[5.4,1/2] libbpf: Extract and generalize CPU mask parsing logic

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b6403712c2f4..281cc65276e0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5905,62 +5905,104 @@  void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
 	}
 }
 
-int libbpf_num_possible_cpus(void)
+int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
 {
-	static const char *fcpu = "/sys/devices/system/cpu/possible";
-	int len = 0, n = 0, il = 0, ir = 0;
-	unsigned int start = 0, end = 0;
-	int tmp_cpus = 0;
-	static int cpus;
-	char buf[128];
-	int error = 0;
-	int fd = -1;
+	int err = 0, n, len, start, end = -1;
+	bool *tmp;
 
-	tmp_cpus = READ_ONCE(cpus);
-	if (tmp_cpus > 0)
-		return tmp_cpus;
+	*mask = NULL;
+	*mask_sz = 0;
+
+	/* Each sub string separated by ',' has format \d+-\d+ or \d+ */
+	while (*s) {
+		if (*s == ',' || *s == '\n') {
+			s++;
+			continue;
+		}
+		n = sscanf(s, "%d%n-%d%n", &start, &len, &end, &len);
+		if (n <= 0 || n > 2) {
+			pr_warning("Failed to get CPU range %s: %d\n", s, n);
+			err = -EINVAL;
+			goto cleanup;
+		} else if (n == 1) {
+			end = start;
+		}
+		if (start < 0 || start > end) {
+			pr_warning("Invalid CPU range [%d,%d] in %s\n",
+				   start, end, s);
+			err = -EINVAL;
+			goto cleanup;
+		}
+		tmp = realloc(*mask, end + 1);
+		if (!tmp) {
+			err = -ENOMEM;
+			goto cleanup;
+		}
+		*mask = tmp;
+		memset(tmp + *mask_sz, 0, start - *mask_sz);
+		memset(tmp + start, 1, end - start + 1);
+		*mask_sz = end + 1;
+		s += len;
+	}
+	if (!*mask_sz) {
+		pr_warning("Empty CPU range\n");
+		return -EINVAL;
+	}
+	return 0;
+cleanup:
+	free(*mask);
+	*mask = NULL;
+	return err;
+}
+
+int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz)
+{
+	int fd, err = 0, len;
+	char buf[128];
 
 	fd = open(fcpu, O_RDONLY);
 	if (fd < 0) {
-		error = errno;
-		pr_warning("Failed to open file %s: %s\n",
-			   fcpu, strerror(error));
-		return -error;
+		err = -errno;
+		pr_warning("Failed to open cpu mask file %s: %d\n", fcpu, err);
+		return err;
 	}
 	len = read(fd, buf, sizeof(buf));
 	close(fd);
 	if (len <= 0) {
-		error = len ? errno : EINVAL;
-		pr_warning("Failed to read # of possible cpus from %s: %s\n",
-			   fcpu, strerror(error));
-		return -error;
+		err = len ? -errno : -EINVAL;
+		pr_warning("Failed to read cpu mask from %s: %d\n", fcpu, err);
+		return err;
 	}
-	if (len == sizeof(buf)) {
-		pr_warning("File %s size overflow\n", fcpu);
-		return -EOVERFLOW;
+	if (len >= sizeof(buf)) {
+		pr_warning("CPU mask is too big in file %s\n", fcpu);
+		return -E2BIG;
 	}
 	buf[len] = '\0';
 
-	for (ir = 0, tmp_cpus = 0; ir <= len; ir++) {
-		/* Each sub string separated by ',' has format \d+-\d+ or \d+ */
-		if (buf[ir] == ',' || buf[ir] == '\0') {
-			buf[ir] = '\0';
-			n = sscanf(&buf[il], "%u-%u", &start, &end);
-			if (n <= 0) {
-				pr_warning("Failed to get # CPUs from %s\n",
-					   &buf[il]);
-				return -EINVAL;
-			} else if (n == 1) {
-				end = start;
-			}
-			tmp_cpus += end - start + 1;
-			il = ir + 1;
-		}
-	}
-	if (tmp_cpus <= 0) {
-		pr_warning("Invalid #CPUs %d from %s\n", tmp_cpus, fcpu);
-		return -EINVAL;
+	return parse_cpu_mask_str(buf, mask, mask_sz);
+}
+
+int libbpf_num_possible_cpus(void)
+{
+	static const char *fcpu = "/sys/devices/system/cpu/possible";
+	static int cpus;
+	int err, n, i, tmp_cpus;
+	bool *mask;
+
+	tmp_cpus = READ_ONCE(cpus);
+	if (tmp_cpus > 0)
+		return tmp_cpus;
+
+	err = parse_cpu_mask_file(fcpu, &mask, &n);
+	if (err)
+		return err;
+
+	tmp_cpus = 0;
+	for (i = 0; i < n; i++) {
+		if (mask[i])
+			tmp_cpus++;
 	}
+	free(mask);
 
 	WRITE_ONCE(cpus, tmp_cpus);
 	return tmp_cpus;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 98216a69c32f..92940ae26ada 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -63,6 +63,8 @@  do {				\
 #define pr_info(fmt, ...)	__pr(LIBBPF_INFO, fmt, ##__VA_ARGS__)
 #define pr_debug(fmt, ...)	__pr(LIBBPF_DEBUG, fmt, ##__VA_ARGS__)
 
+int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz);
+int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz);
 int libbpf__load_raw_btf(const char *raw_types, size_t types_len,
 			 const char *str_sec, size_t str_len);