Android P Image编译

浅浅的花香味﹌ 2023-05-30 08:42 15阅读 0赞

最近尝试着修改Android P的编译脚本，目的是为了将系统源码和BSP源码分开编译。

由于厂家定制，Android内核的源码一般都在vendor目录下，本文尝试去掉vendor中的kernel源码，还能正常编译Android其他源码，便于做系统开发或者app发开，不依赖kernel源码编译。

相关源码：  
build/make/core/Makefile  
device/fsl/imx8q/mek\_8q/AndroidBoard.mk  
device/fsl/imx8q/mek\_8q/BoardConfig.mk  
device/fsl/common/build/dtbo.mk  
system/core/fs\_mgr/fs\_mgr\_avb.cpp  
vendor\\nxp-opensource\\uboot-imx\\lib\\avb\\libavb\\avb\_slot\_verify.c  
vendor\\nxp-opensource\\uboot-imx\\lib\\avb\\libavb\\avb\_vbmeta\_image.h

升级镜像文件包括：  
boot.img  
bootloader-imx8qm.img  
bootloader-imx8qm-xen.img  
dtbo-imx8qm.img  
dtbo-imx8qm-xen.img  
vendor.img  
partition-table-28GB.img  
system.img  
spl-imx8qm.bin  
libusb-1.0.dll  
spl-imx8qm-xen.bin  
u-boot-imx8qm-xen-dom0.imx  
uuu.exe  
uuu\_imx\_android\_flash.bat  
vbmeta-imx8qm.img  
vbmeta-imx8qm-xen.img

### device/fsl/imx8q/mek\_8q/AndroidBoard.mk ###

AndroidBoard.mk中去掉kernel和uboot的编译脚本mk文件：

LOCAL_PATH := $(call my-dir)
    # build without kernel and uboot,rm by sunxiaolin 20191021
    #include device/fsl/common/build/kernel.mk
    #include device/fsl/common/build/uboot.mk
    include device/fsl/common/build/dtbo.mk
    include device/fsl/common/build/imx-recovery.mk
    include device/fsl/common/build/gpt.mk
    include $(LOCAL_PATH)/AndroidUboot.mk
    include $(FSL_PROPRIETARY_PATH)/fsl-proprietary/media-profile/media-profile.mk
    ifneq ($(PRODUCT_IMX_CAR),true)
    include $(FSL_PROPRIETARY_PATH)/fsl-proprietary/sensor/fsl-sensor.mk
    endif

### device/fsl/common/build/dtbo.mk ###

继续去掉dtbo的编译，因为dtbo.mk中包含了vbmeta-imx8qm.img的编译，而且vbmeta需要跟系统镜像system.img放在一起编译。dtbo-imx8qm.img则需要跟kernel，uboot部分一起编译。

1、去掉kernel\_imx相关的编译内容  
2、去掉dtboimage: $(BOARD\_PREBUILT\_DTBOIMAGE)相关的编译内容  
3、修改vbmeta的编译内容，主要去掉

*  去掉$(BOARD\_PREBUILT\_DTBOIMAGE)
 *  去掉DTBO\_IMG=`echo $(PRODUCT_OUT)/dtbo-$${DTS_PLATFORM}.img`; \\
 *  去掉RECOVERY\_IMG=`echo $(PRODUCT_OUT)/recovery-$${DTS_PLATFORM}.img`; \\
 *  去掉–include\_descriptors\_from\_image $$DTBO\_IMG \\
 *  去掉–include\_descriptors\_from\_image $$DTBO\_IMG \\
 *  去掉–include\_descriptors\_from\_image $$RECOVERY\_IMG \\

### device/fsl/imx8q/mek\_8q/BoardConfig.mk ###

1、去掉所有vendor/目录的拷贝操作，例如：PRODUCT\_COPY\_FILES +=  
device/fsl/imx8q/etc/wifi/fw\_bcmdhd.bin:vendor/etc/wifi/fw\_bcmdhd.bin  
2、去掉所有KERNEL\_OUT目录的拷贝操作，例如：

ifeq ($(PRODUCT_IMX_CAR_M4),true)
    BOARD_VENDOR_KERNEL_MODULES += \
                                $(KERNEL_OUT)/drivers/hid/usbhid/usbhid.ko \

BOARD_RECOVERY_KERNEL_MODULES += \
    							$(KERNEL_OUT)/drivers/gpu/drm/bridge/ds90ub947.ko \
    endif

