篇文章中我们介绍了 Android 4.4 新开发的运行时 ART 项目，其中的一个重要模快是 dex2oat，简单讲就是使用 LLVM 把 dex 文件编译成 oat 文件（Optimized ART?）。下面我们详细研究一下 dex2oat 的功能，以及他是如何被调用的。
一、dex2oat 简介
dex2oat 顾名思义 dex file to oat file，就是在新旧两种运行时文件的转换。他是一个可执行 ELF 文件，adb 连接手机以后也可以直接调用。dex2oat 的源码只有一个文件 /art/dex2oat/dex2oat.cc。dex2oat 有很多参数，并且实用方法打印到 logcat里面，看起来非常不便，我们直接看源码 Usage()。我挑了几个比较重要的参数看了一下，先介绍一下，调用过程中可能会用到。
dex2oat 用法
--dex-file=: specifies a .dex file to compile.: 需要转换的 dex 文件，也可以是 apk, jar，dex2oat 会找到里面的 classes.dex 进行转换。 --oat-file=: specifies the oat output destination via a filename.: 指定输出 oat 的文件名。 --boot-image=: provide the image file for the boot class path.: 系统运行时工具类在 ART 下编译后的文件，他的例子是指向/system/framework/boot.art。但其实 boot.art 不在这个目录下，而是在/data/dalvik-cache/system@[email protected]。后面还会详细介绍这个 boot 文件。 --compiler-backend=(Quick|QuickGBC|Portable): select compiler backend": dex2oat 好像只处理了 Quick 和 Portable 两种编译 backend，暂时还不理解有什么区别，待以后继续研究。
其他参数大多都能从他的描述中知道用途，等以后用到的时候再详细看。
oat 文件在哪里？
我们知道选择 ART 作为运行时后，需要重启手机。然后系统会使用 dex2oat 把所有 App 编译成 oat 文件。那么 oat 都存在哪里？我怎么找不到？通过查看代码和开机的 log，发现 oat 文件原来在 /data/dalvik-cache/*@classes.dex。竟然和 odex 文件名字一样！检验一下文件格式：
$ file system@
[email protected]@classes.dex system@
[email protected]@classes.dex: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (GNU/Linux), dynamically linked, stripped
|
|
$
file
system
@
app
@
Email
.apk
@
classes
.dex
system
@
app
@
Email
.apk
@
classes
.dex
:
ELF
32
-
bit
LSB
shared
object
,
ARM
,
EABI5
version
1
(
GNU
/
Linux
)
,
dynamically
linked
,
stripped
|
果然是 ELF 文件。
二、调用过程分析
PackageManagerService 是负责 apk 包管理的服务，包括安装，检查，删除，更新等等所有与 apk 相关的服务。我在源码中研究了一下 dex2oat 详细的调用过程，在下面介绍过程的时候我打算从 PackageManagerService 入手，经过一系列的调用过程才真正执行 dex2oat。
PackageManagerService (PMS)
我们知道 PMS 服务启动之后会监控某些目录（/data/data/ 等）。如果目录多了某个文件，PMS 会调用一些方法对文件进行处理。扫描监控目录的方法是：scanDirLI()，在 PackageManagerService 的构造方法中调用，详见代码 /frameworks/base/services/java/com/android/server/pm/PackageManagerService.java：
// Find base frameworks (resource packages without code). mFrameworkInstallObserver = new AppDirObserver( frameworkDir.getPath(), OBSERVER_EVENTS, true, false); mFrameworkInstallObserver.startWatching(); scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode | SCAN_NO_DEX, 0); // Collected privileged system packages. File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app"); mPrivilegedInstallObserver = new AppDirObserver( privilegedAppDir.getPath(), OBSERVER_EVENTS, true, true); mPrivilegedInstallObserver.startWatching(); scanDirLI(privilegedAppDir, PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR | PackageParser.PARSE_IS_PRIVILEGED, scanMode, 0); // Collect ordinary system packages. File systemAppDir = new File(Environment.getRootDirectory(), "app"); mSystemInstallObserver = new AppDirObserver( systemAppDir.getPath(), OBSERVER_EVENTS, true, false); mSystemInstallObserver.startWatching(); scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0); // Collect all vendor packages. File vendorAppDir = new File("/vendor/app"); mVendorInstallObserver = new AppDirObserver( vendorAppDir.getPath(), OBSERVER_EVENTS, true, false); mVendorInstallObserver.startWatching(); scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
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// Find base frameworks (resource packages without code).
mFrameworkInstallObserver
=
new
AppDirObserver
(
frameworkDir
.
getPath
(
)
,
OBSERVER_EVENTS
,
true
,
false
)
;
mFrameworkInstallObserver
.
startWatching
(
)
;
scanDirLI
(
frameworkDir
,
PackageParser
.
