Re: [PATCH V4 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support

Xianting Tian
2022-10-31T09:10:58Z

在 2022/10/31 下午4:57, Baoquan He 写道:
> On 10/26/22 at 02:47pm, Conor Dooley wrote:
>> On Wed, Oct 26, 2022 at 08:05:41PM +0800, Baoquan He wrote:
>>> Hi Xianting,
>>>
>>> On 10/26/22 at 05:44pm, Xianting Tian wrote:
>>>> 在 2022/10/26 下午5:25, Conor Dooley 写道:
>>>>> On Wed, Oct 26, 2022 at 05:08:11PM +0800, Xianting Tian wrote:
>>>>>> Hi Palmer, Conor
>>>>>>
>>>>>> Is this version OK for you?
>>>>> The weird ifdef/IS_ENABLED thing was the only comment I had. It's a bit
>>>>> odd & I notice Baoquan brought it up too. I didn't (and won't) give you
>>>>> a reviewed by on these patches because I don't understand the area well
>>>>> enough. The general nitpickery seems to be sorted though.
>>>> I checked the KERNEL_LINK_ADDR definition of riscv,  it is valid for
>>>> CONFIG_64BIT and !CONFIG_64BIT.
>>> This series looks good to me. My only minor concern is if we can make
>>> the arch_crash_save_vmcoreinfo() as below. I don't understand why we
>>> have to have the CONFIG_64BIT ifdeffery and the IS_ENABLED(CONFIG_64BIT)
>>> between two adjacent code blocks. Not sure if we are saying the same
>>> thing.
>> I think we can just go and drop the IS_ENABLED(). From looking at it
>> last time, one bit is compileable (but not usable) for !64BIT and the
>> other isn't hence the IS_ENABLED(). I think it would make sense to drop
>> the IS_ENABLED() - I don't think we're too likely to hit some compile
>> testing edge cases that IS_ENABLED() would help with & only having one
>> makes the code look a lot less odd and a lot more intentional.
> I check risc-v code again, and agree we can drop the IS_ENABLED checking
> to export KERNEL_LINK_ADDR anyway. We can surely deduce
> KERNEL_LINK_ADDR in userspace e.g makedumpfile/Crash, while it seems no
> harm to get it from the vmcoreinfo directly.

thanks Baoquan for the confirm,

please help give the Revied-by and promote the patch set to be applied
to Linux 6.1 :)

>
> As for the difference between "#ifdef CONFIG_64BIT" and
> "if (IS_ENABLED(CONFIG_64BIT))", I haven't got what's the Xianting's
> point. Below is the IS_ENABLED definition in include/linux/kconfig.h,
> it's truly different than #ifdef, while the change we are discussing
> here is not related.
>
> /*
> * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
> * 0 otherwise. Note that CONFIG_FOO=y results in "#define CONFIG_FOO 1" in
> * autoconf.h, while CONFIG_FOO=m results in "#define CONFIG_FOO_MODULE 1".
> */
> #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
>
>>> +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);
>>> + vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n", KERNEL_LINK_ADDR);
>>> +#endif
>>> +}
>>>
>>>> Maybe we can remove IS_ENABLED(CONFIG_64BIT)
>>>>
>>>> arch/riscv/include/asm/pgtable.h
>>>> #define ADDRESS_SPACE_END       (UL(-1))
>>>> #ifdef CONFIG_64BIT
>>>> /* Leave 2GB for kernel and BPF at the end of the address space */
>>>> #define KERNEL_LINK_ADDR        (ADDRESS_SPACE_END - SZ_2G + 1)
>>>> #else
>>>> #define KERNEL_LINK_ADDR        PAGE_OFFSET
>>>> #endif
>>>>
>>>> arch/riscv/include/asm/page.h
>>>> #ifdef CONFIG_64BIT
>>>> #ifdef CONFIG_MMU
>>>> #define PAGE_OFFSET             kernel_map.page_offset
>>>> #else
>>>> #define PAGE_OFFSET             _AC(CONFIG_PAGE_OFFSET, UL)
>>>> #endif
>>>> /*
>>>>  * By default, CONFIG_PAGE_OFFSET value corresponds to SV48 address space so
>>>>  * define the PAGE_OFFSET value for SV39.
>>>>  */
>>>> #define PAGE_OFFSET_L4          _AC(0xffffaf8000000000, UL)
>>>> #define PAGE_OFFSET_L3          _AC(0xffffffd800000000, UL)
>>>> #else
>>>> #define PAGE_OFFSET             _AC(CONFIG_PAGE_OFFSET, UL)
>>>> #endif /* CONFIG_64BIT */
>>>>
>>>>> Thanks,
>>>>> Conor.
>>>>>
>>>>>> 在 2022/10/20 下午12:40, Xianting Tian 写道:
>>>>>>> 在 2022/10/20 上午11:05, Baoquan He 写道:
>>>>>>>> On 10/20/22 at 10:17am, Xianting Tian wrote:
>>>>>>>>> 在 2022/10/20 上午10:08, Baoquan He 写道:
>>>>>>>>>> On 10/19/22 at 06:36pm, Xianting Tian wrote:
>>>>>>>>>>> Add arch_crash_save_vmcoreinfo(), which exports VM
>>>>>>>>>>> layout(MODULES, VMALLOC,
>>>>>>>>>>> VMEMMAP ranges and KERNEL_LINK_ADDR), 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 | 23 +++++++++++++++++++++++
>>>>>>>>>>>    2 files changed, 24 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..3e889d0ed7bd
>>>>>>>>>>> --- /dev/null
>>>>>>>>>>> +++ b/arch/riscv/kernel/crash_core.c
>>>>>>>>>>> @@ -0,0 +1,23 @@
>>>>>>>>>>> +// 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))
>>>>>>>>>>> +
>>>>>>>>>>> vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n",
>>>>>>>>>>> KERNEL_LINK_ADDR);
>>>>>>>>>> Wondering why you don't put KERNEL_LINK_ADDR exporting into the above
>>>>>>>>>> ifdeffery scope, with that you can save one line of
>>>>>>>>>> "IS_ENABLED(CONFIG_64BIT)".
>>>>>>>>> I followed the rule in print_vm_layout() of
>>>>>>>>> arch/riscv/mm/init.c, which used
>>>>>>>>> IS_ENABLED when print the value of KERNEL_LINK_ADDR.
>>>>>>>>>
>>>>>>>> I see. There's PAGE_OFFSET in the middle. Thanks.
>>>>>>>>
>>>>>>>>          print_ml("lowmem", (unsigned long)PAGE_OFFSET,
>>>>>>>>                  (unsigned long)high_memory)
>>>>>>>>
>>>>>>>> So now, do you think if it's necessary to have another
>>>>>>>> IS_ENABLED(CONFIG_64BIT) in the current arch_crash_save_vmcoreinfo()?
>>>>>>> For which MACRO?  I think current code for PAGE_OFFSET is OK.
>>>>>>>