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

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Date:   Tue, 18 Oct 2022 17:25:11 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     Baoquan He <bhe@...hat.com>, Kazuhito Hagio <k-hagio-ab@....com>
Cc:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, anup@...infault.org, heiko@...ech.de,
        guoren@...nel.org, mick@....forth.gr,
        alexandre.ghiti@...onical.com, vgoyal@...hat.com,
        dyoung@...hat.com, corbet@....net, Conor.Dooley@...rochip.com,
        bagasdotme@...il.com, kexec@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, crash-utility@...hat.com,
        heinrich.schuchardt@...onical.com, hschauhan@...ltrace.org,
        yixun.lan@...il.com
Subject: Re: [PATCH V3 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support


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/

I add it in case of using in furture.

>
> Thanks
> Baoquan