusive(insn))
+	    aarch64_insn_is_exclusive(insn) ||
+	    aarch64_insn_is_mops(insn))
 		return false;
 
 	return true;