[PATCH v6 6/6] arm64: kprobe: clarify the comment of steppable hint instructions

Amit Daniel Kachhap amit.kachhap at arm.com
Fri Sep 4 06:42:09 EDT 2020

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 at arm.com>
Reviewed-by: Dave Martin <dave.martin at arm.com>
Changes since v5: 
* None.

 arch/arm64/kernel/probes/decode-insn.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
index f9eb8210d6d3..288114d54fb5 100644
--- a/arch/arm64/kernel/probes/decode-insn.c
+++ b/arch/arm64/kernel/probes/decode-insn.c
@@ -44,8 +44,10 @@ static bool __kprobes aarch64_insn_is_steppable(u32 insn)
-		 * 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);

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