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Date: Sat, 14 Mar 2020 10:45:56 +0900
From: "Daniel T. Lee" <danieltimlee@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...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 Sat, Mar 14, 2020 at 3:48 AM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> 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;
>
Since bpf_program__attach_perf_event will return err code such
as ERR_PTR(-EINVAL), so it is natural to reset the pointer to NULL!
Thank you for the heads up!
> > + 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
>
I'll apply this at next version patch.
> > + 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;
>
Also again, bpf_object__open_file will return err code of pointer,
and the pointer needs to be set to NULL for bpf_object__close.
> > + 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)
>
Sorry, but I might not following you, but is there bpf_object__destroy
exist in libbpf? I guess you're talking about bpf_object__close, right?
> > /* 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);
>
Also, I'll apply this at next version patch.
> > + return 1;
> > + }
> > +
> > + /* load BPF program */
> > + if (bpf_object__load(obj)) {
>
> close bpf_object (better do goto clean approach, of course)
>
I will modify this with goto cleanup approach.
> > + 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
> >
Thank you for your time and effort for the review :)
Best,
Daniel
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