bl        kmain

/* called from crt0.S */
void kmain(void) __NO_RETURN __EXTERNALLY_VISIBLE;
void kmain(void)
{// get us into some sort of thread context
    thread_init_early();          //初始化线程上下文#ifdef FEATURE_AFTER_SALE_LOG_LK// do console early init
    console_init_early();          //初始化控制台
#endif// early arch stuff
    arch_early_init();          //架构初始化，如关闭cache，使能mmu// do any super early platform initialization
    platform_early_init();         //平台早期初始化// do any super early target initialization
    target_early_init();               //目标设备早期初始化,初始化串口dprintf(INFO, "welcome to lk\n\n");bs_set_timestamp(BS_BL_START);           // deal with any static constructorsdprintf(SPEW, "calling constructors\n");call_constructors();// bring up the kernel heapdprintf(SPEW, "initializing heap\n");heap_init();                      //堆初始化__stack_chk_guard_setup();// initialize the threading systemdprintf(SPEW, "initializing threads\n");thread_init();                     //线程初始化#ifdef FEATURE_AFTER_SALE_LOG_LK// initialize the console layer
dprintf(SPEW, "initializing console layer\n");console_init();           //初始化控制台
#endif// initialize the dpc systemdprintf(SPEW, "initializing dpc\n");dpc_init();                        //lk系统控制器初始化// initialize kernel timersdprintf(SPEW, "initializing timers\n");timer_init();                //kernel时钟初始化#if (!ENABLE_NANDWRITE)// create a thread to complete system initializationdprintf(SPEW, "creating bootstrap completion thread\n");thread_resume(thread_create("bootstrap2", &bootstrap2, NULL, DEFAULT_PRIORITY, DEFAULT_STACK_SIZE));     //创建一个线程初始化系统// enable interrupts
    exit_critical_section();       //使能中断// become the idle thread
    thread_become_idle();      //本线程切换成idle线程，idle为空闲线程，当没有更高优先级的线程时才执行
#elsebootstrap_nandwrite();
#endif
}

bootable/bootloader/lk/arch/arm/arch.c
void arch_early_init(void)
{/* turn off the cache */arch_disable_cache(UCACHE);      //关闭cache/* set the vector base to our exception vectors so we dont need to double map at 0 */
#if ARM_CPU_CORTEX_A8set_vector_base(MEMBASE);       //设置异常向量基地址
#endif#if ARM_WITH_MMUarm_mmu_init();       //使能mmu#endif/* turn the cache back on */arch_enable_cache(UCACHE);      //打开cache#if ARM_WITH_NEON/* enable cp10 and cp11 */uint32_t val;__asm__ volatile("mrc    p15, 0, %0, c1, c0, 2" : "=r" (val));val |= (3<<22)|(3<<20);__asm__ volatile("mcr    p15, 0, %0, c1, c0, 2" :: "r" (val));isb();/* set enable bit in fpexc */__asm__ volatile("mrc  p10, 7, %0, c8, c0, 0" : "=r" (val));val |= (1<<30);__asm__ volatile("mcr  p10, 7, %0, c8, c0, 0" :: "r" (val));
#endif#if ARM_CPU_CORTEX_A8/* enable the cycle count register */uint32_t en;__asm__ volatile("mrc    p15, 0, %0, c9, c12, 0" : "=r" (en));en &= ~(1<<3); /* cycle count every cycle */en |= 1; /* enable all performance counters */__asm__ volatile("mcr    p15, 0, %0, c9, c12, 0" :: "r" (en));/* enable cycle counter */en = (1<<31);__asm__ volatile("mcr    p15, 0, %0, c9, c12, 1" :: "r" (en));
#endif
}

bootable\bootloader\lk\platform\msm8952\platform.cvoid platform_early_init(void)
{board_init(); //主板初始化platform_clock_init(); //时钟初始化
    qgic_init();qtimer_init();
}

static int bootstrap2(void *arg)
{dprintf(SPEW, "top of bootstrap2()\n");arch_init();     //架构初始化，此函数为空，什么都没做// XXX put this somewhere else
#if WITH_LIB_BIObio_init();
#endif
#if WITH_LIB_FSfs_init();
