[Qemu-devel] [RFC][PATCH] introduce a new monitor command 'dump' to dump guest's memory

[Wen Congyang <wency@cn.fujitsu.com>]

'virsh dump' can not work when host pci device is used by guest. We have
discussed this issue here:
http://lists.nongnu.org/archive/html/qemu-devel/2011-10/msg00736.html

We have determined to introduce a new command dump to dump memory. The core
file's format is elf.

Note:
1. The guest should be x86 or x86_64. The other arch is not supported.
2. gdb can not convert the virtual address to physical address sometimes, because
   the PT_LOAD in the core file does not contain enough information.
3. If you use old gdb, gdb may crash. I use gdb-7.3.1, and it does not crash.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
 Makefile.target |    8 +-
 dump.c          |  772 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dump.h          |    6 +
 hmp-commands.hx |   16 ++
 monitor.c       |    3 +
 qmp-commands.hx |   24 ++
 6 files changed, 825 insertions(+), 4 deletions(-)
 create mode 100644 dump.c
 create mode 100644 dump.h

diff --git a/Makefile.target b/Makefile.target
index a111521..a4f0e6d 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -118,7 +118,7 @@ $(call set-vpath, $(SRC_PATH)/linux-user:$(SRC_PATH)/linux-user/$(TARGET_ABI_DIR
 QEMU_CFLAGS+=-I$(SRC_PATH)/linux-user/$(TARGET_ABI_DIR) -I$(SRC_PATH)/linux-user
 obj-y = main.o syscall.o strace.o mmap.o signal.o thunk.o \
       elfload.o linuxload.o uaccess.o gdbstub.o cpu-uname.o \
-      user-exec.o $(oslib-obj-y)
+      user-exec.o $(oslib-obj-y) dump.o
 
 obj-$(TARGET_HAS_BFLT) += flatload.o
 
@@ -156,7 +156,7 @@ LDFLAGS+=-Wl,-segaddr,__STD_PROG_ZONE,0x1000 -image_base 0x0e000000
 LIBS+=-lmx
 
 obj-y = main.o commpage.o machload.o mmap.o signal.o syscall.o thunk.o \
-        gdbstub.o user-exec.o
+        gdbstub.o user-exec.o dump.o
 
 obj-i386-y += ioport-user.o
 
@@ -178,7 +178,7 @@ $(call set-vpath, $(SRC_PATH)/bsd-user)
 QEMU_CFLAGS+=-I$(SRC_PATH)/bsd-user -I$(SRC_PATH)/bsd-user/$(TARGET_ARCH)
 
 obj-y = main.o bsdload.o elfload.o mmap.o signal.o strace.o syscall.o \
-        gdbstub.o uaccess.o user-exec.o
+        gdbstub.o uaccess.o user-exec.o dump.o
 
 obj-i386-y += ioport-user.o
 
@@ -194,7 +194,7 @@ endif #CONFIG_BSD_USER
 # System emulator target
 ifdef CONFIG_SOFTMMU
 
