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Date: Fri, 13 Mar 2020 11:48:45 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: "Daniel T. Lee" <danieltimlee@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 2/2] samples: bpf: refactor perf_event user
program with libbpf bpf_link
On Fri, Mar 13, 2020 at 4:52 AM Daniel T. Lee <danieltimlee@...il.com> wrote:
>
> The bpf_program__attach of libbpf(using bpf_link) is much more intuitive
> than the previous method using ioctl.
>
> bpf_program__attach_perf_event manages the enable of perf_event and
> attach of BPF programs to it, so there's no neeed to do this
> directly with ioctl.
>
> In addition, bpf_link provides consistency in the use of API because it
> allows disable (detach, destroy) for multiple events to be treated as
> one bpf_link__destroy. Also, bpf_link__destroy manages the close() of
> perf_event fd.
>
> This commit refactors samples that attach the bpf program to perf_event
> by using libbbpf instead of ioctl. Also the bpf_load in the samples were
> removed and migrated to use libbbpf API.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
> ---
> Changes in v2:
> - check memory allocation is successful
> - clean up allocated memory on error
>
> Changes in v3:
> - Improve pointer error check (IS_ERR())
> - change to calloc for easier destroy of bpf_link
> - remove perf_event fd list since bpf_link handles fd
> - use newer bpf_object__{open/load} API instead of bpf_prog_load
> - perf_event for _SC_NPROCESSORS_ONLN instead of _SC_NPROCESSORS_CONF
> - find program with name explicitly instead of bpf_program__next
> - unconditional bpf_link__destroy() on cleanup
> - return error code on int_exit
>
> samples/bpf/Makefile | 4 +-
> samples/bpf/sampleip_user.c | 100 ++++++++++++++++++++++-----------
> samples/bpf/trace_event_user.c | 89 ++++++++++++++++++++---------
> 3 files changed, 131 insertions(+), 62 deletions(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index ff0061467dd3..424f6fe7ce38 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -88,8 +88,8 @@ xdp2-objs := xdp1_user.o
> xdp_router_ipv4-objs := xdp_router_ipv4_user.o
> test_current_task_under_cgroup-objs := bpf_load.o $(CGROUP_HELPERS) \
> test_current_task_under_cgroup_user.o
> -trace_event-objs := bpf_load.o trace_event_user.o $(TRACE_HELPERS)
> -sampleip-objs := bpf_load.o sampleip_user.o $(TRACE_HELPERS)
> +trace_event-objs := trace_event_user.o $(TRACE_HELPERS)
> +sampleip-objs := sampleip_user.o $(TRACE_HELPERS)
> tc_l2_redirect-objs := bpf_load.o tc_l2_redirect_user.o
> lwt_len_hist-objs := bpf_load.o lwt_len_hist_user.o
> xdp_tx_iptunnel-objs := xdp_tx_iptunnel_user.o
> diff --git a/samples/bpf/sampleip_user.c b/samples/bpf/sampleip_user.c
> index b0f115f938bc..05eca7b00e22 100644
> --- a/samples/bpf/sampleip_user.c
> +++ b/samples/bpf/sampleip_user.c
> @@ -10,21 +10,23 @@
> #include <errno.h>
> #include <signal.h>
> #include <string.h>
> -#include <assert.h>
> #include <linux/perf_event.h>
> #include <linux/ptrace.h>
> #include <linux/bpf.h>
> -#include <sys/ioctl.h>
> +#include <bpf/bpf.h>
> #include <bpf/libbpf.h>
> -#include "bpf_load.h"
> #include "perf-sys.h"
> #include "trace_helpers.h"
>
> +#define __must_check
> +#include <linux/err.h>
> +
> #define DEFAULT_FREQ 99
> #define DEFAULT_SECS 5
> #define MAX_IPS 8192
> #define PAGE_OFFSET 0xffff880000000000
>
> +static int map_fd;
> static int nr_cpus;
>
> static void usage(void)
> @@ -34,9 +36,10 @@ static void usage(void)
> printf(" duration # sampling duration (seconds), default 5\n");
> }
>
> -static int sampling_start(int *pmu_fd, int freq)
> +static int sampling_start(int freq, struct bpf_program *prog,
> + struct bpf_link *links[])
> {
> - int i;
> + int i, pmu_fd;
>
> struct perf_event_attr pe_sample_attr = {
> .type = PERF_TYPE_SOFTWARE,
> @@ -47,26 +50,29 @@ static int sampling_start(int *pmu_fd, int freq)
> };
>
> for (i = 0; i < nr_cpus; i++) {
> - pmu_fd[i] = sys_perf_event_open(&pe_sample_attr, -1 /* pid */, i,
> + pmu_fd = sys_perf_event_open(&pe_sample_attr, -1 /* pid */, i,
> -1 /* group_fd */, 0 /* flags */);
> - if (pmu_fd[i] < 0) {
> + if (pmu_fd < 0) {
