introduce a new monitor command 'dump-guest-memory' to dump guest's memory

The command's usage:
   dump-guest-memory [-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:
       a. guest machine in a catastrophic state can have corrupted memory,
          which we cannot trust.
       b. The guest machine can be in read-mode even if paging is enabled.
          For example: the guest machine uses ACPI to sleep, and ACPI sleep
          state goes in real-mode.
  2. 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>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

Makefile.target

@@ -405,6 +405,8 @@ obj-y += $(addprefix ../, $(trace-obj-y))
 
 endif # CONFIG_SOFTMMU
 
+obj-y += dump.o
+
 ifndef CONFIG_LINUX_USER
 ifndef CONFIG_BSD_USER
 # libcacard needs qemu-thread support, and besides is only needed by devices

dump.c

@@ -0,0 +1,883 @@
+/*
+ * 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"
+
+#if defined(CONFIG_HAVE_CORE_DUMP)
+static 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 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 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;
+    size_t note_size;
+    target_phys_addr_t memory_offset;
+    int fd;
+
+    RAMBlock *block;
+    ram_addr_t start;
+    bool has_filter;
+    int64_t begin;
+    int64_t length;
+    Error **errp;
+} DumpState;
+
+static int dump_cleanup(DumpState *s)
+{
+    int ret = 0;
+
+    memory_mapping_list_free(&s->list);
+    if (s->fd != -1) {
+        close(s->fd);
+    }
+    if (s->resume) {
+        vm_start();
+    }
+
+    return ret;
+}
+
+static void dump_error(DumpState *s, const char *reason)
+{
+    dump_cleanup(s);
+}
+
+static int fd_write_vmcore(void *buf, size_t size, void *opaque)
+{
+    DumpState *s = opaque;
+    int fd = s->fd;
+    size_t writen_size;
+
+    /* 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 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, SELFMAG);
+    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 = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
+    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, SELFMAG);
+    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 = fd_write_vmcore(&elf_header, sizeof(elf_header), s);
+    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;
+    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) {
+        /* When the memory is not stored into vmcore, offset will be -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);
+
+    ret = fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s);
+    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;
+    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) {
+        /* When the memory is not stored into vmcore, offset will be -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);
+
+    ret = fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write program header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_elf64_note(DumpState *s)
+{
+    Elf64_Phdr phdr;
+    int endian = s->dump_info.d_endian;
+    target_phys_addr_t begin = s->memory_offset - s->note_size;
+    int ret;
+
+    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(s->note_size, endian);
+    phdr.p_memsz = cpu_convert_to_target64(s->note_size, endian);
+    phdr.p_vaddr = 0;
+
+    ret = fd_write_vmcore(&phdr, sizeof(Elf64_Phdr), s);
+    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)
+{
+    CPUArchState *env;
+    int ret;
+    int id;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        id = cpu_index(env);
+        ret = cpu_write_elf64_note(fd_write_vmcore, env, id, s);
+        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(fd_write_vmcore, env, s);
+        if (ret < 0) {
+            dump_error(s, "dump: failed to write CPU status.\n");
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int write_elf32_note(DumpState *s)
+{
+    target_phys_addr_t begin = s->memory_offset - s->note_size;
+    Elf32_Phdr phdr;
+    int endian = s->dump_info.d_endian;
+    int ret;
+
+    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(s->note_size, endian);
+    phdr.p_memsz = cpu_convert_to_target32(s->note_size, endian);
+    phdr.p_vaddr = 0;
+
+    ret = fd_write_vmcore(&phdr, sizeof(Elf32_Phdr), s);
+    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)
+{
+    CPUArchState *env;
+    int ret;
+    int id;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        id = cpu_index(env);
+        ret = cpu_write_elf32_note(fd_write_vmcore, env, id, s);
+        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(fd_write_vmcore, env, s);
+        if (ret < 0) {
+            dump_error(s, "dump: failed to write CPU status.\n");
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int write_elf_section(DumpState *s, 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 = fd_write_vmcore(&shdr, shdr_size, s);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to write section header table.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+static int write_data(DumpState *s, void *buf, int length)
+{
+    int ret;
+
+    ret = fd_write_vmcore(buf, length, s);
+    if (ret < 0) {
+        dump_error(s, "dump: failed to save memory.\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+/* write the memroy to vmcore. 1 page per I/O. */
+static int write_memory(DumpState *s, RAMBlock *block, ram_addr_t start,