-obj-y = arch_init.o cpus.o monitor.o machine.o gdbstub.o balloon.o ioport.o
+obj-y = arch_init.o cpus.o monitor.o machine.o gdbstub.o balloon.o ioport.o dump.o
 # virtio has to be here due to weird dependency between PCI and virtio-net.
 # need to fix this properly
 obj-$(CONFIG_NO_PCI) += pci-stub.o
diff --git a/dump.c b/dump.c
new file mode 100644
index 0000000..0117ac3
--- /dev/null
+++ b/dump.c
@@ -0,0 +1,772 @@
+/*
+ * QEMU live dump
+ *
+ * Copyright Fujitsu, Corp. 2011
+ *
+ * Authors:
+ *     Wen Congyang <wency@cn.fujitsu.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include <unistd.h>
+#include <elf.h>
+#include <sys/procfs.h>
+#include "cpu.h"
+#include "cpu-all.h"
+#include "targphys.h"
+#include "monitor.h"
+#include "kvm.h"
+#include "dump.h"
+#include "sysemu.h"
+#include "bswap.h"
+
+static inline int cpuid(CPUState *env)
+{
+#if defined(CONFIG_USER_ONLY) && defined(CONFIG_USE_NPTL)
+    return env->host_tid;
+#else
+    return env->cpu_index + 1;
+#endif
+}
+
+#if defined(TARGET_I386)
+
+#ifdef TARGET_X86_64
+typedef struct {
+    target_ulong r15, r14, r13, r12, rbp, rbx, r11, r10;
+    target_ulong r9, r8, rax, rcx, rdx, rsi, rdi, orig_rax;
+    target_ulong rip, cs, eflags;
+    target_ulong rsp, ss;
+    target_ulong fs_base, gs_base;
+    target_ulong ds, es, fs, gs;
+} x86_64_user_regs_struct;
+
+static int x86_64_write_elf64_note(Monitor *mon, int fd, CPUState *env,
+                                   target_phys_addr_t *offset)
+{
+    x86_64_user_regs_struct regs;
+    Elf64_Nhdr *note;
+    char *buf;
+    int descsz, note_size, name_size = 5;
+    const char *name = "CORE";
+    int id = cpuid(env);
+    int ret;
+
+    regs.r15 = env->regs[15];
+    regs.r14 = env->regs[14];
+    regs.r13 = env->regs[13];
+    regs.r12 = env->regs[12];
+    regs.r11 = env->regs[11];
+    regs.r10 = env->regs[10];
+    regs.r9  = env->regs[9];
+    regs.r8  = env->regs[8];
+    regs.rbp = env->regs[R_EBP];
+    regs.rsp = env->regs[R_ESP];
+    regs.rdi = env->regs[R_EDI];
+    regs.rsi = env->regs[R_ESI];
+    regs.rdx = env->regs[R_EDX];
+    regs.rcx = env->regs[R_ECX];
+    regs.rbx = env->regs[R_EBX];
+    regs.rax = env->regs[R_EAX];
+    regs.rip = env->eip;
+    regs.eflags = env->eflags;
+
+    regs.orig_rax = 0; /* FIXME */
+    regs.cs = env->segs[R_CS].selector;
+    regs.ss = env->segs[R_SS].selector;
+    regs.fs_base = env->segs[R_FS].base;
+    regs.gs_base = env->segs[R_GS].base;
+    regs.ds = env->segs[R_DS].selector;
+    regs.es = env->segs[R_ES].selector;
+    regs.fs = env->segs[R_FS].selector;
+    regs.gs = env->segs[R_GS].selector;
+
+    descsz = 336; /* sizeof(prstatus_t) is 336 on x86_64 box */
+    note_size = ((sizeof(Elf64_Nhdr) + 3) / 4 + (name_size + 3) / 4 +
+                (descsz + 3) / 4) * 4;
+    note = g_malloc(note_size);
+
+    memset(note, 0, note_size);
+    note->n_namesz = cpu_to_le32(name_size);
+    note->n_descsz = cpu_to_le32(descsz);
+    note->n_type = cpu_to_le32(NT_PRSTATUS);
+    buf = (char *)note;
+    buf += ((sizeof(Elf64_Nhdr) + 3) / 4) * 4;
+    memcpy(buf, name, name_size);
+    buf += ((name_size + 3) / 4) * 4;
+    memcpy(buf + 32, &id, 4); /* pr_pid */
+    buf += descsz - sizeof(x86_64_user_regs_struct)-sizeof(target_ulong);
+    memcpy(buf, &regs, sizeof(x86_64_user_regs_struct));
+
+    lseek(fd, *offset, SEEK_SET);
+    ret = write(fd, note, note_size);
+    g_free(note);
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write elf prstatus.\n");
+        return -1;
+    }
+
+    *offset += note_size;
+
