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From: Jiri Olsa <jolsa@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andriin@fb.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	Martin KaFai Lau <kafai@fb.com>, David Miller <davem@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Wenbo Zhang <ethercflow@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Brendan Gregg <bgregg@netflix.com>,
	Florent Revest <revest@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v9 bpf-next 08/14] bpf: Add btf_struct_ids_match function
Date: Wed, 5 Aug 2020 19:56:51 +0200
Message-ID: <20200805175651.GC319954@krava> (raw)
In-Reply-To: <CAEf4BzaWGZT-6h8axOupzQ6Z2UiCakgv+v284PuXDZ6_VF5M9Q@mail.gmail.com>

On Tue, Aug 04, 2020 at 11:27:55PM -0700, Andrii Nakryiko wrote:

SNIP

> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 7bacc2f56061..ba05b15ad599 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -4160,6 +4160,37 @@ int btf_struct_access(struct bpf_verifier_log *log,
> >         return -EINVAL;
> >  }
> >
> > +bool btf_struct_ids_match(struct bpf_verifier_log *log,
> > +                         int off, u32 id, u32 need_type_id)
> > +{
> > +       const struct btf_type *type;
> > +       int err;
> > +
> > +       /* Are we already done? */
> > +       if (need_type_id == id && off == 0)
> > +               return true;
> > +
> > +again:
> > +       type = btf_type_by_id(btf_vmlinux, id);
> > +       if (!type)
> > +               return false;
> > +       err = btf_struct_walk(log, type, off, 1, &id);
> 
> nit: this size=1 looks a bit artificial, seems like btf_struct_walk()
> will work with size==0 just as well, no?

right, it will work the same for 0 ... not sure why I put
originaly 1 byte for size.. probably got mixed up by some
condition in btf_struct_walk that I thought 0 wouldn't pass,
but it should work, I'll change it, it's less tricky

> 
> > +       if (err != WALK_STRUCT)
> > +               return false;
> > +
> > +       /* We found nested struct object. If it matches
> > +        * the requested ID, we're done. Otherwise let's
> > +        * continue the search with offset 0 in the new
> > +        * type.
> > +        */
> > +       if (need_type_id != id) {
> > +               off = 0;
> > +               goto again;
> > +       }
> > +
> > +       return true;
> > +}
> > +
> >  int btf_resolve_helper_id(struct bpf_verifier_log *log,
> >                           const struct bpf_func_proto *fn, int arg)
> >  {
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index b6ccfce3bf4c..bb6ca19f282d 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -3960,16 +3960,21 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
> >                                 goto err_type;
> >                 }
> >         } else if (arg_type == ARG_PTR_TO_BTF_ID) {
> > +               bool ids_match = false;
> > +
> >                 expected_type = PTR_TO_BTF_ID;
> >                 if (type != expected_type)
> >                         goto err_type;
> >                 if (!fn->check_btf_id) {
> > -                       if (reg->btf_id != meta->btf_id) {
> > -                               verbose(env, "Helper has type %s got %s in R%d\n",
> > -                                       kernel_type_name(meta->btf_id),
> > -                                       kernel_type_name(reg->btf_id), regno);
> > -
> > -                               return -EACCES;
> > +                       if (reg->btf_id != meta->btf_id || reg->off) {
> 
> Will it ever succeed if reg->btf_id == meta->btf_id, but reg->off > 0?
> That would require recursively nested type, which is not possible,
> right? Or what am I missing? Is it just a simplification of the error
> handling path?

ok, I wanted to cover all possible cases, but did not realized this
one is not possible ;-) will revert it to previous version

thanks,
jirka


  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 17:03 [PATCH v9 bpf-next 00/14] bpf: Add d_path helper Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 01/14] tools resolve_btfids: Add size check to get_id function Jiri Olsa
2020-08-05  6:00   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 02/14] tools resolve_btfids: Add support for set symbols Jiri Olsa
2020-08-05  6:04   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 03/14] bpf: Move btf_resolve_size into __btf_resolve_size Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 04/14] bpf: Add elem_id pointer as argument to __btf_resolve_size Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 05/14] bpf: Add type_id " Jiri Olsa
2020-08-05  6:05   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 06/14] bpf: Remove recursion call in btf_struct_access Jiri Olsa
2020-08-05  6:12   ` Andrii Nakryiko
2020-08-05 17:36     ` Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 07/14] bpf: Factor btf_struct_access function Jiri Olsa
2020-08-05  6:18   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 08/14] bpf: Add btf_struct_ids_match function Jiri Olsa
2020-08-05  6:27   ` Andrii Nakryiko
2020-08-05 17:56     ` Jiri Olsa [this message]
2020-08-05 21:31       ` Jiri Olsa
2020-08-05 21:57         ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 09/14] bpf: Add BTF_SET_START/END macros Jiri Olsa
2020-08-05  6:29   ` Andrii Nakryiko
2020-08-01 17:03 ` [PATCH v9 bpf-next 10/14] bpf: Add d_path helper Jiri Olsa
2020-08-02  3:13   ` Alexei Starovoitov
2020-08-02 18:26     ` Jiri Olsa
2020-08-05  6:35   ` Andrii Nakryiko
2020-08-05 17:58     ` Jiri Olsa
2020-08-05 21:01       ` Jiri Olsa
2020-08-05 21:09         ` Andrii Nakryiko
2020-08-07  0:31   ` KP Singh
2020-08-07  8:35     ` Jiri Olsa
2020-08-07  9:42       ` KP Singh
2020-08-01 17:03 ` [PATCH v9 bpf-next 11/14] bpf: Update .BTF_ids section in btf.rst with sets info Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 12/14] selftests/bpf: Add verifier test for d_path helper Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 13/14] selftests/bpf: Add " Jiri Olsa
2020-08-05  6:40   ` Andrii Nakryiko
2020-08-05 18:00     ` Jiri Olsa
2020-08-01 17:03 ` [PATCH v9 bpf-next 14/14] selftests/bpf: Add set test to resolve_btfids Jiri Olsa
2020-08-05  6:41   ` Andrii Nakryiko

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