PARSE_IS_SYSTEM
|
PackageParser
.
PARSE_IS_SYSTEM_DIR
,
scanMode
|
SCAN_NO_DEX
,
0
)
;
// Collected privileged system packages.
File
privilegedAppDir
=
new
File
(
Environment
.
getRootDirectory
(
)
,
"priv-app"
)
;
mPrivilegedInstallObserver
=
new
AppDirObserver
(
privilegedAppDir
.
getPath
(
)
,
OBSERVER_EVENTS
,
true
,
true
)
;
mPrivilegedInstallObserver
.
startWatching
(
)
;
scanDirLI
(
privilegedAppDir
,
PackageParser
.
PARSE_IS_SYSTEM
|
PackageParser
.
PARSE_IS_SYSTEM_DIR
|
PackageParser
.
PARSE_IS_PRIVILEGED
,
scanMode
,
0
)
;
// Collect ordinary system packages.
File
systemAppDir
=
new
File
(
Environment
.
getRootDirectory
(
)
,
"app"
)
;
mSystemInstallObserver
=
new
AppDirObserver
(
systemAppDir
.
getPath
(
)
,
OBSERVER_EVENTS
,
true
,
false
)
;
mSystemInstallObserver
.
startWatching
(
)
;
scanDirLI
(
systemAppDir
,
PackageParser
.
PARSE_IS_SYSTEM
|
PackageParser
.
PARSE_IS_SYSTEM_DIR
,
scanMode
,
0
)
;
// Collect all vendor packages.
File
vendorAppDir
=
new
File
(
"/vendor/app"
)
;
mVendorInstallObserver
=
new
AppDirObserver
(
vendorAppDir
.
getPath
(
)
,
OBSERVER_EVENTS
,
true
,
false
)
;
mVendorInstallObserver
.
startWatching
(
)
;
scanDirLI
(
vendorAppDir
,
PackageParser
.
PARSE_IS_SYSTEM
|
PackageParser
.
PARSE_IS_SYSTEM_DIR
,
scanMode
,
0
)
;
|
从源码中可以看到，有四个地方调用 scanDirLI()。再调用之前有一个 AppDirObserver 类引起了我的注意，看一下是怎么对目录进行监控的。依然是在 PackageManagerService 中找到了 AppDirObserver 继承于 FileObserver。FileObserver 有一个 native 方法 startWatching 找到了他的实现 /frameworks/base/core/java/android/os/FileObserver.java：
const char* path = env->GetStringUTFChars(pathString, NULL); res = inotify_add_watch(fd, path, mask); env->ReleaseStringUTFChars(pathString, path);
|
|
const
char
*
path
=
env
->
GetStringUTFChars
(
pathString
,
NULL
)
;
res
=
inotify_add_watch
(
fd
,
path
,
mask
)
;
env
->
ReleaseStringUTFChars
(
pathString
,
path
)
;
|
man 一下 inotify_add_watch:
INOTIFY_ADD_WATCH(2) Linux Programmer's Manual INOTIFY_ADD_WATCH(2) NAME inotify_add_watch - add a watch to an initialized inotify instance SYNOPSIS #include <sys/inotify.h> int inotify_add_watch(int fd, const char *pathname, uint32_t mask); DESCRIPTION inotify_add_watch() adds a new watch, or modifies an existing watch, for the file whose location is specified in pathname; the caller must have read permission for this file. The fd argument is a file descrip‐ tor referring to the inotify instance whose watch list is to be modi‐ fied. The events to be monitored for pathname are specified in the mask bit-mask argument. See inotify(7) for a description of the bits that can be set in mask. ...