#endif// initialize the rest of the platformdprintf(SPEW, "initializing platform\n");platform_init();           // 平台初始化,不同的平台要做的事情不一样，可以是初始化系统时钟,超频等// initialize the targetdprintf(SPEW, "initializing target\n");target_init();            //目标设备初始化,主要初始化Flash,整合分区表等dprintf(SPEW, "calling apps_init()\n");apps_init();           //应用功能初始化，主要调用boot_init，启动kernel，加载boot/recovery镜像等return 0;
}

bootable/bootloader/lk/app/app.cvoid apps_init(void)
{const struct app_descriptor *app;/* call all the init routines */for (app = &__apps_start; app != &__apps_end; app++) {if (app->init)app->init(app);}/* start any that want to start on boot */for (app = &__apps_start; app != &__apps_end; app++) {if (app->entry && (app->flags & APP_FLAG_DONT_START_ON_BOOT) == 0) {start_app(app);}}
}

bootable/bootloader/lk/app/aboot/aboot.cvoid aboot_init(const struct app_descriptor *app)
{unsigned reboot_mode = 0;unsigned restart_reason = 0;unsigned hard_reboot_mode = 0;bool boot_into_fastboot = false;uint8_t pon_reason = pm8950_get_pon_reason();                   //pm8950_get_pon_reason()  获取开机原因/* Setup page size information for nv storage */if (target_is_emmc_boot())             //检测是emmc还是flash存储，并设置页大小，一般是2048{page_size = mmc_page_size();page_mask = page_size - 1;}else{page_size = flash_page_size();page_mask = page_size - 1;}ASSERT((MEMBASE + MEMSIZE) > MEMBASE);           //断言，如果内存基地址+内存大小小于内存基地址，则直接终止错误read_device_info(&device);                 //从devinfo分区表read data到device结构体            read_allow_oem_unlock(&device);            //devinfo分区里记录了unlock状态，从device中读取此信息/* Display splash screen if enabled */if (!check_alarm_boot()) {           dprintf(SPEW, "Display Init: Start\n");target_display_init(device.display_panel);          //显示splash，Splash也就是应用程序启动之前先启动一个画面,上面简单的介绍应用程序的厂商,厂商的LOGO,名称和版本等信息,多为一张图片     dprintf(SPEW, "Display Init: Done\n");}#ifdef FEATURE_LOW_POWER_DISP_LKif(is_low_voltage) {           //如果电量低，则显示关机动画，并关闭设备mdelay(2000);//target_uninit();
        target_display_shutdown();shutdown_device();}
#endifis_alarm_boot = check_alarm_boot();                           //检测开机原因是否是由于关机闹钟导致target_serialno((unsigned char *) sn_buf);dprintf(SPEW,"serial number: %s\n",sn_buf);memset(display_panel_buf, '\0', MAX_PANEL_BUF_SIZE);      /** Check power off reason if user force reset,* if yes phone will do normal boot.*/if (is_user_force_reset())                                        //如果强制重启，直接进入normal_bootgoto normal_boot;dprintf(ALWAYS, "pon_reason=0x%02x\n", pon_reason);/* Check if we should do something other than booting up */if ( (pon_reason & USB_CHG)                 //启动原因是插上USB，并且用户同时按住了音量上下键，进入下载模式&& (keys_get_state(KEY_VOLUMEUP) && keys_get_state(KEY_VOLUMEDOWN))){display_dloadimage_on_screen();          //显示下载模式图片volume_keys_init();             //初始化音量按键int i = 0;int j = 0;int k = 0;dload_flag = 1 ;while(1)            //进入下载模式后，通过不同的按键组合进入不同的模式，下面的代码逻辑很简单，就不介绍了{thread_sleep(200);//dprintf(ALWAYS, "in while circle\n");if ( check_volume_up_key() && !check_volume_down_key() && !check_power_key() ){/* Hold volume_up_key 3 sec to download mode, if not enough, need to hold another 3 sec. */for(i = 0;i < 15;++i){thread_sleep(200);if (!check_volume_up_key()){dprintf(ALWAYS, "press volume_up not enough time\n");break;}}if(i == 15){break;}}else if (check_power_key() && !check_volume_up_key() && !check_volume_down_key()){/* Hold power_key 1 sec to normal boot, if not enough, need to hold another 1 sec. */for(j = 0;j < 5;++j){thread_sleep(200);if (!check_power_key()){//dprintf(ALWAYS, "press power_key not enough time\n");break;}}if(j == 5){goto normal_boot;}}else if (!check_volume_down_key() && !check_volume_up_key() && !check_power_key()){/* Hold no key and go to normal boot 30 sec later. */for(k = 0;k < 150;++k){thread_sleep(200);if (check_power_key() || check_volume_up_key()){//dprintf(ALWAYS, "press nothing\n");break;}}if(k == 150){//dprintf(ALWAYS, "goto normal_boot\n");goto normal_boot;}}}dprintf(CRITICAL,"dload mode key sequence detected\n");if (set_download_mode(EMERGENCY_DLOAD)){dprintf(CRITICAL,"dload mode not supported by target\n");}else{reboot_device(DLOAD);dprintf(ALWAYS,"Failed to reboot into dload mode\n");}boot_into_fastboot = true;         //下载模式本质上是进入fastboot}if (!boot_into_fastboot)    //如果不是通过usb+上下键进入下载模式{if (keys_get_state(KEY_HOME) || (keys_get_state(KEY_VOLUMEUP) && !keys_get_state(KEY_VOLUMEDOWN))) //上键+电源键 进入recovery模式
        {boot_into_recovery = 1;struct recovery_message msg;strcpy(msg.recovery, "recovery\n--show_text");}if (!boot_into_recovery &&(keys_get_state(KEY_BACK) || (keys_get_state(KEY_VOLUMEDOWN) && !keys_get_state(KEY_VOLUMEUP))))   //下键+back键进入fastboot模式，我的手机是有back实体键的boot_into_fastboot = true;}reboot_mode = check_reboot_mode();                          //检测开机原因，并且修改相应的标志位hard_reboot_mode = check_hard_reboot_mode();if (reboot_mode == RECOVERY_MODE ||hard_reboot_mode == RECOVERY_HARD_RESET_MODE) {boot_into_recovery = 1;} else if(reboot_mode == FASTBOOT_MODE ||hard_reboot_mode == FASTBOOT_HARD_RESET_MODE) {boot_into_fastboot = true;} else if(reboot_mode == ALARM_BOOT ||hard_reboot_mode == RTC_HARD_RESET_MODE) {boot_reason_alarm = true;}else if (reboot_mode == DM_VERITY_ENFORCING){device.verity_mode = 1;write_device_info(&device);} else if(reboot_mode == DM_VERITY_LOGGING) {device.verity_mode = 0;write_device_info(&device);} else if(reboot_mode == DM_VERITY_KEYSCLEAR) {if(send_delete_keys_to_tz())ASSERT(0);}normal_boot:if(dload_flag){display_image_on_screen();                 //显示界面，上面提到过}if (!boot_into_fastboot)  //如果不是fastboot模式{if (target_is_emmc_boot()){if(emmc_recovery_init())dprintf(ALWAYS,"error in emmc_recovery_init\n");if(target_use_signed_kernel()){if((device.is_unlocked) || (device.is_tampered)){#ifdef TZ_TAMPER_FUSEset_tamper_fuse_cmd();#endif#if USE_PCOM_SECBOOTset_tamper_flag(device.is_tampered);#endif}}boot_linux_from_mmc();     //程序会跑到这里，又一个重点内容，下面会独立分析这个函数。}else{recovery_init();#if USE_PCOM_SECBOOTif((device.is_unlocked) || (device.is_tampered))set_tamper_flag(device.is_tampered);#endifboot_linux_from_flash();}dprintf(CRITICAL, "ERROR: Could not do normal boot. Reverting ""to fastboot mode.\n");}

    //下面的代码是fastboot的准备工作，从中可以看出，进入fastboot模式是不启动kernel的

/* We are here means regular boot did not happen. Start fastboot. *//* register aboot specific fastboot commands */aboot_fastboot_register_commands();     //注册fastboot命令，建议看下此函数的源码，此函数是fastboot支持的命令，如flash、erase等等/* dump partition table for debug info */partition_dump();/* initialize and start fastboot */fastboot_init(target_get_scratch_address(), target_get_max_flash_size());     //初始化fastboot
#if FBCON_DISPLAY_MSGdisplay_fastboot_menu_thread();         //显示fastboot界面
#endif
}

devinfo     Device information including:iis_unlocked, is_tampered, is_verified, charger_screen_enabled, display_panel, bootloader_version, radio_versionAll these attirbutes are set based on some specific conditions and written on devinfo partition.
