On Sat, Dec 5, 2020 at 11:11 AM Yonghong Song <yhs@xxxxxx> wrote:
>
>
>
> On 12/4/20 3:20 PM, Andrii Nakryiko wrote:
> > In case of having so many PID results that they don't fit into a singe page
> > (4096) bytes, bpftool will erroneously conclude that it got corrupted data due
> > to 4096 not being a multiple of struct pid_iter_entry, so the last entry will
> > be partially truncated. Fix this by sizing the buffer to fit exactly N entries
> > with no truncation in the middle of record.
> >
> > Fixes: d53dee3fe013 ("tools/bpftool: Show info for processes holding BPF map/prog/link/btf FDs")
> > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
>
> Ack with one nit below.
>
> Acked-by: Yonghong Song <yhs@xxxxxx>
>
> > ---
> > tools/bpf/bpftool/pids.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c
> > index df7d8ec76036..477e55d59c34 100644
> > --- a/tools/bpf/bpftool/pids.c
> > +++ b/tools/bpf/bpftool/pids.c
> > @@ -89,9 +89,9 @@ libbpf_print_none(__maybe_unused enum libbpf_print_level level,
> >
> > int build_obj_refs_table(struct obj_refs_table *table, enum bpf_obj_type type)
> > {
> > - char buf[4096];
> > - struct pid_iter_bpf *skel;
> > struct pid_iter_entry *e;
> > + char buf[4096 / sizeof(*e) * sizeof(*e)];
> > + struct pid_iter_bpf *skel;
>
> No need to move "struct pid_iter_bpf *skel", right?
It's actually a move of `struct pid_iter_entry *e;` in from of char
buf[], to be able to use sizeof(*e) instead of sizeof(struct
pid_iter_bpf). It's just that diff tool didn't catch this properly :)
>
> > int err, ret, fd = -1, i;
> > libbpf_print_fn_t default_print;
> >
> >
