bpf: add a new API libbpf_num_possible_cpus()
Adding a new API libbpf_num_possible_cpus() that helps user with
per-CPU map operations.
Signed-off-by: Hechao Li <hechaol@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ba89d97..dd8b2cd 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3827,3 +3827,60 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
desc->array_offset, addr);
}
}
+
+int libbpf_num_possible_cpus(void)
+{
+ static const char *fcpu = "/sys/devices/system/cpu/possible";
+ int len = 0, n = 0, il = 0, ir = 0;
+ unsigned int start = 0, end = 0;
+ static int cpus;
+ char buf[128];
+ int error = 0;
+ int fd = -1;
+
+ if (cpus > 0)
+ return cpus;
+
+ fd = open(fcpu, O_RDONLY);
+ if (fd < 0) {
+ error = errno;
+ pr_warning("Failed to open file %s: %s\n",
+ fcpu, strerror(error));
+ return -error;
+ }
+ 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;
+ }
+ if (len == sizeof(buf)) {
+ pr_warning("File %s size overflow\n", fcpu);
+ return -EOVERFLOW;
+ }
+ buf[len] = '\0';
+
+ for (ir = 0, 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;
+ }
+ cpus += end - start + 1;
+ il = ir + 1;
+ }
+ }
+ if (cpus <= 0) {
+ pr_warning("Invalid #CPUs %d from %s\n", cpus, fcpu);
+ return -EINVAL;
+ }
+ return cpus;
+}