2020-01-09 adb架构分析（一）

基于firefly - RK3288系统源码分析。

第一部分：android adb编译和启动

首先看下system/core/adb下Android.mk

# Copyright 2005 The Android Open Source Project
#
# Android.mk for adb
#

LOCAL_PATH:= $(call my-dir)

# adb host tool
# =========================================================
include $(CLEAR_VARS)

# Default to a virtual (sockets) usb interface
USB_SRCS :=
EXTRA_SRCS :=

ifeq ($(HOST_OS),linux)
  USB_SRCS := usb_linux.c
  EXTRA_SRCS := get_my_path_linux.c
  LOCAL_LDLIBS += -lrt -ldl -lpthread
  LOCAL_CFLAGS += -DWORKAROUND_BUG6558362
endif

ifeq ($(HOST_OS),darwin)
  USB_SRCS := usb_osx.c
  EXTRA_SRCS := get_my_path_darwin.c
  LOCAL_LDLIBS += -lpthread -framework CoreFoundation -framework IOKit -framework Carbon
endif

ifeq ($(HOST_OS),freebsd)
  USB_SRCS := usb_libusb.c
  EXTRA_SRCS := get_my_path_freebsd.c
  LOCAL_LDLIBS += -lpthread -lusb
endif

ifeq ($(HOST_OS),windows)
  USB_SRCS := usb_windows.c
  EXTRA_SRCS := get_my_path_windows.c
  EXTRA_STATIC_LIBS := AdbWinApi
  ifneq ($(strip $(USE_CYGWIN)),)
    # Pure cygwin case
    LOCAL_LDLIBS += -lpthread -lgdi32
  endif
  ifneq ($(strip $(USE_MINGW)),)
    # MinGW under Linux case
    LOCAL_LDLIBS += -lws2_32 -lgdi32
    USE_SYSDEPS_WIN32 := 1
  endif
  LOCAL_C_INCLUDES += development/host/windows/usb/api/
endif

LOCAL_SRC_FILES := \
    adb.c \
    console.c \
    transport.c \
    transport_local.c \
    transport_usb.c \
    commandline.c \
    adb_client.c \
    adb_auth_host.c \
    sockets.c \
    services.c \
    file_sync_client.c \
    $(EXTRA_SRCS) \
    $(USB_SRCS) \
    usb_vendors.c

LOCAL_C_INCLUDES += external/openssl/include

ifneq ($(USE_SYSDEPS_WIN32),)
  LOCAL_SRC_FILES += sysdeps_win32.c
else
  LOCAL_SRC_FILES += fdevent.c
endif

LOCAL_CFLAGS += -O2 -g -DADB_HOST=1 -Wall -Wno-unused-parameter -Werror
LOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE
LOCAL_MODULE := adb
LOCAL_MODULE_TAGS := debug

LOCAL_STATIC_LIBRARIES := libzipfile libunz libcrypto_static $(EXTRA_STATIC_LIBS)
ifeq ($(USE_SYSDEPS_WIN32),)
    LOCAL_STATIC_LIBRARIES += libcutils
endif

include $(BUILD_HOST_EXECUTABLE)

$(call dist-for-goals,dist_files sdk,$(LOCAL_BUILT_MODULE))

ifeq ($(HOST_OS),windows)
$(LOCAL_INSTALLED_MODULE): \
    $(HOST_OUT_EXECUTABLES)/AdbWinApi.dll \
    $(HOST_OUT_EXECUTABLES)/AdbWinUsbApi.dll
endif

# adb守护进程
# adbd device daemon
# =========================================================

include $(CLEAR_VARS)

LOCAL_SRC_FILES := \
    adb.c \
    fdevent.c \
    transport.c \
    transport_local.c \
    transport_usb.c \
    adb_auth_client.c \
    sockets.c \
    services.c \
    file_sync_service.c \
    jdwp_service.c \
    framebuffer_service.c \
    remount_service.c \
    disable_verity_service.c \
    usb_linux_client.c

LOCAL_CFLAGS := -O2 -g -DADB_HOST=0 -Wall -Wno-unused-parameter -Werror
LOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE

ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
LOCAL_CFLAGS += -DALLOW_ADBD_ROOT=1
endif

ifneq (,$(filter userdebug,$(TARGET_BUILD_VARIANT)))
LOCAL_CFLAGS += -DALLOW_ADBD_DISABLE_VERITY=1
endif

LOCAL_MODULE := adbd

LOCAL_FORCE_STATIC_EXECUTABLE := true
LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT_SBIN)
LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_SBIN_UNSTRIPPED)
LOCAL_C_INCLUDES += system/extras/ext4_utils system/core/fs_mgr/include

LOCAL_STATIC_LIBRARIES := liblog \
    libfs_mgr \
    libcutils \
    libc \
    libmincrypt \
    libselinux \
    libext4_utils_static

include $(BUILD_EXECUTABLE)

# 
# adb host tool for device-as-host
# =========================================================
ifneq ($(SDK_ONLY),true)
include $(CLEAR_VARS)

LOCAL_SRC_FILES := \
    adb.c \
    console.c \
    transport.c \
    transport_local.c \
    transport_usb.c \
    commandline.c \
    adb_client.c \
    adb_auth_host.c \
    sockets.c \
    services.c \
    file_sync_client.c \
    get_my_path_linux.c \
    usb_linux.c \
    usb_vendors.c \
    fdevent.c

LOCAL_CFLAGS := \
    -O2 \
    -g \
    -DADB_HOST=1 \
    -DADB_HOST_ON_TARGET=1 \
    -Wall -Wno-unused-parameter -Werror \
    -D_XOPEN_SOURCE \
    -D_GNU_SOURCE

LOCAL_C_INCLUDES += external/openssl/include

LOCAL_MODULE := adb

LOCAL_STATIC_LIBRARIES := libzipfile libunz libcutils liblog

LOCAL_SHARED_LIBRARIES := libcrypto

include $(BUILD_EXECUTABLE)
endif

编译后生成三个文件，文件生成目录分别是在：
① out/host/linux-x86/bin/adb
② out/target/product/rk3288_box/root/sbin/adbd
③ out/target/product/rk3288_box/system/bin/adb

init.rc中启动adb：

# adbd is controlled via property triggers in init.<platform>.usb.rc
service adbd /sbin/adbd --root_seclabel=u:r:su:s0
    class core
    socket adbd stream 660 system system
    disabled
    seclabel u:r:adbd:s0
    # 对于进程，u代表user，r代表role，进程貌似u:r都是固定的，adbd代表进程的类型，s0对应的一个安全等级

# adbd on at boot in emulator
on property:ro.kernel.qemu=1
    start adbd

init.rk30board.usb.rc中定义：

on property:sys.usb.config=mtp,adb
    write /sys/class/android_usb/android0/enable 0
    write /sys/class/android_usb/android0/idVendor 2207
    write /sys/class/android_usb/android0/idProduct 0011
    write /sys/class/android_usb/android0/functions ${sys.usb.config}
    write /sys/class/android_usb/android0/enable 1
    start adbd
    setprop sys.usb.state ${sys.usb.config}