bpf: add a new API libbpf_num_possible_cpus() (6446b315) · Commits · e / devices / android_kernel_fairphone_FP5

tools/lib/bpf/libbpf.c

+57 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

+16 −0

Original line number	Diff line number	Diff line
		@@ -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

+1 −0