[PATCH v3 4/8] tracing/kprobes: Support perf-style return probe
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: 2020-09-10 08:57:25
Also in:
linux-kselftest, lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Support perf-style return probe ("SYMBOL%return") for kprobe events.
This will allow boot-time tracing user to define a return probe event.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v3:
- Update README so that user can notice the kernel supports this feature.
- Add a new error message.
---
kernel/trace/trace.c | 2 +-
kernel/trace/trace_kprobe.c | 18 +++++++++++++++++-
kernel/trace/trace_probe.h | 1 +
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f40d850ebabc..2c8c8f7ddef7 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -5122,7 +5122,7 @@ static const char readme_msg[] = "\t -:[<group>/]<event>\n" #ifdef CONFIG_KPROBE_EVENTS "\t place: [<module>:]<symbol>[+<offset>]|<memaddr>\n" - "place (kretprobe): [<module>:]<symbol>[+<offset>]|<memaddr>\n" + "place (kretprobe): [<module>:]<symbol>[+<offset>]%return|<memaddr>\n" #endif #ifdef CONFIG_UPROBE_EVENTS " place (uprobe): <path>:<offset>[(ref_ctr_offset)]\n"
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index aefb6065b508..e33690a12255 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c@@ -717,6 +717,9 @@ static int trace_kprobe_create(int argc, const char *argv[]) * p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS] * - Add kretprobe: * r[MAXACTIVE][:[GRP/]EVENT] [MOD:]KSYM[+0] [FETCHARGS] + * Or + * p:[GRP/]EVENT] [MOD:]KSYM[+0]%return [FETCHARGS] + * * Fetch args: * $retval : fetch return value * $stack : fetch stack address
@@ -746,7 +749,6 @@ static int trace_kprobe_create(int argc, const char *argv[]) switch (argv[0][0]) { case 'r': is_return = true; - flags |= TPARG_FL_RETURN; break; case 'p': break;
@@ -804,12 +806,26 @@ static int trace_kprobe_create(int argc, const char *argv[]) symbol = kstrdup(argv[1], GFP_KERNEL); if (!symbol) return -ENOMEM; + + tmp = strchr(symbol, '%'); + if (tmp) { + if (!strcmp(tmp, "%return")) { + *tmp = '\0'; + is_return = true; + } else { + trace_probe_log_err(tmp - symbol, BAD_ADDR_SUFFIX); + goto parse_error; + } + } + /* TODO: support .init module functions */ ret = traceprobe_split_symbol_offset(symbol, &offset); if (ret || offset < 0 || offset > UINT_MAX) { trace_probe_log_err(0, BAD_PROBE_ADDR); goto parse_error; } + if (is_return) + flags |= TPARG_FL_RETURN; if (kprobe_on_func_entry(NULL, symbol, offset)) flags |= TPARG_FL_FENTRY; if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index a22b62813f8c..04d00987da69 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h@@ -404,6 +404,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(MAXACT_TOO_BIG, "Maxactive is too big"), \ C(BAD_PROBE_ADDR, "Invalid probed address or symbol"), \ C(BAD_RETPROBE, "Retprobe address must be an function entry"), \ + C(BAD_ADDR_SUFFIX, "Invalid probed address suffix"), \ C(NO_GROUP_NAME, "Group name is not specified"), \ C(GROUP_TOO_LONG, "Group name is too long"), \ C(BAD_GROUP_NAME, "Group name must follow the same rules as C identifiers"), \