devinfo是一个独立的分区，里面存放了下面的一些信息，上面是高通对这个分区的介绍。
struct device_info
{unsigned char magic[DEVICE_MAGIC_SIZE];bool is_unlocked;bool is_tampered;bool is_verified;bool charger_screen_enabled;char display_panel[MAX_PANEL_ID_LEN];char bootloader_version[MAX_VERSION_LEN];char radio_version[MAX_VERSION_LEN];
};

int boot_linux_from_mmc(void)
{struct boot_img_hdr *hdr = (void*) buf;       //************buf和hdr指向相同的地址，可以理解为buf就是hdrstruct boot_img_hdr *uhdr;unsigned offset = 0;int rcode;unsigned long long ptn = 0;int index = INVALID_PTN;unsigned char *image_addr = 0;unsigned kernel_actual;unsigned ramdisk_actual;unsigned imagesize_actual;unsigned second_actual = 0;unsigned int dtb_size = 0;unsigned int out_len = 0;unsigned int out_avai_len = 0;unsigned char *out_addr = NULL;uint32_t dtb_offset = 0;unsigned char *kernel_start_addr = NULL;unsigned int kernel_size = 0;int rc;#if DEVICE_TREE                    struct dt_table *table;struct dt_entry dt_entry;unsigned dt_table_offset;uint32_t dt_actual;uint32_t dt_hdr_size;unsigned char *best_match_dt_addr = NULL;
#endifstruct kernel64_hdr *kptr = NULL;if (check_format_bit())                        //查找bootselect分区，查看分区表，没有此分区，所以返回值为falseboot_into_recovery = 1;if (!boot_into_recovery) {                     //此时有两种可能，正常开机/进入ffbm工厂测试模式，进入工厂测试模式是正行启动，但是向kernel传参会多一个字符串"androidboot.mode='ffbm_mode_string'" memset(ffbm_mode_string, '\0', sizeof(ffbm_mode_string));     //ffbm_mode_string = ""rcode = get_ffbm(ffbm_mode_string, sizeof(ffbm_mode_string));  //从misc分区0地址中读取sizeof(ffbm_mode_string)的内容，如果内容是"ffbm-"，返回1，否则返回0if (rcode <= 0) {boot_into_ffbm = false;if (rcode < 0)dprintf(CRITICAL,"failed to get ffbm cookie");} elseboot_into_ffbm = true;} else                                     //boot_into_recovery=trueboot_into_ffbm = false;uhdr = (struct boot_img_hdr *)EMMC_BOOT_IMG_HEADER_ADDR;           //uhdr指向boot分区header地址，header是什么东西，下面会详细介绍if (!memcmp(uhdr->magic, BOOT_MAGIC, BOOT_MAGIC_SIZE)) {      //检查uhdr->magic 是否等于 "ANDROID!",不知到为什么要这么做，觉的没有什么作用dprintf(INFO, "Unified boot method!\n");hdr = uhdr;goto unified_boot;}if (!boot_into_recovery) {    //如果不是recovery模式，可能是正常启动或者进入ffbm，再次生命ffbm和正常启动流程一样启动kernel，只是kernel起来以后，init.c文件会读取是否有"ffbm-"index = partition_get_index("boot");         //读取boot分区ptn = partition_get_offset(index);      //读取boot分区的偏移量if(ptn == 0) {dprintf(CRITICAL, "ERROR: No boot partition found\n");return -1;}}else {index = partition_get_index("recovery");        //进入recovery模式，读取recovery分区，并获得recovery分区的偏移量。recovery.img和boot.img的组成是一样的，下面有介绍ptn = partition_get_offset(index);if(ptn == 0) {dprintf(CRITICAL, "ERROR: No recovery partition found\n");return -1;}}/* Set Lun for boot & recovery partitions */mmc_set_lun(partition_get_lun(index));        if (mmc_read(ptn + offset, (uint32_t *) buf, page_size)) {                 //从boot/recovery分区读取1字节的内容到buf(hdr)中，我们知道在boot/recovery中开始的1字节存放的是hdr的内容，下面有详细的介绍。