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File crash-RISCV64-Make-crash-tool-enter-command-line-and-suppo.patch of Package crash (Revision 79fa6b5df9b8e54a6611dcfbed05e018)

Currently displaying revision 79fa6b5df9b8e54a6611dcfbed05e018 , Show latest

From: Xianting Tian <xianting.tian@linux.alibaba.com>
Date: Thu, 20 Oct 2022 09:50:07 +0800
Subject: RISCV64: Make crash tool enter command line and support some commands
Upstream: merged
Git-commit: e7119d2225e1db3c460285880ea39b69d362178e

1. Add riscv64_init() implementation, do all necessary machine-specific setup,
   which will be called multiple times during initialization.
2. Add riscv64 sv39/48/57 pagetable macro definitions, the function of converting
   virtual address to a physical address via 4K page table.
   For 2M and 1G pagesize, they will be implemented in the future(currently not supported).
3. Add the implementation of the vtop command, which is used to convert a
   virtual address to a physical address(call the functions defined in 2).
4. Add the implementation to get virtual memory layout, va_bits, phys_ram_base
   from vmcoreinfo. As these configurations changes from time to time, we sent
   a Linux kernel patch to export these configurations, which can simplify the
   development of crash tool.
   The kernel commit: 649d6b1019a2 ("RISC-V: Add arch_crash_save_vmcoreinfo")
5. Add riscv64_get_smp_cpus() implementation, get the number of cpus.
6. Add riscv64_get_page_size() implementation, get page size.
And so on.

With this patch, we can enter crash command line, and run "vtop", "mod", "rd",
"*", "p", "kmem" ...

Tested on QEMU RISCV64 end and SoC platform of T-head Xuantie 910 CPU.

KERNEL: vmlinux
    DUMPFILE: vmcore
        CPUS: 1
        DATE: Fri Jul 15 10:24:25 CST 2022
      UPTIME: 00:00:33
LOAD AVERAGE: 0.05, 0.01, 0.00
       TASKS: 41
    NODENAME: buildroot
     RELEASE: 5.18.9
     VERSION: #30 SMP Fri Jul 15 09:47:03 CST 2022
     MACHINE: riscv64  (unknown Mhz)
      MEMORY: 1 GB
       PANIC: "Kernel panic - not syncing: sysrq triggered crash"
         PID: 113
     COMMAND: "sh"
        TASK: ff60000002269600  [THREAD_INFO: ff60000002269600]
         CPU: 0
       STATE: TASK_RUNNING (PANIC)

crash> p mem_map
mem_map = $1 = (struct page *) 0xff6000003effbf00

crash> p /x *(struct page *) 0xff6000003effbf00
$5 = {
  flags = 0x1000,
  {
    {
      {
        lru = {
          next = 0xff6000003effbf08,
          prev = 0xff6000003effbf08
        },
        {
          __filler = 0xff6000003effbf08,
          mlock_count = 0x3effbf08
        }
      },
      mapping = 0x0,
      index = 0x0,
      private = 0x0
    },

crash> mod
     MODULE       NAME             BASE         SIZE  OBJECT FILE
ffffffff0113e740  nvme_core  ffffffff01133000  98304  (not loaded)  [CONFIG_KALLSYMS]
ffffffff011542c0  nvme       ffffffff0114c000  61440  (not loaded)  [CONFIG_KALLSYMS]

crash> rd ffffffff0113e740 8
ffffffff0113e740:  0000000000000000 ffffffff810874f8   .........t......
ffffffff0113e750:  ffffffff011542c8 726f635f656d766e   .B......nvme_cor
ffffffff0113e760:  0000000000000065 0000000000000000   e...............
ffffffff0113e770:  0000000000000000 0000000000000000   ................

crash> vtop ffffffff0113e740
VIRTUAL           PHYSICAL
ffffffff0113e740  8254d740

PGD: ffffffff810e9ff8 => 2ffff001
  P4D: 0000000000000000 => 000000002fffec01
  PUD: 00005605c2957470 => 0000000020949801
  PMD: 00007fff7f1750c0 => 0000000020947401
  PTE: 0 => 209534e7
 PAGE: 000000008254d000

PAGE       PHYSICAL      MAPPING       INDEX CNT FLAGS
ff6000003f0777d8 8254d000                0        0  1 0

Tested-by: Yixun Lan <yixun.lan@gmail.com>
Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
---
 defs.h     |  97 ++++++
 diskdump.c |  10 +
 riscv64.c  | 994 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1101 insertions(+)

diff --git a/defs.h b/defs.h
index 7702ab0..0cff47e 100644
--- a/defs.h
+++ b/defs.h
@@ -3496,6 +3496,85 @@ struct arm64_stackframe {
 #define _64BIT_
 #define MACHINE_TYPE		"RISCV64"
 
