From: Eduard Zingerman <eddyz87@gmail.com>
To: Paul Chaignon <paul.chaignon@gmail.com>, bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Shung-Hsi Yu <shung-hsi.yu@suse.com>
Subject: Re: [PATCH bpf-next 2/2] selftests/bpf: Tests for is_scalar_branch_taken tnum logic
Date: Wed, 13 Aug 2025 11:34:04 -0700 [thread overview]
Message-ID: <a4c4e38b669a05200570fdfc66f4bdfc29dbb3d1.camel@gmail.com> (raw)
In-Reply-To: <85f82f190955844509eb77ae95f4ef20a587acd7.1755098817.git.paul.chaignon@gmail.com>
On Wed, 2025-08-13 at 17:35 +0200, Paul Chaignon wrote:
> This patch adds tests for the new jeq and jne logic in
> is_scalar_branch_taken. The following shows the first test failing
> before the previous patch is applied. Once the previous patch is
> applied, the verifier can use the tnum values to deduce that instruction
> 7 is dead code.
>
> 0: call bpf_get_prandom_u32#7 ; R0_w=scalar()
> 1: w0 = w0 ; R0_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
> 2: r0 >>= 30 ; R0_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=3,var_off=(0x0; 0x3))
> 3: r0 <<= 30 ; R0_w=scalar(smin=0,smax=umax=umax32=0xc0000000,smax32=0x40000000,var_off=(0x0; 0xc0000000))
> 4: r1 = r0 ; R0_w=scalar(id=1,smin=0,smax=umax=umax32=0xc0000000,smax32=0x40000000,var_off=(0x0; 0xc0000000)) R1_w=scalar(id=1,smin=0,smax=umax=umax32=0xc0000000,smax32=0x40000000,var_off=(0x0; 0xc0000000))
> 5: r1 += 1024 ; R1_w=scalar(smin=umin=umin32=1024,smax=umax=umax32=0xc0000400,smin32=0x80000400,smax32=0x40000400,var_off=(0x400; 0xc0000000))
> 6: if r1 != r0 goto pc+1 ; R0_w=scalar(id=1,smin=umin=umin32=1024,smax=umax=umax32=0xc0000000,smin32=0x80000400,smax32=0x40000000,var_off=(0x400; 0xc0000000)) R1_w=scalar(smin=umin=umin32=1024,smax=umax=umax32=0xc0000000,smin32=0x80000400,smax32=0x40000400,var_off=(0x400; 0xc0000000))
> 7: r10 = 0
> frame pointer is read only
>
> Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
> ---
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
[...]
next prev parent reply other threads:[~2025-08-13 18:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-13 15:34 [PATCH bpf-next 1/2] bpf: Use tnums for JEQ/JNE is_branch_taken logic Paul Chaignon
2025-08-13 15:35 ` [PATCH bpf-next 2/2] selftests/bpf: Tests for is_scalar_branch_taken tnum logic Paul Chaignon
2025-08-13 18:34 ` Eduard Zingerman [this message]
2025-08-13 18:08 ` [PATCH bpf-next 1/2] bpf: Use tnums for JEQ/JNE is_branch_taken logic Eduard Zingerman
2025-08-14 12:55 ` Shung-Hsi Yu
2025-08-18 17:44 ` Paul Chaignon
2025-08-20 5:09 ` Shung-Hsi Yu
2025-08-21 9:40 ` Paul Chaignon
2025-08-15 8:24 ` [syzbot ci] " syzbot ci
2025-08-20 11:34 ` Paul Chaignon
2025-08-20 19:37 ` Eduard Zingerman
2025-08-21 10:04 ` Paul Chaignon
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