> fprintf(stderr, "ERROR: Initializing perf sampling\n");
> return 1;
> }
> - assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF,
> - prog_fd[0]) == 0);
> - assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0) == 0);
> + links[i] = bpf_program__attach_perf_event(prog, pmu_fd);
> + if (IS_ERR(links[i])) {
links[i] = NULL;
> + fprintf(stderr, "ERROR: Attach perf event\n");
> + close(pmu_fd);
> + return 1;
> + }
> }
>
> return 0;
> }
>
> -static void sampling_end(int *pmu_fd)
> +static void sampling_end(struct bpf_link *links[])
> {
> int i;
>
> for (i = 0; i < nr_cpus; i++)
> - close(pmu_fd[i]);
> + bpf_link__destroy(links[i]);
> }
>
> struct ipcount {
> @@ -128,14 +134,17 @@ static void print_ip_map(int fd)
> static void int_exit(int sig)
> {
> printf("\n");
> - print_ip_map(map_fd[0]);
> + print_ip_map(map_fd);
> exit(0);
> }
>
> int main(int argc, char **argv)
> {
> + int opt, freq = DEFAULT_FREQ, secs = DEFAULT_SECS, error = 0;
> + struct bpf_program *prog;
> + struct bpf_object *obj;
initialize to NULL here
> + struct bpf_link **links;
> char filename[256];
> - int *pmu_fd, opt, freq = DEFAULT_FREQ, secs = DEFAULT_SECS;
>
> /* process arguments */
> while ((opt = getopt(argc, argv, "F:h")) != -1) {
> @@ -163,38 +172,61 @@ int main(int argc, char **argv)
> }
>
> /* create perf FDs for each CPU */
> - nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
> - pmu_fd = malloc(nr_cpus * sizeof(int));
> - if (pmu_fd == NULL) {
> - fprintf(stderr, "ERROR: malloc of pmu_fd\n");
> - return 1;
> + nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> + links = calloc(nr_cpus, sizeof(struct bpf_link *));
> + if (!links) {
> + fprintf(stderr, "ERROR: malloc of links\n");
> + error = 1;
> + goto cleanup;
> }
>
> - /* load BPF program */
> snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
> - if (load_bpf_file(filename)) {
> - fprintf(stderr, "ERROR: loading BPF program (errno %d):\n",
> - errno);
> - if (strcmp(bpf_log_buf, "") == 0)
> - fprintf(stderr, "Try: ulimit -l unlimited\n");
> - else
> - fprintf(stderr, "%s", bpf_log_buf);
> - return 1;
> + obj = bpf_object__open_file(filename, NULL);
> + if (IS_ERR(obj)) {
obj = NULL;
> + fprintf(stderr, "ERROR: opening BPF object file failed\n");
> + error = 1;
> + goto cleanup;
> + }
> +
> + prog = bpf_object__find_program_by_name(obj, "do_sample");
> + if (!prog) {
> + fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
> + error = 1;
> + goto cleanup;
> }
> +
> + /* load BPF program */
> + if (bpf_object__load(obj)) {
> + fprintf(stderr, "ERROR: loading BPF object file failed\n");
> + error = 1;
> + goto cleanup;
> + }
> +
> + map_fd = bpf_object__find_map_fd_by_name(obj, "ip_map");
> + if (map_fd < 0) {
> + fprintf(stderr, "ERROR: finding a map in obj file failed\n");
> + error = 1;
> + goto cleanup;
> + }
> +
> signal(SIGINT, int_exit);
> signal(SIGTERM, int_exit);
>
> /* do sampling */
> printf("Sampling at %d Hertz for %d seconds. Ctrl-C also ends.\n",
> freq, secs);
> - if (sampling_start(pmu_fd, freq) != 0)
> - return 1;
> + if (sampling_start(freq, prog, links) != 0) {
> + error = 1;
> + goto cleanup;
> + }
> sleep(secs);
> - sampling_end(pmu_fd);
> - free(pmu_fd);
>
> +cleanup:
> + sampling_end(links);
bpf_object__destroy(obj)
> /* output sample counts */
> - print_ip_map(map_fd[0]);
> + if (!error)
> + print_ip_map(map_fd);
>
> - return 0;
> + free(links);
> + return error;
> }
> diff --git a/samples/bpf/trace_event_user.c b/samples/bpf/trace_event_user.c
> index 356171bc392b..5f64ff524cc3 100644
> --- a/samples/bpf/trace_event_user.c
> +++ b/samples/bpf/trace_event_user.c
> @@ -6,22 +6,24 @@
> #include <stdlib.h>
> #include <stdbool.h>
> #include <string.h>
> -#include <fcntl.h>
> -#include <poll.h>
> -#include <sys/ioctl.h>
> #include <linux/perf_event.h>
> #include <linux/bpf.h>
> #include <signal.h>
> -#include <assert.h>
> #include <errno.h>
> #include <sys/resource.h>
> +#include <bpf/bpf.h>
> #include <bpf/libbpf.h>
> -#include "bpf_load.h"
> #include "perf-sys.h"
> #include "trace_helpers.h"
>
> +#define __must_check
> +#include <linux/err.h>
> +
> #define SAMPLE_FREQ 50
>
> +/* counts, stackmap */
> +static int map_fd[2];
