[Qemu-devel] [PATCH 11/11 v10] introduce a new monitor command 'dump-guest-memory' to dump guest's memory

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

The command's usage:
   dump [-p] protocol [begin] [length]
The supported protocol can be file or fd:
1. file: the protocol starts with "file:", and the following string is
   the file's path.
2. fd: the protocol starts with "fd:", and the following string is the
   fd's name.

Note:
  1. If you want to use gdb to process the core, please specify -p option.
     The reason why the -p option is not default is: guest machine in a
     catastrophic state can have corrupted memory, which we cannot trust.
  2. This command doesn't support the fd that is is associated with a pipe,
     socket, or FIFO(lseek will fail with such fd).
  3. If you don't want to dump all guest's memory, please specify the start
     physical address and the length.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
 Makefile.target  |    2 +-
 dump.c           |  841 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 elf.h            |    5 +
 hmp-commands.hx  |   28 ++
 hmp.c            |   22 ++
 hmp.h            |    1 +
 memory_mapping.c |   27 ++
 memory_mapping.h |    3 +
 qapi-schema.json |   18 ++
 qmp-commands.hx  |   38 +++
 10 files changed, 984 insertions(+), 1 deletions(-)
 create mode 100644 dump.c

diff --git a/Makefile.target b/Makefile.target
index c3aa5d7..0e179c9 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -219,7 +219,7 @@ obj-$(CONFIG_NO_KVM) += kvm-stub.o
 obj-$(CONFIG_VGA) += vga.o
 obj-y += memory.o savevm.o
 obj-y += memory_mapping.o
-obj-$(CONFIG_HAVE_CORE_DUMP) += arch_dump.o
+obj-$(CONFIG_HAVE_CORE_DUMP) += arch_dump.o dump.o
 LIBS+=-lz
 
 obj-i386-$(CONFIG_KVM) += hyperv.o
diff --git a/dump.c b/dump.c
new file mode 100644
index 0000000..917bccc
--- /dev/null
+++ b/dump.c
@@ -0,0 +1,841 @@
+/*
+ * QEMU dump
+ *
+ * Copyright Fujitsu, Corp. 2011, 2012
+ *
+ * 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 <glib.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"
+#include "memory_mapping.h"
+#include "error.h"
+#include "qmp-commands.h"
+#include "gdbstub.h"
+
+static inline uint16_t cpu_convert_to_target16(uint16_t val, int endian)
+{
+    if (endian == ELFDATA2LSB) {
+        val = cpu_to_le16(val);
+    } else {
+        val = cpu_to_be16(val);
+    }
+
+    return val;
+}
+
+static inline uint32_t cpu_convert_to_target32(uint32_t val, int endian)
+{
+    if (endian == ELFDATA2LSB) {
+        val = cpu_to_le32(val);
+    } else {
+        val = cpu_to_be32(val);
+    }
+
+    return val;
+}
+
+static inline uint64_t cpu_convert_to_target64(uint64_t val, int endian)
+{
+    if (endian == ELFDATA2LSB) {
+        val = cpu_to_le64(val);
+    } else {
+        val = cpu_to_be64(val);
+    }
+
+    return val;
+}
+
+typedef struct DumpState {
+    ArchDumpInfo dump_info;
+    MemoryMappingList list;
+    uint16_t phdr_num;
+    uint32_t sh_info;
+    bool have_section;
+    bool resume;
+    target_phys_addr_t memory_offset;
+    write_core_dump_function f;
+    void (*cleanup)(void *opaque);
+    void *opaque;
+
+    RAMBlock *block;
+    ram_addr_t start;
+    bool has_filter;
+    int64_t begin;
+    int64_t length;
+} DumpState;
+
+static DumpState *dump_get_current(void)
+{
+    static DumpState current_dump;
+
+    return &current_dump;
+}
+
+static int dump_cleanup(DumpState *s)
+{
+    int ret = 0;
+
+    memory_mapping_list_free(&s->list);
+    s->cleanup(s->opaque);
+    if (s->resume) {
+        vm_start();
+    }
+
+    return ret;
+}
+
+static void dump_error(DumpState *s, const char *reason)
+{
+    dump_cleanup(s);
+}
+
+static int write_elf64_header(DumpState *s)
+{
+    Elf64_Ehdr elf_header;
+    int ret;
+    int endian = s->dump_info.d_endian;
+