+                        int64_t size)
+{
+    int64_t i;
+    int ret;
+
+    for (i = 0; i < size / TARGET_PAGE_SIZE; i++) {
+        ret = write_data(s, block->host + start + i * TARGET_PAGE_SIZE,
+                         TARGET_PAGE_SIZE);
+        if (ret < 0) {
+            return ret;
+        }
+    }
+
+    if ((size % TARGET_PAGE_SIZE) != 0) {
+        ret = write_data(s, block->host + start + i * TARGET_PAGE_SIZE,
+                         size % TARGET_PAGE_SIZE);
+        if (ret < 0) {
+            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;
+}
+
+static int write_elf_loads(DumpState *s)
+{
+    target_phys_addr_t offset;
+    MemoryMapping *memory_mapping;
+    uint32_t phdr_index = 1;
+    int ret;
+    uint32_t max_index;
+
+    if (s->have_section) {
+        max_index = s->sh_info;
+    } else {
+        max_index = s->phdr_num;
+    }
+
+    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;
+        }
+
+        if (phdr_index >= max_index) {
+            break;
+        }
+    }
+
+    return 0;
+}
+
+/* write elf header, PT_NOTE and elf note to vmcore. */
+static int dump_begin(DumpState *s)
+{
+    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;
+    }
+
+    if (s->dump_info.d_class == ELFCLASS64) {
+        /* write PT_NOTE to vmcore */
+        if (write_elf64_note(s) < 0) {
+            return -1;
+        }
+
+        /* write all PT_LOAD to vmcore */
+        if (write_elf_loads(s) < 0) {
+            return -1;
+        }
+
+        /* write section to vmcore */
+        if (s->have_section) {
+            if (write_elf_section(s, 1) < 0) {
+                return -1;
+            }
+        }
+
+        /* write notes to vmcore */
+        if (write_elf64_notes(s) < 0) {
+            return -1;
+        }
+
+    } else {
+        /* write PT_NOTE to vmcore */
+        if (write_elf32_note(s) < 0) {
+            return -1;
+        }
+
+        /* write all PT_LOAD to vmcore */
+        if (write_elf_loads(s) < 0) {
+            return -1;
+        }
+
+        /* write section to vmcore */
+        if (s->have_section) {
+            if (write_elf_section(s, 0) < 0) {
+                return -1;
+            }
+        }
+
+        /* write notes to vmcore */
+        if (write_elf32_notes(s) < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+/* write PT_LOAD to vmcore */
+static int dump_completed(DumpState *s)
+{
+    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;
+    int64_t size;
+    int ret;
+
+    while (1) {
+        block = s->block;
+
+        size = block->length;
+        if (s->has_filter) {
+            size -= s->start;
+            if (s->begin + s->length < block->offset + block->length) {
+                size -= block->offset + block->length - (s->begin + s->length);
+            }
+        }
+        ret = write_memory(s, block, s->start, 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 int dump_init(DumpState *s, int fd, bool paging, bool has_filter,
+                     int64_t begin, int64_t length, Error **errp)
+{
+    CPUArchState *env;
+    int nr_cpus;
+    int ret;
+
+    if (runstate_is_running()) {
+        vm_stop(RUN_STATE_SAVE_VM);
+        s->resume = true;
+    } else {
+        s->resume = false;
+    }
+
+    s->errp = errp;
+    s->fd = fd;
+    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.
+     */
+    nr_cpus = 0;
+    for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        cpu_synchronize_state(env);
+        nr_cpus++;
+    }
+
+    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;
+        }
+    }
+
+    s->note_size = cpu_get_note_size(s->dump_info.d_class,
+                                     s->dump_info.d_machine, nr_cpus);
+    if (s->dump_info.d_class == ELFCLASS64) {
+        if (s->have_section) {
+            s->memory_offset = sizeof(Elf64_Ehdr) +
+                               sizeof(Elf64_Phdr) * s->sh_info +
+                               sizeof(Elf64_Shdr) + s->note_size;
+        } else {
+            s->memory_offset = sizeof(Elf64_Ehdr) +
+                               sizeof(Elf64_Phdr) * s->phdr_num + s->note_size;
+        }
+    } else {
+        if (s->have_section) {
+            s->memory_offset = sizeof(Elf32_Ehdr) +
+                               sizeof(Elf32_Phdr) * s->sh_info +
+                               sizeof(Elf32_Shdr) + s->note_size;
+        } else {
+            s->memory_offset = sizeof(Elf32_Ehdr) +
+                               sizeof(Elf32_Phdr) * s->phdr_num + s->note_size;
+        }
+    }
+
+    return 0;
+
+cleanup:
+    if (s->resume) {
+        vm_start();
+    }
+
+    return -1;
+}
+
+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;
+    int ret;
+
+    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, "protocol");
+        return;
+    }
+
+    s = g_malloc(sizeof(DumpState));
+
+    ret = dump_init(s, fd, paging, has_begin, begin, length, errp);
+    if (ret < 0) {
+        g_free(s);
+        return;
+    }
+
+    if (create_vmcore(s) < 0 && !error_is_set(s->errp)) {
+        error_set(errp, QERR_IO_ERROR);
+    }
+
+    g_free(s);
+}
+
+#else
+/* we need this function in hmp.c */
+void qmp_dump_guest_memory(bool paging, const char *file, bool has_begin,
+                           int64_t begin, bool has_length, int64_t length,
+                           Error **errp)
+{
+    error_set(errp, QERR_UNSUPPORTED);
+}
+#endif

