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author | Dmitrii Dolgov <9erthalion6@gmail.com> | 2022-03-09 19:31:12 +0300 |
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committer | Andrii Nakryiko <andrii@kernel.org> | 2022-03-16 01:07:27 +0300 |
commit | cbdaf71f7e65a45d6e96378ee7bfe3da39c30908 (patch) | |
tree | 8a74ca4a585b1b5d6b8a3b47e2d26bafa097f0d1 /tools/bpf/bpftool/skeleton/pid_iter.bpf.c | |
parent | f98d6dd1e79d4b04c2e13e91a9348473cfa805a6 (diff) | |
download | linux-cbdaf71f7e65a45d6e96378ee7bfe3da39c30908.tar.xz |
bpftool: Add bpf_cookie to link output
Commit 82e6b1eee6a8 ("bpf: Allow to specify user-provided bpf_cookie for
BPF perf links") introduced the concept of user specified bpf_cookie,
which could be accessed by BPF programs using bpf_get_attach_cookie().
For troubleshooting purposes it is convenient to expose bpf_cookie via
bpftool as well, so there is no need to meddle with the target BPF
program itself.
Implemented using the pid iterator BPF program to actually fetch
bpf_cookies, which allows constraining code changes only to bpftool.
$ bpftool link
1: type 7 prog 5
bpf_cookie 123
pids bootstrap(81)
Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220309163112.24141-1-9erthalion6@gmail.com
Diffstat (limited to 'tools/bpf/bpftool/skeleton/pid_iter.bpf.c')
-rw-r--r-- | tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c index f70702fcb224..eb05ea53afb1 100644 --- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c +++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c @@ -38,6 +38,17 @@ static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type) } } +/* could be used only with BPF_LINK_TYPE_PERF_EVENT links */ +static __u64 get_bpf_cookie(struct bpf_link *link) +{ + struct bpf_perf_link *perf_link; + struct perf_event *event; + + perf_link = container_of(link, struct bpf_perf_link, link); + event = BPF_CORE_READ(perf_link, perf_file, private_data); + return BPF_CORE_READ(event, bpf_cookie); +} + SEC("iter/task_file") int iter(struct bpf_iter__task_file *ctx) { @@ -69,8 +80,19 @@ int iter(struct bpf_iter__task_file *ctx) if (file->f_op != fops) return 0; + __builtin_memset(&e, 0, sizeof(e)); e.pid = task->tgid; e.id = get_obj_id(file->private_data, obj_type); + + if (obj_type == BPF_OBJ_LINK) { + struct bpf_link *link = (struct bpf_link *) file->private_data; + + if (BPF_CORE_READ(link, type) == BPF_LINK_TYPE_PERF_EVENT) { + e.has_bpf_cookie = true; + e.bpf_cookie = get_bpf_cookie(link); + } + } + bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm), task->group_leader->comm); bpf_seq_write(ctx->meta->seq, &e, sizeof(e)); |