> +struct bpf_program *prog;
> static bool sys_read_seen, sys_write_seen;
>
> static void print_ksym(__u64 addr)
> @@ -136,23 +138,34 @@ static inline int generate_load(void)
>
> static void test_perf_event_all_cpu(struct perf_event_attr *attr)
> {
> - int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
> - int *pmu_fd = malloc(nr_cpus * sizeof(int));
> - int i, error = 0;
> + int nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> + struct bpf_link **links = calloc(nr_cpus, sizeof(struct bpf_link *));
> + int i, pmu_fd, error = 0;
> +
> + if (!links) {
> + printf("malloc of links failed\n");
> + error = 1;
> + goto err;
> + }
>
> /* system wide perf event, no need to inherit */
> attr->inherit = 0;
>
> /* open perf_event on all cpus */
> for (i = 0; i < nr_cpus; i++) {
> - pmu_fd[i] = sys_perf_event_open(attr, -1, i, -1, 0);
> - if (pmu_fd[i] < 0) {
> + pmu_fd = sys_perf_event_open(attr, -1, i, -1, 0);
> + if (pmu_fd < 0) {
> printf("sys_perf_event_open failed\n");
> error = 1;
> goto all_cpu_err;
> }
> - assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);
> - assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE) == 0);
> + links[i] = bpf_program__attach_perf_event(prog, pmu_fd);
> + if (IS_ERR(links[i])) {
> + printf("bpf_program__attach_perf_event failed\n");
> + close(pmu_fd);
> + error = 1;
> + goto all_cpu_err;
> + }
> }
>
> if (generate_load() < 0) {
> @@ -161,18 +174,18 @@ static void test_perf_event_all_cpu(struct perf_event_attr *attr)
> }
> print_stacks();
> all_cpu_err:
> - for (i--; i >= 0; i--) {
> - ioctl(pmu_fd[i], PERF_EVENT_IOC_DISABLE);
> - close(pmu_fd[i]);
> - }
> - free(pmu_fd);
> + for (i--; i >= 0; i--)
> + bpf_link__destroy(links[i]);
> +err:
> + free(links);
> if (error)
> - int_exit(0);
> + int_exit(error);
> }
>
> static void test_perf_event_task(struct perf_event_attr *attr)
> {
> int pmu_fd, error = 0;
> + struct bpf_link *link;
>
> /* per task perf event, enable inherit so the "dd ..." command can be traced properly.
> * Enabling inherit will cause bpf_perf_prog_read_time helper failure.
> @@ -185,8 +198,12 @@ static void test_perf_event_task(struct perf_event_attr *attr)
> printf("sys_perf_event_open failed\n");
> int_exit(0);
> }
> - assert(ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);
> - assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE) == 0);
> + link = bpf_program__attach_perf_event(prog, pmu_fd);
> + if (IS_ERR(link)) {
> + printf("bpf_program__attach_perf_event failed\n");
> + close(pmu_fd);
> + int_exit(0);
> + }
>
> if (generate_load() < 0) {
> error = 1;
> @@ -194,10 +211,9 @@ static void test_perf_event_task(struct perf_event_attr *attr)
> }
> print_stacks();
> err:
> - ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
> - close(pmu_fd);
> + bpf_link__destroy(link);
> if (error)
> - int_exit(0);
> + int_exit(error);
> }
>
> static void test_bpf_perf_event(void)
> @@ -282,6 +298,7 @@ static void test_bpf_perf_event(void)
> int main(int argc, char **argv)
> {
> struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
> + struct bpf_object *obj;
> char filename[256];
>
> snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
> @@ -295,9 +312,29 @@ int main(int argc, char **argv)
> return 1;
> }
>
> - if (load_bpf_file(filename)) {
> - printf("%s", bpf_log_buf);
> - return 2;
> + obj = bpf_object__open_file(filename, NULL);
> + if (IS_ERR(obj)) {
> + printf("opening BPF object file failed\n");
> + return 1;
> + }
> +
> + prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
> + if (!prog) {
> + printf("finding a prog in obj file failed\n");
bpf_object__close(obj);
> + return 1;
> + }
> +
> + /* load BPF program */
> + if (bpf_object__load(obj)) {
close bpf_object (better do goto clean approach, of course)
> + printf("loading BPF object file failed\n");
> + return 1;
> + }
> +
> + map_fd[0] = bpf_object__find_map_fd_by_name(obj, "counts");
> + map_fd[1] = bpf_object__find_map_fd_by_name(obj, "stackmap");
> + if (map_fd[0] < 0 || map_fd[1] < 0) {
> + printf("finding a counts/stackmap map in obj file failed\n");
> + return 1;
> }
>
> if (fork() == 0) {
> --
> 2.25.1
>
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