Received-SPF: pass (google.com: domain of linux-kernel+bounces-116706-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Mon, 25 Mar 2024 09:42:08 +0100
From: Benjamin Tissoires <bentiss@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>, 
	Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, 
	Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>, 
	Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>, 
	Yonghong Song <yonghong.song@linux.dev>, John Fastabend <john.fastabend@gmail.com>, 
	KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, 
	Jiri Olsa <jolsa@kernel.org>, Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>, 
	bpf <bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH bpf-next v5 2/6] bpf/verifier: add bpf_timer as a kfunc
 capable type
Message-ID: <d3qeziyeiqfdofuzj266r47g4jpno56jd4dy2wgnm4h7z6fhmu@sltzwlkwj4z5>
References: <20240322-hid-bpf-sleepable-v5-0-179c7b59eaaa@kernel.org>
 <20240322-hid-bpf-sleepable-v5-2-179c7b59eaaa@kernel.org>
 <CAP01T76oYpkNdgxXo+6v53afjObvYU4LWRLfkg2S7pNivzaEvg@mail.gmail.com>
 <CAADnVQL_mQgN8uKsNFR0FBtWoaweCkzXw03EvbnQ-iFVWvXxuw@mail.gmail.com>
 <CAP01T753_FjFdj1CbCX5Bh1itYUWf8DUh41F7R_7Fdb=2SEL8g@mail.gmail.com>
 <CAADnVQ+5mSEW-LJwS30hED1cJeHOhqfCTKdBzYCcRd8EiVNvtA@mail.gmail.com>
 <CAP01T757ddmmFR+Cnj70DrTLFcEu+9uAcbscrO-uOmSVGB8eJA@mail.gmail.com>
 <CAADnVQK=aAcNt-8BBJNnp3QGkxVWLYhZ9=9dizo-7eQosjNtow@mail.gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CAADnVQK=aAcNt-8BBJNnp3QGkxVWLYhZ9=9dizo-7eQosjNtow@mail.gmail.com>

On Mar 24 2024, Alexei Starovoitov wrote:
> On Sat, Mar 23, 2024 at 9:57 PM Kumar Kartikeya Dwivedi
> <memxor@gmail.com> wrote:
> 
> > > > >
> > > > > Observation is correct. The patch is buggy,
> > > > > but the suggestion to follow process_dynptr_func() will lead
> > > > > to unnecessary complexity.
> > > > > dynptr-s are on stack with plenty of extra checks.
> > > >
> > > > The suggestion was to call process_timer_func, not process_dynptr_func.
> > > >
> > > > > In this case bpf_timer is in map_value.
> > > > > Much simpler is to follow KF_ARG_PTR_TO_MAP approach.
> > > >
> > > > What I meant by the example was that dynptr handling does the same
> > > > thing for kfuncs and helpers (using the same function), so timer
> > > > arguments should do the same (i.e. use process_timer_func), which will
> > > > do all checks for constant offset (ensuring var_off is tnum_is_const)
> > > > and match it against btf_record->timer_off.
> > >
> > > I don't follow. Please elaborate with a patch.
> > > The var_off and off is a part of the bug, but it's not the biggest part of it.
> >
> > Not compile tested.

Compiles just fine :)

> 
> I see. All makes sense to me.
> 
> Benjamin,
> pls incorporate it in your set.
> 

OK, done!

I just had to revert to the following or KF_ARG_TIMER_ID was not
recognized by the verifier:

---
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7ee20e9d14bd..a5e147468ac8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10848,7 +10848,7 @@ BTF_ID(struct, bpf_list_head)
 BTF_ID(struct, bpf_list_node)
 BTF_ID(struct, bpf_rb_root)
 BTF_ID(struct, bpf_rb_node)
-BTF_ID(struct, bpf_timer)
+BTF_ID(struct, bpf_timer_kern)
 
 static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
 				    const struct btf_param *arg, int type)
---

Cheers,
Benjamin