+typedef struct { ulong pgd; } pgd_t;
+typedef struct { ulong p4d; } p4d_t;
+typedef struct { ulong pud; } pud_t;
+typedef struct { ulong pmd; } pmd_t;
+typedef struct { ulong pte; } pte_t;
+typedef signed int s32;
+
+/* arch/riscv/include/asm/pgtable-64.h */
+#define PGD_SHIFT_L3		(30)
+#define PGD_SHIFT_L4		(39)
+#define PGD_SHIFT_L5		(48)
+
+#define P4D_SHIFT		(39)
+#define PUD_SHIFT		(30)
+#define PMD_SHIFT		(21)
+
+#define PTRS_PER_PGD		(512)
+#define PTRS_PER_P4D		(512)
+#define PTRS_PER_PUD		(512)
+#define PTRS_PER_PMD		(512)
+#define PTRS_PER_PTE		(512)
+
+/*
+ * Mask for bit 0~53(PROT and PPN) of PTE
+ * 63 6261  60    54  53 10  9 8 7 6 5 4 3 2 1 0
+ * N  PBMT  Reserved  P P N  RSW D A G U X W R V
+ */
+#define PTE_PFN_PROT_MASK	0x3FFFFFFFFFFFFF
+
+/*
+ * 3-levels / 4K pages
+ *
+ * sv39
+ * PGD  |  PMD  |  PTE  |  OFFSET  |
+ *  9   |   9   |   9   |    12    |
+ */
+#define pgd_index_l3_4k(addr) (((addr) >> PGD_SHIFT_L3) & (PTRS_PER_PGD - 1))
+#define pmd_index_l3_4k(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
+#define pte_index_l3_4k(addr) (((addr) >> PAGESHIFT()) & (PTRS_PER_PTE - 1))
+
+/*
+ * 4-levels / 4K pages
+ *
+ * sv48
+ * PGD  |  PUD  |  PMD  |   PTE   |  OFFSET  |
+ *  9   |   9   |   9   |    9    |    12    |
+ */
+#define pgd_index_l4_4k(addr) (((addr) >> PGD_SHIFT_L4) & (PTRS_PER_PGD - 1))
+#define pud_index_l4_4k(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
+#define pmd_index_l4_4k(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
+#define pte_index_l4_4k(addr) (((addr) >> PAGESHIFT()) & (PTRS_PER_PTE - 1))
+
+/*
+ * 5-levels / 4K pages
+ *
+ * sv57
+ * PGD  |  P4D  |  PUD  |  PMD  |   PTE   |  OFFSET  |
+ *  9   |   9   |   9   |   9   |    9    |    12    |
+ */
+#define pgd_index_l5_4k(addr) (((addr) >> PGD_SHIFT_L5) & (PTRS_PER_PGD - 1))
+#define p4d_index_l5_4k(addr) (((addr) >> P4D_SHIFT) & (PTRS_PER_P4D - 1))
+#define pud_index_l5_4k(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
+#define pmd_index_l5_4k(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
+#define pte_index_l5_4k(addr) (((addr) >> PAGESHIFT()) & (PTRS_PER_PTE - 1))
+
+#define VM_L3_4K	(0x2)
+#define VM_L3_2M	(0x4)
+#define VM_L3_1G	(0x8)
+#define VM_L4_4K	(0x10)
+#define VM_L4_2M	(0x20)
+#define VM_L4_1G	(0x40)
+#define VM_L5_4K	(0x80)
+#define VM_L5_2M	(0x100)
+#define VM_L5_1G	(0x200)
+
+#define VM_FLAGS	(VM_L3_4K | VM_L3_2M | VM_L3_1G | \
+			 VM_L4_4K | VM_L4_2M | VM_L4_1G | \
+			 VM_L5_4K | VM_L5_2M | VM_L5_1G)
+
 /*
  * Direct memory mapping
  */
@@ -3547,6 +3626,14 @@ struct arm64_stackframe {
 #define PHYS_MASK_SHIFT 	_MAX_PHYSMEM_BITS
 #define PHYS_MASK		(((1UL) << PHYS_MASK_SHIFT) - 1)
 
+#define IS_LAST_P4D_READ(p4d)	((ulong)(p4d) == machdep->machspec->last_p4d_read)
+#define FILL_P4D(P4D, TYPE, SIZE)					      \
+    if (!IS_LAST_P4D_READ(P4D)) {					      \
+	    readmem((ulonglong)((ulong)(P4D)), TYPE, machdep->machspec->p4d,  \
+		     SIZE, "p4d page", FAULT_ON_ERROR);                       \
+	    machdep->machspec->last_p4d_read = (ulong)(P4D);                  \
+    }
+
 #endif  /* RISCV64 */
 
 #ifdef X86
@@ -6834,6 +6921,10 @@ struct machine_specific {
 	ulong _page_soft;
 
 	ulong _pfn_shift;
+	ulong va_bits;
+	char *p4d;
+	ulong last_p4d_read;
+	ulong struct_page_size;
 
 	struct riscv64_register *crash_task_regs;
 };
@@ -6857,6 +6948,12 @@ struct machine_specific {
 #define _PAGE_PROT_NONE _PAGE_READ
 #define _PAGE_PFN_SHIFT 10
 
+/* from 'struct pt_regs' definitions of RISC-V arch */
+#define RISCV64_REGS_EPC  0
+#define RISCV64_REGS_RA   1
+#define RISCV64_REGS_SP   2
+#define RISCV64_REGS_FP   8
+
 #endif /* RISCV64 */
 
 /*
diff --git a/diskdump.c b/diskdump.c
index 28503bc..cf5f5d9 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -1531,6 +1531,12 @@ get_diskdump_regs_mips(struct bt_info *bt, ulong *eip, ulong *esp)
 	machdep->get_stack_frame(bt, eip, esp);
 }
 
+static void
+get_diskdump_regs_riscv64(struct bt_info *bt, ulong *eip, ulong *esp)
+{
+	machdep->get_stack_frame(bt, eip, esp);
+}
+
 static void
 get_diskdump_regs_sparc64(struct bt_info *bt, ulong *eip, ulong *esp)
 {
@@ -1610,6 +1616,10 @@ get_diskdump_regs(struct bt_info *bt, ulong *eip, ulong *esp)
 		get_diskdump_regs_sparc64(bt, eip, esp);
 		break;
 
+	case EM_RISCV:
+		get_diskdump_regs_riscv64(bt, eip, esp);
+		break;
+
 	default:
 		error(FATAL, "%s: unsupported machine type: %s\n",
 			DISKDUMP_VALID() ? "diskdump" : "compressed kdump",
diff --git a/riscv64.c b/riscv64.c
index 4f858a4..d8de3d5 100644
--- a/riscv64.c
+++ b/riscv64.c
@@ -16,10 +16,314 @@
 #ifdef RISCV64
 
