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

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
 
     {