From fd264ca020948a743e4c36731dfdecc4a812153c Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Sun, 20 Nov 2022 11:54:32 -0800 Subject: bpf: Add a kfunc to type cast from bpf uapi ctx to kernel ctx 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 Link: https://lore.kernel.org/r/20221120195432.3113982-1-yhs@fb.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/btf.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'kernel/bpf/btf.c') diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 1c78d4df9e18..1a59cc7ad730 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5603,6 +5603,26 @@ 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; + /* get member for kernel ctx type */ + kctx_member = btf_type_member(conv_struct) + bpf_ctx_convert_map[prog_type] * 2 + 1; + kctx_type_id = kctx_member->type; + kctx_type = btf_type_by_id(btf_vmlinux, kctx_type_id); + if (!btf_type_is_struct(kctx_type)) { + bpf_log(log, "kern ctx type id %u is not a struct\n", kctx_type_id); + return -EINVAL; + } + + return kctx_type_id; +} + BTF_ID_LIST(bpf_ctx_convert_btf_id) BTF_ID(struct, bpf_ctx_convert) -- cgit v1.2.3