Hi Michael, Alexei,
On 2023-07-21 14:06, Michael Weiß wrote:
> Since commit c3494801cd1785e2 ("bpf: check pending signals while
> verifying programs", bpf() may also fail with EAGAIN if the verifier
> detects pending signals.
>
> This was triggered in the cmld of GyroidOS when loading a cgroups
> device program during container start. We had a look in the man page
> and where confused that EAGAIN was not listed as possible error.
> Digging in the kernel source revealed the EAGAIN in the verifier
> introduced by the commit above. Further investigation showed that
> libbpf already wraps that case, by a retry loop.
>
> Since GyroidOS uses the system call directly and not libbpf, we missed
> to handle this error correctly. Thus, this hint in the man page for
> the bpf() system call should be helpful for others who implement on
> the low-level interface, too.
>
> Signed-off-by: Michael Weiß <michael.weiss@xxxxxxxxxxxxxxxxxxx>
Thanks for the patch! I find a few sentences have some minor wording
issues. I'll propose a small change to your proposal. Please check.
If you confirm it, I'll amend your commit, so you don't need to resend.
See below
Cheers,
Alex
> ---
> man2/bpf.2 | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/man2/bpf.2 b/man2/bpf.2
> index d32435a1d..7cef7f24d 100644
> --- a/man2/bpf.2
> +++ b/man2/bpf.2
> @@ -991,6 +991,16 @@ and examine
> .I log_buf
> for the specific reason provided by the verifier.
> .TP
> +.B EAGAIN
> +For
> +.BR BPF_PROG_LOAD ,
> +indicates that needed resources are blocked.
> +This is due to the verifier detects pending signals while it is checking
> +the bpf program about its validity.
> +In this case, just call
> +.BR bpf ()
> +again with the same parameters.
> +.TP
diff --git a/man2/bpf.2 b/man2/bpf.2
index 7cef7f24d..ea68e1293 100644
--- a/man2/bpf.2
+++ b/man2/bpf.2
@@ -995,8 +995,8 @@ .SH ERRORS
For
.BR BPF_PROG_LOAD ,
indicates that needed resources are blocked.
-This is due to the verifier detects pending signals while it is checking
-the bpf program about its validity.
+This happens when the verifier detects pending signals
+while it is checking the validity of the bpf program.
In this case, just call
.BR bpf ()
again with the same parameters.
> .B EBADF
> .I fd
> is not an open file descriptor.
--
<http://www.alejandro-colomar.es/>
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