@@ -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;
+}
@@ -454,6 +454,22 @@ bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear);
LIBBPF_API void
bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear);
+/*
+ * A helper function to get the number of possible CPUs before looking up
+ * per-CPU maps. Negative errno is returned on failure.
+ *
+ * Example usage:
+ *
+ * int ncpus = libbpf_num_possible_cpus();
+ * if (ncpus < 0) {
+ * // error handling
+ * }
+ * long values[ncpus];
+ * bpf_map_lookup_elem(per_cpu_map_fd, key, values);
+ *
+ */
+LIBBPF_API int libbpf_num_possible_cpus(void);
+
#ifdef __cplusplus
} /* extern "C" */
#endif
@@ -172,4 +172,5 @@ LIBBPF_0.0.4 {
btf_dump__new;
btf__parse_elf;
bpf_object__load_xattr;
+ libbpf_num_possible_cpus;
} LIBBPF_0.0.3;
Adding a new API libbpf_num_possible_cpus() that helps user with per-CPU map operations. Signed-off-by: Hechao Li <hechaol@fb.com> --- tools/lib/bpf/libbpf.c | 57 ++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 16 +++++++++++ tools/lib/bpf/libbpf.map | 1 + 3 files changed, 74 insertions(+)