dprintf(CRITICAL, "ERROR: Cannot read boot image header\n");return -1;}if (memcmp(hdr->magic, BOOT_MAGIC, BOOT_MAGIC_SIZE)) {                   //上面已经从boot/recovery分区读取了header到hdr，这里对比magic是否等于"ANDROID！",如果不是，则表明读取的header是错误的，也算是校验吧dprintf(CRITICAL, "ERROR: Invalid boot image header\n");return -1;}if (hdr->page_size && (hdr->page_size != page_size)) {                   //比较也的大小是否相同，应该都是相同的2048字节if (hdr->page_size > BOOT_IMG_MAX_PAGE_SIZE) {dprintf(CRITICAL, "ERROR: Invalid page size\n");return -1;}page_size = hdr->page_size;page_mask = page_size - 1;}/* ensure commandline is terminated */hdr->cmdline[BOOT_ARGS_SIZE-1] = 0;         kernel_actual  = ROUND_TO_PAGE(hdr->kernel_size,  page_mask);          //kernel所占的页的总大小       例如kernel大小0x01,kernel_actual = 2048ramdisk_actual = ROUND_TO_PAGE(hdr->ramdisk_size, page_mask);          //ramdisk所占的页的总大小image_addr = (unsigned char *)target_get_scratch_address();            #if DEVICE_TREEdt_actual = ROUND_TO_PAGE(hdr->dt_size, page_mask);     //dt所占的页的大小imagesize_actual = (page_size + kernel_actual + ramdisk_actual + dt_actual);          //image占的页的总大小
#elseimagesize_actual = (page_size + kernel_actual + ramdisk_actual);
#endif#if VERIFIED_BOOTboot_verifier_init();   //校验boot
#endifif (check_aboot_addr_range_overlap((uint32_t) image_addr, imagesize_actual))       //校验image_addr是否被覆盖{dprintf(CRITICAL, "Boot image buffer address overlaps with aboot addresses.\n");return -1;}/** Update loading flow of bootimage to support compressed/uncompressed* bootimage on both 64bit and 32bit platform.* 1. Load bootimage from emmc partition onto DDR.* 2. Check if bootimage is gzip format. If yes, decompress compressed kernel* 3. Check kernel header and update kernel load addr for 64bit and 32bit*    platform accordingly.* 4. Sanity Check on kernel_addr and ramdisk_addr and copy data.*/dprintf(INFO, "Loading boot image (%d): start\n", imagesize_actual);bs_set_timestamp(BS_KERNEL_LOAD_START);/* Read image without signature */if (mmc_read(ptn + offset, (void *)image_addr, imagesize_actual))        //读取boot/recovery分区到image_addr{dprintf(CRITICAL, "ERROR: Cannot read boot image\n");return -1;}dprintf(INFO, "Loading boot image (%d): done\n", imagesize_actual);bs_set_timestamp(BS_KERNEL_LOAD_DONE);/* Authenticate Kernel */dprintf(INFO, "use_signed_kernel=%d, is_unlocked=%d, is_tampered=%d.\n",(int) target_use_signed_kernel(),device.is_unlocked,device.is_tampered);if(target_use_signed_kernel() && (!device.is_unlocked))               //这里是false ，感兴趣可以追target_use_signed_kernel(),会发现这个函数返回的是0{offset = imagesize_actual;uhdr->magicif (check_aboot_addr_range_overlap((uint32_t)image_addr + offset, page_size)){dprintf(CRITICAL, "Signature read buffer address overlaps with aboot addresses.\n");return -1;}/* Read signature */if(mmc_read(ptn + offset, (voidffbm_mode_string *)(image_addr + offset), page_size)){dprintf(CRITICAL, "ERROR: Cannot read boot image signature\n");return -1;}verify_signed_bootimg((uint32_t)image_addr, imagesize_actual);} else {second_actual  = ROUND_TO_PAGE(hdr->second_size,  page_mask);     #ifdef TZ_SAVE_KERNEL_HASHaboot_save_boot_hash_mmc((uint32_t) image_addr, imagesize_actual);#endif /* TZ_SAVE_KERNEL_HASH */#if VERIFIED_BOOTif(boot_verify_get_state() == ORANGE)    //校验boot{