### build/make/core/Makefile ###

build/make/core/Makefile文件是整个Android编译的核心文件。

1、去掉boot.img部分的编译内容，例如：  
\#INSTALLED\_BOOTIMAGE\_TARGET := $(PRODUCT\_OUT)/boot.img  
2、去掉vendor.img部分的编译内容。例如：  
\#BUILT\_VENDORIMAGE\_TARGET := $(PRODUCT\_OUT)/vendor.img  
3、去掉dtbo.img部分的编译内容。例如：  
\#INSTALLED\_DTBOIMAGE\_TARGET := $(PRODUCT\_OUT)/dtbo.img  
4、去掉avb校验，注释一下部分的代码：

#ifdef BOARD_AVB_BOOT_KEY_PATH
    #$(eval $(call check-and-set-avb-chain-args,BOOT))
    #else
    #INTERNAL_AVB_MAKE_VBMETA_IMAGE_ARGS += \
    #    --include_descriptors_from_image $(INSTALLED_BOOTIMAGE_TARGET)
    #endif

修改了以上这么多之后，系统可以分开编译过。

分开之后，Android系统打包升级Image包括:  
partition-table-28GB.img  
system.img  
spl-imx8qm.bin  
libusb-1.0.dll  
spl-imx8qm-xen.bin  
u-boot-imx8qm-xen-dom0.imx  
uuu.exe  
uuu\_imx\_android\_flash.bat  
vbmeta-imx8qm.img  
vbmeta-imx8qm-xen.img

Android系统内核打包升级Image包括:  
boot.img  
bootloader-imx8qm.img  
bootloader-imx8qm-xen.img  
dtbo-imx8qm.img  
dtbo-imx8qm-xen.img  
vendor.img

使用uuu.exe工具进行正常升级，发现系统起不来，报错：

Read public key error
    AVB TIPC client not initialized

vendor.img avb校验失败：![vendor.img avb校验失败][vendor.img avb]  
avb主要是bootloader的校验和vendor的校验，校验失败后系统启动不了。

### avb校验 ###

vendor\\nxp-opensource\\uboot-imx\\lib\\avb\\libavb\\avb\_slot\_verify.c  
vendor\\nxp-opensource\\uboot-imx\\lib\\avb\\libavb\\avb\_vbmeta\_image.h

#### bootloader校验 ####

avb\_vbmeta\_image.h中定义了

/* Flags for the vbmeta image. * * AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED: If this flag is set, * hashtree image verification will be disabled. * * AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED: If this flag is set, * verification will be disabled and descriptors will not be parsed. */
    typedef enum { 
      AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED = (1 << 0),
      AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED = (1 << 1)
    } AvbVBMetaImageFlags;

位运算：  
(1 << 0)，即0x00000001  
(1 << 1)，即0x00000010

这两个flag分别表示是否使能dm-verity和verification功能，默认是会开启这两个验证功能。

### 禁止avb校验功能，即verification功能；禁止dm-verity ###

vendor\\nxp-opensource\\uboot-imx\\lib\\avb\\libavb\\avb\_slot\_verify.c

static AvbSlotVerifyResult load_and_verify_vbmeta(）{ 
    	//省略一部分代码
    	//...
    	
    	/* If verification has been disabled by setting a bit in the image, * we're done... except that we need to load the entirety of the * requested partitions. */
    	 //修改vbmeta_header.flags标志为AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED
    	vbmeta_header.flags = AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED;
    	if (vbmeta_header.flags & AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED) { 
    	  AvbSlotVerifyResult sub_ret;
    	  avb_debugv(
    	      full_partition_name, ": VERIFICATION_DISABLED bit is set.\n", NULL);
    	  /* If load_requested_partitions() fail it is always a fatal * failure (e.g. ERROR_INVALID_ARGUMENT, ERROR_OOM, etc.) rather * than recoverable (e.g. one where result_should_continue() * returns true) and we want to convey that error. */
    	  sub_ret = load_requested_partitions(
    	      ops, requested_partitions, ab_suffix, slot_data);
    	  if (sub_ret != AVB_SLOT_VERIFY_RESULT_OK) { 
    	    ret = sub_ret;
    	  }
    	  goto out;
    	}
    
    	//省略一部分代码
    	//...
    