 #include <elf.h>
+#include <math.h>
+
+static ulong riscv64_get_page_size(void);
+static int riscv64_vtop_3level_4k(ulong *pgd, ulong vaddr,
+				   physaddr_t *paddr, int verbose);
+static int riscv64_vtop_4level_4k(ulong *pgd, ulong vaddr,
+				   physaddr_t *paddr, int verbose);
+static int riscv64_vtop_5level_4k(ulong *pgd, ulong vaddr,
+				   physaddr_t *paddr, int verbose);
+static void riscv64_page_type_init(void);
+static int riscv64_is_kvaddr(ulong vaddr);
+static int riscv64_is_uvaddr(ulong vaddr, struct task_context *tc);
+static int riscv64_uvtop(struct task_context *tc, ulong vaddr,
+			  physaddr_t *paddr, int verbose);
+static int riscv64_kvtop(struct task_context *tc, ulong kvaddr,
+			  physaddr_t *paddr, int verbose);
+static void riscv64_cmd_mach(void);
+static int riscv64_translate_pte(ulong, void *, ulonglong);
+static int riscv64_init_active_task_regs(void);
+static int riscv64_get_crash_notes(void);
+static int riscv64_get_elf_notes(void);
+static void riscv64_get_va_range(struct machine_specific *ms);
+static void riscv64_get_va_bits(struct machine_specific *ms);
+static void riscv64_get_struct_page_size(struct machine_specific *ms);
+
+#define REG_FMT 	"%016lx"
+#define SZ_2G		0x80000000
+
+/*
+ * Holds registers during the crash.
+ */
+static struct riscv64_register *panic_task_regs;
+
+/* from arch/riscv/include/asm/stacktrace.h */
+struct stackframe {
+	ulong fp;
+	ulong ra;
+};
+
+static struct machine_specific riscv64_machine_specific = {
+	._page_present = (1 << 0),
+	._page_read = (1 << 1),
+	._page_write = (1 << 2),
+	._page_exec = (1 << 3),
+	._page_user = (1 << 4),
+	._page_global = (1 << 5),
+	._page_accessed = (1 << 6),
+	._page_dirty = (1 << 7),
+	._page_soft = (1 << 8),
+
+	.va_bits = 0,
+	.struct_page_size = 0,
+};
+
+static void
+pt_level_alloc(char **lvl, char *name)
+{
+	size_t sz = PAGESIZE();
+	void *pointer = malloc(sz);
+
+	if (!pointer)
+		error(FATAL, name);
+	*lvl = pointer;
+}
+
+static ulong
+riscv64_get_page_size(void)
+{
+	return memory_page_size();
+}
+
+static ulong
+riscv64_vmalloc_start(void)
+{
+	return ((ulong)VMALLOC_START);
+}
+
+/* Get the size of struct page {} */
+static void riscv64_get_struct_page_size(struct machine_specific *ms)
+{
+	char *string;
+
+	string = pc->read_vmcoreinfo("SIZE(page)");
+	if (string) {
+		ms->struct_page_size = atol(string);
+		free(string);
+	}
+}
+
+static void
+riscv64_cmd_mach(void)
+{
+	/* TODO: */
+}
+
+static int
+riscv64_verify_symbol(const char *name, ulong value, char type)
+{
+	/* TODO: */
+	return TRUE;
+}
 