+    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] = s->dump_info.d_endian;
+    elf_header.e_ident[EI_VERSION] = EV_CURRENT;
+    elf_header.e_type = cpu_convert_to_target16(ET_CORE, endian);
+    elf_header.e_machine = cpu_convert_to_target16(s->dump_info.d_machine,
+                                                   endian);
+    elf_header.e_version = cpu_convert_to_target32(EV_CURRENT, endian);
+    elf_header.e_ehsize = cpu_convert_to_target16(sizeof(elf_header), endian);
+    elf_header.e_phoff = cpu_convert_to_target64(sizeof(Elf64_Ehdr), endian);
+    elf_header.e_phentsize = cpu_convert_to_target16(sizeof(Elf64_Phdr),
+                                                     endian);
+    elf_header.e_phnum = cpu_convert_to_target16(s->phdr_num, endian);
+    if (s->have_section) {
+        uint64_t shoff = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr) * s->sh_info;
+
+        elf_header.e_shoff = cpu_convert_to_target64(shoff, endian);
+        elf_header.e_shentsize = cpu_convert_to_target16(sizeof(Elf64_Shdr),
+                                                         endian);
+        elf_header.e_shnum = cpu_convert_to_target16(1, endian);
+    }
+
+    ret = s->f(0, &elf_header, sizeof(elf_header), s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write elf header.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf32_header(DumpState *s)
+{
+    Elf32_Ehdr elf_header;
+    int ret;
+    int endian = s->dump_info.d_endian;
+
+    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_convert_to_target16(ET_CORE, endian);
+    elf_header.e_machine = cpu_convert_to_target16(s->dump_info.d_machine,
+                                                   endian);
+    elf_header.e_version = cpu_convert_to_target32(EV_CURRENT, endian);
+    elf_header.e_ehsize = cpu_convert_to_target16(sizeof(elf_header), endian);
+    elf_header.e_phoff = cpu_convert_to_target32(sizeof(Elf32_Ehdr), endian);
+    elf_header.e_phentsize = cpu_convert_to_target16(sizeof(Elf32_Phdr),
+                                                     endian);
+    elf_header.e_phnum = cpu_convert_to_target16(s->phdr_num, endian);
+    if (s->have_section) {
+        uint32_t shoff = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr) * s->sh_info;
+
+        elf_header.e_shoff = cpu_convert_to_target32(shoff, endian);
+        elf_header.e_shentsize = cpu_convert_to_target16(sizeof(Elf32_Shdr),
+                                                         endian);
+        elf_header.e_shnum = cpu_convert_to_target16(1, endian);
+    }
+
+    ret = s->f(0, &elf_header, sizeof(elf_header), s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write elf header.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf64_load(DumpState *s, MemoryMapping *memory_mapping,
+                            int phdr_index, target_phys_addr_t offset)
+{
+    Elf64_Phdr phdr;
+    off_t phdr_offset;
+    int ret;
+    int endian = s->dump_info.d_endian;
+
+    memset(&phdr, 0, sizeof(Elf64_Phdr));
+    phdr.p_type = cpu_convert_to_target32(PT_LOAD, endian);
+    phdr.p_offset = cpu_convert_to_target64(offset, endian);
+    phdr.p_paddr = cpu_convert_to_target64(memory_mapping->phys_addr, endian);
+    if (offset == -1) {
+        phdr.p_filesz = 0;
+    } else {
+        phdr.p_filesz = cpu_convert_to_target64(memory_mapping->length, endian);
+    }
+    phdr.p_memsz = cpu_convert_to_target64(memory_mapping->length, endian);
+    phdr.p_vaddr = cpu_convert_to_target64(memory_mapping->virt_addr, endian);
+
+    phdr_offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr)*phdr_index;
+    ret = s->f(phdr_offset, &phdr, sizeof(Elf64_Phdr), s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf32_load(DumpState *s, MemoryMapping *memory_mapping,
+                            int phdr_index, target_phys_addr_t offset)
+{
+    Elf32_Phdr phdr;