+    return 0;
+}
+#endif
+
+/* This function is copied from crash, gdb also needs this virtual address */
+static target_ulong get_phys_base_addr(CPUState *env, target_ulong *base_vaddr)
+{
+    int i;
+    target_ulong kernel_base = -1;
+    target_ulong last, mask;
+
+    for (i = 30, last = -1; (kernel_base == -1) && (i >= 20); i--) {
+        mask = ~((1LL << i) - 1);
+        *base_vaddr = env->idt.base & mask;
+        if (*base_vaddr == last) {
+            continue;
+        }
+
+        kernel_base = cpu_get_phys_page_debug(env, *base_vaddr);
+        last = *base_vaddr;
+    }
+
+    return kernel_base;
+}
+
+/* This function likes get_phys_base_addr(). */
+static target_ulong get_page_offset_addr(CPUState *env,
+                                         target_ulong *page_offset_vaddr)
+{
+    int i;
+    target_ulong kernel_base = -1;
+    target_ulong last, mask;
+
+    for (i = 30, last = -1; (kernel_base == -1) && (i >= 20); i--) {
+        mask = ~((1LL << i) - 1);
+        *page_offset_vaddr = env->gdt.base & mask;
+        if (*page_offset_vaddr == last) {
+            continue;
+        }
+
+        kernel_base = cpu_get_phys_page_debug(env, *page_offset_vaddr);
+        last = *page_offset_vaddr;
+    }
+
+    return kernel_base;
+}
+
+typedef struct {
+    uint32_t ebx, ecx, edx, esi, edi, ebp, eax;
+    unsigned short ds, __ds, es, __es;
+    unsigned short fs, __fs, gs, __gs;
+    uint32_t orig_eax, eip;
+    unsigned short cs, __cs;
+    uint32_t eflags, esp;
+    unsigned short ss, __ss;
+} x86_user_regs_struct;
+
+static int x86_write_elf64_note(Monitor *mon, int fd, CPUState *env,
+                                target_phys_addr_t *offset)
+{
+    x86_user_regs_struct regs;
+    Elf64_Nhdr *note;
+    char *buf;
+    int descsz, note_size, name_size = 5;
+    const char *name = "CORE";
+    int id = cpuid(env);
+    int ret;
+
+    regs.ebp = env->regs[R_EBP] & 0xffffffff;
+    regs.esp = env->regs[R_ESP] & 0xffffffff;
+    regs.edi = env->regs[R_EDI] & 0xffffffff;
+    regs.esi = env->regs[R_ESI] & 0xffffffff;
+    regs.edx = env->regs[R_EDX] & 0xffffffff;
+    regs.ecx = env->regs[R_ECX] & 0xffffffff;
+    regs.ebx = env->regs[R_EBX] & 0xffffffff;
+    regs.eax = env->regs[R_EAX] & 0xffffffff;
+    regs.eip = env->eip & 0xffffffff;
+    regs.eflags = env->eflags & 0xffffffff;
+
+    regs.cs = env->segs[R_CS].selector;
+    regs.__cs = 0;
+    regs.ss = env->segs[R_SS].selector;
+    regs.__ss = 0;
+    regs.ds = env->segs[R_DS].selector;
+    regs.__ds = 0;
+    regs.es = env->segs[R_ES].selector;
+    regs.__es = 0;
+    regs.fs = env->segs[R_FS].selector;
+    regs.__fs = 0;
+    regs.gs = env->segs[R_GS].selector;
+    regs.__gs = 0;
+
+    descsz = 144; /* sizeof(prstatus_t) is 144 on x86 box */
+    note_size = ((sizeof(Elf64_Nhdr) + 3) / 4 + (name_size + 3) / 4 +
+                (descsz + 3) / 4) * 4;
+    note = g_malloc(note_size);
+
+    memset(note, 0, note_size);
+    note->n_namesz = cpu_to_le32(name_size);
+    note->n_descsz = cpu_to_le32(descsz);
+    note->n_type = cpu_to_le32(NT_PRSTATUS);
+    buf = (char *)note;
+    buf += ((sizeof(Elf64_Nhdr) + 3) / 4) * 4;
+    memcpy(buf, name, name_size);
+    buf += ((name_size + 3) / 4) * 4;
+    memcpy(buf + 24, &id, 4); /* pr_pid */
+    buf += descsz - sizeof(x86_user_regs_struct)-4;
+    memcpy(buf, &regs, sizeof(x86_user_regs_struct));
+
+    lseek(fd, *offset, SEEK_SET);
+    ret = write(fd, note, note_size);
+    g_free(note);
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write elf prstatus.\n");
