On Wed, Jun 28, 2023 at 4:53 AM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> Add a new helper bpf_perf_link_fill_common(), which will be used by
> perf_link based tracepoint, kprobe and uprobe.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> kernel/bpf/syscall.c | 34 ++++++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 4aa6e5776a04..72de91beabbc 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3364,6 +3364,40 @@ static void bpf_perf_link_dealloc(struct bpf_link *link)
> kfree(perf_link);
> }
>
> +static int bpf_perf_link_fill_common(const struct perf_event *event,
> + char __user *uname, u32 ulen,
> + u64 *probe_offset, u64 *probe_addr,
> + u32 *fd_type)
> +{
> + const char *buf;
> + u32 prog_id;
> + size_t len;
> + int err;
> +
> + if (!ulen ^ !uname)
> + return -EINVAL;
> + if (!uname)
> + return 0;
> +
> + err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,
> + probe_offset, probe_addr);
> + if (err)
> + return err;
> +
> + len = strlen(buf);
> + if (buf) {
if buf is NULL, strlen above will crash, so you need to calculate len
inside this if branch
> + err = bpf_copy_to_user(uname, buf, ulen, len);
> + if (err)
> + return err;
> + } else {
> + char zero = '\0';
> +
> + if (put_user(zero, uname))
> + return -EFAULT;
> + }
> + return 0;
> +}
> +
> static const struct bpf_link_ops bpf_perf_link_lops = {
> .release = bpf_perf_link_release,
> .dealloc = bpf_perf_link_dealloc,
> --
> 2.39.3
>
