[PATCH 2/2] trace-cmd record: add --cpu-list option

[Luiz Capitulino]

With --cpu-list you can do:

  # trace-cmd record --cpu-list 1,4,10-15 [...]

Which is much more human friendly than -M.

Support for --cpu-list is implemented by dynamically
allocating a cpu_set_t object and setting the parsed
CPUs. Using the CPU_SET API allows for more robost
error detection.

Signed-off-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
---
 Documentation/trace-cmd-record.1.txt |   4 +
 trace-record.c                       | 208 +++++++++++++++++++++++++++++++++++
 2 files changed, 212 insertions(+)

diff --git a/Documentation/trace-cmd-record.1.txt b/Documentation/trace-cmd-record.1.txt
index b80520e..d7e806a 100644
--- a/Documentation/trace-cmd-record.1.txt
+++ b/Documentation/trace-cmd-record.1.txt
@@ -304,6 +304,10 @@ OPTIONS
     executed will not be changed. This is useful if you want to monitor the
     output of the command being executed, but not see the output from trace-cmd.
 
+*--cpu-list list*::
+    List of CPUs to be traced. The "list" argument can be comma separated
+    (eg. 1,2,4,5), a range (eg. 1-10) or a mix of the two (eg. 1,2,10-15).
+
 EXAMPLES
 --------
 
diff --git a/trace-record.c b/trace-record.c
index 0f1f2c4..49d76db 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -23,6 +23,7 @@
 #include <string.h>
 #include <stdarg.h>
 #include <getopt.h>
+#include <limits.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/time.h>
@@ -2080,6 +2081,208 @@ static void update_pid_event_filters(struct buffer_instance *instance)
 	update_event_filters(instance);
 }
 
