Re: [PATCH bpf-next v9 04/11] bpf: move prog->aux->linked_prog and trampoline into bpf_link on attach

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Jiri Olsa <jolsa@redhat.com>,
	Eelco Chaudron <echaudro@redhat.com>,
	KP Singh <kpsingh@chromium.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next v9 04/11] bpf: move prog->aux->linked_prog and trampoline into bpf_link on attach
Date: Mon, 28 Sep 2020 17:05:22 -0700	[thread overview]
Message-ID: <20200929000522.n5g2hcahqjxwseye@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <160106910382.27725.8204173893583455016.stgit@toke.dk>

On Fri, Sep 25, 2020 at 11:25:03PM +0200, Toke Høiland-Jørgensen wrote:
>  
>  int bpf_check_attach_target(struct bpf_verifier_log *log,
>  			    const struct bpf_prog *prog,
> -			    const struct bpf_prog *tgt_prog,
> +			    const struct bpf_prog *dst_prog,

so you really did blind search and replace?
That's not at all what I was asking.
The function is called check_attach_target and the argument name
'tgt_prog' fits perfectly.

>  			    u32 btf_id,
>  			    struct bpf_attach_target_info *tgt_info);
>  
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 868c03a24d0a..faf57c6f8804 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -3706,10 +3706,10 @@ struct btf *btf_parse_vmlinux(void)
>  
>  struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
>  {
> -	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
> +	struct bpf_prog *dst_prog = prog->aux->dst_prog;

same here. tgt_prog fits just fine as a name.

>  
> -	if (tgt_prog) {
> -		return tgt_prog->aux->btf;
> +	if (dst_prog) {
> +		return dst_prog->aux->btf;
>  	} else {
>  		return btf_vmlinux;
>  	}
> @@ -3733,7 +3733,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
>  		    struct bpf_insn_access_aux *info)
>  {
>  	const struct btf_type *t = prog->aux->attach_func_proto;
> -	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
> +	struct bpf_prog *dst_prog = prog->aux->dst_prog;

here as well.
it's a tgt_prog being checked.

> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 2740df19f55e..099a651efe8b 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2154,14 +2154,14 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
>  	prog->expected_attach_type = attr->expected_attach_type;
>  	prog->aux->attach_btf_id = attr->attach_btf_id;
>  	if (attr->attach_prog_fd) {
> -		struct bpf_prog *tgt_prog;
> +		struct bpf_prog *dst_prog;
>  
> -		tgt_prog = bpf_prog_get(attr->attach_prog_fd);
> -		if (IS_ERR(tgt_prog)) {
> -			err = PTR_ERR(tgt_prog);
> +		dst_prog = bpf_prog_get(attr->attach_prog_fd);
> +		if (IS_ERR(dst_prog)) {
> +			err = PTR_ERR(dst_prog);
>  			goto free_prog_nouncharge;
>  		}
> -		prog->aux->linked_prog = tgt_prog;
> +		prog->aux->dst_prog = dst_prog;

Here 'dst_prog' makes logical sense, but I wouldn't bother renaming.
You can keep this hunk, if you like.

>  int bpf_check_attach_target(struct bpf_verifier_log *log,
>  			    const struct bpf_prog *prog,
> -			    const struct bpf_prog *tgt_prog,
> +			    const struct bpf_prog *dst_prog,

pls keep it as 'tgt_prog' here and through the function.

>  static int check_attach_btf_id(struct bpf_verifier_env *env)
>  {
>  	struct bpf_prog *prog = env->prog;
> -	struct bpf_prog *tgt_prog = prog->aux->linked_prog;
> +	struct bpf_prog *dst_prog = prog->aux->dst_prog;

no need to rename either. It's a target program being checked.