rtla: Fix parsing of multi-character short options

A bug was reported where the parsing of multi-character short options,
be it a short option with an argument specified without space (e.g.
"-p100") or multiple short options in one argument (e.g. -un), ignores
options specific to individual tools.

Furthermore, if the rest of the option is supposed to be an argument, it
gets reinterpreted as a string of options. For example, -p100 gets
interpreted as -100, which is due to hackish implementation read as
--no-thread --no-irq --no-irq with timerlat hist, causing rtla to error
out:

$ rtla timerlat hist -p100
no-irq and no-thread set, there is nothing to do here

This behavior is caused by getopt_long() being called twice on each
argument, once in common_parse_options(), once in [tool]_parse_args():

- common_parse_options() calls getopt_long() with an array of options
  common for all rtla tools, while suppressing errors (opterr = 0).
- If the option fails to parse, common_parse_options() returns 0.
- If 0 is returned from common_parse_options(), [tool]_parse_args()
  calls getopt_long() again, with its own set of options.

* [tool] means one of {osnoise,timerlat}_{top,hist}

At least in glibc, getopt_long() increments its internal nextchar
variable even if the option is not recognized. That means that in the
case of "-p100", common_parse_options() sets nextchar pointing to '1',
and timerlat_hist_parse_args() sees '1', not 'p'; the same then repeats
for the first and second '0'.

As there is no way to restore the correct internal state of
getopt_long() reliably, fix the issue by merging the common options back
to the longopt array and option string of the [tool]_parse_args()
functions using a macro; only the switch part is left in the original
function, which is renamed to set_common_option().

Fixes: 850cd24cb6 ("tools/rtla: Add common_parse_options()")
Reported-by: John Kacur <jkacur@redhat.com>
Tested-by: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/r/20260602125506.3325345-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

tools/tracing/rtla/src/common.c

@@ -84,37 +84,20 @@ int getopt_auto(int argc, char **argv, const struct option *long_opts)
 }
 
 /*
- * common_parse_options - parse common command line options
+ * set_common_option - set common options
  *
+ * @c: option character
  * @argc: argument count
  * @argv: argument vector
  * @common: common parameters structure
  *
  * Parse command line options that are common to all rtla tools.
  *
- * Returns: non zero if a common option was parsed, or 0
+ * Returns: 1 if the option was set, 0 otherwise.
- * if the option should be handled by tool-specific parsing.
  */
-int common_parse_options(int argc, char **argv, struct common_params *common)
+int set_common_option(int c, int argc, char **argv, struct common_params *common)
 {
 	struct trace_events *tevent;
-	int saved_state = optind;
-	int c;
-
-	static struct option long_options[] = {
-		{"cpus",                required_argument,      0, 'c'},
-		{"cgroup",              optional_argument,      0, 'C'},
-		{"debug",               no_argument,            0, 'D'},
-		{"duration",            required_argument,      0, 'd'},
-		{"event",               required_argument,      0, 'e'},
-		{"house-keeping",       required_argument,      0, 'H'},
-		{"priority",            required_argument,      0, 'P'},
-		{0, 0, 0, 0}
-	};
-
-	opterr = 0;
-	c = getopt_auto(argc, argv, long_options);
-	opterr = 1;
 
 	switch (c) {
 	case 'c':
@@ -154,11 +137,10 @@ int common_parse_options(int argc, char **argv, struct common_params *common)
 		common->set_sched = 1;
 		break;
 	default:
-		optind = saved_state;
 		return 0;
 	}
 