+    off_t phdr_offset;
+    int ret;
+    int endian = s->dump_info.d_endian;
+
+    memset(&phdr, 0, sizeof(Elf32_Phdr));
+    phdr.p_type = cpu_convert_to_target32(PT_LOAD, endian);
+    phdr.p_offset = cpu_convert_to_target32(offset, endian);
+    phdr.p_paddr = cpu_convert_to_target32(memory_mapping->phys_addr, endian);
+    if (offset == -1) {
+        phdr.p_filesz = 0;
+    } else {
+        phdr.p_filesz = cpu_convert_to_target32(memory_mapping->length, endian);
+    }
+    phdr.p_memsz = cpu_convert_to_target32(memory_mapping->length, endian);
+    phdr.p_vaddr = cpu_convert_to_target32(memory_mapping->virt_addr, endian);
+
+    phdr_offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr)*phdr_index;
+    ret = s->f(phdr_offset, &phdr, sizeof(Elf32_Phdr), s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf64_notes(DumpState *s, int phdr_index,
+                             target_phys_addr_t *offset)
+{
+    CPUArchState *env;
+    int ret;
+    target_phys_addr_t begin = *offset;
+    Elf64_Phdr phdr;
+    off_t phdr_offset;
+    int id;
+    int endian = s->dump_info.d_endian;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        id = gdb_id(env);
+        ret = cpu_write_elf64_note(s->f, env, id, offset, s->opaque);
+        if (ret < 0) {
+            dump_error(s, "dump: failed to write elf notes.\n");
+            return -1;
+        }
+    }
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        ret = cpu_write_elf64_qemunote(s->f, env, offset, s->opaque);
+        if (ret < 0) {
+            dump_error(s, "dump: failed to write CPU status.\n");
+            return -1;
+        }
+    }
+
+    memset(&phdr, 0, sizeof(Elf64_Phdr));
+    phdr.p_type = cpu_convert_to_target32(PT_NOTE, endian);
+    phdr.p_offset = cpu_convert_to_target64(begin, endian);
+    phdr.p_paddr = 0;
+    phdr.p_filesz = cpu_convert_to_target64(*offset - begin, endian);
+    phdr.p_memsz = cpu_convert_to_target64(*offset - begin, endian);
+    phdr.p_vaddr = 0;
+
+    phdr_offset = sizeof(Elf64_Ehdr);
+    ret = s->f(phdr_offset, &phdr, sizeof(Elf64_Phdr), s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf32_notes(DumpState *s, int phdr_index,
+                             target_phys_addr_t *offset)
+{
+    CPUArchState *env;
+    int ret;
+    target_phys_addr_t begin = *offset;
+    Elf32_Phdr phdr;
+    off_t phdr_offset;
+    int id;
+    int endian = s->dump_info.d_endian;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        id = gdb_id(env);
+        ret = cpu_write_elf32_note(s->f, env, id, offset, s->opaque);
+        if (ret < 0) {
+            dump_error(s, "dump: failed to write elf notes.\n");
+            return -1;
+        }
+    }
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        ret = cpu_write_elf32_qemunote(s->f, env, offset, s->opaque);
+        if (ret < 0) {
+            dump_error(s, "dump: failed to write CPU status.\n");
+            return -1;
+        }
+    }
+
+    memset(&phdr, 0, sizeof(Elf32_Phdr));
+    phdr.p_type = cpu_convert_to_target32(PT_NOTE, endian);
+    phdr.p_offset = cpu_convert_to_target32(begin, endian);
+    phdr.p_paddr = 0;
+    phdr.p_filesz = cpu_convert_to_target32(*offset - begin, endian);
+    phdr.p_memsz = cpu_convert_to_target32(*offset - begin, endian);
+    phdr.p_vaddr = 0;
+
+    phdr_offset = sizeof(Elf32_Ehdr);
+    ret = s->f(phdr_offset, &phdr, sizeof(Elf32_Phdr), s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf_section(DumpState *s, target_phys_addr_t *offset, int type)
+{
+    Elf32_Shdr shdr32;
+    Elf64_Shdr shdr64;
+    int endian = s->dump_info.d_endian;
+    int shdr_size;
+    void *shdr;
+    int ret;
+
+    if (type == 0) {
+        shdr_size = sizeof(Elf32_Shdr);
+        memset(&shdr32, 0, shdr_size);
+        shdr32.sh_info = cpu_convert_to_target32(s->sh_info, endian);