 void
 riscv64_dump_machdep_table(ulong arg)
 {
+	/* TODO: */
+}
+
+static ulong
+riscv64_processor_speed(void)
+{
+	/* TODO: */
+	return 0;
+}
+
+static unsigned long riscv64_get_kernel_version(void)
+{
+	char *string;
+	char buf[BUFSIZE];
+	char *p1, *p2;
+
+	if (THIS_KERNEL_VERSION)
+		return THIS_KERNEL_VERSION;
+
+	string = pc->read_vmcoreinfo("OSRELEASE");
+	if (string) {
+		strcpy(buf, string);
+
+		p1 = p2 = buf;
+		while (*p2 != '.')
+			p2++;
+		*p2 = NULLCHAR;
+		kt->kernel_version[0] = atoi(p1);
+
+		p1 = ++p2;
+		while (*p2 != '.')
+			p2++;
+		*p2 = NULLCHAR;
+		kt->kernel_version[1] = atoi(p1);
+
+		p1 = ++p2;
+		while ((*p2 >= '0') && (*p2 <= '9'))
+			p2++;
+		*p2 = NULLCHAR;
+		kt->kernel_version[2] = atoi(p1);
+		free(string);
+	}
+	return THIS_KERNEL_VERSION;
+}
+
+static void
+riscv64_get_phys_ram_base(struct machine_specific *ms)
+{
+	unsigned long kernel_version = riscv64_get_kernel_version();
+
+	/*
+	 * phys_ram_base is defined in Linux kernel since 5.14.
+	 */
+	if (kernel_version >= LINUX(5,14,0)) {
+		char *string;
+		if ((string = pc->read_vmcoreinfo("NUMBER(phys_ram_base)"))) {
+			ms->phys_base = atol(string);
+			free(string);
+		} else
+			error(FATAL, "cannot read phys_ram_base\n");
+	} else
+		/*
+		 * For qemu rv64 env and hardware platform, default phys base
+		 * may different, eg,
+		 *	hardware platform: 0x200000
+		 *	qemu   rv64   env: 0x80200000
+		 *
+		 * But we only can set one default value, in this case, qemu
+		 * rv64 env may can't work.
+		 */
+		ms->phys_base = 0x200000;
+}
+
+static void riscv64_get_va_bits(struct machine_specific *ms)
+{
+	unsigned long kernel_version = riscv64_get_kernel_version();
+
+	/*
+	 * VA_BITS is defined in Linux kernel since 5.17. So we use the
+	 * default va bits 39 when Linux version < 5.17.
+	 */
+	if (kernel_version >= LINUX(5,17,0)) {
+		char *string;
+		if ((string = pc->read_vmcoreinfo("NUMBER(VA_BITS)"))) {
+			ms->va_bits = atol(string);
+			free(string);
+		}
+	} else
+		ms->va_bits = 39;
+}
+
+static void riscv64_get_va_range(struct machine_specific *ms)
+{
+	unsigned long kernel_version = riscv64_get_kernel_version();
+	char *string;
+
+	if ((string = pc->read_vmcoreinfo("NUMBER(PAGE_OFFSET)"))) {
+		ms->page_offset = htol(string, QUIET, NULL);
+		free(string);
+	} else
+		goto error;
+
+	if ((string = pc->read_vmcoreinfo("NUMBER(VMALLOC_START)"))) {
+		ms->vmalloc_start_addr = htol(string, QUIET, NULL);
+		free(string);
+	} else
+		goto error;
+
+	if ((string = pc->read_vmcoreinfo("NUMBER(VMALLOC_END)"))) {
+		ms->vmalloc_end = htol(string, QUIET, NULL);
+                free(string);
+	} else
+		goto error;
+
+	if ((string = pc->read_vmcoreinfo("NUMBER(VMEMMAP_START)"))) {
+		ms->vmemmap_vaddr = htol(string, QUIET, NULL);
+		free(string);
+	} else
+		goto error;
+
+	if ((string = pc->read_vmcoreinfo("NUMBER(VMEMMAP_END)"))) {
+		ms->vmemmap_end = htol(string, QUIET, NULL);
+		free(string);
+	} else
+		goto error;
+
+	if ((string = pc->read_vmcoreinfo("NUMBER(KERNEL_LINK_ADDR)"))) {
+		ms->kernel_link_addr = htol(string, QUIET, NULL);
+		free(string);
+	} else
+		goto error;
+
+	/*
+	 * From Linux 5.13, the kernel mapping is moved to the last 2GB
+	 * of the address space, modules use the 2GB memory range right
+	 * before the kernel. Before Linux 5.13, modules area is embedded
+	 * in vmalloc area.
+	 *
+	 */
+	if (kernel_version >= LINUX(5,13,0)) {
+		if ((string = pc->read_vmcoreinfo("NUMBER(MODULES_VADDR)"))) {
+			ms->modules_vaddr = htol(string, QUIET, NULL);
+			free(string);
+		} else
+			goto error;
+
+		if ((string = pc->read_vmcoreinfo("NUMBER(MODULES_END)"))) {
+			ms->modules_end = htol(string, QUIET, NULL);
+			free(string);
+		} else
+			goto error;
+	} else {
+		ms->modules_vaddr = ms->vmalloc_start_addr;
+		ms->modules_end = ms->vmalloc_end;
+	}
+
+	if (CRASHDEBUG(1)) {
+		fprintf(fp, "vmemmap	: 0x%lx - 0x%lx\n",
+			ms->vmemmap_vaddr, ms->vmemmap_end);
+		fprintf(fp, "vmalloc	: 0x%lx - 0x%lx\n",
+			ms->vmalloc_start_addr, ms->vmalloc_end);
+		fprintf(fp, "mudules	: 0x%lx - 0x%lx\n",
+			ms->modules_vaddr, ms->modules_end);
+		fprintf(fp, "lowmem	: 0x%lx -\n", ms->page_offset);
+		fprintf(fp, "kernel link addr	: 0x%lx\n",
+			ms->kernel_link_addr);
+	}
+	return;
+error:
+	error(FATAL, "cannot get vm layout\n");
+}
+
+static int
+riscv64_is_kvaddr(ulong vaddr)
+{
+	if (IS_VMALLOC_ADDR(vaddr))
+		return TRUE;
+
+	return (vaddr >= machdep->kvbase);
+}
+
+static int
+riscv64_is_uvaddr(ulong vaddr, struct task_context *unused)
+{
+	if (IS_VMALLOC_ADDR(vaddr))
+		return FALSE;
+
+	return (vaddr < machdep->kvbase);
+}
+
+static int
+riscv64_is_task_addr(ulong task)
+{
+	if (tt->flags & THREAD_INFO)
+		return IS_KVADDR(task);
+
+	return (IS_KVADDR(task) && ALIGNED_STACK_OFFSET(task) == 0);
+}
+
+static int
+riscv64_get_smp_cpus(void)
+{
+	return (get_cpus_present() > 0) ? get_cpus_present() : kt->cpus;
 }
 
 /*
@@ -33,11 +337,701 @@ riscv64_IS_VMALLOC_ADDR(ulong vaddr)
 		(vaddr >= MODULES_VADDR && vaddr <= MODULES_END));
 }
 