-	return c;
+	return 1;
 }
 
 /*

tools/tracing/rtla/src/common.h

@@ -178,7 +178,17 @@ int osnoise_set_stop_total_us(struct osnoise_context *context,
 			      long long stop_total_us);
 
 int getopt_auto(int argc, char **argv, const struct option *long_opts);
-int common_parse_options(int argc, char **argv, struct common_params *common);
+
+#define COMMON_OPTIONS \
+	{"cpus",                required_argument,      0, 'c'},\
+	{"cgroup",              optional_argument,      0, 'C'},\
+	{"debug",               no_argument,            0, 'D'},\
+	{"duration",            required_argument,      0, 'd'},\
+	{"event",               required_argument,      0, 'e'},\
+	{"house-keeping",       required_argument,      0, 'H'},\
+	{"priority",            required_argument,      0, 'P'}
+int set_common_option(int c, int argc, char **argv, struct common_params *common);
+
 int common_apply_config(struct osnoise_tool *tool, struct common_params *params);
 int top_main_loop(struct osnoise_tool *tool);
 int hist_main_loop(struct osnoise_tool *tool);

tools/tracing/rtla/src/osnoise_hist.c

@@ -475,6 +475,7 @@ static struct common_params
 
 	while (1) {
 		static struct option long_options[] = {
+			COMMON_OPTIONS,
 			{"auto",		required_argument,	0, 'a'},
 			{"bucket-size",		required_argument,	0, 'b'},
 			{"entries",		required_argument,	0, 'E'},
@@ -498,15 +499,15 @@ static struct common_params
 			{0, 0, 0, 0}
 		};
 
-		if (common_parse_options(argc, argv, &params->common))
-			continue;
-
 		c = getopt_auto(argc, argv, long_options);
 
 		/* detect the end of the options. */
 		if (c == -1)
 			break;
 
+		if (set_common_option(c, argc, argv, &params->common))
+			continue;
+
 		switch (c) {
 		case 'a':
 			/* set sample stop to auto_thresh */

tools/tracing/rtla/src/osnoise_top.c

@@ -328,6 +328,7 @@ struct common_params *osnoise_top_parse_args(int argc, char **argv)
 
 	while (1) {
 		static struct option long_options[] = {
+			COMMON_OPTIONS,
 			{"auto",		required_argument,	0, 'a'},
 			{"help",		no_argument,		0, 'h'},
 			{"period",		required_argument,	0, 'p'},
@@ -346,15 +347,15 @@ struct common_params *osnoise_top_parse_args(int argc, char **argv)
 			{0, 0, 0, 0}
 		};
 
-		if (common_parse_options(argc, argv, &params->common))
-			continue;
-
 		c = getopt_auto(argc, argv, long_options);
 
 		/* Detect the end of the options. */
 		if (c == -1)
 			break;
 
+		if (set_common_option(c, argc, argv, &params->common))
+			continue;
+
 		switch (c) {
 		case 'a':
 			/* set sample stop to auto_thresh */

tools/tracing/rtla/src/timerlat_hist.c

@@ -785,6 +785,7 @@ static struct common_params
 
 	while (1) {
 		static struct option long_options[] = {
+			COMMON_OPTIONS,
 			{"auto",		required_argument,	0, 'a'},
 			{"bucket-size",		required_argument,	0, 'b'},
 			{"entries",		required_argument,	0, 'E'},
@@ -819,11 +820,11 @@ static struct common_params
 			{0, 0, 0, 0}
 		};
 
-		if (common_parse_options(argc, argv, &params->common))
-			continue;
-
 		c = getopt_auto(argc, argv, long_options);
 
+		if (set_common_option(c, argc, argv, &params->common))
+			continue;
+
 		/* detect the end of the options. */
 		if (c == -1)
 			break;

tools/tracing/rtla/src/timerlat_top.c

@@ -549,6 +549,7 @@ static struct common_params
 
 	while (1) {
 		static struct option long_options[] = {
+			COMMON_OPTIONS,
 			{"auto",		required_argument,	0, 'a'},
 			{"help",		no_argument,		0, 'h'},
 			{"irq",			required_argument,	0, 'i'},
@@ -577,11 +578,11 @@ static struct common_params
 			{0, 0, 0, 0}
 		};
 
-		if (common_parse_options(argc, argv, &params->common))
-			continue;
-
 		c = getopt_auto(argc, argv, long_options);
 
+		if (set_common_option(c, argc, argv, &params->common))
+			continue;
+
 		/* detect the end of the options. */
 		if (c == -1)
 			break;