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INOTIFY_ADD_WATCH
(
2
)
Linux
Programmer'
s
Manual
INOTIFY_ADD_WATCH
(
2
)
NAME
inotify_add_watch
-
add
a
watch
to
an
initialized
inotify
instance
SYNOPSIS
#include <sys/inotify.h>
int
inotify_add_watch
(
int
fd
,
const
char
*
pathname
,
uint32_t
mask
)
;
DESCRIPTION
inotify_add_watch
(
)
adds
a
new
watch
,
or
modifies
an
existing
watch
,
for
the
file
whose
location
is
specified
in
pathname
;
the
caller
must
have
read
permission
for
this
file
.
The
fd
argument
is
a
file
descrip‐
tor
referring
to
the
inotify
instance
whose
watch
list
is
to
be
modi‐
fied
.
The
events
to
be
monitored
for
pathname
are
specified
in
the
mask
bit
-
mask
argument
.
See
inotify
(
7
)
for
a
description
of
the
bits
that
can
be
set
in
mask
.
.
.
.
|
原来 inotify_add_watch() 是监控目录的。
PackageManagerService.scanDirLI()
回到正题，我们从构造方法中找到了 scanDirLI()，现在来看一下 scanDirLI() 都做了什么：
for (i=0; i<files.length; i++) { File file = new File(dir, files[i]); if (!isPackageFilename(files[i])) { // Ignore entries which are not apk's continue; } PackageParser.Package pkg = scanPackageLI(file, flags|PackageParser.PARSE_MUST_BE_APK, scanMode, currentTime, null);
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|
for
(
i
=
0
;
i
<
files
.
length
;
i
++
)
{
File
file
=
new
File
(
dir
,
files
[
i
]
)
;
if
(
!
isPackageFilename
(
files
[
i
]
)
)
{
// Ignore entries which are not apk's
continue
;
}
PackageParser
.
Package
pkg
=
scanPackageLI
(
file
,
flags
|
PackageParser
.
PARSE_MUST_BE_APK
,
scanMode
,
currentTime
,
null
)
;
|
scanDirLI() 便利所有目录下的 apk 文件并调用 scanPackageLI()，我们继续。
PackageManagerService.scanPackageLI()
scanPackageLI() 先对文件的设置进行读取，还包含其他处理。我们跳过直接看
// Note that we invoke the following method only if we are about to unpack an application PackageParser.Package scannedPkg = scanPackageLI(pkg, parseFlags, scanMode | SCAN_UPDATE_SIGNATURE, currentTime, user);
|
|
// Note that we invoke the following method only if we are about to unpack an application
PackageParser
.
Package
scannedPkg
=
scanPackageLI
(
pkg
,
parseFlags
,
scanMode
|
SCAN_UPDATE_SIGNATURE
,
currentTime
,
user
)
;
|
又调用了另外一个重载的 scanPackageLI()。在这个 scanPackageLI() 里面又进行了一系列的包的解析，都与我们的目标无关，直接跳到这里：
if ((scanMode&SCAN_NO_DEX) == 0) { if (performDexOptLI(pkg, forceDex, (scanMode&SCAN_DEFER_DEX) != 0, false) == DEX_OPT_FAILED) { mLastScanError = PackageManager.INSTALL_FAILED_DEXOPT; return null; } }
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if
(
(
scanMode
&
SCAN_NO_DEX
)
==
0
)
{
if
(
performDexOptLI
(
pkg
,
forceDex
,
(
scanMode
&
SCAN_DEFER_DEX
)
!=
0
,
false
)
==
DEX_OPT_FAILED
)
{
mLastScanError
=
PackageManager
.
INSTALL_FAILED_DEXOPT
;
return
null
;
}
}
|
在这里又调用 performDexOptLI() 来处理进行 dex 优化，参数就是这个 package。这里已经感觉到有点快到 dex2oat 的调用点了。我们继续看 performDexOptLI()。
PackageManagerService.performDexOptLI()
performDexOptLI 先检查 dex 是否需要优化，然后再有一些判断，忽略他，看到这里：
if (forceDex || dalvik.system.DexFile.isDexOptNeeded(path)) { if (!forceDex && defer) { if (mDeferredDexOpt == null) { mDeferredDexOpt = new HashSet<PackageParser.Package>(); } mDeferredDexOpt.add(pkg); return DEX_OPT_DEFERRED; } else { Log.i(TAG, "Running dexopt on: " + pkg.applicationInfo.packageName); final int sharedGid = UserHandle.getSharedAppGid(pkg.applicationInfo. uid); ret = mInstaller.dexopt(path, sharedGid, !isForwardLocked(pkg)); pkg.mDidDexOpt = true; performed = true; } }
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if
(
forceDex
||
dalvik
.
system
.