+/*
+ * Translate a PTE, returning TRUE if the page is present.
+ * If a physaddr pointer is passed in, don't print anything.
+ */
+static int
+riscv64_translate_pte(ulong pte, void *physaddr, ulonglong unused)
+{
+	char ptebuf[BUFSIZE];
+	char physbuf[BUFSIZE];
+	char buf[BUFSIZE];
+	int page_present;
+	int len1, len2, others;
+	ulong paddr;
+
+	paddr = PTOB(pte >> _PAGE_PFN_SHIFT);
+	page_present = !!(pte & _PAGE_PRESENT);
+
+	if (physaddr) {
+		*(ulong *)physaddr = paddr;
+		return page_present;
+	}
+
+	sprintf(ptebuf, "%lx", pte);
+	len1 = MAX(strlen(ptebuf), strlen("PTE"));
+	fprintf(fp, "%s  ", mkstring(buf, len1, CENTER | LJUST, "PTE"));
+
+	if (!page_present)
+		return page_present;
+
+	sprintf(physbuf, "%lx", paddr);
+	len2 = MAX(strlen(physbuf), strlen("PHYSICAL"));
+	fprintf(fp, "%s  ", mkstring(buf, len2, CENTER | LJUST, "PHYSICAL"));
+
+	fprintf(fp, "FLAGS\n");
+	fprintf(fp, "%s  %s  ",
+		mkstring(ptebuf, len1, CENTER | RJUST, NULL),
+		mkstring(physbuf, len2, CENTER | RJUST, NULL));
+
+	fprintf(fp, "(");
+	others = 0;
+
+#define CHECK_PAGE_FLAG(flag)				\
+	if ((_PAGE_##flag) && (pte & _PAGE_##flag))	\
+		fprintf(fp, "%s" #flag, others++ ? "|" : "")
+	if (pte) {
+		CHECK_PAGE_FLAG(PRESENT);
+		CHECK_PAGE_FLAG(READ);
+		CHECK_PAGE_FLAG(WRITE);
+		CHECK_PAGE_FLAG(EXEC);
+		CHECK_PAGE_FLAG(USER);
+		CHECK_PAGE_FLAG(GLOBAL);
+		CHECK_PAGE_FLAG(ACCESSED);
+		CHECK_PAGE_FLAG(DIRTY);
+		CHECK_PAGE_FLAG(SOFT);
+	} else {
+		fprintf(fp, "no mapping");
+	}
+
+	fprintf(fp, ")\n");
+
+	return page_present;
+}
+
+static void
+riscv64_page_type_init(void)
+{
+	ulong va_bits = machdep->machspec->va_bits;
+
+	/*
+	 * For RISCV64 arch, any level of PTE may be a leaf PTE,
+	 * so in addition to 4KiB pages,
+	 * Sv39 supports 2 MiB megapages, 1 GiB gigapages;
+	 * Sv48 supports 2 MiB megapages, 1 GiB gigapages, 512 GiB terapages;
+	 * Sv57 supports 2 MiB megapages, 1 GiB gigapages, 512 GiB terapages, and 256 TiB petapages.
+	 *
+	 * refs to riscv-privileged spec.
+	 *
+	 * We just support 4KiB, 2MiB, 1GiB now.
+	 */
+	switch (machdep->pagesize)
+	{
+	case 0x1000:		// 4 KiB
+		machdep->flags |= (va_bits == 57 ? VM_L5_4K :
+				  (va_bits == 48 ? VM_L4_4K : VM_L3_4K));
+		break;
+	case 0x200000:		// 2 MiB
+		/* TODO: */
+	case 0x40000000: 	// 1 GiB
+		/* TODO: */
+	default:
+		if (machdep->pagesize)
+			error(FATAL, "invalid/unsupported page size: %d\n",
+			      machdep->pagesize);
+		else
+			error(FATAL, "cannot determine page size\n");
+	}
+}
+
+static int
+riscv64_vtop_3level_4k(ulong *pgd, ulong vaddr, physaddr_t *paddr, int verbose)
+{
+	ulong *pgd_ptr, pgd_val;
+	ulong pmd_val;
+	ulong pte_val, pte_pfn;
+	ulong pt_phys;
+
+	/* PGD */
+	pgd_ptr = pgd + pgd_index_l3_4k(vaddr);
+	FILL_PGD(pgd, KVADDR, PAGESIZE());
+	pgd_val = ULONG(machdep->pgd + PAGEOFFSET(pgd_ptr));
+	if (verbose)
+		fprintf(fp, "  PGD: %lx => %lx\n", (ulong)pgd_ptr, pgd_val);
+	if (!pgd_val)
+		goto no_page;
+	pgd_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pgd_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PMD */
+	FILL_PMD(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pmd_val = ULONG(machdep->pmd + PAGEOFFSET(sizeof(pmd_t) *
+			pmd_index_l3_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PMD: %016lx => %016lx\n", pt_phys, pmd_val);
+	if (!pmd_val)
+		goto no_page;
+	pmd_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pmd_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PTE */
+	FILL_PTBL(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pte_val = ULONG(machdep->ptbl + PAGEOFFSET(sizeof(pte_t) *
+			pte_index_l3_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PTE: %lx => %lx\n", pt_phys, pte_val);
+	if (!pte_val)
+		goto no_page;
+	pte_val &= PTE_PFN_PROT_MASK;
+	pte_pfn = pte_val >> _PAGE_PFN_SHIFT;
+
+	if (!(pte_val & _PAGE_PRESENT)) {
+		if (verbose) {
+			fprintf(fp, "\n");
+			riscv64_translate_pte((ulong)pte_val, 0, 0);
+		}
+		fprintf(fp, " PAGE: %016lx not present\n\n", PAGEBASE(*paddr));
+		return FALSE;
+	}
+
+	*paddr = PTOB(pte_pfn) + PAGEOFFSET(vaddr);
+
+	if (verbose) {
+		fprintf(fp, " PAGE: %016lx\n\n", PAGEBASE(*paddr));
+		riscv64_translate_pte(pte_val, 0, 0);
+	}
+
+	return TRUE;
+no_page:
+	fprintf(fp, "invalid\n");
+	return FALSE;
+}
+
+static int
+riscv64_vtop_4level_4k(ulong *pgd, ulong vaddr, physaddr_t *paddr, int verbose)
+{
+	ulong *pgd_ptr, pgd_val;
+	ulong pud_val;
+	ulong pmd_val;
+	ulong pte_val, pte_pfn;
+	ulong pt_phys;
+
+	/* PGD */
+	pgd_ptr = pgd + pgd_index_l4_4k(vaddr);
+	FILL_PGD(pgd, KVADDR, PAGESIZE());
+	pgd_val = ULONG(machdep->pgd + PAGEOFFSET(pgd_ptr));
+	if (verbose)
+		fprintf(fp, "  PGD: %lx => %lx\n", (ulong)pgd_ptr, pgd_val);
+	if (!pgd_val)
+		goto no_page;
+	pgd_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pgd_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PUD */
