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libbpf: add ability to attach/detach BPF program to perf event

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bpf_program__attach_perf_event allows to attach BPF program to existing
perf event hook, providing most generic and most low-level way to attach BPF
programs. It returns struct bpf_link, which should be passed to
bpf_link__destroy to detach and free resources, associated with a link.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Andrii Nakryiko 2019-07-01 16:58:57 -07:00 committed by Daniel Borkmann
parent 1c2e9efc26
commit 63f2f5ee85
3 changed files with 67 additions and 0 deletions
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63
tools/lib/bpf/libbpf.c
View File

@ -32,6 +32,7 @@
#include <linux/limits.h>
#include <linux/perf_event.h>
#include <linux/ring_buffer.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/vfs.h>
@ -3958,6 +3959,68 @@ int bpf_link__destroy(struct bpf_link *link)
return err;
}
struct bpf_link_fd {
struct bpf_link link; /* has to be at the top of struct */
int fd; /* hook FD */
};
static int bpf_link__destroy_perf_event(struct bpf_link *link)
{
struct bpf_link_fd *l = (void *)link;
int err;
err = ioctl(l->fd, PERF_EVENT_IOC_DISABLE, 0);
if (err)
err = -errno;
close(l->fd);
return err;
}
struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,
int pfd)
{
char errmsg[STRERR_BUFSIZE];
struct bpf_link_fd *link;
int prog_fd, err;
if (pfd < 0) {
pr_warning("program '%s': invalid perf event FD %d\n",
bpf_program__title(prog, false), pfd);
return ERR_PTR(-EINVAL);
}
prog_fd = bpf_program__fd(prog);
if (prog_fd < 0) {
pr_warning("program '%s': can't attach BPF program w/o FD (did you load it?)\n",
bpf_program__title(prog, false));
return ERR_PTR(-EINVAL);
}
link = malloc(sizeof(*link));
if (!link)
return ERR_PTR(-ENOMEM);
link->link.destroy = &bpf_link__destroy_perf_event;
link->fd = pfd;
if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) {
err = -errno;
free(link);
pr_warning("program '%s': failed to attach to pfd %d: %s\n",
bpf_program__title(prog, false), pfd,
libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
return ERR_PTR(err);
}
if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
err = -errno;
free(link);
pr_warning("program '%s': failed to enable pfd %d: %s\n",
bpf_program__title(prog, false), pfd,
libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
return ERR_PTR(err);
}
return (struct bpf_link *)link;
}
enum bpf_perf_event_ret
bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
void **copy_mem, size_t *copy_size,

3
tools/lib/bpf/libbpf.h
View File

@ -169,6 +169,9 @@ struct bpf_link;
LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
LIBBPF_API struct bpf_link *
bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);
struct bpf_insn;
/*

1
tools/lib/bpf/libbpf.map
View File

@ -169,6 +169,7 @@ LIBBPF_0.0.4 {
global:
bpf_link__destroy;
bpf_object__load_xattr;
bpf_program__attach_perf_event;
btf_dump__dump_type;
btf_dump__free;
btf_dump__new;