+        shdr = &shdr32;
+    } else {
+        shdr_size = sizeof(Elf64_Shdr);
+        memset(&shdr64, 0, shdr_size);
+        shdr64.sh_info = cpu_convert_to_target32(s->sh_info, endian);
+        shdr = &shdr64;
+    }
+
+    ret = s->f(*offset, &shdr, shdr_size, s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write section header table.\n");
+        return -1;
+    }
+
+    *offset += shdr_size;
+    return 0;
+}
+
+static int write_data(DumpState *s, void *buf, int length,
+                      target_phys_addr_t *offset)
+{
+    int ret;
+
+    ret = s->f(*offset, buf, length, s->opaque);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to save memory.\n");
+        return -1;
+    }
+
+    *offset += length;
+    return 0;
+}
+
+/* write the memroy to vmcore. 1 page per I/O. */
+static int write_memory(DumpState *s, RAMBlock *block, ram_addr_t start,
+                        target_phys_addr_t *offset, int64_t *size)
+{
+    int i, ret;
+    int64_t writen_size = 0;
+
+    *size = block->length - start;
+    for (i = 0; i < *size / TARGET_PAGE_SIZE; i++) {
+        ret = write_data(s, block->host + start + i * TARGET_PAGE_SIZE,
+                         TARGET_PAGE_SIZE, offset);
+        if (ret < 0) {
+            *size = writen_size;
+            return ret;
+        }
+
+        writen_size += TARGET_PAGE_SIZE;
+    }
+
+    if ((*size % TARGET_PAGE_SIZE) != 0) {
+        ret = write_data(s, block->host + start + i * TARGET_PAGE_SIZE,
+                         *size % TARGET_PAGE_SIZE, offset);
+        if (ret < 0) {
+            *size = writen_size;
+            return ret;
+        }
+    }
+
+    return 0;
+}
+
+/* get the memory's offset in the vmcore */
+static target_phys_addr_t get_offset(target_phys_addr_t phys_addr,
+                                     DumpState *s)
+{
+    RAMBlock *block;
+    target_phys_addr_t offset = s->memory_offset;
+    int64_t size_in_block, start;
+
+    if (s->has_filter) {
+        if (phys_addr < s->begin || phys_addr >= s->begin + s->length) {
+            return -1;
+        }
+    }
+
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        if (s->has_filter) {
+            if (block->offset >= s->begin + s->length ||
+                block->offset + block->length <= s->begin) {
+                /* This block is out of the range */
+                continue;
+            }
+
+            if (s->begin <= block->offset) {
+                start = block->offset;
+            } else {
+                start = s->begin;
+            }
+
+            size_in_block = block->length - (start - block->offset);
+            if (s->begin + s->length < block->offset + block->length) {
+                size_in_block -= block->offset + block->length -
+                                 (s->begin + s->length);
+            }
+        } else {
+            start = block->offset;
+            size_in_block = block->length;
+        }
+
+        if (phys_addr >= start && phys_addr < start + size_in_block) {
+            return phys_addr - start + offset;
+        }
+
+        offset += size_in_block;
+    }
+
+    return -1;
+}
+
+/* write elf header, PT_NOTE and elf note to vmcore. */
+static int dump_begin(DumpState *s)
+{
+    target_phys_addr_t offset;
+    int ret;
+
+    /*
+     * the vmcore's format is:
+     *   --------------
+     *   |  elf header |
+     *   --------------
+     *   |  PT_NOTE    |
+     *   --------------
+     *   |  PT_LOAD    |
+     *   --------------
+     *   |  ......     |
+     *   --------------
+     *   |  PT_LOAD    |
+     *   --------------
+     *   |  sec_hdr    |
+     *   --------------
+     *   |  elf note   |
+     *   --------------
+     *   |  memory     |
+     *   --------------
+     *
+     * we only know where the memory is saved after we write elf note into
+     * vmcore.
