From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Kumar Kartikeya Dwivedi" <memxor@gmail.com>
Cc: <bpf@vger.kernel.org>, "Andrii Nakryiko" <andrii@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Emil Tsalapatis" <emil@etsalapatis.com>,
"Ihor Solodrai" <ihor.solodrai@linux.dev>,
"Tejun Heo" <tj@kernel.org>, <kkd@meta.com>,
<kernel-team@meta.com>
Subject: Re: [PATCH bpf-next v3 06/15] bpf: Recognize __nullable on pointer members of kernel structs
Date: Fri, 16 Oct 2026 01:31:26 +0000 [thread overview]
Message-ID: <DM5VHTPNK75L.25IC5ASG1QDJ9@gmail.com> (raw)
In-Reply-To: <CAP01T743a5wuvP=5cc8Aqb=PHGhSFWcir0sCSWMvMT_=gk8Kjw@mail.gmail.com>
On Fri Oct 16, 2026 at 1:24 AM UTC, Kumar Kartikeya Dwivedi wrote:
> On Fri, 16 Oct 2026 at 03:10, Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
>>
>> On Fri, Oct 16, 2026 at 01:41 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>> > it on, as the tag says. A tagged member of an existing struct thus asks
>> > every program that reads it for a check, including one that reads it
>> > through a probed pointer and relied on a NULL dereference reading as
>> > zero.
>>
>> Commit log reads like BTF_TYPE_SAFE_*() can go away one day,
>> but with this change adding __nullable to a member of task_struct
>> breaks every tracing prog that walks through it without a check.
>> So the tag cannot be added to existing structs and
>> BTF_TYPE_SAFE_*_OR_NULL lists are here to stay, right?
>>
>
> Well, BTF_TYPE_SAFE_*_OR_NULL also enforces a NULL check, so not clear
> to me how using the annotation over that will break a program (see
> type_is_trusted_or_null() usage). The only difference is that this
> annotation works with type tags applied directly on the struct.
>
> The only reason I did not drop those macros yet is because our
> baseline GCC version does not support type tags, once we move to that
> point we can drop both the macros, rework kfunc suffixes, etc.
> sched_ext is fine taking that dependency. The tag when specified on a
> struct member directly will do the right thing, just like
> BTF_TYPE_SAFE_*_OR_NULL does.
Got it.
Can we start moving into this direction?
At least for clang compiled kernels we can drop BTF_TYPE_SAFE_*_OR_NULL ?
next prev parent reply other threads:[~2026-10-16 1:31 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 23:41 [PATCH bpf-next v3 00/15] Fix some arena paper cuts Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 01/15] bpf: Compute the program digest before resolving the fd_array Kumar Kartikeya Dwivedi
2026-10-16 0:28 ` bot+bpf-ci
2026-10-15 23:41 ` [PATCH bpf-next v3 02/15] selftests/bpf: Bind an exclusive map through a continuous fd_array Kumar Kartikeya Dwivedi
2026-10-15 23:53 ` sashiko-bot
2026-10-16 0:00 ` Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 03/15] libbpf: Keep the fd_array fill index out of bpf_program__clone() Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 04/15] selftests/bpf: Clone a program that calls a module kfunc Kumar Kartikeya Dwivedi
2026-10-16 0:12 ` bot+bpf-ci
2026-10-15 23:41 ` [PATCH bpf-next v3 05/15] compiler_types: Add __arena and __nullable BTF type tag qualifiers Kumar Kartikeya Dwivedi
2026-10-16 1:08 ` Alexei Starovoitov
2026-10-16 1:15 ` Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 06/15] bpf: Recognize __nullable on pointer members of kernel structs Kumar Kartikeya Dwivedi
2026-10-15 23:54 ` sashiko-bot
2026-10-16 0:00 ` Kumar Kartikeya Dwivedi
2026-10-16 1:09 ` Alexei Starovoitov
2026-10-16 1:24 ` Kumar Kartikeya Dwivedi
2026-10-16 1:31 ` Alexei Starovoitov [this message]
2026-10-15 23:41 ` [PATCH bpf-next v3 07/15] bpf: Turn loads of __arena pointer members into arena pointers Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 08/15] selftests/bpf: Test __nullable pointer members Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 09/15] selftests/bpf: Test __arena " Kumar Kartikeya Dwivedi
2026-10-16 1:11 ` Alexei Starovoitov
2026-10-15 23:41 ` [PATCH bpf-next v3 10/15] libbpf: Bind the arena of an object to every program in it Kumar Kartikeya Dwivedi
2026-10-16 0:28 ` bot+bpf-ci
2026-10-15 23:41 ` [PATCH bpf-next v3 11/15] selftests/bpf: Test arena binding by libbpf Kumar Kartikeya Dwivedi
2026-10-16 0:28 ` bot+bpf-ci
2026-10-15 23:41 ` [PATCH bpf-next v3 12/15] bpf: Set up the arena base only in functions that use it Kumar Kartikeya Dwivedi
2026-10-16 1:13 ` Alexei Starovoitov
2026-10-15 23:41 ` [PATCH bpf-next v3 13/15] libbpf: Render the arena type tag with its address space Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 14/15] selftests/bpf: Test the address space rendering of the arena type tag Kumar Kartikeya Dwivedi
2026-10-15 23:41 ` [PATCH bpf-next v3 15/15] selftests/bpf: Test an arena kfunc argument passed from a subprogram Kumar Kartikeya Dwivedi
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