On Tue, Aug 10, 2021 at 2:29 AM Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx> wrote:
>
> /proc/net/unix uses "%c" to print a single-byte character to escape '\0' in
> the name of the abstract UNIX domain socket. The following selftest uses
> it, so this patch adds support for "%c". Note that it does not support
> wide character ("%lc" and "%llc") for simplicity.
>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx>
> ---
> kernel/bpf/helpers.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 15746f779fe1..6d3aaf94e9ac 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -907,6 +907,20 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
> tmp_buf += err;
> num_spec++;
>
> + continue;
> + } else if (fmt[i] == 'c') {
you are adding new features to printk-like helpers, please add
corresponding tests as well. I'm particularly curious how something
like "% 9c" (which is now allowed, along with a few other unusual
combinations) will work.
> + if (!tmp_buf)
> + goto nocopy_fmt;
> +
> + if (tmp_buf_end == tmp_buf) {
> + err = -ENOSPC;
> + goto out;
> + }
> +
> + *tmp_buf = raw_args[num_spec];
> + tmp_buf++;
> + num_spec++;
> +
> continue;
> }
>
> --
> 2.30.2
>
