On 12/9/22 12:05 PM, Xin Liu wrote:
> This is a small improvement in libbpf_strerror. When libbpf_strerror
> is used to obtain the system error description, if the length of the
> buf is insufficient, libbpf_sterror returns ERANGE and sets errno to
> ERANGE.
>
> However, this processing is not performed when the error code
> customized by libbpf is obtained. Make some minor improvements here,
> return -ERANGE and set errno to ERANGE when buf is not enough for
> custom description.
nit: $subject line got corrupted?
> Signed-off-by: Xin Liu <[email protected]>
> ---
>
> v2:
> Check the return value of snprintf to determine whether the buffer is
> too small.
>
> v1:
> https://lore.kernel.org/bpf/[email protected]/T/#t
>
> tools/lib/bpf/libbpf_errno.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf_errno.c b/tools/lib/bpf/libbpf_errno.c
> index 96f67a772a1b..6240c7cb7472 100644
> --- a/tools/lib/bpf/libbpf_errno.c
> +++ b/tools/lib/bpf/libbpf_errno.c
> @@ -39,14 +39,13 @@ static const char *libbpf_strerror_table[NR_ERRNO] = {
>
> int libbpf_strerror(int err, char *buf, size_t size)
> {
> + int ret;
nit: newline after declaration
> if (!buf || !size)
> return libbpf_err(-EINVAL);
>
> err = err > 0 ? err : -err;
>
> if (err < __LIBBPF_ERRNO__START) {
> - int ret;
> -
> ret = strerror_r(err, buf, size);
> buf[size - 1] = '\0';
> return libbpf_err_errno(ret);
> @@ -56,12 +55,20 @@ int libbpf_strerror(int err, char *buf, size_t size)
> const char *msg;
>
> msg = libbpf_strerror_table[ERRNO_OFFSET(err)];
> - snprintf(buf, size, "%s", msg);
> + ret = snprintf(buf, size, "%s", msg);
> buf[size - 1] = '\0';
> + if (ret < 0)
> + return libbpf_err_errno(ret);
This would pass in ret == -1 and then eventually return 1 which
is misleading, no?
We have buf and msg non-NULL and a positive size, afaik, the only
case where you could get a negative error now is when you pass in
a buf with size exceeding INT_MAX..
> + if (ret >= size)
> + return libbpf_err(-ERANGE);
> return 0;
> }
>
> - snprintf(buf, size, "Unknown libbpf error %d", err);
> + ret = snprintf(buf, size, "Unknown libbpf error %d", err);
> buf[size - 1] = '\0';
> + if (ret < 0)
> + return libbpf_err_errno(ret);
> + if (ret >= size)
> + return libbpf_err(-ERANGE);
> return libbpf_err(-ENOENT);
> }
>