diff options
| author | Yonghong Song <yhs@fb.com> | 2020-05-13 11:02:18 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-05-13 12:30:50 -0700 |
| commit | 2e3ed68bfcd9c5ca2cf8b88ba23a34992ccd0b1f (patch) | |
| tree | 7a6512153de614c5ef0f5ef361da4ba3d19d5b7b /kernel/bpf | |
| parent | 21aef70eade22a656297c28d5da93301915d2ac2 (diff) | |
| download | linux-2e3ed68bfcd9c5ca2cf8b88ba23a34992ccd0b1f.tar.bz2 | |
bpf: Add comments to interpret bpf_prog return values
Add a short comment in bpf_iter_run_prog() function to
explain how bpf_prog return value is converted to
seq_ops->show() return value:
bpf_prog return seq_ops()->show() return
0 0
1 -EAGAIN
When show() return value is -EAGAIN, the current
bpf_seq_read() will end. If the current seq_file buffer
is empty, -EAGAIN will return to user space. Otherwise,
the buffer will be copied to user space.
In both cases, the next bpf_seq_read() call will
try to show the same object which returned -EAGAIN
previously.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200513180218.2949517-1-yhs@fb.com
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/bpf_iter.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c index 30efd15cd4a0..0a45a6cdfabd 100644 --- a/kernel/bpf/bpf_iter.c +++ b/kernel/bpf/bpf_iter.c @@ -526,5 +526,11 @@ int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx) migrate_enable(); rcu_read_unlock(); + /* bpf program can only return 0 or 1: + * 0 : okay + * 1 : retry the same object + * The bpf_iter_run_prog() return value + * will be seq_ops->show() return value. + */ return ret == 0 ? 0 : -EAGAIN; } |