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: b7564127ffcb ("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>

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index 8c0a36f72d6fcd8947229247dca4a8178b1fa783..bc77869dbd43b233c12a7405d2dab05bc8736d72 100644 (file)
--- a/arch/arm64/include/asm/insn.h
+++ b/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)

diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
index 968d5fffe2330202c731d5f6c022222db5b7a180..77f3c8eb0916cc42625209bf62c4cccaf0158228 100644 (file)
--- a/arch/arm64/kernel/probes/decode-insn.c
+++ b/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;