[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CA+khW7iLeSZPweZEz_tfP+LRtpvZbfvstZWgUbNrEDK-Ntxyxw@mail.gmail.com>
Date: Fri, 29 Jul 2022 15:48:54 -0700
From: Hao Luo <haoluo@...gle.com>
To: Youlin Li <liulin063@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
yhs@...com, kpsingh@...nel.org, sdf@...gle.com, jolsa@...nel.org,
bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf] bpf: Do more tight ALU bounds tracking
On Fri, Jul 29, 2022 at 3:43 PM Youlin Li <liulin063@...il.com> wrote:
>
> In adjust_scalar_min_max_vals(), let 32bit bounds learn from 64bit bounds
> to get more tight bounds tracking. Similar operation can be found in
> reg_set_min_max().
>
> Also, we can now fold reg_bounds_sync() into zext_32_to_64().
>
> Before:
>
> func#0 @0
> 0: R1=ctx(off=0,imm=0) R10=fp0
> 0: (b7) r0 = 0 ; R0_w=0
> 1: (b7) r1 = 0 ; R1_w=0
> 2: (87) r1 = -r1 ; R1_w=scalar()
> 3: (87) r1 = -r1 ; R1_w=scalar()
> 4: (c7) r1 s>>= 63 ; R1_w=scalar(smin=-1,smax=0)
> 5: (07) r1 += 2 ; R1_w=scalar(umin=1,umax=2,var_off=(0x0; 0xffffffff)) <--- [*]
> 6: (95) exit
>
> It can be seen that even if the 64bit bounds is clear here, the 32bit
> bounds is still in the state of 'UNKNOWN'.
>
> After:
>
> func#0 @0
> 0: R1=ctx(off=0,imm=0) R10=fp0
> 0: (b7) r0 = 0 ; R0_w=0
> 1: (b7) r1 = 0 ; R1_w=0
> 2: (87) r1 = -r1 ; R1_w=scalar()
> 3: (87) r1 = -r1 ; R1_w=scalar()
> 4: (c7) r1 s>>= 63 ; R1_w=scalar(smin=-1,smax=0)
> 5: (07) r1 += 2 ; R1_w=scalar(umin=1,umax=2,var_off=(0x0; 0x3)) <--- [*]
> 6: (95) exit
>
> Signed-off-by: Youlin Li <liulin063@...il.com>
Looks good to me. Thanks Youlin.
Acked-by: Hao Luo <haoluo@...gle.com>
Hao
Powered by blists - more mailing lists