+        return -1;
+    }
+
+    *offset += note_size;
+
+    return 0;
+}
+
+static int x86_write_elf32_note(Monitor *mon, int fd, CPUState *env,
+                                target_phys_addr_t *offset)
+{
+    x86_user_regs_struct regs;
+    Elf32_Nhdr *note;
+    char *buf;
+    int descsz, note_size, name_size = 5;
+    const char *name = "CORE";
+    int id = cpuid(env);
+    int ret;
+
+    regs.ebp = env->regs[R_EBP] & 0xffffffff;
+    regs.esp = env->regs[R_ESP] & 0xffffffff;
+    regs.edi = env->regs[R_EDI] & 0xffffffff;
+    regs.esi = env->regs[R_ESI] & 0xffffffff;
+    regs.edx = env->regs[R_EDX] & 0xffffffff;
+    regs.ecx = env->regs[R_ECX] & 0xffffffff;
+    regs.ebx = env->regs[R_EBX] & 0xffffffff;
+    regs.eax = env->regs[R_EAX] & 0xffffffff;
+    regs.eip = env->eip & 0xffffffff;
+    regs.eflags = env->eflags & 0xffffffff;
+
+    regs.cs = env->segs[R_CS].selector;
+    regs.__cs = 0;
+    regs.ss = env->segs[R_SS].selector;
+    regs.__ss = 0;
+    regs.ds = env->segs[R_DS].selector;
+    regs.__ds = 0;
+    regs.es = env->segs[R_ES].selector;
+    regs.__es = 0;
+    regs.fs = env->segs[R_FS].selector;
+    regs.__fs = 0;
+    regs.gs = env->segs[R_GS].selector;
+    regs.__gs = 0;
+
+    descsz = 144; /* sizeof(prstatus_t) is 144 on x86 box */
+    note_size = ((sizeof(Elf32_Nhdr) + 3) / 4 + (name_size + 3) / 4 +
+                (descsz + 3) / 4) * 4;
+    note = g_malloc(note_size);
+
+    memset(note, 0, note_size);
+    note->n_namesz = cpu_to_le32(name_size);
+    note->n_descsz = cpu_to_le32(descsz);
+    note->n_type = cpu_to_le32(NT_PRSTATUS);
+    buf = (char *)note;
+    buf += ((sizeof(Elf32_Nhdr) + 3) / 4) * 4;
+    memcpy(buf, name, name_size);
+    buf += ((name_size + 3) / 4) * 4;
+    memcpy(buf + 24, &id, 4); /* pr_pid */
+    buf += descsz - sizeof(x86_user_regs_struct)-4;
+    memcpy(buf, &regs, sizeof(x86_user_regs_struct));
+
+    lseek(fd, *offset, SEEK_SET);
+    ret = write(fd, note, note_size);
+    g_free(note);
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write elf prstatus.\n");
+        return -1;
+    }
+
+    *offset += note_size;
+
+    return 0;
+}
+#endif
+
+static int write_elf64_header(Monitor *mon, int fd, int phdr_num, int machine,
+                              int endian)
+{
+    Elf64_Ehdr elf_header;
+    int ret;
+
+    memset(&elf_header, 0, sizeof(Elf64_Ehdr));
+    memcpy(&elf_header, ELFMAG, 4);
+    elf_header.e_ident[EI_CLASS] = ELFCLASS64;
+    elf_header.e_ident[EI_DATA] = endian;
+    elf_header.e_ident[EI_VERSION] = EV_CURRENT;
+    elf_header.e_type = cpu_to_le16(ET_CORE);
+    elf_header.e_machine = cpu_to_le16(machine);
+    elf_header.e_version = cpu_to_le32(EV_CURRENT);
+    elf_header.e_ehsize = cpu_to_le16(sizeof(elf_header));
+    elf_header.e_phoff = cpu_to_le64(sizeof(Elf64_Ehdr));
+    elf_header.e_phentsize = cpu_to_le16(sizeof(Elf64_Phdr));
+    elf_header.e_phnum = cpu_to_le16(phdr_num);
+
+    lseek(fd, 0, SEEK_SET);
+    ret = write(fd, &elf_header, sizeof(elf_header));
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write elf header.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf32_header(Monitor *mon, int fd, int phdr_num, int machine,
+                              int endian)
+{
+    Elf32_Ehdr elf_header;
+    int ret;
+
+    memset(&elf_header, 0, sizeof(Elf32_Ehdr));
+    memcpy(&elf_header, ELFMAG, 4);
+    elf_header.e_ident[EI_CLASS] = ELFCLASS32;
+    elf_header.e_ident[EI_DATA] = endian;
+    elf_header.e_ident[EI_VERSION] = EV_CURRENT;
+    elf_header.e_type = cpu_to_le16(ET_CORE);
