Re: [PATCH V3 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support

[HAGIO KAZUHITO(萩尾 一仁)]

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@xxxxxxxxxxxxxxxxx>
>>>>> ---
>>>>>    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@xxxxxxxxxxxxxxxxx/
>> 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@xxxxxxxxxxxxxxxxx/

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.

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