Commit 5e2ac390 authored by Daniel Borkmann's avatar Daniel Borkmann
Browse files

Merge branch 'bpf-libbpf-num-cpus' 



Hechao Li says:

====================
Getting number of possible CPUs is commonly used for per-CPU BPF maps
and perf_event_maps. Add a new API libbpf_num_possible_cpus() that
helps user with per-CPU related operations and remove duplicate
implementations in bpftool and selftests.

v2: Save errno before calling pr_warning in case it is changed.
v3: Make sure libbpf_num_possible_cpus never returns 0 so that user only
    has to check if ret value < 0.
v4: Fix error code when reading 0 bytes from possible CPU file.
v5: Fix selftests compliation issue.
v6: Split commit to reuse libbpf_num_possible_cpus() into two commits:
    One commit to remove bpf_util.h from test BPF C programs.
    One commit to reuse libbpf_num_possible_cpus() in bpftools
    and bpf_util.h.
====================

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parents 89cceaa9 4c587c19

tools/bpf/bpftool/common.c

+5 −48
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <sys/vfs.h>



#include <bpf.h>

#include <libbpf.h> /* libbpf_num_possible_cpus */



#include "main.h"
@@ -439,57 +440,13 @@ unsigned int get_page_size(void) 


unsigned int get_possible_cpus(void)

{

	static unsigned int result;

	char buf[128];

	long int n;

	char *ptr;

	int fd;



	if (result)

		return result;



	fd = open("/sys/devices/system/cpu/possible", O_RDONLY);

	if (fd < 0) {

		p_err("can't open sysfs possible cpus");

		exit(-1);

	}



	n = read(fd, buf, sizeof(buf));

	if (n < 2) {

		p_err("can't read sysfs possible cpus");

		exit(-1);

	}

	close(fd);

	int cpus = libbpf_num_possible_cpus();



	if (n == sizeof(buf)) {

		p_err("read sysfs possible cpus overflow");

	if (cpus < 0) {

		p_err("Can't get # of possible cpus: %s", strerror(-cpus));

		exit(-1);

	}



	ptr = buf;

	n = 0;

	while (*ptr && *ptr != '\n') {

		unsigned int a, b;



		if (sscanf(ptr, "%u-%u", &a, &b) == 2) {

			n += b - a + 1;



			ptr = strchr(ptr, '-') + 1;

		} else if (sscanf(ptr, "%u", &a) == 1) {

			n++;

		} else {

			assert(0);

		}



		while (isdigit(*ptr))

			ptr++;

		if (*ptr == ',')

			ptr++;

	}



	result = n;



	return result;

	return cpus;

}



static char *

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;

}

tools/lib/bpf/libbpf.h

+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

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -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;

tools/testing/selftests/bpf/bpf_endian.h

+1 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#ifndef __BPF_ENDIAN__

#define __BPF_ENDIAN__



#include <linux/stddef.h>

#include <linux/swab.h>



/* LLVM's BPF target selects the endianness of the CPU

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