linux-kernel - Re: [PATCH V3 1/2] RISC-V: Add arch_crash_save

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Message-ID: <5fa1f75a-1641-771e-3670-2d8978c99d2a@linux.alibaba.com>
Date:   Thu, 20 Oct 2022 09:52:36 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     HAGIO KAZUHITO(萩尾 一仁) 
        <k-hagio-ab@....com>, Baoquan He <bhe@...hat.com>,
        lijiang <lijiang@...hat.com>
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Subject: Re: [PATCH V3 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support


在 2022/10/20 上午9:35, HAGIO KAZUHITO(萩尾 一仁) 写道:
> On 2022/10/19 12:17, Xianting Tian wrote:
>
>>>>>>>> +    if (IS_ENABLED(CONFIG_64BIT)) {
>>>>>>>> +#ifdef CONFIG_KASAN
>>>>>>>> +        vmcoreinfo_append_str("NUMBER(KASAN_SHADOW_START)=0x%lx\n", KASAN_SHADOW_START);
>>>>>>>> +        vmcoreinfo_append_str("NUMBER(KASAN_SHADOW_END)=0x%lx\n", KASAN_SHADOW_END);
>>>>>>>> +#endif
>>>>>>>> +        vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n", KERNEL_LINK_ADDR);
>>>>>>>> +        vmcoreinfo_append_str("NUMBER(ADDRESS_SPACE_END)=0x%lx\n", ADDRESS_SPACE_END);
>>>>>>> Seems this is the firsr ARCH where kasan and kernel link/bpf space are
>>>>>>> added to dump and analyze. Just curious, have you got code change to
>>>>>>> make use of them to do dumping and analyze?
>>>>>> KASAN_SHADOW_START is not used, KERNEL_LINK_ADDR is used in the crash patch set:
>>>>>> https://patchwork.kernel.org/project/linux-riscv/cover/20220813031753.3097720-1-xianting.tian@linux.alibaba.com/
>>>>> Oh, I would say please no. Sometime we got tons of objection when adding an
>>>>> necessary one, we definitely should not add one for possible future
>>>>> use.
>>>>>
>>>>> For this kind of newly added one, we need get ack from
>>>>> makedumpfile/crash utility maintainer so that we know they are necessary
>>>>> to have. At least they don't oppose.
>>>> Hi Kazu, Li Jiang
>>>>
>>>> Could you help comment whether we need KASAN_SHADOW_START and KERNEL_LINK_ADDR area export for vmcore from crash point of view？
>>>>
>>>> In my crash patch set, I don't use KASAN_SHADOW_START,
>>>> And only get the value of KERNEL_LINK_ADDR, not realy use it.
>>>> https://patchwork.kernel.org/project/linux-riscv/cover/20220813031753.3097720-1-xianting.tian@linux.alibaba.com/
>>> In your crash patch set, KERNEL_LINK_ADDR is used in VTOP() and looks
>>> necessary to me.
>>>
>>> The others (KASAN_SHADOW_START, KASAN_SHADOW_END and ADDRESS_SPACE_END)
>>> are not currently used.  It may be better to add them when they are
>>> really used.
>> I am very sorry, I missed it , KERNEL_LINK_ADDR is used indeed.
>>
>> KASAN_SHADOW_START is not used, so I don't need to send crash patch set> again. only need to remove KASAN_SHADOW_END in kernel patch set.
> I see that your v4 kernel patch set does not have ADDRESS_SPACE_END,
> so it seems there would be need to change this part and related ones
> at crash side.
>
>           if ((string = pc->read_vmcoreinfo("NUMBER(ADDRESS_SPACE_END)"))) {
>                   ms->address_space_end = htol(string, QUIET, NULL);
>                   free(string);
>           } else
>                   goto error;
> ...
> error:
>           error(FATAL, "cannot get vm layout\n");

thanks,

I just send V4 of crash patch set, the issue is also fixed in V4.

>
> Thanks,
> Kazu