+     */
+
+    /* write elf header to vmcore */
+    if (s->dump_info.d_class == ELFCLASS64) {
+        ret = write_elf64_header(s);
+    } else {
+        ret = write_elf32_header(s);
+    }
+    if (ret < 0) {
+        return -1;
+    }
+
+    /* write elf section and notes to vmcore */
+    if (s->dump_info.d_class == ELFCLASS64) {
+        if (s->have_section) {
+            offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr)*s->sh_info;
+            if (write_elf_section(s, &offset, 1) < 0) {
+                return -1;
+            }
+        } else {
+            offset = sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr)*s->phdr_num;
+        }
+        ret = write_elf64_notes(s, 0, &offset);
+    } else {
+        if (s->have_section) {
+            offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr)*s->sh_info;
+            if (write_elf_section(s, &offset, 0) < 0) {
+                return -1;
+            }
+        } else {
+            offset = sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr)*s->phdr_num;
+        }
+        ret = write_elf32_notes(s, 0, &offset);
+    }
+
+    if (ret < 0) {
+        return -1;
+    }
+
+    s->memory_offset = offset;
+    return 0;
+}
+
+/* write PT_LOAD to vmcore */
+static int dump_completed(DumpState *s)
+{
+    target_phys_addr_t offset;
+    MemoryMapping *memory_mapping;
+    int phdr_index = 1, ret;
+
+    QTAILQ_FOREACH(memory_mapping, &s->list.head, next) {
+        offset = get_offset(memory_mapping->phys_addr, s);
+        if (s->dump_info.d_class == ELFCLASS64) {
+            ret = write_elf64_load(s, memory_mapping, phdr_index++, offset);
+        } else {
+            ret = write_elf32_load(s, memory_mapping, phdr_index++, offset);
+        }
+        if (ret < 0) {
+            return -1;
+        }
+    }
+
+    dump_cleanup(s);
+    return 0;
+}
+
+static int get_next_block(DumpState *s, RAMBlock *block)
+{
+    while (1) {
+        block = QLIST_NEXT(block, next);
+        if (!block) {
+            /* no more block */
+            return 1;
+        }
+
+        s->start = 0;
+        s->block = block;
+        if (s->has_filter) {
+            if (block->offset >= s->begin + s->length ||
+                block->offset + block->length <= s->begin) {
+                /* This block is out of the range */
+                continue;
+            }
+
+            if (s->begin > block->offset) {
+                s->start = s->begin - block->offset;
+            }
+        }
+
+        return 0;
+    }
+}
+
+/* write all memory to vmcore */
+static int dump_iterate(DumpState *s)
+{
+    RAMBlock *block;
+    target_phys_addr_t offset = s->memory_offset;
+    int64_t size;
+    int ret;
+
+    while(1) {
+        block = s->block;
+        ret = write_memory(s, block, s->start, &offset, &size);
+        if (ret == -1) {
+            return ret;
+        }
+
+        ret = get_next_block(s, block);
+        if (ret == 1) {
+            dump_completed(s);
+            return 0;
+        }
+    }
+}
+
+static int create_vmcore(DumpState *s)
+{
+    int ret;
+
+    ret = dump_begin(s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    ret = dump_iterate(s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static ram_addr_t get_start_block(DumpState *s)
+{
+    RAMBlock *block;
+
+    if (!s->has_filter) {
+        s->block = QLIST_FIRST(&ram_list.blocks);
+        return 0;
+    }
+
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        if (block->offset >= s->begin + s->length ||
+            block->offset + block->length <= s->begin) {
+            /* This block is out of the range */
+            continue;
+        }
+
+        s->block = block;
+        if (s->begin > block->offset ) {
+            s->start = s->begin - block->offset;
+        } else {
+            s->start = 0;
+        }
+        return s->start;
+    }
+
+    return -1;
+}
+
+static DumpState *dump_init(bool paging, bool has_filter, int64_t begin,
+                            int64_t length, Error **errp)
+{
+    CPUArchState *env;
+    DumpState *s = dump_get_current();
+    int ret;
+
+    if (runstate_is_running()) {
+        vm_stop(RUN_STATE_SAVE_VM);
+        s->resume = true;
+    } else {
+        s->resume = false;
+    }
+
+    s->has_filter = has_filter;
+    s->begin = begin;
+    s->length = length;
+    s->start = get_start_block(s);
+    if (s->start == -1) {
+        error_set(errp, QERR_INVALID_PARAMETER, "begin");
+        goto cleanup;
+    }
+
+    /*
+     * get dump info: endian, class and architecture.