+    elf_header.e_machine = cpu_to_le16(machine);
+    elf_header.e_version = cpu_to_le32(EV_CURRENT);
+    elf_header.e_ehsize = cpu_to_le16(sizeof(elf_header));
+    elf_header.e_phoff = cpu_to_le32(sizeof(Elf32_Ehdr));
+    elf_header.e_phentsize = cpu_to_le16(sizeof(Elf32_Phdr));
+    elf_header.e_phnum = cpu_to_le16(phdr_num);
+
+    lseek(fd, 0, SEEK_SET);
+    ret = write(fd, &elf_header, sizeof(elf_header));
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write elf header.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf64_load(Monitor *mon, int fd, RAMBlock *block,
+                            int phdr_index, target_phys_addr_t *offset,
+                            target_ulong base_vaddr)
+{
+    Elf64_Phdr phdr;
+    off_t phdr_offset;
+    int ret;
+
+    memset(&phdr, 0, sizeof(Elf64_Phdr));
+    phdr.p_type = cpu_to_le32(PT_LOAD);
+    phdr.p_offset = cpu_to_le64(*offset);
+    phdr.p_paddr = cpu_to_le64(block->offset);
+    phdr.p_filesz = cpu_to_le64(block->length);
+    phdr.p_memsz = cpu_to_le64(block->length);
+    phdr.p_vaddr = cpu_to_le64(base_vaddr);
+
+    phdr_offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr)*phdr_index;
+    lseek(fd, phdr_offset, SEEK_SET);
+    ret = write(fd, &phdr, sizeof(Elf64_Phdr));
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    lseek(fd, *offset, SEEK_SET);
+    ret = write(fd, block->host, block->length);
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write program segment.\n");
+        return -1;
+    }
+    *offset += block->length;
+
+    return 0;
+}
+
+static int write_elf32_load(Monitor *mon, int fd, RAMBlock *block,
+                            int phdr_index, target_phys_addr_t *offset,
+                            target_ulong base_vaddr)
+{
+    Elf32_Phdr phdr;
+    off_t phdr_offset;
+    int ret;
+
+    memset(&phdr, 0, sizeof(Elf32_Phdr));
+    phdr.p_type = cpu_to_le32(PT_LOAD);
+    phdr.p_offset = cpu_to_le32(*offset);
+    phdr.p_paddr = cpu_to_le32(block->offset);
+    phdr.p_filesz = cpu_to_le32(block->length);
+    phdr.p_memsz = cpu_to_le32(block->length);
+    phdr.p_vaddr = cpu_to_le32(base_vaddr);
+
+    phdr_offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr)*phdr_index;
+    lseek(fd, phdr_offset, SEEK_SET);
+    ret = write(fd, &phdr, sizeof(Elf32_Phdr));
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    lseek(fd, *offset, SEEK_SET);
+    ret = write(fd, block->host, block->length);
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write program segment.\n");
+        return -1;
+    }
+    *offset += block->length;
+
+    return 0;
+}
+
+static int write_elf_load(Monitor *mon, int fd, RAMBlock *block,
+                          int phdr_index, target_phys_addr_t *offset,
+                          target_ulong virtual_addr,
+                          target_phys_addr_t phys_addr,
+                          target_phys_addr_t length, int type)
+{
+    RAMBlock temp_block;
+    int ret;
+
+    temp_block.host = block->host + (phys_addr - block->offset);
+    temp_block.offset = phys_addr;
+    temp_block.length = length;
+    if (type == 1) {
+        ret = write_elf64_load(mon, fd, &temp_block, phdr_index,
+                               offset, virtual_addr);
+    } else  {
+        ret = write_elf32_load(mon, fd, &temp_block, phdr_index,
+                               offset, virtual_addr);
+    }
+    return ret;
+}
+
+static int write_elf64_notes(Monitor *mon, int fd, int phdr_index,
+                             target_phys_addr_t *offset, bool lma)
