diff mbox series

[05/11] bpf: Remove btf_id helpers resolving

Message ID 20200616100512.2168860-6-jolsa@kernel.org
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series bpf: Add d_path helper | expand

Commit Message

Jiri Olsa June 16, 2020, 10:05 a.m. UTC 
Now when we moved the helpers btf_id into .BTF_ids section,
we can remove the code that resolve those IDs in runtime.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/bpf/btf.c | 88 +++---------------------------------------------
 1 file changed, 4 insertions(+), 84 deletions(-)

Comments

Andrii Nakryiko June 19, 2020, 1:10 a.m. UTC | #1 
On Tue, Jun 16, 2020 at 3:06 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Now when we moved the helpers btf_id into .BTF_ids section,
> we can remove the code that resolve those IDs in runtime.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---

Nice! :)

BTW, have you looked at bpf_ctx_convert stuff? Would we be able to
replace it with your btfids thing as well?


>  kernel/bpf/btf.c | 88 +++---------------------------------------------
>  1 file changed, 4 insertions(+), 84 deletions(-)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 58c9af1d4808..aea7b2cc8d26 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -4049,96 +4049,16 @@ int btf_struct_access(struct bpf_verifier_log *log,
>         return -EINVAL;
>  }
>

[...]

>  int btf_resolve_helper_id(struct bpf_verifier_log *log,
>                           const struct bpf_func_proto *fn, int arg)
>  {
> -       int *btf_id = &fn->btf_id[arg];
> -       int ret;
> -
>         if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
>                 return -EINVAL;
>
> -       ret = READ_ONCE(*btf_id);
> -       if (ret)
> -               return ret;
> -       /* ok to race the search. The result is the same */
> -       ret = __btf_resolve_helper_id(log, fn->func, arg);
> -       if (!ret) {
> -               /* Function argument cannot be type 'void' */
> -               bpf_log(log, "BTF resolution bug\n");
> -               return -EFAULT;
> -       }
> -       WRITE_ONCE(*btf_id, ret);
> -       return ret;
> +       if (WARN_ON_ONCE(!fn->btf_id))
> +               return -EINVAL;
> +
> +       return fn->btf_id[arg];

It probably would be a good idea to add some sanity checking here,
making sure that btf_id is >0 (void is never a right type) and <=
nr_types in vmlinux_btf?

>  }
>
>  static int __get_type_size(struct btf *btf, u32 btf_id,
> --
> 2.25.4
>
Jiri Olsa June 19, 2020, 1:18 p.m. UTC | #2 
On Thu, Jun 18, 2020 at 06:10:29PM -0700, Andrii Nakryiko wrote:
> On Tue, Jun 16, 2020 at 3:06 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Now when we moved the helpers btf_id into .BTF_ids section,
> > we can remove the code that resolve those IDs in runtime.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> 
> Nice! :)
> 
> BTW, have you looked at bpf_ctx_convert stuff? Would we be able to
> replace it with your btfids thing as well?

good, another usage ;-) I'll check

> 
> 
> >  kernel/bpf/btf.c | 88 +++---------------------------------------------
> >  1 file changed, 4 insertions(+), 84 deletions(-)
> >
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 58c9af1d4808..aea7b2cc8d26 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -4049,96 +4049,16 @@ int btf_struct_access(struct bpf_verifier_log *log,
> >         return -EINVAL;
> >  }
> >
> 
> [...]
> 
> >  int btf_resolve_helper_id(struct bpf_verifier_log *log,
> >                           const struct bpf_func_proto *fn, int arg)
> >  {
> > -       int *btf_id = &fn->btf_id[arg];
> > -       int ret;
> > -
> >         if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
> >                 return -EINVAL;
> >
> > -       ret = READ_ONCE(*btf_id);
> > -       if (ret)
> > -               return ret;
> > -       /* ok to race the search. The result is the same */
> > -       ret = __btf_resolve_helper_id(log, fn->func, arg);
> > -       if (!ret) {
> > -               /* Function argument cannot be type 'void' */
> > -               bpf_log(log, "BTF resolution bug\n");
> > -               return -EFAULT;
> > -       }
> > -       WRITE_ONCE(*btf_id, ret);
> > -       return ret;
> > +       if (WARN_ON_ONCE(!fn->btf_id))
> > +               return -EINVAL;
> > +
> > +       return fn->btf_id[arg];
> 
> It probably would be a good idea to add some sanity checking here,
> making sure that btf_id is >0 (void is never a right type) and <=
> nr_types in vmlinux_btf?