+     * If the target architecture is not supported, cpu_get_dump_info() will
+     * return -1.
+     *
+     * if we use kvm, we should synchronize the register before we get dump
+     * info.
+     */
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        cpu_synchronize_state(env);
+    }
+
+    ret = cpu_get_dump_info(&s->dump_info);
+    if (ret < 0) {
+        error_set(errp, QERR_UNSUPPORTED);
+        goto cleanup;
+    }
+
+    /* get memory mapping */
+    memory_mapping_list_init(&s->list);
+    if (paging) {
+        qemu_get_guest_memory_mapping(&s->list);
+    } else {
+        qemu_get_guest_simple_memory_mapping(&s->list);
+    }
+
+    if (s->has_filter) {
+        memory_mapping_filter(&s->list, s->begin, s->length);
+    }
+
+    /*
+     * calculate phdr_num
+     *
+     * the type of ehdr->e_phnum is uint16_t, so we should avoid overflow
+     */
+    s->phdr_num = 1; /* PT_NOTE */
+    if (s->list.num < UINT16_MAX - 2) {
+        s->phdr_num += s->list.num;
+        s->have_section = false;
+    } else {
+        s->have_section = true;
+        s->phdr_num = PN_XNUM;
+        s->sh_info = 1; /* PT_NOTE */
+
+        /* the type of shdr->sh_info is uint32_t, so we should avoid overflow */
+        if (s->list.num <= UINT32_MAX -1) {
+            s->sh_info += s->list.num;
+        } else {
+            s->sh_info = UINT32_MAX;
+        }
+    }
+
+    return s;
+
+cleanup:
+    if (s->resume) {
+        vm_start();
+    }
+
+    return NULL;
+}
+
+static int fd_write_vmcore(target_phys_addr_t offset, void *buf, size_t size,
+                           void *opaque)
+{
+    int fd = (int)(intptr_t)opaque;
+    off_t ret;
+    size_t writen_size;
+
+    while(1) {
+        ret = lseek(fd, offset, SEEK_SET);
+        if (ret < 0) {
+            if (errno != EINTR && errno != EAGAIN) {
+                return -1;
+            }
+            continue;
+        }
+        break;
+    }
+
+    /* The fd may be passed from user, and it can be non-blocked */
+    while(size) {
+        writen_size = qemu_write_full(fd, buf, size);
+        if (writen_size != size && errno != EAGAIN) {
+            return -1;
+        }
+
+        buf += writen_size;
+        size -= writen_size;
+    }
+
+    return 0;
+}
+
+static void fd_cleanup(void *opaque)
+{
+    int fd = (int)(intptr_t)opaque;
+
+    if (fd != -1) {
+        close(fd);
+    }
+}
+
+static DumpState *dump_init_fd(int fd, bool paging, bool has_filter,
+                               int64_t begin, int64_t length, Error **errp)
+{
+    DumpState *s = dump_init(paging, has_filter, begin, length, errp);
+
+    if (s == NULL) {
+        return NULL;
+    }
+
+    s->f = fd_write_vmcore;
+    s->cleanup = fd_cleanup;
+    s->opaque = (void *)(intptr_t)fd;
+
+    return s;
+}
+
+void qmp_dump_guest_memory(bool paging, const char *file, bool has_begin,
+                           int64_t begin, bool has_length, int64_t length,
+                           Error **errp)
+{
+    const char *p;
+    int fd = -1;
+    DumpState *s;
+
+    if (has_begin && !has_length) {
+        error_set(errp, QERR_MISSING_PARAMETER, "length");
+        return;
+    }
+    if (!has_begin && has_length) {
+        error_set(errp, QERR_MISSING_PARAMETER, "begin");
+        return;
+    }
+
+#if !defined(WIN32)
+    if (strstart(file, "fd:", &p)) {
+        fd = monitor_get_fd(cur_mon, p);
+        if (fd == -1) {
+            error_set(errp, QERR_FD_NOT_FOUND, p);
+            return;
+        }
+    }
+#endif
+
+    if  (strstart(file, "file:", &p)) {
+        fd = qemu_open(p, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR);
+        if (fd < 0) {
+            error_set(errp, QERR_OPEN_FILE_FAILED, p);
