On Fri, Mar 10, 2023 at 7:13 AM liupan <patteliu@xxxxxxxxx> wrote:
>
> Write data to fd by calling "vdprintf", in most implementations
> of the standard library, the data is finally written by the writev syscall.
> But "uprobe_events/kprobe_events" does not allow segmented writes,
> so switch the "append_to_file" function to explicit write() call.
>
> Signed-off-by: liupan <patteliu@xxxxxxxxx>
please specify your real full name in Signed-off-by tag
> ---
> tools/lib/bpf/libbpf.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index a557718401e4..7d865ca95c81 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9912,16 +9912,20 @@ static int append_to_file(const char *file, const char *fmt, ...)
> {
> int fd, n, err = 0;
> va_list ap;
> + char buf[1024];
> +
> + va_start(ap, fmt);
> + n = vsnprintf(buf, sizeof(buf), fmt, ap);
> + va_end(ap);
> +
> + if (n < 0 || n >= sizeof(buf))
> + return -EINVAL;
if n < 0 we should return -errno here
and if n >= sizeof(buf) let's return -E2BIG
>
> fd = open(file, O_WRONLY | O_APPEND | O_CLOEXEC, 0);
> if (fd < 0)
> return -errno;
>
> - va_start(ap, fmt);
> - n = vdprintf(fd, fmt, ap);
> - va_end(ap);
> -
> - if (n < 0)
> + if (write(fd, buf, n) < 0)
> err = -errno;
>
> close(fd);
> --
> 2.20.1
>
