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Date: Thu, 27 Jun 2019 22:52:57 -0700
From: Andrii Nakryiko <andriin@...com>
To: <andrii.nakryiko@...il.com>, <ast@...com>, <daniel@...earbox.net>,
<netdev@...r.kernel.org>, <bpf@...r.kernel.org>, <sdf@...ichev.me>,
<kernel-team@...com>
CC: Andrii Nakryiko <andriin@...com>
Subject: [PATCH v3 bpf-next 3/9] libbpf: add ability to attach/detach BPF program to perf event
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@...com>
---
tools/lib/bpf/libbpf.c | 58 ++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 3 +++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 62 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 455795e6f8af..606705f878ba 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -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 +3959,63 @@ 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;
+
+ if (l->fd < 0)
+ return 0;
+
+ err = ioctl(l->fd, PERF_EVENT_IOC_DISABLE, 0);
+ 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 bpf_fd, err;
+
+ bpf_fd = bpf_program__fd(prog);
+ if (bpf_fd < 0) {
+ pr_warning("program '%s': can't attach before loaded\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, bpf_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,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 5082a5ebb0c2..1bf66c4a9330 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -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;
/*
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 3cde850fc8da..756f5aa802e9 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -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;
--
2.17.1
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