elf.h

@@ -1037,6 +1037,11 @@ 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;

hmp-commands.hx

@@ -878,6 +878,34 @@ 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?",

hmp.c

@@ -947,3 +947,25 @@ void hmp_device_del(Monitor *mon, const QDict *qdict)
     qmp_device_del(id, &err);
     hmp_handle_error(mon, &err);
 }
+
+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);
+}

hmp.h

@@ -61,5 +61,6 @@ 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_device_del(Monitor *mon, const QDict *qdict);
+void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict);
 
 #endif

memory_mapping.c

@@ -220,3 +220,30 @@ 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;
+        }
+    }
+}

memory_mapping.h

@@ -63,6 +63,9 @@ 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);
+
 #else
 
 /* We use MemoryMappingList* in cpu-all.h */

qapi-schema.json

@@ -1755,3 +1755,46 @@
 # Since: 0.14.0
 ##
 { 'command': 'device_del', 'data': {'id': 'str'} }
+
+##
+# @dump-guest-memory
+#
+# Dump guest's memory to vmcore. It is a synchronous operation that can take
+# very long depending on the amount of guest memory. This command is only
+# supported only on i386 and x86_64
+#
+# @paging: if true, do paging to get guest's memory mapping. The @paging's
+# default value of @paging is false, If you want to use gdb to process the
+# core, please set @paging to true. The reason why the @paging's value is
+# false:
+#   1. guest machine in a catastrophic state can have corrupted memory,
+#      which we cannot trust.
+#   2. The guest machine can be in read-mode even if paging is enabled.
+#      For example: the guest machine uses ACPI to sleep, and ACPI sleep
+#      state goes in real-mode
+# @protocol: the filename or file descriptor of the vmcore. 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.
+# @begin: #optional if specified, the starting physical address.
+# @length: #optional if specified, the memory size, in bytes. If you don't
+# want to dump all guest's memory, please specify the start @begin and
+# @length
+#
+# Returns: nothing on success
+#          If @begin contains an invalid address, InvalidParameter
+#          If only one of @begin and @length is specified, MissingParameter
+#          If @protocol stats with "fd:", and the fd cannot be found, FdNotFound
+#          If @protocol starts with "file:", and the file cannot be
+#          opened, OpenFileFailed
+#          If @protocol does not start with "fd:" or "file:", InvalidParameter
+#          If an I/O error occurs while writing the file, IOError
+#          If the target does not support this command, Unsupported
+#
+# Since: 1.2
+##
+{ 'command': 'dump-guest-memory',
+  'data': { 'paging': 'bool', 'protocol': 'str', '*begin': 'int',
+            '*length': 'int' } }

qmp-commands.hx

@@ -601,6 +601,42 @@ Example:
                     "port": 1234 } }
 <- { "return": {} }
 
+EQMP
+
+    {
+        .name       = "dump-guest-memory",
+        .args_type  = "paging:b,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
 
     {