+{
+    CPUState *env;
+    int ret;
+    target_phys_addr_t begin = *offset;
+    Elf64_Phdr phdr;
+    off_t phdr_offset;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+#if defined(TARGET_I386)
+#ifdef TARGET_X86_64
+        if (lma) {
+            ret = x86_64_write_elf64_note(mon, fd, env, offset);
+        } else {
+#endif
+            ret = x86_write_elf64_note(mon, fd, env, offset);
+#ifdef TARGET_X86_64
+        }
+#endif
+#else
+        ret = -1; /* Not supported */
+#endif
+
+        if (ret < 0) {
+            monitor_printf(mon, "dump: failed to write elf notes.\n");
+            return -1;
+        }
+    }
+
+    memset(&phdr, 0, sizeof(Elf64_Phdr));
+    phdr.p_type = cpu_to_le32(PT_NOTE);
+    phdr.p_offset = cpu_to_le64(begin);
+    phdr.p_paddr = 0;
+    phdr.p_filesz = cpu_to_le64(*offset - begin);
+    phdr.p_memsz = cpu_to_le64(*offset - begin);
+    phdr.p_vaddr = 0;
+
+    phdr_offset = sizeof(Elf64_Ehdr);
+    lseek(fd, phdr_offset, SEEK_SET);
+    ret = write(fd, &phdr, sizeof(Elf64_Phdr));
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf32_notes(Monitor *mon, int fd, int phdr_index,
+                             target_phys_addr_t *offset)
+{
+    CPUState *env;
+    int ret;
+    target_phys_addr_t begin = *offset;
+    Elf32_Phdr phdr;
+    off_t phdr_offset;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+#if defined(TARGET_I386)
+        ret = x86_write_elf32_note(mon, fd, env, offset);
+#else
+        ret = -1; /* Not supported */
+#endif
+
+        if (ret < 0) {
+            monitor_printf(mon, "dump: failed to write elf notes.\n");
+            return -1;
+        }
+    }
+
+    memset(&phdr, 0, sizeof(Elf32_Phdr));
+    phdr.p_type = cpu_to_le32(PT_NOTE);
+    phdr.p_offset = cpu_to_le32(begin);
+    phdr.p_paddr = 0;
+    phdr.p_filesz = cpu_to_le32(*offset - begin);
+    phdr.p_memsz = cpu_to_le32(*offset - begin);
+    phdr.p_vaddr = 0;
+
+    phdr_offset = sizeof(Elf32_Ehdr);
+    lseek(fd, phdr_offset, SEEK_SET);
+    ret = write(fd, &phdr, sizeof(Elf32_Phdr));
+    if (ret < 0) {
+        monitor_printf(mon, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int create_vmcore(Monitor *mon, int fd)
+{
+    CPUState *env;
+    target_ulong kernel_base = -1, base_vaddr;
+    target_ulong page_offset = -1, page_offset_vaddr;
+    target_phys_addr_t offset;
+    int phdr_num, phdr_index;
+    RAMBlock *block;
+    bool lma = false;
+    int ret;
+    int type, machine, endian;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        cpu_synchronize_state(env);
+    }
+
+#if defined(TARGET_I386)
+
+#ifdef TARGET_X86_64
+    lma = !!(first_cpu->hflags & HF_LMA_MASK);
+#endif
+
+    kernel_base = get_phys_base_addr(first_cpu, &base_vaddr);
+    if (kernel_base == -1) {
+        monitor_printf(mon, "dump: can not get phys_base\n");
+        return -1;
+    }
+    page_offset = get_page_offset_addr(first_cpu, &page_offset_vaddr);
+    if (page_offset == -1) {
+        monitor_printf(mon, "dump: can not get page_offset\n");
+        return -1;
+    }
+#endif
+
+#if defined(TARGET_I386)
+    if (lma) {
+        machine = EM_X86_64;
+    } else {
+        machine = EM_386;
+    }
+    endian = ELFDATA2LSB;
+#else
+    monitor_printf(mon, "dump: unsupported target.\n")
+    return -1;
+#endif
+
+    if (sizeof(ram_addr_t) == 4) {
+        type = 0; /* use elf32 */
+#if defined(TARGET_I386)
+    } else if (!lma) {
+        type = 0; /* the guest os is not in IA-32e mode */
+#endif
+    } else {
+        type = 1; /* use elf64 */
+    }
+