#if FBCON_DISPLAY_MSGdisplay_bootverify_menu_thread(DISPLAY_MENU_ORANGE);wait_for_users_action();
#elsedprintf(CRITICAL,"Your device has been unlocked and can't be trusted.\nWait for 5 seconds before proceeding\n");mdelay(5000);
#endifset_root_flag(ORANGE,1);}
#endif#ifdef MDTP_SUPPORT{/* Verify MDTP lock.* For boot & recovery partitions, MDTP will use boot_verifier APIs,* since verification was skipped in aboot. The signature is not part of the loaded image.*/mdtp_ext_partition_verification_t ext_partition;ext_partition.partition = boot_into_recovery ? MDTP_PARTITION_RECOVERY : MDTP_PARTITION_BOOT;ext_partition.integrity_state = MDTP_PARTITION_STATE_UNSET;ext_partition.page_size = page_size;ext_partition.image_addr = (uint32)image_addr;ext_partition.image_size = imagesize_actual;ext_partition.sig_avail = FALSE;mdtp_fwlock_verify_lock(&ext_partition);}
#endif /* MDTP_SUPPORT */}#if VERIFIED_BOOT
#if !VBOOT_MOTA// send root of trustif(!send_rot_command((uint32_t)device.is_unlocked))ASSERT(0);
#endif
#endif/** Check if the kernel image is a gzip package. If yes, need to decompress it.* If not, continue booting.*/       //检测kernel image是否是gzip的包，如果是，解压，如果不是，继续boot。得到kernel的起始地址和大小if (is_gzip_package((unsigned char *)(image_addr + page_size), hdr->kernel_size)){out_addr = (unsigned char *)(image_addr + imagesize_actual + page_size);out_avai_len = target_get_max_flash_size() - imagesize_actual - page_size;dprintf(INFO, "decompressing kernel image: start\n");rc = decompress((unsigned char *)(image_addr + page_size),hdr->kernel_size, out_addr, out_avai_len,&dtb_offset, &out_len);if (rc){dprintf(CRITICAL, "decompressing kernel image failed!!!\n");ASSERT(0);}dprintf(INFO, "decompressing kernel image: done\n");kptr = (struct kernel64_hdr *)out_addr;kernel_start_addr = out_addr;kernel_size = out_len;} else {kptr = (struct kernel64_hdr *)(image_addr + page_size);kernel_start_addr = (unsigned char *)(image_addr + page_size);   //kernel_start起始地址kernel_size = hdr->kernel_size; //kernel大小}/** Update the kernel/ramdisk/tags address if the boot image header* has default values, these default values come from mkbootimg when* the boot image is flashed using fastboot flash:raw*/update_ker_tags_rdisk_addr(hdr, IS_ARM64(kptr)); //更新kernel/tags/ramdisk地址   /* Get virtual addresses since the hdr saves physical addresses. */hdr->kernel_addr = VA((addr_t)(hdr->kernel_addr));        //保存虚拟地址（mmu）hdr->ramdisk_addr = VA((addr_t)(hdr->ramdisk_addr));hdr->tags_addr = VA((addr_t)(hdr->tags_addr));kernel_size = ROUND_TO_PAGE(kernel_size,  page_mask);/* Check if the addresses in the header are valid. */if (check_aboot_addr_range_overlap(hdr->kernel_addr, kernel_size) ||                      //检测kernel/ramdisk/tags地址是否超出emmc地址check_aboot_addr_range_overlap(hdr->ramdisk_addr, ramdisk_actual)){dprintf(CRITICAL, "kernel/ramdisk addresses overlap with aboot addresses.\n");return -1;}#ifndef DEVICE_TREEif (check_aboot_addr_range_overlap(hdr->tags_addr, MAX_TAGS_SIZE)){dprintf(CRITICAL, "Tags addresses overlap with aboot addresses.\n");return -1;}
