Re: [PATCH V5 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support

[Deepak Gupta]

On Wed, Oct 26, 2022 at 10:42:07PM +0800, 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@xxxxxxxxxxxxxxxxx>
> ---
> arch/riscv/kernel/Makefile     |  1 +
> arch/riscv/kernel/crash_core.c | 21 +++++++++++++++++++++
> 2 files changed, 22 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..b351a3c01355
> --- /dev/null
> +++ b/arch/riscv/kernel/crash_core.c
> @@ -0,0 +1,21 @@
> +// 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
> +	vmcoreinfo_append_str("NUMBER(KERNEL_LINK_ADDR)=0x%lx\n", KERNEL_LINK_ADDR);
> +}
> --
> 2.17.1

I had been looking around to play around with crash-utility.
Applied v5 patches, triggered a crash and have been able to use crash tool with commands 
like vtop/bt.

Tested-by: Deepak Gupta <debug@xxxxxxxxxxxx>

Thanks
debug