DexFile
.
isDexOptNeeded
(
path
)
)
{
if
(
!
forceDex
&&
defer
)
{
if
(
mDeferredDexOpt
==
null
)
{
mDeferredDexOpt
=
new
HashSet
<
PackageParser
.
Package
>
(
)
;
}
mDeferredDexOpt
.
add
(
pkg
)
;
return
DEX_OPT_DEFERRED
;
}
else
{
Log
.
i
(
TAG
,
"Running dexopt on: "
+
pkg
.
applicationInfo
.
packageName
)
;
final
int
sharedGid
=
UserHandle
.
getSharedAppGid
(
pkg
.
applicationInfo
.
uid
)
;
ret
=
mInstaller
.
dexopt
(
path
,
sharedGid
,
!
isForwardLocked
(
pkg
)
)
;
pkg
.
mDidDexOpt
=
true
;
performed
=
true
;
}
}
|
最后 mInstaller.dexopt 调用的优化 dex 的函数，Google 在这里把 dex2oat 和 dex2odex 统称为 dexopt。mInstaller 是 Installer 类。下面我们详细了解一下 Installer 的运行机制。
Installer
从 Installer 的代码中我们可以看到 connect(), disconnect(), readBytes(), writeCommand() 等方法。在 connect() 方法中可以看到，Installer 就是与 installd daemon 进行通信的辅助类。代码在这里：
mSocket = new LocalSocket(); LocalSocketAddress address = new LocalSocketAddress("installd", LocalSocketAddress.Namespace.RESERVED); mSocket.connect(address); mIn = mSocket.getInputStream(); mOut = mSocket.getOutputStream();
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mSocket
=
new
LocalSocket
(
)
;
LocalSocketAddress
address
=
new
LocalSocketAddress
(
"installd"
,
LocalSocketAddress
.
Namespace
.
RESERVED
)
;
mSocket
.
connect
(
address
)
;
mIn
=
mSocket
.
getInputStream
(
)
;
mOut
=
mSocket
.
getOutputStream
(
)
;
|
了解了这个之后，我们找一下 dexopt 看看 Installer 向 installd 发送了什么信息：
public int dexopt(String apkPath, int uid, boolean isPublic) { StringBuilder builder = new StringBuilder("dexopt"); builder.append(' '); builder.append(apkPath); builder.append(' '); builder.append(uid); builder.append(isPublic ? " 1" : " 0"); return execute(builder.toString()); }
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public
int
dexopt
(
String
apkPath
,
int
uid
,
boolean
isPublic
)
{
StringBuilder
builder
=
new
StringBuilder
(
"dexopt"
)
;
builder
.
append
(
' '
)
;
builder
.
append
(
apkPath
)
;
builder
.
append
(
' '
)
;
builder
.
append
(
uid
)
;
builder
.
append
(
isPublic
?
" 1"
:
" 0"
)
;
return
execute
(
builder
.