#endif/* Move kernel, ramdisk and device tree to correct address */memmove((void*) hdr->kernel_addr, kernel_start_addr, kernel_size);       //把kernel/ramdisk放在相应的地址上memmove((void*) hdr->ramdisk_addr, (char *)(image_addr + page_size + kernel_actual), hdr->ramdisk_size);#if DEVICE_TREE   //读取设备树信息，放在相应的地址上if(hdr->dt_size) {dt_table_offset = ((uint32_t)image_addr + page_size + kernel_actual + ramdisk_actual + second_actual);table = (struct dt_table*) dt_table_offset;if (dev_tree_validate(table, hdr->page_size, &dt_hdr_size) != 0) {dprintf(CRITICAL, "ERROR: Cannot validate Device Tree Table \n");return -1;}/* Find index of device tree within device tree table */if(dev_tree_get_entry_info(table, &dt_entry) != 0){dprintf(CRITICAL, "ERROR: Getting device tree address failed\n");return -1;}if (is_gzip_package((unsigned char *)dt_table_offset + dt_entry.offset, dt_entry.size)){unsigned int compressed_size = 0;out_addr += out_len;out_avai_len -= out_len;dprintf(INFO, "decompressing dtb: start\n");rc = decompress((unsigned char *)dt_table_offset + dt_entry.offset,dt_entry.size, out_addr, out_avai_len,&compressed_size, &dtb_size);if (rc){dprintf(CRITICAL, "decompressing dtb failed!!!\n");ASSERT(0);}dprintf(INFO, "decompressing dtb: done\n");best_match_dt_addr = out_addr;} else {best_match_dt_addr = (unsigned char *)dt_table_offset + dt_entry.offset;dtb_size = dt_entry.size;}/* Validate and Read device device tree in the tags_addr */if (check_aboot_addr_range_overlap(hdr->tags_addr, dtb_size)){dprintf(CRITICAL, "Device tree addresses overlap with aboot addresses.\n");return -1;}memmove((void *)hdr->tags_addr, (char *)best_match_dt_addr, dtb_size);} else {/* Validate the tags_addr */if (check_aboot_addr_range_overlap(hdr->tags_addr, kernel_actual)){dprintf(CRITICAL, "Device tree addresses overlap with aboot addresses.\n");return -1;}/** If appended dev tree is found, update the atags with* memory address to the DTB appended location on RAM.* Else update with the atags address in the kernel header*/void *dtb;dtb = dev_tree_appended((void*)(image_addr + page_size),hdr->kernel_size, dtb_offset,(void *)hdr->tags_addr);if (!dtb) {dprintf(CRITICAL, "ERROR: Appended Device Tree Blob not found\n");return -1;}}#endifif (boot_into_recovery && !device.is_unlocked && !device.is_tampered)target_load_ssd_keystore();unified_boot:boot_linux((void *)hdr->kernel_addr, (void *)hdr->tags_addr,           //进入boot_linux函数，此函数比较简单，更新cmdline。(const char *)hdr->cmdline, board_machtype(),(void *)hdr->ramdisk_addr, hdr->ramdisk_size);return 0;
}

int get_ffbm(char *ffbm, unsigned size)