+	FILL_PUD(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pud_val = ULONG(machdep->pud + PAGEOFFSET(sizeof(pud_t) *
+			pud_index_l4_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PUD: %016lx => %016lx\n", pt_phys, pud_val);
+	if (!pud_val)
+		goto no_page;
+	pud_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pud_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PMD */
+	FILL_PMD(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pmd_val = ULONG(machdep->pmd + PAGEOFFSET(sizeof(pmd_t) *
+			pmd_index_l4_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PMD: %016lx => %016lx\n", pt_phys, pmd_val);
+	if (!pmd_val)
+		goto no_page;
+	pmd_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pmd_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PTE */
+	FILL_PTBL(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pte_val = ULONG(machdep->ptbl + PAGEOFFSET(sizeof(pte_t) *
+			pte_index_l4_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PTE: %lx => %lx\n", pt_phys, pte_val);
+	if (!pte_val)
+		goto no_page;
+	pte_val &= PTE_PFN_PROT_MASK;
+	pte_pfn = pte_val >> _PAGE_PFN_SHIFT;
+
+	if (!(pte_val & _PAGE_PRESENT)) {
+		if (verbose) {
+			fprintf(fp, "\n");
+			riscv64_translate_pte((ulong)pte_val, 0, 0);
+		}
+		fprintf(fp, " PAGE: %016lx not present\n\n", PAGEBASE(*paddr));
+		return FALSE;
+	}
+
+	*paddr = PTOB(pte_pfn) + PAGEOFFSET(vaddr);
+
+	if (verbose) {
+		fprintf(fp, " PAGE: %016lx\n\n", PAGEBASE(*paddr));
+		riscv64_translate_pte(pte_val, 0, 0);
+	}
+
+	return TRUE;
+no_page:
+	fprintf(fp, "invalid\n");
+	return FALSE;
+}
+
+static int
+riscv64_vtop_5level_4k(ulong *pgd, ulong vaddr, physaddr_t *paddr, int verbose)
+{
+	ulong *pgd_ptr, pgd_val;
+	ulong p4d_val;
+	ulong pud_val;
+	ulong pmd_val;
+	ulong pte_val, pte_pfn;
+	ulong pt_phys;
+
+	/* PGD */
+	pgd_ptr = pgd + pgd_index_l5_4k(vaddr);
+	FILL_PGD(pgd, KVADDR, PAGESIZE());
+	pgd_val = ULONG(machdep->pgd + PAGEOFFSET(pgd_ptr));
+	if (verbose)
+		fprintf(fp, "  PGD: %lx => %lx\n", (ulong)pgd_ptr, pgd_val);
+	if (!pgd_val)
+		goto no_page;
+	pgd_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pgd_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* P4D */
+	FILL_P4D(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	p4d_val = ULONG(machdep->machspec->p4d + PAGEOFFSET(sizeof(p4d_t) *
+			p4d_index_l5_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  P4D: %016lx => %016lx\n", pt_phys, p4d_val);
+	if (!p4d_val)
+		goto no_page;
+	p4d_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (p4d_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PUD */
+	FILL_PUD(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pud_val = ULONG(machdep->pud + PAGEOFFSET(sizeof(pud_t) *
+			pud_index_l5_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PUD: %016lx => %016lx\n", pt_phys, pud_val);
+	if (!pud_val)
+		goto no_page;
+	pud_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pud_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PMD */
+	FILL_PMD(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pmd_val = ULONG(machdep->pmd + PAGEOFFSET(sizeof(pmd_t) *
+			pmd_index_l4_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PMD: %016lx => %016lx\n", pt_phys, pmd_val);
+	if (!pmd_val)
+		goto no_page;
+	pmd_val &= PTE_PFN_PROT_MASK;
+	pt_phys = (pmd_val >> _PAGE_PFN_SHIFT) << PAGESHIFT();
+
+	/* PTE */
+	FILL_PTBL(PAGEBASE(pt_phys), PHYSADDR, PAGESIZE());
+	pte_val = ULONG(machdep->ptbl + PAGEOFFSET(sizeof(pte_t) *
+			pte_index_l4_4k(vaddr)));
+	if (verbose)
+		fprintf(fp, "  PTE: %lx => %lx\n", pt_phys, pte_val);
+	if (!pte_val)
+		goto no_page;
+	pte_val &= PTE_PFN_PROT_MASK;
+	pte_pfn = pte_val >> _PAGE_PFN_SHIFT;
+
+	if (!(pte_val & _PAGE_PRESENT)) {
+		if (verbose) {
+			fprintf(fp, "\n");
+			riscv64_translate_pte((ulong)pte_val, 0, 0);
+		}
+		printf("!_PAGE_PRESENT\n");
+		return FALSE;
+	}
+
+	*paddr = PTOB(pte_pfn) + PAGEOFFSET(vaddr);
+
+	if (verbose) {
+		fprintf(fp, " PAGE: %016lx\n\n", PAGEBASE(*paddr));
+		riscv64_translate_pte(pte_val, 0, 0);
+	}
+
+	return TRUE;
+no_page:
+	fprintf(fp, "invalid\n");
+	return FALSE;
+}
+
+static int
+riscv64_init_active_task_regs(void)
+{
+	int retval;
+
+	retval = riscv64_get_crash_notes();
+	if (retval == TRUE)
+		return retval;
+
+	return riscv64_get_elf_notes();
+}
+
+/*
+ * Retrieve task registers for the time of the crash.
+ */
+static int
+riscv64_get_crash_notes(void)
+{
+	struct machine_specific *ms = machdep->machspec;
+	ulong crash_notes;
+	Elf64_Nhdr *note;
+	ulong offset;
+	char *buf, *p;
+	ulong *notes_ptrs;
+	ulong i;
+
+	/*
+	 * crash_notes contains per cpu memory for storing cpu states
+	 * in case of system crash.
+	 */
+	if (!symbol_exists("crash_notes"))
+		return FALSE;
+
+	crash_notes = symbol_value("crash_notes");
+
+	notes_ptrs = (ulong *)GETBUF(kt->cpus*sizeof(notes_ptrs[0]));
+
+	/*
