Re: [PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy

From: Akira Tsukamoto <akira.tsukamoto@gmail.com>
To: Qiu Wenbo <qiuwenbo@kylinos.com.cn>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: akira.tsukamoto@gmail.com
Subject: Re: [PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy
Date: Tue, 17 Aug 2021 16:32:52 +0900	[thread overview]
Message-ID: <62b045c0-28ae-5d59-a91b-a2edaf060a62@gmail.com> (raw)
In-Reply-To: <611a33ac.1c69fb81.12aae.89a5SMTPIN_ADDED_BROKEN@mx.google.com>

Hi Qiu,

On 8/16/2021 6:45 PM, Qiu Wenbo wrote:
> Hi Akira,
> 
> 
> I can reproduce it on my HiFive Unmatched with a custom Gentoo rootfs. As pointed out by Andreas, there might be a missing fixup.  I'm going to debug this issue myself since I can reproduce it fairly stable.

Ah! Now I understand the bug.

> +    REG_L    a5, 0(a1)

should be 

+    fixup REG_L    a5, 0(a1)

If you do not mind, could you make the patch to add 'fixup' to all REG_S and REG_L?
Then I will resubmit them to Palmer with your patch.

Thanks,

Akira

> 
> 
> Qiu
> 
> 
> On 8/16/21 14:24, Akira Tsukamoto wrote:
>> Hi Qiu,
>>
>> On 8/15/2021 11:30 AM, Qiu Wenbo wrote:
>>> Hi Akira,
>>>
>>>
>>> This patch breaks my userspace  and I can't boot my system after applying this. Here is the stack trace:
>>>
>>>
>>> [   10.349080] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
>>> [   10.357116] Oops [#15]
>>> [   10.359433] CPU: 2 PID: 169 Comm: (networkd) Tainted: G D           5.14.0-rc5 #53
>>> [   10.367422] Hardware name: SiFive HiFive Unmatched A00 (DT)
>>> [   10.372981] epc : __asm_copy_from_user+0x48/0xf0
>>> [   10.377584]  ra : _copy_from_user+0x28/0x68
>>> [   10.381754] epc : ffffffff8099a280 ra : ffffffff803614a8 sp : ffffffd00416bd90
>>> [   10.388963]  gp : ffffffff811ee540 tp : ffffffe0841b3680 t0 : ffffffd00416bde0
>>> [   10.396172]  t1 : ffffffd00416bdd8 t2 : 0000003ff09ca3a0 s0 : ffffffd00416bdc0
>>> [   10.403381]  s1 : 0000000000000000 a0 : ffffffd00416bdd8 a1 : 0000000000000000
>>> [   10.410590]  a2 : 0000000000000010 a3 : 0000000000000040 a4 : ffffffd00416be18
>>> [   10.417800]  a5 : 0000003ffffffff0 a6 : 000000000000000f a7 : ffffffe085d58540
>>> [   10.425009]  s2 : 0000000000000010 s3 : ffffffd00416bdd8 s4 : 0000000000000002
>>> [   10.432218]  s5 : 0000000000000000 s6 : 0000000000000000 s7 : ffffffe0841b3680
>>> [   10.439427]  s8 : 0000002aad788040 s9 : 0000000000000000 s10: 0000000000000001
>>> [   10.446636]  s11: 0000000000000000 t3 : 0000000000000000 t4 : 0000000000000001
>>> [   10.453845]  t5 : 0000000000000010 t6 : 0000000000040000
>>> [   10.459144] status: 0000000200040120 badaddr: 0000000000000000 cause: 000000000000000d
>>> [   10.467049] [<ffffffff8099a280>] __asm_copy_from_user+0x48/0xf0
>>> [   10.472955] [<ffffffff8009a562>] do_seccomp+0x62/0x8be
>>> [   10.478079] [<ffffffff8009af58>] prctl_set_seccomp+0x24/0x32
>>> [   10.483725] [<ffffffff80020756>] sys_prctl+0xf6/0x450
>>> [   10.488763] [<ffffffff800034f2>] ret_from_syscall+0x0/0x2
>>>
>>>
>>> The PC register points to this line:
>>>
>>> +1:
>>> +    REG_L    a5, 0(a1)
>> Thanks for testing! Do you mind teaching me how to reproduce the error?
>>
>> Akira
>>
> 
> 
> 