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Subject: Re: [PATCH 3/4] LoongArch: Add stacktrace support
To:     Huacai Chen <chenhuacai@kernel.org>
Cc:     WANG Xuerui <kernel@xen0n.name>, loongarch@lists.linux.dev,
        LKML <linux-kernel@vger.kernel.org>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Jinyang He <hejinyang@loongson.cn>
References: <20220801121726.9681-1-zhangqing@loongson.cn>
 <20220801121726.9681-4-zhangqing@loongson.cn>
 <CAAhV-H6Az_X1afvAO+JxnDaW-Ey_8wmozehd++qOZoGmimM+6g@mail.gmail.com>
 <3cc6aebc-87e7-f0d0-2a88-e7e742e1e5ee@loongson.cn>
 <CAAhV-H61ZXvF2xvXsyrxRYj6impet0w83svkt94FUhJhzj-2EQ@mail.gmail.com>
From:   Qing Zhang <zhangqing@loongson.cn>
Message-ID: <59d9ef26-d378-b311-82a9-95fc8d14a8a6@loongson.cn>
Date:   Tue, 2 Aug 2022 10:01:15 +0800
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On 2022/8/2 上午9:30, Huacai Chen wrote:
> Hi, Qing,
> 
> On Tue, Aug 2, 2022 at 9:20 AM zhangqing <zhangqing@loongson.cn> wrote:
>>
>>
>>
>> On 2022/8/1 下午11:30, Huacai Chen wrote:
>>> Hi, Qing,
>>>
>>> On Mon, Aug 1, 2022 at 8:17 PM Qing Zhang <zhangqing@loongson.cn> wrote:
>>>>
>>>> Use common arch_stack_walk infrastructure to avoid duplicated code and
>>>> avoid taking care of the stack storage and filtering.
>>>> Add sra (means __schedule return address) and scfa (means __schedule call
>>>> frame address) to thread_info and store it in switch_to().
>>>>
>>>> Now we can print the process stack by cat /proc/*/stack and can better
>>>> support ftrace.
>>>>
>>>> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
>>>> ---
>>>>    arch/loongarch/Kconfig                 |  5 ++++
>>>>    arch/loongarch/include/asm/processor.h |  9 +++++++
>>>>    arch/loongarch/include/asm/switch_to.h | 14 ++++++----
>>>>    arch/loongarch/include/asm/uaccess.h   |  4 +--
>>>>    arch/loongarch/kernel/Makefile         |  1 +
>>>>    arch/loongarch/kernel/asm-offsets.c    |  2 ++
>>>>    arch/loongarch/kernel/process.c        |  3 +++
>>>>    arch/loongarch/kernel/stacktrace.c     | 37 ++++++++++++++++++++++++++
>>>>    arch/loongarch/kernel/switch.S         |  2 ++
>>>>    9 files changed, 70 insertions(+), 7 deletions(-)
>>>>    create mode 100644 arch/loongarch/kernel/stacktrace.c
>>>>
>>>> diff --git a/arch/loongarch/include/asm/uaccess.h b/arch/loongarch/include/asm/uaccess.h
>>>> index 2b44edc604a2..a8ae2af4025a 100644
>>>> --- a/arch/loongarch/include/asm/uaccess.h
>>>> +++ b/arch/loongarch/include/asm/uaccess.h
>>>> @@ -229,13 +229,13 @@ extern unsigned long __copy_user(void *to, const void *from, __kernel_size_t n);
>>>>    static inline unsigned long __must_check
>>>>    raw_copy_from_user(void *to, const void __user *from, unsigned long n)
>>>>    {
>>>> -       return __copy_user(to, from, n);
>>>> +       return __copy_user(to, (__force const void *)from, n);
>>>>    }
>>>>
>>>>    static inline unsigned long __must_check
>>>>    raw_copy_to_user(void __user *to, const void *from, unsigned long n)
>>>>    {
>>>> -       return __copy_user(to, from, n);
>>>> +       return __copy_user((__force void *)to, from, n);
>>> Why this? Does it have something to do with stacktrace?
>>>
>>> Huacai
>>
>> Hi, huacai
>>
>> This is kernel test robot report sparse warnings:
>> I reproduced locally and found that other architectures calling
>> __copy_user also use __force conversion, Is this modification appropriate?
>>
>> kernel/trace/trace_events_user.c: note: in included file (through
>> include/linux/uaccess.h, include/linux/sched/task.h,
>> include/linux/sched/signal.h, ...):
>>      arch/loongarch/include/asm/uaccess.h:232:32: sparse: sparse:
>> incorrect type in argument 2 (different address spaces) @@     expected
>> void const *from @@     got void const [noderef] __user *from @@
>>      arch/loongarch/include/asm/uaccess.h:232:32: sparse:     expected
>> void const *from
>>      arch/loongarch/include/asm/uaccess.h:232:32: sparse:     got void
>> const [noderef] __user *from
> The modification might be correct, but should it be in this patch?
> 
> Huacai
I will send this patch separately,  it has nothing to do with the series 
patch.

arch/loongarch/kernel/ptrace.c: note: in included file (through 
include/linux/uaccess.h, include/linux/sched/task.h, 
include/linux/sched/signal.h, include/linux/ptrace.h, include/linux/audit.h)

-Qing
>>
>> Thanks,
>> -Qing
>>
>>
>>