On Thu, Apr 22, 2021 at 5:27 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> Add new helper:
>
> long bpf_btf_find_by_name_kind(u32 btf_fd, char *name, u32 kind, int flags)
> Description
> Find given name with given type in BTF pointed to by btf_fd.
> If btf_fd is zero look for the name in vmlinux BTF and in module's BTFs.
> Return
> Returns btf_id and btf_obj_fd in lower and upper 32 bits.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 8 ++++
> kernel/bpf/btf.c | 68 ++++++++++++++++++++++++++++++++++
> kernel/bpf/syscall.c | 2 +
> tools/include/uapi/linux/bpf.h | 8 ++++
> 5 files changed, 87 insertions(+)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 0f841bd0cb85..4cf361eb6a80 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1972,6 +1972,7 @@ extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
> extern const struct bpf_func_proto bpf_task_storage_get_proto;
> extern const struct bpf_func_proto bpf_task_storage_delete_proto;
> extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
> +extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
>
> const struct bpf_func_proto *bpf_tracing_func_proto(
> enum bpf_func_id func_id, const struct bpf_prog *prog);
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index de58a714ed36..253f5f031f08 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -4748,6 +4748,13 @@ union bpf_attr {
> * Execute bpf syscall with given arguments.
> * Return
> * A syscall result.
> + *
> + * long bpf_btf_find_by_name_kind(u32 btf_fd, char *name, u32 kind, int flags)
> + * Description
> + * Find given name with given type in BTF pointed to by btf_fd.
"Find BTF type with given name"? Should the limits on name length be
specified? KSYM_NAME_LEN is a pretty arbitrary restriction. Also,
would it still work fine if the caller provides a pointer to a much
shorter piece of memory?
Why not add name_sz right after name, as we do with a lot of other
arguments like this?
> + * If btf_fd is zero look for the name in vmlinux BTF and in module's BTFs.
> + * Return
> + * Returns btf_id and btf_obj_fd in lower and upper 32 bits.
Mention that for vmlinux BTF btf_obj_fd will be zero? Also who "owns"
the FD? If the BPF program doesn't close it, when are they going to be
cleaned up?
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -4917,6 +4924,7 @@ union bpf_attr {
> FN(for_each_map_elem), \
> FN(snprintf), \
> FN(sys_bpf), \
> + FN(btf_find_by_name_kind), \
> /* */
>
[...]