+struct cpuset {
+	int nr_cpus;
+	size_t size;
+	cpu_set_t *set;
+};
+
+static void set_cpu(int cpu, struct cpuset *set)
+{
+	if (cpu < 0 || cpu > set->nr_cpus - 1)
+		die("invalid cpu in range");
+	CPU_SET_S(cpu, set->size, set->set);
+}
+
+static int read_cpu_nr(const char *str, int *ret)
+{
+	char *endptr;
+	int val;
+
+	errno = 0;
+	val = strtol(str, &endptr, 10);
+
+	if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN))
+			|| (errno != 0 && val == 0))
+				return -1;
+
+	if (endptr == str)
+		return -1;
+
+	if (*endptr != '\0')
+		return -1;
+
+	*ret = val;
+	return 0;
+}
+
+static int parse_single_cpu(const char *str, struct cpuset *set)
+{
+	int cpu, err;
+
+	err = read_cpu_nr(str, &cpu);
+	if (err)
+		return -1;
+
+	set_cpu(cpu, set);
+	return 0;
+}
+
+static int parse_range_one(char *str, char **saveptr)
+{
+	int err, cpu;
+	char *p;
+
+	p = strtok_r(str, "-", saveptr);
+	if (!p)
+		return -1;
+
+	err = read_cpu_nr(p, &cpu);
+	if (err)
+		return -1;
+
+	return cpu;
+}
+
+static int parse_range(const char *str, int *begin, int *end)
+{
+	char *saveptr, *range;
+	int ret;
+
+	range = strdup(str);
+	if (!range)
+		return -1;
+
+	ret = parse_range_one(range, &saveptr);
+	if (ret < 0)
+		goto out;
+	*begin = ret;
+
+	ret = parse_range_one(NULL, &saveptr);
+	if (ret < 0)
+		goto out;
+	*end = ret;
+
+out:
+	free(range);
+	return ret < 0 ? -1 : 0;
+}
+
+static int parse_cpu_range(const char *str, struct cpuset *set)
+{
+	int i, ret, begin, end;
+
+	ret = parse_range(str, &begin, &end);
+	if (ret < 0 || begin > end)
+		return -1;
+
+	for (i = begin; i <= end; i++)
+		set_cpu(i, set);
+
+	return 0;
+}
+
+static int has_range(const char *str)
+{
+	return strchr(str, '-') != NULL;
+}
+
+static int parse_cpu_list(const char *cpu_list, struct cpuset *set)
+{
+	char *saveptr, *str, *p;
+	int err = 0;
+
+	str = strdup(cpu_list);
+	if (!str)
+		return -1;
+
+	p = strtok_r(str, ",", &saveptr);
+	while (p) {
+		if (has_range(p))
+			err = parse_cpu_range(p, set);
+		else
+			err = parse_single_cpu(p, set);
+		if (err)
+			goto out;
+		p = strtok_r(NULL, ",", &saveptr);
+	}
+
+out:
+	free(str);
+	return err;
+}
+
+static int val_to_char(int v)
+{
+	if (v >= 0 && v < 10)
+		return '0' + v;
+	else if (v >= 10 && v < 16)
+		return ('a' - 10) + v;
+	else
+		return -1;
+}
+
+/* From util-linux */
+static char *cpu_set_to_str(char *str, size_t len, struct cpuset *set)
+{
+	char *ptr = str;
+	char *ret = NULL;
+	int cpu;
+
+	for (cpu = (8 * set->size) - 4; cpu >= 0; cpu -= 4) {
+		char val = 0;
+
+		if (len == (size_t) (ptr - str))
+			break;
+
+		if (CPU_ISSET_S(cpu, set->size, set->set))
+			val |= 1;
+		if (CPU_ISSET_S(cpu + 1, set->size, set->set))
+			val |= 2;
+		if (CPU_ISSET_S(cpu + 2, set->size, set->set))
+			val |= 4;
+		if (CPU_ISSET_S(cpu + 3, set->size, set->set))
+			val |= 8;
+
+		if (!ret && val)
+			ret = ptr;
+		*ptr++ = val_to_char(val);
+	}
+
+	*ptr = '\0';
+	return ret ? ret : ptr - 1;
+}
+
+static char *alloc_mask_from_list(const char *cpu_list)
+{
+	struct cpuset set;
+	char *str;
+	int ret;
+
+	set.nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+	if (set.nr_cpus < 0)
+		die("can't get number of processors\n");
+
+	set.set = CPU_ALLOC(set.nr_cpus);
+	if (!set.set)
+		die("can't allocate cpu_set\n");
+
+	set.size = CPU_ALLOC_SIZE(set.nr_cpus);
+	CPU_ZERO_S(set.size, set.set);
+
+	ret = parse_cpu_list(cpu_list, &set);
+	if (ret < 0)
+		die("invalid cpu list specified");
+
+	str = malloc(CPUMASK_STR_MAX);
+	if (!str)
+		die("can't allocate memory\n");
+
+	cpu_set_to_str(str, CPUMASK_STR_MAX, &set);
+	CPU_FREE(set.set);
+
+	return str;
+}
 
 static char *alloc_mask_from_hex(const char *str)
 {
@@ -4137,6 +4340,7 @@ enum {
 	OPT_nosplice		= 253,
 	OPT_funcstack		= 254,
 	OPT_date		= 255,
+	OPT_cpulist			= 256,
 };
 
 void trace_record (int argc, char **argv)
@@ -4338,6 +4542,7 @@ void trace_record (int argc, char **argv)
 			{"stderr", no_argument, NULL, OPT_stderr},
 			{"by-comm", no_argument, NULL, OPT_bycomm},
 			{"ts-offset", required_argument, NULL, OPT_tsoffset},
+			{"cpu-list", required_argument, NULL, OPT_cpulist},
 			{"max-graph-depth", required_argument, NULL, OPT_max_graph_depth},
 			{"debug", no_argument, NULL, OPT_debug},
 			{"help", no_argument, NULL, '?'},
@@ -4546,6 +4751,9 @@ void trace_record (int argc, char **argv)
 		case 'M':
 			instance->cpumask = alloc_mask_from_hex(optarg);
 			break;
+		case OPT_cpulist:
+			instance->cpumask = alloc_mask_from_list(optarg);
+			break;
 		case 't':
 			if (extract)
 				topt = 1; /* Extract top instance also */
-- 
2.5.5