+	 * Read crash_notes for the first CPU. crash_notes are in standard ELF
+	 * note format.
+	 */
+	if (!readmem(crash_notes, KVADDR, &notes_ptrs[kt->cpus-1],
+	    sizeof(notes_ptrs[kt->cpus-1]), "crash_notes",
+		     RETURN_ON_ERROR)) {
+		error(WARNING, "cannot read crash_notes\n");
+		FREEBUF(notes_ptrs);
+		return FALSE;
+	}
+
+	if (symbol_exists("__per_cpu_offset")) {
+
+		/*
+		 * Add __per_cpu_offset for each cpu to form the pointer to the notes
+		 */
+		for (i = 0; i < kt->cpus; i++)
+			notes_ptrs[i] = notes_ptrs[kt->cpus-1] + kt->__per_cpu_offset[i];
+	}
+
+	buf = GETBUF(SIZE(note_buf));
+
+	if (!(panic_task_regs = calloc((size_t)kt->cpus, sizeof(*panic_task_regs))))
+		error(FATAL, "cannot calloc panic_task_regs space\n");
+
+	for (i = 0; i < kt->cpus; i++) {
+
+		if (!readmem(notes_ptrs[i], KVADDR, buf, SIZE(note_buf), "note_buf_t",
+			     RETURN_ON_ERROR)) {
+			error(WARNING,
+				"cannot find NT_PRSTATUS note for cpu: %d\n", i);
+			goto fail;
+		}
+
+		/*
+		 * Do some sanity checks for this note before reading registers from it.
+		 */
+		note = (Elf64_Nhdr *)buf;
+		p = buf + sizeof(Elf64_Nhdr);
+
+		/*
+		 * dumpfiles created with qemu won't have crash_notes, but there will
+		 * be elf notes; dumpfiles created by kdump do not create notes for
+		 * offline cpus.
+		 */
+		if (note->n_namesz == 0 && (DISKDUMP_DUMPFILE() || KDUMP_DUMPFILE())) {
+			if (DISKDUMP_DUMPFILE())
+				note = diskdump_get_prstatus_percpu(i);
+			else if (KDUMP_DUMPFILE())
+				note = netdump_get_prstatus_percpu(i);
+			if (note) {
+				/*
+				 * SIZE(note_buf) accounts for a "final note", which is a
+				 * trailing empty elf note header.
+				 */
+				long notesz = SIZE(note_buf) - sizeof(Elf64_Nhdr);
+
+				if (sizeof(Elf64_Nhdr) + roundup(note->n_namesz, 4) +
+				    note->n_descsz == notesz)
+					BCOPY((char *)note, buf, notesz);
+			} else {
+				error(WARNING,
+					"cannot find NT_PRSTATUS note for cpu: %d\n", i);
+				continue;
+			}
+		}
+
+		/*
+		 * Check the sanity of NT_PRSTATUS note only for each online cpu.
+		 */
+		if (note->n_type != NT_PRSTATUS) {
+			error(WARNING, "invalid NT_PRSTATUS note (n_type != NT_PRSTATUS)\n");
+			goto fail;
+		}
+		if (!STRNEQ(p, "CORE")) {
+			error(WARNING, "invalid NT_PRSTATUS note (name != \"CORE\"\n");
+			goto fail;
+		}
+
+		/*
+		 * Find correct location of note data. This contains elf_prstatus
+		 * structure which has registers etc. for the crashed task.
+		 */
+		offset = sizeof(Elf64_Nhdr);
+		offset = roundup(offset + note->n_namesz, 4);
+		p = buf + offset; /* start of elf_prstatus */
+
+		BCOPY(p + OFFSET(elf_prstatus_pr_reg), &panic_task_regs[i],
+		      sizeof(panic_task_regs[i]));
+	}
+
+	/*
+	 * And finally we have the registers for the crashed task. This is
+	 * used later on when dumping backtrace.
+	 */
+	ms->crash_task_regs = panic_task_regs;
+
+	FREEBUF(buf);
+	FREEBUF(notes_ptrs);
+	return TRUE;
+
+fail:
+	FREEBUF(buf);
+	FREEBUF(notes_ptrs);
+	free(panic_task_regs);
+	return FALSE;
+}
+
+static int
+riscv64_get_elf_notes(void)
+{
+	struct machine_specific *ms = machdep->machspec;
+	int i;
+
+	if (!DISKDUMP_DUMPFILE() && !KDUMP_DUMPFILE())
+		return FALSE;
+
+	panic_task_regs = calloc(kt->cpus, sizeof(*panic_task_regs));
+	if (!panic_task_regs)
+		error(FATAL, "cannot calloc panic_task_regs space\n");
+
+	for (i = 0; i < kt->cpus; i++) {
+		Elf64_Nhdr *note = NULL;
+		size_t len;
+
+		if (DISKDUMP_DUMPFILE())
+			note = diskdump_get_prstatus_percpu(i);
+		else if (KDUMP_DUMPFILE())
+			note = netdump_get_prstatus_percpu(i);
+
+		if (!note) {
+			error(WARNING,
+				"cannot find NT_PRSTATUS note for cpu: %d\n", i);
+			continue;
+		}
+
+		len = sizeof(Elf64_Nhdr);
+		len = roundup(len + note->n_namesz, 4);
+
+		BCOPY((char *)note + len + OFFSET(elf_prstatus_pr_reg),
+		      &panic_task_regs[i], sizeof(panic_task_regs[i]));
+	}
+
+	ms->crash_task_regs = panic_task_regs;
+
+	return TRUE;
+}
+
+/*
+ * Translates a user virtual address to its physical address.
+ */
+static int
+riscv64_uvtop(struct task_context *tc, ulong uvaddr, physaddr_t *paddr, int verbose)
+{
+	ulong mm, active_mm;
+	ulong *pgd;
+
+	if (!tc)
+		error(FATAL, "current context invalid\n");
+
+	*paddr = 0;
+
+	if (is_kernel_thread(tc->task) && IS_KVADDR(uvaddr)) {
+		readmem(tc->task + OFFSET(task_struct_active_mm),
+			KVADDR, &active_mm, sizeof(void *),
+			"task active_mm contents", FAULT_ON_ERROR);
+
+		if (!active_mm)
+			error(FATAL,
+			      "no active_mm for this kernel thread\n");
+
+		readmem(active_mm + OFFSET(mm_struct_pgd),
+			KVADDR, &pgd, sizeof(long),
+			"mm_struct pgd", FAULT_ON_ERROR);
+	} else {
+		if ((mm = task_mm(tc->task, TRUE)))
+			pgd = ULONG_PTR(tt->mm_struct + OFFSET(mm_struct_pgd));
+		else
+			readmem(tc->mm_struct + OFFSET(mm_struct_pgd),
+				KVADDR, &pgd, sizeof(long), "mm_struct pgd",