         /* Compare the flags for top-level VBMeta struct with flags in * the command-line descriptor so command-line snippets only * intended for a certain mode (dm-verity enabled/disabled) * are skipped if applicable. */
        apply_cmdline = true;
         //修改toplevel_vbmeta_flags标志为AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED
        toplevel_vbmeta_flags = AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED;
        if (toplevel_vbmeta_flags & AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED) { 
          if (kernel_cmdline_desc.flags &
              AVB_KERNEL_CMDLINE_FLAGS_USE_ONLY_IF_HASHTREE_NOT_DISABLED) { 
            apply_cmdline = false;
          }
        } else { 
          if (kernel_cmdline_desc.flags &
              AVB_KERNEL_CMDLINE_FLAGS_USE_ONLY_IF_HASHTREE_DISABLED) { 
            apply_cmdline = false;
          }
        }
    }

AvbSlotVerifyResult avb_slot_verify(）{ 
    	//省略一部分代码
    	//...
    	
        /* If verification is disabled, we are done ... we specifically * don't want to add any androidboot.* options since verification * is disabled. */
         //add by sunxiaolin 20191107
         //修改toplevel_vbmeta.flags标志为AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED
         toplevel_vbmeta.flags = (1 << 1);
        if (toplevel_vbmeta.flags & AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED) { 
          /* Since verification is disabled we didn't process any * descriptors and thus there's no cmdline... so set root= such * that the system partition is mounted. */
          avb_assert(slot_data->cmdline == NULL);
          slot_data->cmdline =
              avb_strdup("root=PARTUUID=$(ANDROID_SYSTEM_PARTUUID)");
          if (slot_data->cmdline == NULL) { 
            ret = AVB_SLOT_VERIFY_RESULT_ERROR_OOM;
            goto fail;
          }
        } else { 
          /* Add options - any failure in avb_append_options() is either an * I/O or OOM error. */
          AvbSlotVerifyResult sub_ret = avb_append_options(ops,
                                                           slot_data,
                                                           &toplevel_vbmeta,
                                                           algorithm_type,
                                                           hashtree_error_mode);
          if (sub_ret != AVB_SLOT_VERIFY_RESULT_OK) { 
            ret = sub_ret;
            goto fail;
          }
        }
        
    	//省略一部分代码
    	//...
    }

禁止dm-verity还有一种方法，即在升级成功后，使用：  
adb disable-verity  
重启生效。

还需要修改vendor校验

#### vendor校验 ####

system/core/fs\_mgr/fs\_mgr\_avb.cpp

FsManagerAvbUniquePtr FsManagerAvbHandle::DoOpen(FsManagerAvbOps* avb_ops) { 
    	//省略一部分代码
    	//...
    
        // Checks whether FLAGS_VERIFICATION_DISABLED is set:
        // - Only the top-level vbmeta struct is read.
        // - vbmeta struct in other partitions are NOT processed, including AVB HASH descriptor(s)
        // and AVB HASHTREE descriptor(s).
        AvbVBMetaImageHeader vbmeta_header;
        avb_vbmeta_image_header_to_host_byte_order(
            (AvbVBMetaImageHeader*)avb_handle->avb_slot_data_->vbmeta_images[0].vbmeta_data,
            &vbmeta_header);
        //将vbmeta_header.flags设置为：AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED
        vbmeta_header.flags = AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED;
        bool verification_disabled =
            ((AvbVBMetaImageFlags)vbmeta_header.flags & AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED);
    
        if (verification_disabled) { 
            avb_handle->status_ = kAvbHandleVerificationDisabled;
        } else { 
            // Verifies vbmeta structs against the digest passed from bootloader in kernel cmdline.
            std::unique_ptr<FsManagerAvbVerifier> avb_verifier = FsManagerAvbVerifier::Create();
            if (!avb_verifier) { 
                LERROR << "Failed to create FsManagerAvbVerifier";
                return nullptr;
            }
            if (!avb_verifier->VerifyVbmetaImages(*avb_handle->avb_slot_data_)) { 
                LERROR << "VerifyVbmetaImages failed";
                return nullptr;
            }
    
            // Checks whether FLAGS_HASHTREE_DISABLED is set.
            bool hashtree_disabled =
                ((AvbVBMetaImageFlags)vbmeta_header.flags & AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED);
            if (hashtree_disabled) { 
                avb_handle->status_ = kAvbHandleHashtreeDisabled;
            }
        }
    
    	//省略一部分代码
    	//...
    }

[vendor.img avb]: https://img-blog.csdnimg.cn/20191108144925425.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1N1bnhpYW9saW4yMDE2,size_16,color_FFFFFF,t_70