arm64: kprobe: clarify the comment of steppable hint instructions

The existing comment about steppable hint instruction is not complete
and only describes NOP instructions as steppable. As the function
aarch64_insn_is_steppable_hint allows all white-listed instruction
to be probed so the comment is updated to reflect this.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Link: https://lore.kernel.org/r/20200914083656.21428-7-amit.kachhap@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
index c541fb48886e3b5b620d66a4ba4f200882c59e3c..104101f633b10e2df2cc760fbed83522d63f2e88 100644 (file)
--- a/arch/arm64/kernel/probes/decode-insn.c
+++ b/arch/arm64/kernel/probes/decode-insn.c
@@ -43,8 +43,10 @@ static bool __kprobes aarch64_insn_is_steppable(u32 insn)
                             != AARCH64_INSN_SPCLREG_DAIF;
 
                /*
-                * The HINT instruction is is problematic when single-stepping,
-                * except for the NOP case.
+                * The HINT instruction is steppable only if it is in whitelist
+                * and the rest of other such instructions are blocked for
+                * single stepping as they may cause exception or other
+                * unintended behaviour.
                 */
                if (aarch64_insn_is_hint(insn))
                        return aarch64_insn_is_steppable_hint(insn);