On Fri, Jun 28, 2019 at 8:49 PM Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> 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@xxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
With one nit below.
> ---
> tools/lib/bpf/libbpf.c | 61 ++++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h | 3 ++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 65 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 455795e6f8af..98c155ec3bfa 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 +3959,66 @@ 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);
> + 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;
> +
> + prog_fd = bpf_program__fd(prog);
> + if (prog_fd < 0) {
> + pr_warning("program '%s': can't attach before loaded\n",
> + bpf_program__title(prog, false));
This warning message is not very easy to follow.
> + 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,
> 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
>
