diff options
| author | Stanislav Fomichev <sdf@google.com> | 2022-08-24 00:25:54 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-08-24 01:08:22 +0200 |
| commit | 2172fb8007eaafbef18563afb6c1ae5a976bf787 (patch) | |
| tree | 6fd2a47910c543142915bf19bf17c92892f28ab6 /tools/include | |
| parent | bpf: expose bpf_strtol and bpf_strtoul to all program types (diff) | |
| download | linux-2172fb8007eaafbef18563afb6c1ae5a976bf787.tar.xz linux-2172fb8007eaafbef18563afb6c1ae5a976bf787.zip | |
bpf: update bpf_{g,s}et_retval documentation
* replace 'syscall' with 'upper layers', still mention that it's being
exported via syscall errno
* describe what happens in set_retval(-EPERM) + return 1
* describe what happens with bind's 'return 3'
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220823222555.523590-5-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools/include')
| -rw-r--r-- | tools/include/uapi/linux/bpf.h | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index f38814fbb618..4fb685591035 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -5085,17 +5085,29 @@ union bpf_attr { * * int bpf_get_retval(void) * Description - * Get the syscall's return value that will be returned to userspace. + * Get the BPF program's return value that will be returned to the upper layers. * - * This helper is currently supported by cgroup programs only. + * This helper is currently supported by cgroup programs and only by the hooks + * where BPF program's return value is returned to the userspace via errno. * Return - * The syscall's return value. + * The BPF program's return value. * * int bpf_set_retval(int retval) * Description - * Set the syscall's return value that will be returned to userspace. + * Set the BPF program's return value that will be returned to the upper layers. + * + * This helper is currently supported by cgroup programs and only by the hooks + * where BPF program's return value is returned to the userspace via errno. + * + * Note that there is the following corner case where the program exports an error + * via bpf_set_retval but signals success via 'return 1': + * + * bpf_set_retval(-EPERM); + * return 1; + * + * In this case, the BPF program's return value will use helper's -EPERM. This + * still holds true for cgroup/bind{4,6} which supports extra 'return 3' success case. * - * This helper is currently supported by cgroup programs only. * Return * 0 on success, or a negative error in case of failure. * |