+    phdr_num = 1; /* PT_NOTE */
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+#if defined(TARGET_I386)
+        if (kernel_base > block->offset &&
+            kernel_base < (block->offset + block->length)) {
+            phdr_num++;
+        }
+        if (page_offset != kernel_base && page_offset > block->offset &&
+            page_offset < (block->offset + block->length)) {
+            phdr_num++;
+        }
+        if (!lma && (block->offset + block->length > UINT_MAX)) {
+            type = 1; /* The memory size is greater than 4G */
+        }
+#endif
+        phdr_num++;
+    }
+
+    if (type == 1) {
+        ret = write_elf64_header(mon, fd, phdr_num, machine, endian);
+    } else {
+        ret = write_elf32_header(mon, fd, phdr_num, machine, endian);
+    }
+    if (ret < 0) {
+        return -1;
+    }
+
+    phdr_index = 0;
+    if (type == 1) {
+        offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr)*phdr_num;
+        ret = write_elf64_notes(mon, fd, phdr_index++, &offset, lma);
+    } else {
+        offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr)*phdr_num;
+        ret = write_elf32_notes(mon, fd, phdr_index++, &offset);
+    }
+
+    if (ret < 0) {
+        return -1;
+    }
+
+#if defined(TARGET_I386)
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        bool kernel_base_in_block, page_offset_in_block;
+        target_ulong length;
+        target_phys_addr_t paddr, vaddr;
+
+        kernel_base_in_block = kernel_base >= block->offset &&
+                               kernel_base < (block->offset + block->length);
+        page_offset_in_block = page_offset >= block->offset &&
+                               page_offset < (block->offset + block->length);
+        if (!kernel_base_in_block && !page_offset_in_block) {
+            continue;
+        }
+
+        if (kernel_base_in_block) {
+            paddr = kernel_base;
+            vaddr = base_vaddr;
+            if (page_offset_in_block && page_offset > paddr) {
+                length = page_offset - paddr;
+            } else {
+                length = block->length - (paddr - block->offset);
+            }
+
+            ret = write_elf_load(mon, fd, block, phdr_index++, &offset,
+                                 vaddr, paddr, length, type);
+            if (ret < 0) {
+                return -1;
+            }
+        }
+
+        if (page_offset != kernel_base && page_offset_in_block) {
+            paddr = page_offset;
+            vaddr = page_offset_vaddr;
+            if (kernel_base_in_block && kernel_base > paddr) {
+                length = kernel_base - paddr;
+            } else {
+                length = block->length - (paddr - block->offset);
+            }
+
+            ret = write_elf_load(mon, fd, block, phdr_index++, &offset,
+                                 vaddr, paddr, length, type);
+            if (ret < 0) {
+                return -1;
+            }
+        }
+
+        if ((kernel_base_in_block && kernel_base == block->offset) ||
+            (page_offset_in_block && page_offset == block->offset)) {
+            continue;
+        }
+
+        if (kernel_base_in_block && page_offset_in_block) {
+            if (page_offset >= kernel_base) {
+                length = kernel_base - block->offset;
+            } else {
+                length = page_offset - block->offset;
+            }
+        } else if (kernel_base_in_block) {
+            length = kernel_base - block->offset;
+        } else if (page_offset_in_block) {
+            length = page_offset - block->offset;
