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

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Message-ID: <811bdf09-be38-ce2a-a1d3-ada9f7c85b97@linux.alibaba.com>
Date:   Wed, 19 Oct 2022 11:17:16 +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 2022/10/19 上午10:50, HAGIO KAZUHITO(萩尾 一仁) 写道:
> On 2022/10/19 10:50, Xianting Tian wrote:
>> 在 2022/10/18 下午6:03, Baoquan He 写道:
>>> On 10/18/22 at 05:25pm, Xianting Tian wrote:
>>>> 在 2022/10/18 下午5:10, Baoquan He 写道:
>>>>> On 10/18/22 at 04:17pm, Xianting Tian wrote:
>>>>>> Add arch_crash_save_vmcoreinfo(), which exports VM layout(MODULES, VMALLOC,
>>>>>> VMEMMAP and KERNEL_LINK_ADDR ranges), va bits and ram base for vmcore.
>>>>>>
>>>>>> Default pagetable levels and PAGE_OFFSET aren't same for different kernel
>>>>>> version as below. For pagetable levels, it sets sv57 by default and falls
>>>>>> back to setting sv48 at boot time if sv57 is not supported by the hardware.
>>>>>>
>>>>>> For ram base, the default value is 0x80200000 for qemu riscv64 env and,
>>>>>> for example, is 0x200000 on the XuanTie 910 CPU.
>>>>>>
>>>>>>     * Linux Kernel 5.18 ~
>>>>>>     *      PGTABLE_LEVELS = 5
>>>>>>     *      PAGE_OFFSET = 0xff60000000000000
>>>>>>     * Linux Kernel 5.17 ~
>>>>>>     *      PGTABLE_LEVELS = 4
>>>>>>     *      PAGE_OFFSET = 0xffffaf8000000000
>>>>>>     * Linux Kernel 4.19 ~
>>>>>>     *      PGTABLE_LEVELS = 3
>>>>>>     *      PAGE_OFFSET = 0xffffffe000000000
>>>>>>
>>>>>> Since these configurations change from time to time and version to version,
>>>>>> it is preferable to export them via vmcoreinfo than to change the crash's
>>>>>> code frequently, it can simplify the development of crash tool.
>>>>>>
>>>>>> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
>>>>>> ---
>>>>>>     arch/riscv/kernel/Makefile     |  1 +
>>>>>>     arch/riscv/kernel/crash_core.c | 29 +++++++++++++++++++++++++++++
>>>>>>     2 files changed, 30 insertions(+)
>>>>>>     create mode 100644 arch/riscv/kernel/crash_core.c
>>>>>>
>>>>>> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
>>>>>> index db6e4b1294ba..4cf303a779ab 100644
>>>>>> --- a/arch/riscv/kernel/Makefile
>>>>>> +++ b/arch/riscv/kernel/Makefile
>>>>>> @@ -81,6 +81,7 @@ obj-$(CONFIG_KGDB)        += kgdb.o
>>>>>>     obj-$(CONFIG_KEXEC_CORE)    += kexec_relocate.o crash_save_regs.o machine_kexec.o
>>>>>>     obj-$(CONFIG_KEXEC_FILE)    += elf_kexec.o machine_kexec_file.o
>>>>>>     obj-$(CONFIG_CRASH_DUMP)    += crash_dump.o
>>>>>> +obj-$(CONFIG_CRASH_CORE)    += crash_core.o
>>>>>>     obj-$(CONFIG_JUMP_LABEL)    += jump_label.o
>>>>>> diff --git a/arch/riscv/kernel/crash_core.c b/arch/riscv/kernel/crash_core.c
>>>>>> new file mode 100644
>>>>>> index 000000000000..8d7f5ff108da
>>>>>> --- /dev/null
>>>>>> +++ b/arch/riscv/kernel/crash_core.c
>>>>>> @@ -0,0 +1,29 @@
>>>>>> +// SPDX-License-Identifier: GPL-2.0-only
>>>>>> +
>>>>>> +#include <linux/crash_core.h>
>>>>>> +#include <linux/pagemap.h>
>>>>>> +
>>>>>> +void arch_crash_save_vmcoreinfo(void)
>>>>>> +{
>>>>>> +    VMCOREINFO_NUMBER(VA_BITS);
>>>>>> +    VMCOREINFO_NUMBER(phys_ram_base);
>>>>>> +
>>>>>> +    vmcoreinfo_append_str("NUMBER(PAGE_OFFSET)=0x%lx\n", PAGE_OFFSET);
>>>>>> +    vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n", VMALLOC_START);
>>>>>> +    vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END);
>>>>>> +    vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", VMEMMAP_START);
>>>>>> +    vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END);
>>>>>> +#ifdef CONFIG_64BIT
>>>>>> +    vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
>>>>>> +    vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
>>>>>> +#endif
>>>>>> +
>>>>>> +    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.

>
> Thanks,
> Kazu
>
>> If we need to remove the two areas, I will resend the crash patch set and kernel patch set.
>> thanks
>>
>>>> I add it in case of using in furture.
>>>>
>>>>> Thanks
>>>>> Baoquan