Re: [PATCH V2 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support

[Conor.Dooley]

On 18/10/2022 03:28, Xianting Tian wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> 在 2022/10/18 上午3:54, Conor Dooley 写道:
> 
>> On Fri, Oct 14, 2022 at 09:41:38PM +0800, Xianting Tian wrote:

>>>   * 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)) {
>> You've already got a #ifdef CONFIG_64BIT above, is there a reason why
>> you'd use the IS_ENABLED here rather than merge this with the above
>> section? I'm a big fan of IS_ENABLED but I'm not sure what it adds here,
>> maybe you can show me the light :)
> The IS_ENABLED() check prevents the line from getting executed, but
> unlike an #ifdef it relies on it to be parsable.

Hey Xianting,
Firstly, neither this nor the other version of this message made it to
the mailing list - and since I usually use lei to get my mails that is
a bit of a problem :(

Yeah, I know that that is what IS_ENABLED() does, it's just in this
situation it does not look very intentional & more like disjoint bits
of copy-paste. It's fine though, leave it as it is.

Thanks,
Conor.

> 
> I wrote this arch_crash_save_vmcoreinfo() func with reference to this: static void __init print_vm_layout(void) // arch/riscv/mm/init.c
> {
>          pr_notice("Virtual kernel memory layout:\n");
>          print_ml("fixmap", (unsigned long)FIXADDR_START,
>                  (unsigned long)FIXADDR_TOP);
>          print_ml("pci io", (unsigned long)PCI_IO_START,
>                  (unsigned long)PCI_IO_END);
>          print_ml("vmemmap", (unsigned long)VMEMMAP_START,
>                  (unsigned long)VMEMMAP_END);
>          print_ml("vmalloc", (unsigned long)VMALLOC_START,
>                  (unsigned long)VMALLOC_END);
> #ifdef CONFIG_64BIT
>          print_ml("modules", (unsigned long)MODULES_VADDR,
>                  (unsigned long)MODULES_END);
> #endif
>          print_ml("lowmem", (unsigned long)PAGE_OFFSET,
>                  (unsigned long)high_memory);
>          if (IS_ENABLED(CONFIG_64BIT)) {
> #ifdef CONFIG_KASAN
>                  print_ml("kasan", KASAN_SHADOW_START, KASAN_SHADOW_END);
> #endif
> 
>                  print_ml("kernel", (unsigned long)KERNEL_LINK_ADDR,
>                           (unsigned long)ADDRESS_SPACE_END);
>          }
> }
> 
>> Thanks,
>> Conor.
>>
>>
>>> +#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);
>>> +	}
>>> +}
>>> -- 
>>> 2.17.1
>>>
>>>