Load state snapshot rather than booting to start emulator.

This patch adds support for an optional file "snapshots.img" in the
data directory of an AVD. This file should be an image formatted with
the qcow2 file system and will be mounted on -hdb when the emulator
starts up. If present, the emulator will attempt to load the snapshot
named "default-boot" from this image, rather than going through the
full boot procedure.

To control the behaviour of this functionality, this patch introduces
the following new command line options for the emulator:

  -snapstorage <file>: override the default location of the
     snapshot storage file.
  -no-snapstorage: do not load the snapshots file, even if an explicit
     path is given.
  -snapshot <name>: instead of loading "default-boot", load the state
     snapshot with the given name.
  -no-snapshot: do not load a snapshot, but force a full boot
     sequence, even if a snapshots file is mounted. Useful for
     creating snapshots.

Note that this functionality is experimental and will be enabled
only if the constant CONFIG_ANDROID_SNAPSHOTS in
android/config/config.h is set to "1" before building. It is turned
off by default.

Change-Id: Iee2e9096a27f3414bacfc271f90ef93a98730c82

1 files changed, 88 insertions, 6 deletions

diff --git a/android/help.c b/android/help.c
index ea419f3..17e7a90 100644
--- a/android/help.c
+++ b/android/help.c
@@ -166,6 +166,9 @@ help_disk_images( stralloc_t*  out )
     "    system-qemu.img    an *optional* persistent system image\n"
     "    cache.img          an *optional* cache partition image\n"
     "    sdcard.img         an *optional* SD Card partition image\n\n"
+#if CONFIG_ANDROID_SNAPSHOTS
+    "    snapshots.img      an *optional* state snapshots image\n\n"
+#endif
 
     "  If you use a virtual device, its content directory should store\n"
     "  all writable images, and read-only ones will be found from the\n"
@@ -181,7 +184,11 @@ help_disk_images( stralloc_t*  out )
     "  can still run the emulator by explicitely providing the paths to\n"
     "  *all* required disk images through a combination of the following\n"
     "  options: -sysdir, -datadir, -kernel, -ramdisk, -system, -data, -cache\n"
-    "  and -sdcard\n\n"
+#if CONFIG_ANDROID_SNAPSHOTS
+    "  -sdcard and -snapstorage.\n\n"
+#else
+    "  and -sdcard.\n\n"
+#endif
 
     "  The actual logic being that the emulator should be able to find all\n"
     "  images from the options you give it.\n\n"
@@ -190,13 +197,18 @@ help_disk_images( stralloc_t*  out )
 
     "  Other related options are:\n\n"
 
-    "      -init-data   Specify an alernative *initial* user data image\n\n"
+    "      -init-data       Specify an alternative *initial* user data image\n\n"
 
-    "      -wipe-data   Copy the content of the *initial* user data image\n"
-    "                   (userdata.img) into the writable one (userdata-qemu.img)\n\n"
+    "      -wipe-data       Copy the content of the *initial* user data image\n"
+"                           (userdata.img) into the writable one (userdata-qemu.img)\n\n"
 
-    "      -no-cache    do not use a cache partition, even if one is\n"
-    "                   available.\n\n"
+    "      -no-cache        do not use a cache partition, even if one is\n"
+    "                       available.\n\n"
+
+#if CONFIG_ANDROID_SNAPSHOTS
+    "      -no-snapstorage  do not use a state snapshot image, even if one is\n"
+    "                       available.\n\n"
+#endif
     ,
     datadir );
 }
@@ -620,6 +632,76 @@ help_sdcard(stralloc_t*  out)
     );
 }
 
+#if CONFIG_ANDROID_SNAPSHOTS
+static void
+help_snapstorage(stralloc_t*  out)
+{
+    PRINTF(
+    "  Use '-snapstorage <file>' to specify a repository file for snapshots.\n"
+    "  All snapshots made during execution will be saved in this file, and only\n"
+    "  snapshots in this file can be restored during the emulator run.\n\n"
+
+    "  If the option is not specified, it defaults to 'snapshots.img' in the\n"
+    "  data directory. If the specified file does not exist, the emulator will\n"
+    "  start, but without support for saving or loading state snapshots.\n\n"
+
+    "  see '-help-disk-images' for more information about disk image files\n"
+    "  see '-help-snapshot' for more information about snapshots\n\n"
+    );
+}
+
+static void
+help_no_snapstorage(stralloc_t*  out)
+{
+    PRINTF(
+    "  This starts the emulator without mounting a file to store or load state\n"
+    "  snapshots, forcing a full boot and disabling state snapshot functionality.\n\n"
+    ""
+    "  This command overrides the configuration specified by the parameters\n"
+    "  '-snapstorage' and '-snapshot'. A warning will be raised if either\n"
+    "  of those parameters was specified anyway.\n\n"
+     );
+ }
+
+static void
+help_snapshot(stralloc_t*  out)
+{
+    PRINTF(
+    "  Rather than executing a full boot sequence, the Android emulator can\n"
+    "  resume execution from an earlier state snapshot (which is usually\n"
+    "  significantly faster). When the parameter '-snapshot <name>' is given,\n"
+    "  the emulator loads the snapshot of that name from the snapshot image.\n\n"
+
+    "  If the option is not specified, it defaults to 'default-boot'. If the\n"
+    "  specified snapshot does not exist, the emulator will perform a full boot\n"
+    "  sequence instead.\n\n"
+
+    "  WARNING: In the process of loading, all contents of the system, userdata\n"
+    "           and SD card images will be OVERWRITTEN with the contents they\n"
+    "           held when the snapshot was made. Unless saved in a different\n"
+    "           snapshot, any changes since will be lost!\n\n"
+
+    "  If you want to create a snapshot, connect to the emulator console:\n\n"
+
+    "      telnet localhost <port>\n\n"
+
+    "  Then execute the command 'avd snapshot save <name>'. See '-help-port' for\n"
+    "  information on obtaining <port>.\n\n"
+    );
+}
+
+static void
+help_no_snapshot(stralloc_t*  out)
+{
+    PRINTF(
+    "  This forces the emulator to perform a full boot sequence, rather than\n"
+    "  loading the default snapshot. It overrides the '-snapshot' parameter.\n"
+    "  If '-snapshot' was specified anyway, a warning is raised.\n\n"
+    );
+}
+
+#endif
+
 static void
 help_skindir(stralloc_t*  out)
 {