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libbpf: Add bpf_cookie support to bpf_link_create() API

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Add ability to specify bpf_cookie value when creating BPF perf link with
bpf_link_create() low-level API.

Given BPF_LINK_CREATE command is growing and keeps getting new fields that are
specific to the type of BPF_LINK, extend libbpf side of bpf_link_create() API
and corresponding OPTS struct to accomodate such changes. Add extra checks to
prevent using incompatible/unexpected combinations of fields.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210815070609.987780-11-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
2021-08-15 00:06:03 -07:00
committed by Daniel Borkmann
parent 668ace0ea5
commit 3ec84f4b16
3 changed files with 54 additions and 18 deletions
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32
tools/lib/bpf/bpf.c
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@ -684,8 +684,13 @@ int bpf_link_create(int prog_fd, int target_fd,
iter_info_len = OPTS_GET(opts, iter_info_len, 0);
target_btf_id = OPTS_GET(opts, target_btf_id, 0);
if (iter_info_len && target_btf_id)
return libbpf_err(-EINVAL);
/* validate we don't have unexpected combinations of non-zero fields */
if (iter_info_len || target_btf_id) {
if (iter_info_len && target_btf_id)
return libbpf_err(-EINVAL);
if (!OPTS_ZEROED(opts, target_btf_id))
return libbpf_err(-EINVAL);
}
memset(&attr, 0, sizeof(attr));
attr.link_create.prog_fd = prog_fd;
@ -693,14 +698,27 @@ int bpf_link_create(int prog_fd, int target_fd,
attr.link_create.attach_type = attach_type;
attr.link_create.flags = OPTS_GET(opts, flags, 0);
if (iter_info_len) {
attr.link_create.iter_info =
ptr_to_u64(OPTS_GET(opts, iter_info, (void *)0));
attr.link_create.iter_info_len = iter_info_len;
} else if (target_btf_id) {
if (target_btf_id) {
attr.link_create.target_btf_id = target_btf_id;
goto proceed;
}
switch (attach_type) {
case BPF_TRACE_ITER:
attr.link_create.iter_info = ptr_to_u64(OPTS_GET(opts, iter_info, (void *)0));
attr.link_create.iter_info_len = iter_info_len;
break;
case BPF_PERF_EVENT:
attr.link_create.perf_event.bpf_cookie = OPTS_GET(opts, perf_event.bpf_cookie, 0);
if (!OPTS_ZEROED(opts, perf_event))
return libbpf_err(-EINVAL);
break;
default:
if (!OPTS_ZEROED(opts, flags))
return libbpf_err(-EINVAL);
break;
}
proceed:
fd = sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr));
return libbpf_err_errno(fd);
}