{const char *ffbm_cmd = "ffbm-";uint32_t page_size = get_page_size();char *ffbm_page_buffer = NULL;int retval = 0;if (size < FFBM_MODE_BUF_SIZE || size >= page_size){dprintf(CRITICAL, "Invalid size argument passed to get_ffbm\n");retval = -1;goto cleanup;}ffbm_page_buffer = (char*)malloc(page_size);if (!ffbm_page_buffer){dprintf(CRITICAL, "Failed to alloc buffer for ffbm cookie\n");retval = -1;goto cleanup;}if (read_misc(0, ffbm_page_buffer, page_size)){dprintf(CRITICAL, "Error reading MISC partition\n");retval = -1;goto cleanup;}ffbm_page_buffer[size] = '\0';if (strncmp(ffbm_cmd, ffbm_page_buffer, strlen(ffbm_cmd))){retval = 0;goto cleanup;}else{if (strlcpy(ffbm, ffbm_page_buffer, size) <FFBM_MODE_BUF_SIZE -1){dprintf(CRITICAL, "Invalid string in misc partition\n");retval = -1;}elseretval = 1;}
cleanup:if(ffbm_page_buffer)free(ffbm_page_buffer);return retval;
}

bootable/bootloader/lk/app/aboot/bootimg.h#ifndef _BOOT_IMAGE_H_
#define _BOOT_IMAGE_H_typedef struct boot_img_hdr boot_img_hdr;#define BOOT_MAGIC "ANDROID!"
#define BOOT_MAGIC_SIZE 8
#define BOOT_NAME_SIZE  16
#define BOOT_ARGS_SIZE  512
#define BOOT_IMG_MAX_PAGE_SIZE 4096struct boot_img_hdr
{unsigned char magic[BOOT_MAGIC_SIZE];unsigned kernel_size;  /* size in bytes */unsigned kernel_addr;  /* physical load addr */unsigned ramdisk_size; /* size in bytes */unsigned ramdisk_addr; /* physical load addr */unsigned second_size;  /* size in bytes */unsigned second_addr;  /* physical load addr */unsigned tags_addr;    /* physical addr for kernel tags */unsigned page_size;    /* flash page size we assume */unsigned dt_size;      /* device_tree in bytes */unsigned unused;    /* future expansion: should be 0 */unsigned char name[BOOT_NAME_SIZE]; /* asciiz product name */unsigned char cmdline[BOOT_ARGS_SIZE];unsigned id[8]; /* timestamp / checksum / sha1 / etc */
};/*
** +-----------------+
** | boot header     | 1 page
** +-----------------+
** | kernel          | n pages
** +-----------------+
** | ramdisk         | m pages
** +-----------------+
** | second stage    | o pages
** +-----------------+
** | device tree     | p pages
** +-----------------+
**
** n = (kernel_size + page_size - 1) / page_size
** m = (ramdisk_size + page_size - 1) / page_size
** o = (second_size + page_size - 1) / page_size
** p = (dt_size + page_size - 1) / page_size
** 0. all entities are page_size aligned in flash
** 1. kernel and ramdisk are required (size != 0)
** 2. second is optional (second_size == 0 -> no second)
** 3. load each element (kernel, ramdisk, second) at
**    the specified physical address (kernel_addr, etc)
** 4. prepare tags at tag_addr.  kernel_args[] is
**    appended to the kernel commandline in the tags.
** 5. r0 = 0, r1 = MACHINE_TYPE, r2 = tags_addr
** 6. if second_size != 0: jump to second_addr
**    else: jump to kernel_addr
*/boot_img_hdr *mkbootimg(void *kernel, unsigned kernel_size,void *ramdisk, unsigned ramdisk_size,void *second, unsigned second_size,unsigned page_size,unsigned *bootimg_size);void bootimg_set_cmdline(boot_img_hdr *hdr, const char *cmdline);                #define KERNEL64_HDR_MAGIC 0x644D5241 /* ARM64 */struct kernel64_hdr
{uint32_t insn;uint32_t res1;uint64_t text_offset;uint64_t res2;uint64_t res3;uint64_t res4;uint64_t res5;uint64_t res6;uint32_t magic_64;uint32_t res7;
};#endif