toString
(
)
)
;
}
|
其实发送了 dexopt apkpath uid 1|0 给 installd。好了，Installer 分析结束，我们转战 installd。
installd.c
installd 是 socket 通信的 server，会 accept 连接，并读取数据。从下面的两个死循环就能看出来：
for (;;) { alen = sizeof(addr); s = accept(lsocket, &addr, &alen); if (s < 0) { ALOGE("Accept failed: %s\n", strerror(errno)); continue; } fcntl(s, F_SETFD, FD_CLOEXEC); ALOGI("new connection\n"); for (;;) { unsigned short count; if (readx(s, &count, sizeof(count))) {
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558
559
560
561
562
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564
565
566
|
for
(
;
;
)
{
alen
=
sizeof
(
addr
)
;
s
=
accept
(
lsocket
,
&
addr
,
&
alen
)
;
if
(
s
<
0
)
{
ALOGE
(
"Accept failed: %s\n"
,
strerror
(
errno
)
)
;
continue
;
}
fcntl
(
s
,
F_SETFD
,
FD_CLOEXEC
)
;
ALOGI
(
"new connection\n"
)
;
for
(
;
;
)
{
unsigned
short
count
;
if
(
readx
(
s
,
&
count
,
sizeof
(
count
)
)
)
{
|
之后会调用 execute 函数：
if (execute(s, buf)) break;
|
|
if
(
execute
(
s
,
buf
)
)
break
;
|
execute() 函数先把 cmd 分割然后通过 cmds 表查询函数名称：
struct cmdinfo { const char *name; unsigned numargs; int (*func)(char **arg, char reply[REPLY_MAX]); }; struct cmdinfo cmds[] = { { "ping", 0, do_ping }, { "install", 4, do_install }, { "dexopt", 3, do_dexopt }, { "movedex", 2, do_move_dex }, { "rmdex", 1, do_rm_dex }, { "remove", 2, do_remove }, { "rename", 2, do_rename }, { "fixuid", 3, do_fixuid }, { "freecache", 1, do_free_cache }, { "rmcache", 2, do_rm_cache }, { "getsize", 6, do_get_size }, { "rmuserdata", 2, do_rm_user_data }, { "movefiles", 0, do_movefiles }, { "linklib", 3, do_linklib }, { "mkuserdata", 3, do_mk_user_data }, { "rmuser", 1, do_rm_user }, };
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|
struct
cmdinfo
{
const
char
*
name
;
unsigned
numargs
;
int
(
*
func
)
(
char
*
*
arg
,
char
reply
[
REPLY_MAX
]
)
;
}
;
struct
cmdinfo
cmds
[
]
=
{
{
"ping"
,
0
,
do
_ping
}
,
{
"install"
,
4
,
do
_install
}
,
{
"dexopt"
,
3
,
do
_dexopt
}
,
{
"movedex"
,
2
,
do_move
_dex
}
,
{
"rmdex"
,
1
,
do_rm
_dex
}
,
{
"remove"
,
2
,
do
_remove
}
,
{
"rename"
,
2
,
do
_rename
}
,
{
"fixuid"
,
3
,
do
_fixuid
}
,
{
"freecache"
,
1
,
do_free
_cache
}
,
{
"rmcache"
,
2
,
do_rm
_cache
}
,
{
"getsize"
,
6
,
do_get
_size
}
,
{
"rmuserdata"
,
2
,
do_rm_user
_data
}
,
{
"movefiles"
,
0
,
do
_movefiles
}
,
{
"linklib"
,
3
,
do
_linklib
}
,
{
"mkuserdata"
,
3
,
do_mk_user
_data
}
,
{
"rmuser"
,
1
,
do_rm
_user
}
,
}
;
|
dexopt 对应的是 do_dexopt() 函数，do_dexopt() 又调用了 commands.c 里面的 dexopt() 函数。感觉离我们的目标不远了，继续看 commands.c。
commands.c
在 commands.c 中的 dexopt() 函数，我们看到此函数从 property 中获得 dalvik.vm.dexopt-flags 和 persist.sys.dalvik.vm.lib:
/* platform-specific flags affecting optimization and verification */ property_get("dalvik.vm.dexopt-flags", dexopt_flags, ""); ALOGV("dalvik.vm.dexopt_flags=%s\n", dexopt_flags); /* The command to run depend ones the value of persist.sys.dalvik.vm.lib */ property_get("persist.sys.dalvik.vm.lib", persist_sys_dalvik_vm_lib, "libdvm.so");
|
|
/* platform-specific flags affecting optimization and verification */
