[PATCH v5 7/9] tracing/fprobe-event: Assume fprobe is a return event by $retval

Masami Hiramatsu (Google)
2023-08-07T02:55:43Z

Assume the fprobe event is a return event if there is $retval is
used in the probe's argument without %return. e.g.

echo 'f:myevent vfs_read $retval' >> dynamic_events

then 'myevent' is a return probe event.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
kernel/trace/trace_fprobe.c | 58 +++++++++++++++-----
.../ftrace/test.d/dynevent/fprobe_syntax_errors.tc | 2 -
2 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 8f43f1f65b1b..8bfe23af9c73 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -898,6 +898,46 @@ static struct tracepoint *find_tracepoint(const char *tp_name)
return data.tpoint;
}

+static int parse_symbol_and_return(int argc, const char *argv[],
+ char **symbol, bool *is_return,
+ bool is_tracepoint)
+{
+ char *tmp = strchr(argv[1], '%');
+ int i;
+
+ if (tmp) {
+ int len = tmp - argv[1];
+
+ if (!is_tracepoint && !strcmp(tmp, "%return")) {
+ *is_return = true;
+ } else {
+ trace_probe_log_err(len, BAD_ADDR_SUFFIX);
+ return -EINVAL;
+ }
+ *symbol = kmemdup_nul(argv[1], len, GFP_KERNEL);
+ } else
+ *symbol = kstrdup(argv[1], GFP_KERNEL);
+ if (!*symbol)
+ return -ENOMEM;
+
+ if (*is_return)
+ return 0;
+
+ /* If there is $retval, this should be a return fprobe. */
+ for (i = 2; i < argc; i++) {
+ tmp = strstr(argv[i], "$retval");
+ if (tmp && !isalnum(tmp[7]) && tmp[7] != '_') {
+ *is_return = true;
+ /*
+ * NOTE: Don't check is_tracepoint here, because it will
+ * be checked when the argument is parsed.
+ */
+ break;
+ }
+ }
+ return 0;
+}
+
static int __trace_fprobe_create(int argc, const char *argv[])
{
/*
@@ -927,7 +967,7 @@ static int __trace_fprobe_create(int argc, const char *argv[])
struct trace_fprobe *tf = NULL;
int i, len, new_argc = 0, ret = 0;
bool is_return = false;
- char *symbol = NULL, *tmp = NULL;
+ char *symbol = NULL;
const char *event = NULL, *group = FPROBE_EVENT_SYSTEM;
const char **new_argv = NULL;
int maxactive = 0;
@@ -983,20 +1023,10 @@ static int __trace_fprobe_create(int argc, const char *argv[])
trace_probe_log_set_index(1);

/* a symbol(or tracepoint) must be specified */
- symbol = kstrdup(argv[1], GFP_KERNEL);
- if (!symbol)
- return -ENOMEM;
+ ret = parse_symbol_and_return(argc, argv, &symbol, &is_return, is_tracepoint);
+ if (ret < 0)
+ goto parse_error;

- tmp = strchr(symbol, '%');
- if (tmp) {
- if (!is_tracepoint && !strcmp(tmp, "%return")) {
- *tmp = '\0';
- is_return = true;
- } else {
- trace_probe_log_err(tmp - symbol, BAD_ADDR_SUFFIX);
- goto parse_error;
- }
- }
if (!is_return && maxactive) {
trace_probe_log_set_index(0);
trace_probe_log_err(1, BAD_MAXACT_TYPE);
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
index 812f5b3f6055..72563b2e0812 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/fprobe_syntax_errors.tc
@@ -30,11 +30,11 @@ check_error 'f:^ vfs_read' # NO_EVENT_NAME
check_error 'f:foo/^12345678901234567890123456789012345678901234567890123456789012345 vfs_read' # EVENT_TOO_LONG
check_error 'f:foo/^bar.1 vfs_read' # BAD_EVENT_NAME

-check_error 'f vfs_read ^$retval' # RETVAL_ON_PROBE
check_error 'f vfs_read ^$stack10000' # BAD_STACK_NUM

check_error 'f vfs_read ^$arg10000' # BAD_ARG_NUM

+check_error 'f vfs_read $retval ^$arg1' # BAD_VAR
check_error 'f vfs_read ^$none_var' # BAD_VAR
check_error 'f vfs_read ^'$REG # BAD_VAR