On Wed, Mar 18, 2020 at 10:10 AM Martin KaFai Lau <kafai@xxxxxx> wrote:
>
> On Tue, Mar 17, 2020 at 11:09:24PM -0700, Andrii Nakryiko wrote:
> > On Tue, Mar 17, 2020 at 8:15 PM Martin KaFai Lau <kafai@xxxxxx> wrote:
> > >
> > > This patch prints the enum's name if there is one found in
> > > the array of btf_enum.
> > >
> > > The commit 9eea98497951 ("bpf: fix BTF verification of enums")
> > > has details about an enum could have any power-of-2 size (up to 8 bytes).
> > > This patch also takes this chance to accommodate these non 4 byte
> > > enums.
> > >
> > > Acked-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
> > > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
> > > ---
> > > tools/bpf/bpftool/btf_dumper.c | 39 +++++++++++++++++++++++++++++++---
> > > 1 file changed, 36 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
> > > index 01cc52b834fa..079f9171b1a3 100644
> > > --- a/tools/bpf/bpftool/btf_dumper.c
> > > +++ b/tools/bpf/bpftool/btf_dumper.c
> > > @@ -43,9 +43,42 @@ static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
> > > return btf_dumper_do_type(d, actual_type_id, bit_offset, data);
> > > }
> > >
> > > -static void btf_dumper_enum(const void *data, json_writer_t *jw)
> > > +static void btf_dumper_enum(const struct btf_dumper *d,
> > > + const struct btf_type *t,
> > > + const void *data)
> > > {
> > > - jsonw_printf(jw, "%d", *(int *)data);
> > > + const struct btf_enum *enums = btf_enum(t);
> > > + __s64 value;
> > > + __u16 i;
> > > +
> > > + switch (t->size) {
> > > + case 8:
> > > + value = *(__s64 *)data;
> > > + break;
> > > + case 4:
> > > + value = *(__s32 *)data;
> > > + break;
> > > + case 2:
> > > + value = *(__s16 *)data;
> > > + break;
> > > + case 1:
> > > + value = *(__s8 *)data;
> > > + break;
> > > + default:
> > > + jsonw_string(d->jw, "<invalid_enum_size>");
> >
> > Why not return error and let it propagate, similar to how
> > btf_dumper_array() can return an error? BTF is malformed if this
> > happened, so there is no point in continuing dumping, it's most
> > probably going to be a garbage.
> I can send v4 to return -EINVAL here.
>
> However, the caller of btf_dump*() is pretty loose on checking it.
> It won't be difficult to find other existing codes that will
> continue on btf_type's related error cases. I also don't
> think fixing all these error checking/returning is the
> right answer here
Disagree about fixing error checking in general, but I don't insist either.
>
> The proper place to check malformed BTF is in btf__new().
I agree.
> Check it once there like how the kernel does.
> [ btw, the data and btf here are obtained from the kernel
> which has verified it ].
>
> >
> > > + return;
> > > + }
> > > +
> > > + for (i = 0; i < btf_vlen(t); i++) {
> > > + if (value == enums[i].val) {
> > > + jsonw_string(d->jw,
> > > + btf__name_by_offset(d->btf,
> > > + enums[i].name_off));
> >
> > nit: local variable will make it cleaner
> I prefer to keep it as is. There are many other uses like this.
Ok.
>
> >
> > > + return;
> > > + }
> > > + }
> > > +
> > > + jsonw_int(d->jw, value);
> > > }
> > >
> > > static int btf_dumper_array(const struct btf_dumper *d, __u32 type_id,
> > > @@ -366,7 +399,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id,
> > > case BTF_KIND_ARRAY:
> > > return btf_dumper_array(d, type_id, data);
> > > case BTF_KIND_ENUM:
> > > - btf_dumper_enum(data, d->jw);
> > > + btf_dumper_enum(d, t, data);
> > > return 0;
> > > case BTF_KIND_PTR:
> > > btf_dumper_ptr(data, d->jw, d->is_plain_text);
> > > --
> > > 2.17.1
> > >