+        }
+        paddr = block->offset;
+        vaddr = 0;
+        ret = write_elf_load(mon, fd, block, phdr_index++, &offset,
+                             vaddr, paddr, length, type);
+        if (ret < 0) {
+            return -1;
+        }
+    }
+#endif
+
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+#if defined(TARGET_I386)
+        if (kernel_base >= block->offset &&
+            kernel_base < (block->offset + block->length)) {
+            continue;
+        }
+        if (page_offset >= block->offset &&
+            page_offset < (block->offset + block->length)) {
+            continue;
+        }
+#endif
+
+        if (type == 1) {
+            ret = write_elf64_load(mon, fd, block, phdr_index++, &offset, 0);
+        } else {
+            ret = write_elf32_load(mon, fd, block, phdr_index++, &offset, 0);
+        }
+        if (ret < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+int do_dump(Monitor *mon, const QDict *qdict, QObject **ret_data)
+{
+    const char *file = qdict_get_str(qdict, "file");
+    const char *p;
+    int fd = -1;
+
+#if !defined(WIN32)
+    if (strstart(file, "fd:", &p)) {
+        fd = monitor_get_fd(mon, p);
+        if (fd == -1) {
+            monitor_printf(mon, "dump: invalid file descriptor"
+                           " identifier\n");
+            return -1;
+        }
+    }
+#endif
+
+    if  (strstart(file, "file:", &p)) {
+        fd = open(p, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY);
+        if (fd < 0) {
+            monitor_printf(mon, "dump: failed to open %s\n", p);
+            return -1;
+        }
+    }
+
+    if (fd == -1) {
+        monitor_printf(mon, "unknown dump protocol: %s\n", file);
+        return -1;
+    }
+
+    vm_stop(RUN_STATE_PAUSED);
+    if (create_vmcore(mon, fd) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/dump.h b/dump.h
new file mode 100644
index 0000000..c91fa2c
--- /dev/null
+++ b/dump.h
@@ -0,0 +1,6 @@
+#ifndef DUMP_H
+#define DUMP_H
+
+int do_dump(Monitor *mon, const QDict *qdict, QObject **ret_data);
+
+#endif
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 089c1ac..ebbce8c 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -772,6 +772,22 @@ Migrate to @var{uri} (using -d to not wait for completion).
 ETEXI
 
     {
+        .name       = "dump",
+        .args_type  = "file:s",
+        .params     = "file",
+        .help       = "dump to file",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_dump,
+    },
+
+
+STEXI
+@item dump @var{file}
+@findex dump
+Dump to @var{file}.
+ETEXI
+
+    {
         .name       = "migrate_cancel",
         .args_type  = "",
         .params     = "",
diff --git a/monitor.c b/monitor.c
index 1be222e..9f26c3d 100644
--- a/monitor.c
+++ b/monitor.c
@@ -73,6 +73,9 @@
 #endif
 #include "hw/lm32_pic.h"
 
+/* for dump */
+#include "dump.h"
+
 //#define DEBUG
 //#define DEBUG_COMPLETION
 
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 97975a5..5cf21c5 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -485,6 +485,30 @@ Notes:
 EQMP
 
     {
+        .name       = "dump",
+        .args_type  = "file:s",
+        .params     = "file",
+        .help       = "dump to file",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_dump,
+    },
+
+SQMP
+dump
+-------
+
+Dump to file.
+
+Arguments: None.
+
+Example:
+
+-> { "execute": "dump", "arguments": { "file": "fd:dump" } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "migrate_cancel",
         .args_type  = "",
         .params     = "",
-- 
1.7.1