Commit 4725cd89 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt (VMware)
Browse files

tracing/kprobes: Support perf-style return probe 

Support perf-style return probe ("SYMBOL%return") for kprobe events.
This will allow boot-time tracing user to define a return probe event.

Link: https://lkml.kernel.org/r/159972813535.428528.4437029657208468954.stgit@devnote2



Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent c51ba517

kernel/trace/trace.c

+1 −1
Original line number Diff line number Diff line
@@ -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"

kernel/trace/trace_kprobe.c

+17 −1
Original line number Diff line number Diff line
@@ -718,6 +718,9 @@ 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
@@ -747,7 +750,6 @@ 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;
@@ -805,12 +807,26 @@ 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)) {

kernel/trace/trace_probe.h

+1 −0
Original line number Diff line number Diff line
@@ -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"), \

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