+            return;
+        }
+    }
+
+    if (fd == -1) {
+        error_set(errp, QERR_INVALID_PARAMETER, "file");
+        return;
+    }
+
+    s = dump_init_fd(fd, paging, has_begin, begin, length, errp);
+    if (!s) {
+        return;
+    }
+
+    if (create_vmcore(s) < 0) {
+        error_set(errp, QERR_IO_ERROR);
+    }
+}
diff --git a/elf.h b/elf.h
index 2e05d34..6a10657 100644
--- a/elf.h
+++ b/elf.h
@@ -1000,6 +1000,11 @@ typedef struct elf64_sym {
 
 #define EI_NIDENT	16
 
+/* Special value for e_phnum.  This indicates that the real number of
+   program headers is too large to fit into e_phnum.  Instead the real
+   value is in the field sh_info of section 0.  */
+#define PN_XNUM         0xffff
+
 typedef struct elf32_hdr{
   unsigned char	e_ident[EI_NIDENT];
   Elf32_Half	e_type;
diff --git a/hmp-commands.hx b/hmp-commands.hx
index bd35a3e..d270fd1 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -879,6 +879,34 @@ server will ask the spice/vnc client to automatically reconnect using the
 new parameters (if specified) once the vm migration finished successfully.
 ETEXI
 
+#if defined(CONFIG_HAVE_CORE_DUMP)
+    {
+        .name       = "dump-guest-memory",
+        .args_type  = "paging:-p,protocol:s,begin:i?,length:i?",
+        .params     = "[-p] protocol [begin] [length]",
+        .help       = "dump guest memory to file"
+                      "\n\t\t\t begin(optional): the starting physical address"
+                      "\n\t\t\t length(optional): the memory size, in bytes",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd = hmp_dump_guest_memory,
+    },
+
+
+STEXI
+@item dump-guest-memory [-p] @var{protocol} @var{begin} @var{length}
+@findex dump-guest-memory
+Dump guest memory to @var{protocol}. The file can be processed with crash or
+gdb.
+  protocol: destination file(started with "file:") or destination file
+            descriptor (started with "fd:")
+    paging: do paging to get guest's memory mapping
+     begin: the starting physical address. It's optional, and should be
+            specified with length together.
+    length: the memory size, in bytes. It's optional, and should be specified
+            with begin together.
+ETEXI
+#endif
+
     {
         .name       = "snapshot_blkdev",
         .args_type  = "reuse:-n,device:B,snapshot-file:s?,format:s?",
diff --git a/hmp.c b/hmp.c
index 9cf2d13..75ec9a9 100644
--- a/hmp.c
+++ b/hmp.c
@@ -934,3 +934,25 @@ void hmp_migrate(Monitor *mon, const QDict *qdict)
         qemu_mod_timer(status->timer, qemu_get_clock_ms(rt_clock));
     }
 }
+
+void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict)
+{
+    Error *errp = NULL;
+    int paging = qdict_get_try_bool(qdict, "paging", 0);
+    const char *file = qdict_get_str(qdict, "protocol");
+    bool has_begin = qdict_haskey(qdict, "begin");
+    bool has_length = qdict_haskey(qdict, "length");
+    int64_t begin = 0;
+    int64_t length = 0;
+
+    if (has_begin) {
+        begin = qdict_get_int(qdict, "begin");
+    }
+    if (has_length) {
+        length = qdict_get_int(qdict, "length");
+    }
+
+    qmp_dump_guest_memory(paging, file, has_begin, begin, has_length, length,
+                          &errp);
+    hmp_handle_error(mon, &errp);
+}
diff --git a/hmp.h b/hmp.h
index 8807853..36d69c6 100644
--- a/hmp.h
+++ b/hmp.h
@@ -60,5 +60,6 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict);
 void hmp_block_job_set_speed(Monitor *mon, const QDict *qdict);
 void hmp_block_job_cancel(Monitor *mon, const QDict *qdict);
 void hmp_migrate(Monitor *mon, const QDict *qdict);
+void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);
 
 #endif