property_get
(
"dalvik.vm.dexopt-flags"
,
dexopt_flags
,
""
)
;
ALOGV
(
"dalvik.vm.dexopt_flags=%s\n"
,
dexopt_flags
)
;
/* The command to run depend ones the value of persist.sys.dalvik.vm.lib */
property_get
(
"persist.sys.dalvik.vm.lib"
,
persist_sys_dalvik_vm_lib
,
"libdvm.so"
)
;
|
dalvik.vm.dexopt-flags 暂时不知道是什么意思，persist.sys.dalvik.vm.lib 就是当前系统使用的运行时默认是 Dalvik VM，如果选择了 ART，应该就是 libart.so 了。
之后函数通过检查是否有 odex 文件来判断是否已经进行过 dexopt。然后进行一系列检查 chmod 和 chown。最后函数 fork 了一个子进程处理 dexopt：
pid_t pid; pid = fork(); if (pid == 0) { /* child -- drop privileges before continuing */ if (setgid(uid) != 0) { ALOGE("setgid(%d) failed in installd during dexopt\n", uid); exit(64); } if (setuid(uid) != 0) { ALOGE("setuid(%d) failed in installd during dexopt\n", uid); exit(65); } // drop capabilities struct __user_cap_header_struct capheader; struct __user_cap_data_struct capdata[2]; memset(&capheader, 0, sizeof(capheader)); memset(&capdata, 0, sizeof(capdata)); capheader.version = _LINUX_CAPABILITY_VERSION_3; if (capset(&capheader, &capdata[0]) < 0) { ALOGE("capset failed: %s\n", strerror(errno)); exit(66); } if (flock(out_fd, LOCK_EX | LOCK_NB) != 0) { ALOGE("flock(%s) failed: %s\n", out_path, strerror(errno)); exit(67); } if (strncmp(persist_sys_dalvik_vm_lib, "libdvm", 6) == 0) { run_dexopt(zip_fd, out_fd, apk_path, out_path, dexopt_flags); } else if (strncmp(persist_sys_dalvik_vm_lib, "libart", 6) == 0) { run_dex2oat(zip_fd, out_fd, apk_path, out_path, dexopt_flags); } else { exit(69); /* Unexpected persist.sys.dalvik.vm.lib value */ } exit(68); /* only get here on exec failure */ } else { res = wait_dexopt(pid, apk_path); if (res != 0) { ALOGE("dexopt in='%s' out='%s' res=%d\n", apk_path, out_path, res); goto fail; } }
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|
pid_t
pid
;
pid
=
fork
(
)
;
if
(
pid
==
0
)
{
/* child -- drop privileges before continuing */
if
(
setgid
(
uid
)
!=
0
)
{
ALOGE
(
"setgid(%d) failed in installd during dexopt\n"
,
uid
)
;
exit
(
64
)
;
}
if
(
setuid
(
uid
)
!=
0
)
{
ALOGE
(
"setuid(%d) failed in installd during dexopt\n"
,
uid
)
;
exit
(
65
)
;
}
// drop capabilities
struct
__user_cap_header_struct
capheader
;
struct
__user_cap_data_struct
capdata
[
2
]
;
memset
(
&
capheader
,
0
,
sizeof
(
capheader
)
)
;
memset
(
&
capdata
,
0
,
sizeof
(
capdata
)
)
;
capheader
.
version
=
_LINUX_CAPABILITY_VERSION_3
;
if
(
capset
(
&
capheader
,
&
capdata
[
0
]
)
<
0
)
{
ALOGE
(
"capset failed: %s\n"
,
strerror
(
errno
)
)
;
exit
(
66
)
;
}
if
(
flock
(
out_fd
,
LOCK_EX
|
LOCK_NB
)
!=
0
)
{
ALOGE
(
"flock(%s) failed: %s\n"
,
out_path
,
strerror
(
errno
)
)
;
exit
(
67
)
;
}
if
(
strncmp
(
persist_sys_dalvik_vm_lib
,
"libdvm"
,
6
)
==
0
)
{
run_dexopt
(
zip_fd
,
out_fd
,
apk_path
,
out_path
,
dexopt_flags
)
;
}
else
if
(
strncmp
(
persist_sys_dalvik_vm_lib
,
"libart"
,
6
)
==
0
)
{
run_dex2oat
(
zip_fd
,
out_fd
,
apk_path
,
out_path
,
dexopt_flags
)
;
}
else
{
exit
(
69
)
;
/* Unexpected persist.sys.dalvik.vm.lib value */
}
