On Fri, Jul 17, 2020 at 01:13:23AM +0200, KP Singh wrote:
>
>
> On 6/28/20 9:42 PM, Jiri Olsa wrote:
> > On Fri, Jun 26, 2020 at 01:38:27PM -0700, Andrii Nakryiko wrote:
> >> On Thu, Jun 25, 2020 at 4:49 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >>>
> >>> Adding d_path helper function that returns full path
> >>> for give 'struct path' object, which needs to be the
> >>> kernel BTF 'path' object.
> >>>
> >>> The helper calls directly d_path function.
> >>>
> >>> Updating also bpf.h tools uapi header and adding
> >>> 'path' to bpf_helpers_doc.py script.
> >>>
> >>> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> >>> ---
> >>> include/uapi/linux/bpf.h | 14 +++++++++-
> >>> kernel/trace/bpf_trace.c | 47 ++++++++++++++++++++++++++++++++++
> >>> scripts/bpf_helpers_doc.py | 2 ++
> >>> tools/include/uapi/linux/bpf.h | 14 +++++++++-
> >>> 4 files changed, 75 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> >>> index 0cb8ec948816..23274c81f244 100644
> >>> --- a/include/uapi/linux/bpf.h
> >>> +++ b/include/uapi/linux/bpf.h
> >>> @@ -3285,6 +3285,17 @@ union bpf_attr {
> >>> * Dynamically cast a *sk* pointer to a *udp6_sock* pointer.
> >>> * Return
> >>> * *sk* if casting is valid, or NULL otherwise.
> >>> + *
> >>> + * int bpf_d_path(struct path *path, char *buf, u32 sz)
> >>> + * Description
> >>> + * Return full path for given 'struct path' object, which
> >>> + * needs to be the kernel BTF 'path' object. The path is
> >>> + * returned in buffer provided 'buf' of size 'sz'.
> >>> + *
> >>> + * Return
> >>> + * length of returned string on success, or a negative
> >>> + * error in case of failure
> >>
> >> It's important to note whether string is always zero-terminated (I'm
> >> guessing it is, right?).
> >
> > right, will add
>
> Also note that bpf_probe_read_{kernel, user}_str return the length including
> the NUL byte:
>
> * Return
> * On success, the strictly positive length of the string,
> * including the trailing NUL character. On error, a negative
> * value.
>
> It would be good to keep this uniform. So you will need a len += 1 here as well.
good point, will keep it that way
thanks,
jirka