diff --git a/memory_mapping.c b/memory_mapping.c
index 9a2ffe6..ff52c9d 100644
--- a/memory_mapping.c
+++ b/memory_mapping.c
@@ -207,3 +207,30 @@ void qemu_get_guest_simple_memory_mapping(MemoryMappingList *list)
         create_new_memory_mapping(list, block->offset, 0, block->length);
     }
 }
+
+void memory_mapping_filter(MemoryMappingList *list, int64_t begin,
+                           int64_t length)
+{
+    MemoryMapping *cur, *next;
+
+    QTAILQ_FOREACH_SAFE(cur, &list->head, next, next) {
+        if (cur->phys_addr >= begin + length ||
+            cur->phys_addr + cur->length <= begin) {
+            QTAILQ_REMOVE(&list->head, cur, next);
+            list->num--;
+            continue;
+        }
+
+        if (cur->phys_addr < begin) {
+            cur->length -= begin - cur->phys_addr;
+            if (cur->virt_addr) {
+                cur->virt_addr += begin - cur->phys_addr;
+            }
+            cur->phys_addr = begin;
+        }
+
+        if (cur->phys_addr + cur->length > begin + length) {
+            cur->length -= cur->phys_addr + cur->length - begin - length;
+        }
+    }
+}
diff --git a/memory_mapping.h b/memory_mapping.h
index a583e44..b795678 100644
--- a/memory_mapping.h
+++ b/memory_mapping.h
@@ -62,4 +62,7 @@ static inline int qemu_get_guest_memory_mapping(MemoryMappingList *list)
 /* get guest's memory mapping without do paging(virtual address is 0). */
 void qemu_get_guest_simple_memory_mapping(MemoryMappingList *list);
 
+void memory_mapping_filter(MemoryMappingList *list, int64_t begin,
+                           int64_t length);
+
 #endif
diff --git a/qapi-schema.json b/qapi-schema.json
index 0d11d6e..b0d885f 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1701,3 +1701,21 @@
 # Since: 1.1
 ##
 { 'command': 'xen-save-devices-state', 'data': {'filename': 'str'} }
+
+##
+# @dump-guest-memory
+#
+# Dump guest's memory to vmcore.
+#
+# @paging: if true, do paging to get guest's memory mapping
+# @protocol: the filename or file descriptor of the vmcore.
+# @begin: #optional if specified, the starting physical address.
+# @length: #optional if specified, the memory size, in bytes.
+#
+# Returns: nothing on success
+#
+# Since: 1.1
+##
+{ 'command': 'dump-guest-memory',
+  'data': { 'paging': 'bool', 'protocol': 'str', '*begin': 'int',
+            '*length': 'int' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index c626ba8..ca4484b 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -606,6 +606,44 @@ Example:
 
 EQMP
 
+#if defined(CONFIG_HAVE_CORE_DUMP)
+    {
+        .name       = "dump-guest-memory",
+        .args_type  = "paging:-p,protocol:s,begin:i?,end:i?",
+        .params     = "[-p] protocol [begin] [length]",
+        .help       = "dump guest memory to file",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = qmp_marshal_input_dump_guest_memory,
+    },
+
+SQMP
+dump
+
+
+Dump guest memory to file. The file can be processed with crash or gdb.
+
+Arguments:
+
+- "paging": do paging to get guest's memory mapping (json-bool)
+- "protocol": destination file(started with "file:") or destination file
+              descriptor (started with "fd:") (json-string)
+- "begin": the starting physical address. It's optional, and should be specified
+           with length together (json-int)
+- "length": the memory size, in bytes. It's optional, and should be specified
+            with begin together (json-int)
+
+Example:
+
+-> { "execute": "dump-guest-memory", "arguments": { "protocol": "fd:dump" } }
+<- { "return": {} }
+
+Notes:
+
+(1) All boolean arguments default to false
+
+EQMP
+#endif
+
     {
         .name       = "netdev_add",
         .args_type  = "netdev:O",
-- 
1.7.1