exit
(
68
)
;
/* only get here on exec failure */
}
else
{
res
=
wait_dexopt
(
pid
,
apk_path
)
;
if
(
res
!=
0
)
{
ALOGE
(
"dexopt in='%s' out='%s' res=%d\n"
,
apk_path
,
out_path
,
res
)
;
goto
fail
;
}
}
|
开始先 drop capabilities（关于 Linux capabilities: man capabilities）。最后比较 persist_sys_dalvik_vm_lib，如果是 libart 则调用 run_dex2oat()。Good，终于有头绪了，再看 run_dex2oat()：
static void run_dex2oat(int zip_fd, int oat_fd, const char* input_file_name, const char* output_file_name, const char* dexopt_flags) { static const char* DEX2OAT_BIN = "/system/bin/dex2oat"; static const int MAX_INT_LEN = 12; // '-'+10dig+'\0' -OR- 0x+8dig char zip_fd_arg[strlen("--zip-fd=") + MAX_INT_LEN]; char zip_location_arg[strlen("--zip-location=") + PKG_PATH_MAX]; char oat_fd_arg[strlen("--oat-fd=") + MAX_INT_LEN]; char oat_location_arg[strlen("--oat-name=") + PKG_PATH_MAX]; sprintf(zip_fd_arg, "--zip-fd=%d", zip_fd); sprintf(zip_location_arg, "--zip-location=%s", input_file_name); sprintf(oat_fd_arg, "--oat-fd=%d", oat_fd); sprintf(oat_location_arg, "--oat-location=%s", output_file_name); ALOGV("Running %s in=%s out=%s\n", DEX2OAT_BIN, input_file_name, output_file_name); execl(DEX2OAT_BIN, DEX2OAT_BIN, zip_fd_arg, zip_location_arg, oat_fd_arg, oat_location_arg, (char*) NULL); ALOGE("execl(%s) failed: %s\n", DEX2OAT_BIN, strerror(errno)); }
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|
static
void
run_dex2oat
(
int
zip_fd
,
int
oat_fd
,
const
char
*
input_file_name
,
const
char
*
output_file_name
,
const
char
*
dexopt_flags
)
{
static
const
char
*
DEX2OAT_BIN
=
"/system/bin/dex2oat"
;
static
const
int
MAX_INT_LEN
=
12
;
// '-'+10dig+'\0' -OR- 0x+8dig
char
zip_fd_arg
[
strlen
(
"--zip-fd="
)
+
MAX_INT_LEN
]
;
char
zip_location_arg
[
strlen
(
"--zip-location="
)
+
PKG_PATH_MAX
]
;
char
oat_fd_arg
[
strlen
(
"--oat-fd="
)
+
MAX_INT_LEN
]
;
char
oat_location_arg
[
strlen
(
"--oat-name="
)
+
PKG_PATH_MAX
]
;
sprintf
(
zip_fd_arg
,
"--zip-fd=%d"
,
zip_fd
)
;
sprintf
(
zip_location_arg
,
"--zip-location=%s"
,
input_file_name
)
;
sprintf
(
oat_fd_arg
,
"--oat-fd=%d"
,
oat_fd
)
;
sprintf
(
oat_location_arg
,
"--oat-location=%s"
,
output_file_name
)
;
ALOGV
(
"Running %s in=%s out=%s\n"
,
DEX2OAT_BIN
,
input_file_name
,
output_file_name
)
;
execl
(
DEX2OAT_BIN
,
DEX2OAT_BIN
,
zip_fd_arg
,
zip_location_arg
,
oat_fd_arg
,
oat_location_arg
,
(
char
*
)
NULL
)
;
ALOGE
(
"execl(%s) failed: %s\n"
,
DEX2OAT_BIN
,
strerror
(
errno
)
)
;
}
|
终于找到了，这就是调用 dex2oat 的地方，写的非常清楚。–zip-fd 是 apk 的 fd，–oat-fd 是输出 oat 的 fd。最终使用 execl() 执行 /system/bin/dex2oat 程序对 apk 进行编译。
三、总结
dex2oat 对所有 apk 进行编译并保存在 dalvik-cache 目录里。PMS 会持续扫描安装目录，如果有新的 App 安装则马上调用 dex2oat 进行编译。
最后，之前我们提到的 boot.art 我在 logcat 中找到了他的来源：
/system/bin/dex2oat --image=/data/dalvik-cache/system@
