On Thu, 20 Jul 2023 23:34:42 +0100
Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:
> On 17/07/2023 16:23, Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> >
> > Add btf_find_struct_member() API to search a member of a given data structure
> > or union from the member's name.
> >
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>
> A few small things below, but
>
> Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
Thanks
>
> > ---
> > include/linux/btf.h | 3 +++
> > kernel/bpf/btf.c | 38 ++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 41 insertions(+)
> >
> > diff --git a/include/linux/btf.h b/include/linux/btf.h
> > index 98fbbcdd72ec..097fe9b51562 100644
> > --- a/include/linux/btf.h
> > +++ b/include/linux/btf.h
> > @@ -225,6 +225,9 @@ const struct btf_type *btf_find_func_proto(struct btf *btf,
> > const char *func_name);
> > const struct btf_param *btf_get_func_param(const struct btf_type *func_proto,
> > s32 *nr);
> > +const struct btf_member *btf_find_struct_member(struct btf *btf,
> > + const struct btf_type *type,
> > + const char *member_name);
> >
> > #define for_each_member(i, struct_type, member) \
> > for (i = 0, member = btf_type_member(struct_type); \
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index e015b52956cb..452ffb0393d6 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -1992,6 +1992,44 @@ const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s3
> > return NULL;
> > }
> >
> > +/*
> > + * Find a member of data structure/union by name and return it.
> > + * Return NULL if not found, or -EINVAL if parameter is invalid.
> > + */
> > +const struct btf_member *btf_find_struct_member(struct btf *btf,
> > + const struct btf_type *type,
> > + const char *member_name)
> > +{
> > + const struct btf_member *members, *ret;
> > + const char *name;
> > + int i, vlen;
> > +
> > + if (!btf || !member_name || !btf_type_is_struct(type))
> > + return ERR_PTR(-EINVAL);
> > +
> > + vlen = btf_type_vlen(type);
> > + members = (const struct btf_member *)(type + 1);
> > +
> > + for (i = 0; i < vlen; i++) {
>
> could use for_each_member() here I think, or perhaps use
> btf_type_member(type) when getting member pointer above.
Thanks! I missed that macro.
>
> > + if (!members[i].name_off) {
> > + /* unnamed union: dig deeper */
> > + type = btf_type_by_id(btf, members[i].type);
> > + if (!IS_ERR_OR_NULL(type)) {
> > + ret = btf_find_struct_member(btf, type,
> > + member_name);
>
> You'll need to skip modifiers before calling btf_find_struct_member()
> here I think; it's possible to have a const anonymous union for example,
Yeah, it is possible. Let me add it.
> so to get to the union you'd need to skip the modifiers first. Otherwise
> you could fail the btf_type_is_struct() test on re-entry.
Indeed.
Thank you!
>
>
> > + if (!IS_ERR_OR_NULL(ret))
> > + return ret;
> > + }
> > + } else {
> > + name = btf_name_by_offset(btf, members[i].name_off);
> > + if (name && !strcmp(member_name, name))
> > + return &members[i];
> > + }
> > + }
> > +
> > + return NULL;
> > +}
> > +
> > static u32 btf_resolved_type_id(const struct btf *btf, u32 type_id)
> > {
> > while (type_id < btf->start_id)
> >
> >
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