+				FAULT_ON_ERROR);
+	}
+
+	switch (machdep->flags & VM_FLAGS)
+	{
+	case VM_L3_4K:
+		return riscv64_vtop_3level_4k(pgd, uvaddr, paddr, verbose);
+	case VM_L4_4K:
+		return riscv64_vtop_4level_4k(pgd, uvaddr, paddr, verbose);
+	case VM_L5_4K:
+		return riscv64_vtop_5level_4k(pgd, uvaddr, paddr, verbose);
+	default:
+		return FALSE;
+	}
+}
+
+static int
+riscv64_kvtop(struct task_context *tc, ulong kvaddr, physaddr_t *paddr, int verbose)
+{
+	ulong kernel_pgd;
+
+	if (!IS_KVADDR(kvaddr))
+		return FALSE;
+
+	if (!vt->vmalloc_start) {
+		*paddr = VTOP(kvaddr);
+		return TRUE;
+	}
+
+	if (!IS_VMALLOC_ADDR(kvaddr)) {
+		*paddr = VTOP(kvaddr);
+		if (!verbose)
+			return TRUE;
+	}
+
+	kernel_pgd = vt->kernel_pgd[0];
+	*paddr = 0;
+
+	switch (machdep->flags & VM_FLAGS)
+	{
+	case VM_L3_4K:
+		return riscv64_vtop_3level_4k((ulong *)kernel_pgd, kvaddr, paddr, verbose);
+	case VM_L4_4K:
+		return riscv64_vtop_4level_4k((ulong *)kernel_pgd, kvaddr, paddr, verbose);
+	case VM_L5_4K:
+		return riscv64_vtop_5level_4k((ulong *)kernel_pgd, kvaddr, paddr, verbose);
+	default:
+		return FALSE;
+	}
+}
+
 void
 riscv64_init(int when)
 {
+	switch (when) {
+	case SETUP_ENV:
+		machdep->process_elf_notes = process_elf64_notes;
+		break;
+
+	case PRE_SYMTAB:
+		machdep->verify_symbol = riscv64_verify_symbol;
+		machdep->machspec = &riscv64_machine_specific;
+		if (pc->flags & KERNEL_DEBUG_QUERY)
+			return;
+
+		machdep->verify_paddr = generic_verify_paddr;
+		machdep->ptrs_per_pgd = PTRS_PER_PGD;
+		break;
+
+	case PRE_GDB:
+		machdep->pagesize = riscv64_get_page_size();
+		machdep->pageshift = ffs(machdep->pagesize) - 1;
+		machdep->pageoffset = machdep->pagesize - 1;
+		machdep->pagemask = ~((ulonglong)machdep->pageoffset);
+		machdep->stacksize = machdep->pagesize << THREAD_SIZE_ORDER;
+
+		riscv64_get_phys_ram_base(machdep->machspec);
+		riscv64_get_struct_page_size(machdep->machspec);
+		riscv64_get_va_bits(machdep->machspec);
+		riscv64_get_va_range(machdep->machspec);
+
+		pt_level_alloc(&machdep->pgd, "cannot malloc pgd space.");
+		pt_level_alloc(&machdep->machspec->p4d, "cannot malloc p4d space.");
+		pt_level_alloc(&machdep->pud, "cannot malloc pud space.");
+		pt_level_alloc(&machdep->pmd, "cannot malloc pmd space.");
+		pt_level_alloc(&machdep->ptbl, "cannot malloc ptbl space.");
+
+		machdep->last_pgd_read = 0;
+		machdep->machspec->last_p4d_read = 0;
+		machdep->last_pud_read = 0;
+		machdep->last_pmd_read = 0;
+		machdep->last_ptbl_read = 0;
+
+		machdep->kvbase = machdep->machspec->page_offset;
+		machdep->identity_map_base = machdep->kvbase;
+		machdep->is_kvaddr = riscv64_is_kvaddr;
+		machdep->is_uvaddr = riscv64_is_uvaddr;
+		machdep->uvtop = riscv64_uvtop;
+		machdep->kvtop = riscv64_kvtop;
+		machdep->cmd_mach = riscv64_cmd_mach;
+
+		machdep->vmalloc_start = riscv64_vmalloc_start;
+		machdep->processor_speed = riscv64_processor_speed;
+		machdep->get_stackbase = generic_get_stackbase;
+		machdep->get_stacktop = generic_get_stacktop;
+		machdep->translate_pte = riscv64_translate_pte;
+		machdep->memory_size = generic_memory_size;
+		machdep->is_task_addr = riscv64_is_task_addr;
+		machdep->get_smp_cpus = riscv64_get_smp_cpus;
+		machdep->value_to_symbol = generic_machdep_value_to_symbol;
+		machdep->show_interrupts = generic_show_interrupts;
+		machdep->get_irq_affinity = generic_get_irq_affinity;
+		machdep->init_kernel_pgd = NULL; /* pgd set by symbol_value("swapper_pg_dir") */
+		break;
+
+	case POST_GDB:
+		machdep->section_size_bits = _SECTION_SIZE_BITS;
+		machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
+		riscv64_page_type_init();
+
+		if (!machdep->hz)
+			machdep->hz = 250;
+
+		if (symbol_exists("irq_desc"))
+			ARRAY_LENGTH_INIT(machdep->nr_irqs, irq_desc,
+					  "irq_desc", NULL, 0);
+		else if (kernel_symbol_exists("nr_irqs"))
+			get_symbol_data("nr_irqs", sizeof(unsigned int),
+					&machdep->nr_irqs);
+
+		MEMBER_OFFSET_INIT(elf_prstatus_pr_reg, "elf_prstatus",
+				   "pr_reg");
+
+		STRUCT_SIZE_INIT(note_buf, "note_buf_t");
+		break;
+
+	case POST_VM:
+		/*
+		 * crash_notes contains machine specific information about the
+		 * crash. In particular, it contains CPU registers at the time
+		 * of the crash. We need this information to extract correct
+		 * backtraces from the panic task.
+		 */
+		if (!ACTIVE() && !riscv64_init_active_task_regs())
+			error(WARNING,
+				"cannot retrieve registers for active task%s\n\n",
+				kt->cpus > 1 ? "s" : "");
+		break;
+	}
 }
 
+/*
+ * 'help -r' command output
+ */
 void
 riscv64_display_regs_from_elf_notes(int cpu, FILE *ofp)
 {
-- 
2.40.0

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File crash-RISCV64-Make-crash-tool-enter-command-line-and-suppo.patch of Package crash (Revision 79fa6b5df9b8e54a6611dcfbed05e018)

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