On Sun, Nov 20, 2022 at 10:37:02AM -0800, Yonghong Song wrote:
> Implement bpf_cast_to_kern_ctx() kfunc which does a type cast
> of a uapi ctx object to the corresponding kernel ctx. Previously
> if users want to access some data available in kctx but not
> in uapi ctx, bpf_probe_read_kernel() helper is needed.
> The introduction of bpf_cast_to_kern_ctx() allows direct
> memory access which makes code simpler and easier to understand.
>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
> include/linux/btf.h | 5 +++++
> kernel/bpf/btf.c | 25 +++++++++++++++++++++++++
> kernel/bpf/helpers.c | 6 ++++++
> kernel/bpf/verifier.c | 21 +++++++++++++++++++++
> 4 files changed, 57 insertions(+)
>
> diff --git a/include/linux/btf.h b/include/linux/btf.h
> index d38aa4251c28..9ed00077db6e 100644
> --- a/include/linux/btf.h
> +++ b/include/linux/btf.h
> @@ -487,6 +487,7 @@ const struct btf_member *
> btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
> const struct btf_type *t, enum bpf_prog_type prog_type,
> int arg);
> +int get_kern_ctx_btf_id(struct bpf_verifier_log *log, enum bpf_prog_type prog_type);
> bool btf_types_are_same(const struct btf *btf1, u32 id1,
> const struct btf *btf2, u32 id2);
> #else
> @@ -531,6 +532,10 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
> {
> return NULL;
> }
> +static inline int get_kern_ctx_btf_id(struct bpf_verifier_log *log,
> + enum bpf_prog_type prog_type) {
> + return -EINVAL;
> +}
> static inline bool btf_types_are_same(const struct btf *btf1, u32 id1,
> const struct btf *btf2, u32 id2)
> {
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 1c78d4df9e18..3c662b00d54a 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -5603,6 +5603,31 @@ static int btf_translate_to_vmlinux(struct bpf_verifier_log *log,
> return kern_ctx_type->type;
> }
>
> +int get_kern_ctx_btf_id(struct bpf_verifier_log *log, enum bpf_prog_type prog_type)
> +{
> + const struct btf_member *kctx_member;
> + const struct btf_type *conv_struct;
> + const struct btf_type *kctx_type;
> + u32 kctx_type_id;
> +
> + conv_struct = bpf_ctx_convert.t;
> + if (!conv_struct) {
> + bpf_log(log, "btf_vmlinux is malformed\n");
> + return -EINVAL;
> + }
same comments as in v2.
