linux-kernel - Re: [PATCH V5 1/2] RISC-V: Add arch_crash_save

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Date:   Wed, 16 Nov 2022 20:15:51 -0800
From:   Deepak Gupta <debug@...osinc.com>
To:     Xianting Tian <xianting.tian@...ux.alibaba.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, bhe@...hat.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, k-hagio-ab@....com,
        hschauhan@...ltrace.org, yixun.lan@...il.com
Subject: Re: [PATCH V5 1/2] RISC-V: Add arch_crash_save_vmcoreinfo support

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@...ux.alibaba.com>
>---
> 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@...osinc.com>

Thanks
debug