From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: Dave Marchevsky <davemarchevsky@meta.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Delyan Kratunov <delyank@meta.com>
Subject: Re: [PATCH bpf-next v2 10/25] bpf: Introduce local kptrs
Date: Tue, 25 Oct 2022 23:41:57 +0530 [thread overview]
Message-ID: <20221025181157.lx2idthc5zdoclg7@apollo> (raw)
In-Reply-To: <bf1c4d27-e2e0-2309-d2eb-f83e5a387adf@meta.com>
On Tue, Oct 25, 2022 at 10:02:49PM IST, Dave Marchevsky wrote:
> On 10/13/22 2:22 AM, Kumar Kartikeya Dwivedi wrote:
> > Introduce the idea of local kptrs, i.e. PTR_TO_BTF_ID that point to a
> > type in program BTF. This is indicated by the presence of MEM_TYPE_LOCAL
> > type tag in reg->type to avoid having to check btf_is_kernel when trying
> > to match argument types in helpers.
> >
> > For now, these local kptrs will always be referenced in verifier
> > context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
> > to such objects, as long fields that are special are not touched
> > (support for which will be added in subsequent patches).
> >
> > No PROBE_MEM handling is hence done since they can never be in an
> > undefined state, and their lifetime will always be valid.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
>
> One nit unrelated to the other thread we have going for this patch.
>
> [...]
>
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 066984d73a8b..65f444405d9c 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -6019,11 +6019,13 @@ static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf,
> > return -EINVAL;
> > }
> >
> > -int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
> > +int btf_struct_access(struct bpf_verifier_log *log,
> > + const struct bpf_reg_state *reg, const struct btf *btf,
> > const struct btf_type *t, int off, int size,
> > enum bpf_access_type atype __maybe_unused,
> > u32 *next_btf_id, enum bpf_type_flag *flag)
> > {
> > + bool local_type = reg && (type_flag(reg->type) & MEM_TYPE_LOCAL);
>
> Can you add a type_is_local_kptr helper (or similar name) to reduce this
> type_flag(reg->type) & MEM_TYPE_LOCAL repetition here and elsewhere in the patch?
> Some examples of repetition in verifier.c below.
>
Good point, it was there in RFC but for some reason I decided against it. I will
include it in v3.
next prev parent reply other threads:[~2022-10-25 18:12 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-13 6:22 [PATCH bpf-next v2 00/25] Local kptrs, BPF linked lists Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 01/25] bpf: Document UAPI details for special BPF types Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 02/25] bpf: Allow specifying volatile type modifier for kptrs Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 03/25] bpf: Clobber stack slot when writing over spilled PTR_TO_BTF_ID Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 04/25] bpf: Fix slot type check in check_stack_write_var_off Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 05/25] bpf: Drop reg_type_may_be_refcounted_or_null Kumar Kartikeya Dwivedi
2022-10-19 16:04 ` Dave Marchevsky
2022-10-13 6:22 ` [PATCH bpf-next v2 06/25] bpf: Refactor kptr_off_tab into fields_tab Kumar Kartikeya Dwivedi
2022-10-19 1:35 ` Alexei Starovoitov
2022-10-19 5:42 ` Kumar Kartikeya Dwivedi
2022-10-19 15:54 ` Alexei Starovoitov
2022-10-19 23:57 ` Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 07/25] bpf: Consolidate spin_lock, timer management " Kumar Kartikeya Dwivedi
2022-10-19 1:40 ` Alexei Starovoitov
2022-10-19 5:43 ` Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 08/25] bpf: Refactor map->off_arr handling Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 09/25] bpf: Support bpf_list_head in map values Kumar Kartikeya Dwivedi
2022-10-19 1:59 ` Alexei Starovoitov
2022-10-19 5:48 ` Kumar Kartikeya Dwivedi
2022-10-19 15:57 ` Alexei Starovoitov
2022-10-19 23:59 ` Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 10/25] bpf: Introduce local kptrs Kumar Kartikeya Dwivedi
2022-10-13 13:48 ` kernel test robot
2022-10-19 17:15 ` Dave Marchevsky
2022-10-20 0:48 ` Kumar Kartikeya Dwivedi
2022-10-25 16:27 ` Dave Marchevsky
2022-10-25 18:11 ` Kumar Kartikeya Dwivedi
2022-10-25 16:32 ` Dave Marchevsky
2022-10-25 18:11 ` Kumar Kartikeya Dwivedi [this message]
2022-10-13 6:22 ` [PATCH bpf-next v2 11/25] bpf: Recognize bpf_{spin_lock,list_head,list_node} in " Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 12/25] bpf: Verify ownership relationships for owning types Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 13/25] bpf: Support locking bpf_spin_lock in local kptr Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 14/25] bpf: Allow locking bpf_spin_lock global variables Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 15/25] bpf: Rewrite kfunc argument handling Kumar Kartikeya Dwivedi
2022-10-13 13:48 ` kernel test robot
2022-10-13 6:22 ` [PATCH bpf-next v2 16/25] bpf: Drop kfunc bits from btf_check_func_arg_match Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 17/25] bpf: Support constant scalar arguments for kfuncs Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 18/25] bpf: Teach verifier about non-size constant arguments Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 19/25] bpf: Introduce bpf_kptr_new Kumar Kartikeya Dwivedi
2022-10-19 2:31 ` Alexei Starovoitov
2022-10-19 5:58 ` Kumar Kartikeya Dwivedi
2022-10-19 16:31 ` Alexei Starovoitov
2022-10-20 0:44 ` Kumar Kartikeya Dwivedi
2022-10-20 1:11 ` Alexei Starovoitov
2022-10-13 6:22 ` [PATCH bpf-next v2 20/25] bpf: Introduce bpf_kptr_drop Kumar Kartikeya Dwivedi
2022-10-13 6:22 ` [PATCH bpf-next v2 21/25] bpf: Permit NULL checking pointer with non-zero fixed offset Kumar Kartikeya Dwivedi
2022-10-13 6:23 ` [PATCH bpf-next v2 22/25] bpf: Introduce single ownership BPF linked list API Kumar Kartikeya Dwivedi
2022-10-25 17:45 ` Dave Marchevsky
2022-10-25 19:00 ` Kumar Kartikeya Dwivedi
2022-10-13 6:23 ` [PATCH bpf-next v2 23/25] libbpf: Add support for private BSS map section Kumar Kartikeya Dwivedi
2022-10-18 4:03 ` Andrii Nakryiko
2022-10-13 6:23 ` [PATCH bpf-next v2 24/25] selftests/bpf: Add __contains macro to bpf_experimental.h Kumar Kartikeya Dwivedi
2022-10-13 6:23 ` [PATCH bpf-next v2 25/25] selftests/bpf: Add BPF linked list API tests Kumar Kartikeya Dwivedi
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