yep, will add it ;-)

jirka
diff mbox series

Patch

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 58c9af1d4808..aea7b2cc8d26 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4049,96 +4049,16 @@  int btf_struct_access(struct bpf_verifier_log *log,
 	return -EINVAL;
 }
 
-static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn,
-				   int arg)
-{
-	char fnname[KSYM_SYMBOL_LEN + 4] = "btf_";
-	const struct btf_param *args;
-	const struct btf_type *t;
-	const char *tname, *sym;
-	u32 btf_id, i;
-
-	if (IS_ERR(btf_vmlinux)) {
-		bpf_log(log, "btf_vmlinux is malformed\n");
-		return -EINVAL;
-	}
-
-	sym = kallsyms_lookup((long)fn, NULL, NULL, NULL, fnname + 4);
-	if (!sym) {
-		bpf_log(log, "kernel doesn't have kallsyms\n");
-		return -EFAULT;
-	}
-
-	for (i = 1; i <= btf_vmlinux->nr_types; i++) {
-		t = btf_type_by_id(btf_vmlinux, i);
-		if (BTF_INFO_KIND(t->info) != BTF_KIND_TYPEDEF)
-			continue;
-		tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
-		if (!strcmp(tname, fnname))
-			break;
-	}
-	if (i > btf_vmlinux->nr_types) {
-		bpf_log(log, "helper %s type is not found\n", fnname);
-		return -ENOENT;
-	}
-
-	t = btf_type_by_id(btf_vmlinux, t->type);
-	if (!btf_type_is_ptr(t))
-		return -EFAULT;
-	t = btf_type_by_id(btf_vmlinux, t->type);
-	if (!btf_type_is_func_proto(t))
-		return -EFAULT;
-
-	args = (const struct btf_param *)(t + 1);
-	if (arg >= btf_type_vlen(t)) {
-		bpf_log(log, "bpf helper %s doesn't have %d-th argument\n",
-			fnname, arg);
-		return -EINVAL;
-	}
-
-	t = btf_type_by_id(btf_vmlinux, args[arg].type);
-	if (!btf_type_is_ptr(t) || !t->type) {
-		/* anything but the pointer to struct is a helper config bug */
-		bpf_log(log, "ARG_PTR_TO_BTF is misconfigured\n");
-		return -EFAULT;
-	}
-	btf_id = t->type;
-	t = btf_type_by_id(btf_vmlinux, t->type);
-	/* skip modifiers */
-	while (btf_type_is_modifier(t)) {
-		btf_id = t->type;
-		t = btf_type_by_id(btf_vmlinux, t->type);
-	}
-	if (!btf_type_is_struct(t)) {
-		bpf_log(log, "ARG_PTR_TO_BTF is not a struct\n");
-		return -EFAULT;
-	}
-	bpf_log(log, "helper %s arg%d has btf_id %d struct %s\n", fnname + 4,
-		arg, btf_id, __btf_name_by_offset(btf_vmlinux, t->name_off));
-	return btf_id;
-}
-
 int btf_resolve_helper_id(struct bpf_verifier_log *log,
 			  const struct bpf_func_proto *fn, int arg)
 {
-	int *btf_id = &fn->btf_id[arg];
-	int ret;
-
 	if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
 		return -EINVAL;
 
-	ret = READ_ONCE(*btf_id);
-	if (ret)
-		return ret;
-	/* ok to race the search. The result is the same */
-	ret = __btf_resolve_helper_id(log, fn->func, arg);
-	if (!ret) {
-		/* Function argument cannot be type 'void' */
-		bpf_log(log, "BTF resolution bug\n");
-		return -EFAULT;
-	}
-	WRITE_ONCE(*btf_id, ret);
-	return ret;
+	if (WARN_ON_ONCE(!fn->btf_id))
+		return -EINVAL;
+
+	return fn->btf_id[arg];
 }
 
 static int __get_type_size(struct btf *btf, u32 btf_id,