linux-kernel - Re: [PATCH bpf-next v4 2/2] selftests/bpf: Add test for conditional jumps on same scalar register

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Message-ID: <CAADnVQL9kfkasqd0+dg+PSjrji9KrMTbWTZaajwYKzW2vJ1czQ@mail.gmail.com>
Date: Mon, 3 Nov 2025 17:55:20 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: KaFai Wan <kafai.wan@...ux.dev>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, Paul Chaignon <paul.chaignon@...il.com>, 
	Matan Shachnai <m.shachnai@...il.com>, 
	Harishankar Vishwanathan <harishankar.vishwanathan@...il.com>, colin.i.king@...il.com, 
	Luis Gerhorst <luis.gerhorst@....de>, bpf <bpf@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 2/2] selftests/bpf: Add test for conditional
 jumps on same scalar register

On Mon, Nov 3, 2025 at 10:14 AM Eduard Zingerman <eddyz87@...il.com> wrote:
>
> On Mon, 2025-11-03 at 14:31 +0800, KaFai Wan wrote:
> > Add test cases to verify the correctness of the BPF verifier's branch analysis
> > when conditional jumps are performed on the same scalar register. And make sure
> > that JGT does not trigger verifier BUG.
> >
> > Signed-off-by: KaFai Wan <kafai.wan@...ux.dev>
> > ---
>
> Thank you for adding these.
>
> Acked-by: Eduard Zingerman <eddyz87@...il.com>
>
> (but a comment needs a fix)
>
> [...]
>
> > +SEC("socket")
> > +__description("jset on same register, scalar value unknown branch 3")
> > +__msg("4: (b7) r0 = 0 {{.*}} R0=0")
> > +__msg("6: (b7) r0 = 1 {{.*}} R0=1")
> > +__success __log_level(2)
> > +__flag(BPF_F_TEST_REG_INVARIANTS)
> > +__naked void jset_on_same_register_5(void *ctx)
> > +{
> > +     asm volatile("                  \
> > +     /* range [-1;-1] */             \
>                      ^^
>    Typo, should be [-1;1].

Eagle eye.

Fixed while applying.