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

[Xianting Tian <xianting.tian@linux.alibaba.com>]

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@linux.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/

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

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