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>
> ---
> 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.
> + 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,
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.
> + 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)
>
>