[email protected] --runtime-arg -Xms64m --runtime-arg -Xmx64m --dex-file=/system/framework/core-libart.jar --dex-file=/system/framework/conscrypt.jar --dex-file=/system/framework/okhttp.jar --dex-file=/system/framework/core-junit.jar --dex-file=/system/framework/bouncycastle.jar --dex-file=/system/framework/ext.jar --dex-file=/system/framework/framework.jar --dex-file=/system/framework/framework2.jar --dex-file=/system/framework/telephony-common.jar --dex-file=/system/framework/voip-common.jar --dex-file=/system/framework/mms-common.jar --dex-file=/system/framework/android.policy.jar --dex-file=/system/framework/services.jar --dex-file=/system/framework/apache-xml.jar --dex-file=/system/framework/webviewchromium.jar --oat-file=/data/dalvik-cache/system@
[email protected] --base=0x60000000 --image-classes-zip=/system/framework/framework.jar --image-classes=preloaded-classes
|
|
/
system
/
bin
/
dex2oat
--
image
=
/
data
/
dalvik
-
cache
/
system
@
framework
@
boot
.art
--
runtime
-
arg
-
Xms64m
--
runtime
-
arg
-
Xmx64m
--
dex
-
file
=
/
system
/
framework
/
core
-
libart
.jar
--
dex
-
file
=
/
system
/
framework
/
conscrypt
.jar
--
dex
-
file
=
/
system
/
framework
/
okhttp
.jar
--
dex
-
file
=
/
system
/
framework
/
core
-
junit
.jar
--
dex
-
file
=
/
system
/
framework
/
bouncycastle
.jar
--
dex
-
file
=
/
system
/
framework
/
ext
.jar
--
dex
-
file
=
/
system
/
framework
/
framework
.jar
--
dex
-
file
=
/
system
/
framework
/
framework2
.jar
--
dex
-
file
=
/
system
/
framework
/
telephony
-
common
.jar
--
dex
-
file
=
/
system
/
framework
/
voip
-
common
.jar
--
dex
-
file
=
/
system
/
framework
/
mms
-
common
.jar
--
dex
-
file
=
/
system
/
framework
/
android
.policy
.jar
--
dex
-
file
=
/
system
/
framework
/
services
.jar
--
dex
-
file
=
/
system
/
framework
/
apache
-
xml
.jar
--
dex
-
file
=
/
system
/
framework
/
webviewchromium
.jar
--
oat
-
file
=
/
data
/
dalvik
-
cache
/
system
@
framework
@
boot
.oat
--
base
=
0x60000000
--
image
-
classes
-
zip
=
/
system
/
framework
/
framework
.jar
--
image
-
classes
=
preloaded
-
classes
|
似乎是把所有 framework 的 jar 编译成 boot.art，在 dex2oat 的时候使用。还是有很多不理解的地方，相信在以后的分析中应该有更深入的理解。
附：相关代码链接
- PackageManagerService constructor: http://androidxref.com/4.4_r1/xref/frameworks/base/services/java/com/android/server/pm/PackageManagerService.java#1062
- scanDirLI(): http://androidxref.com/4.4_r1/xref/frameworks/base/services/java/com/android/server/pm/PackageManagerService.java#3445
- scanPackageLI(): http://androidxref.com/4.4_r1/xref/frameworks/base/services/java/com/android/server/pm/PackageManagerService.java#4103
- performDexOptLI(): http://androidxref.com/4.4_r1/xref/frameworks/base/services/java/com/android/server/pm/PackageManagerService.java#3860
- Installer.dexopt(): http://androidxref.com/4.4_r1/xref/frameworks/base/services/java/com/android/server/pm/Installer.java#204
- do_dexopt(): http://androidxref.com/4.4_r1/xref/frameworks/native/cmds/installd/installd.c#37
- dexopt(): http://androidxref.com/4.4_r1/xref/frameworks/native/cmds/installd/commands.c#653
- run_dex2oat(): http://androidxref.com/4.4_r1/xref/frameworks/native/cmds/installd/commands.c#run_dex2oat
This entry was posted in Android, Technology and tagged Android, ART Runtime, dex2oat on January 10, 2014
by Mingshen Sun.
