本文转载自:http://blog.csdn.net/dkleikesa/article/details/9792747
本人用的android平台用的bootloader用的是uboot,貌似大多数手持设备平台都不用这个,因为功能过于强大用不上,反而显得太复杂了。不知道这个平台开发者是怎么想的。既然用了那就来分析一下,顺便修改一下其中的几个小问题,以符合我们的要求。
uboot等同于其他所有的bootloader程序,从根本上讲是一个稍复杂的裸机程序,是最底层的东西,要分析裸机程序我们要从它的连接文件开始。连接文件(.lds文件)定义了程序编译之后整个连接过程,这样我们就可以找到这个程序的第一句汇编代码,进而来下一步分析。uboot的链接文件代码在androidootableootloaderuboot-imxu-boot.lds
- OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm") //文件输出格式
- OUTPUT_ARCH(arm)
- ENTRY(_start) //首地址标示符
- SECTIONS
- {
- . = 0x00000000; //其实地址0
- . = ALIGN(4); //4字节对齐
- .text : //代码段
- {
- board/freescale/mx6q_sabresd/flash_header.o (.text.flasheader) //第一个文件是board/freescale/mx6q_sabresd/flash_header.o
- cpu/arm_cortexa8/start.o //第二个cpu/arm_cortexa8/start.o
- board/freescale/mx6q_sabresd/libmx6q_sabresd.a (.text)
- lib_arm/libarm.a (.text)
- net/libnet.a (.text)
- drivers/mtd/libmtd.a (.text)
- drivers/mmc/libmmc.a (.text)
- . = DEFINED(env_offset) ? env_offset : .;
- common/env_embedded.o(.text)
- *(.text) //剩余的所有代码
- }
- . = ALIGN(4);
- .rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) } //readonly data 段
- . = ALIGN(4);
- .data : { *(.data) } //所有的readonly data
- . = ALIGN(4);
- .got : { *(.got) }
- . = .;
- __u_boot_cmd_start = .; //u_boot_cmd段,里面是所有uboot命令的一个列表
- .u_boot_cmd : { *(.u_boot_cmd) }
- __u_boot_cmd_end = .;
- . = ALIGN(4);
- _end_of_copy = .;
- __bss_start = .; //bss段 就是内存数据段
- .bss : { *(.bss) }
- _end = .;
- }
从上面的代码可以看出我们编译生成的二进制应用程序组成是:代码段->rodata段->uboot命令列表->bss段。我们启动这个应用程序时候是从,0地址开始的,因此我们来看
board/freescale/mx6q_sabresd/flash_header.s这个文件。
这个文件中除了分配内存和宏定义的伪汇编指令以外,真正执行的命令有一条
- .section ".text.flasheader", "x"
- b _start
- .org CONFIG_FLASH_HEADER_OFFSET
也就是说,这个文件一执行就直接跳到_start 位置处。_start 在androidootableootloaderuboot-imxcpuarm_cortexa8 start.S中,因此我们来看这个文件代码
- .globl _start
- _start: b reset
这里直接跳转的reset中接下来看
- reset:
- /*
- * set the cpu to SVC32 mode cpu设置成32位管理模式
- */
- mrs r0, cpsr
- bic r0, r0, #0x1f
- orr r0, r0, #0xd3
- msr cpsr,r0
- #if (CONFIG_OMAP34XX) //因为我们的cpu不是ompa的 所以这段不会编译
- .............................
- #endif
- /* the mask ROM code should have PLL and others stable */
- #ifndef CONFIG_SKIP_LOWLEVEL_INIT
- bl cpu_init_crit
- #endif
这里接下来执行cpu_init_crit
- /*************************************************************************
- *
- * CPU_init_critical registers
- *
- * setup important registers
- * setup memory timing
- *
- *************************************************************************/
- cpu_init_crit:
- /*
- * Invalidate L1 I/D
- */
- mov r0, #0 @ set up for MCR
- mcr p15, 0, r0, c8, c7, 0 @ invalidate TLBs
- mcr p15, 0, r0, c7, c5, 0 @ invalidate icache
- /*
- * disable MMU stuff and caches //关闭mmu
- */
- mrc p15, 0, r0, c1, c0, 0
- bic r0, r0, #0x00002000 @ clear bits 13 (--V-)
- bic r0, r0, #0x00000007 @ clear bits 2:0 (-CAM)
- orr r0, r0, #0x00000002 @ set bit 1 (--A-) Align
- orr r0, r0, #0x00000800 @ set bit 12 (Z---) BTB
- mcr p15, 0, r0, c1, c0, 0
- /*
- * Jump to board specific initialization...
- * The Mask ROM will have already initialized
- * basic memory. Go here to bump up clock rate and handle
- * wake up conditions.
- */
- mov ip, lr @ persevere link reg across call
- bl lowlevel_init @ go setup pll,mux,memory//执行lowlevel_init这个函数代码在
- @ootloaderuboot-imxoardfreescalemx6q_sabresdlowlevel_init.S中
- @主要对时钟,外部ram,rom等进行了初始化代码不贴了。
- mov lr, ip @ restore link
- mov pc, lr @ back to my caller
初始化完成后,接下来执行
- #ifndef CONFIG_SKIP_RELOCATE_UBOOT
- relocate: @ relocate U-Boot to RAM 将uboot重新定位到内存中
- adr r0, _start @ r0 <- current position of code
- ldr r1, _TEXT_BASE @ test if we run from flash or RAM
- cmp r0, r1 @ don't reloc during debug测试当前代码是否已经在内存中
- beq stack_setup @如果在的话就直接跳转到stack_setup
- ldr r2, _armboot_start @如果不在的话,加载_armboot_start地址到r2中。_armboot_start是uboot执行的主体c函数。
- ldr r3, _bss_start
- sub r2, r3, r2 @ r2 <- size of armboot计算bss_start-armboot_start 保存到R2中,也就是uboot的总大小
- add r2, r0, r2 @ r2 <- source end address 计算出uboot代码和rodata地址
- copy_loop: @ copy 32 bytes at a time //开始拷贝
- ldmia r0!, {r3 - r10} @ copy from source address [r0]
- stmia r1!, {r3 - r10} @ copy to target address [r1]
- cmp r0, r2 @ until source end addreee [r2]
- ble copy_loop
- #endif /* CONFIG_SKIP_RELOCATE_UBOOT */
- /* Set up the stack */
- stack_setup:
- ldr r0, _TEXT_BASE @ upper 128 KiB: relocated uboot
- sub r0, r0, #CONFIG_SYS_MALLOC_LEN @ malloc area//为c语言malloc函数分配内存
- sub r0, r0, #CONFIG_SYS_GBL_DATA_SIZE @ bdinfo
- #ifdef CONFIG_USE_IRQ
- sub r0, r0, #(CONFIG_STACKSIZE_IRQ + CONFIG_STACKSIZE_FIQ)
- #endif
- sub sp, r0, #12 @ leave 3 words for abort-stack//分配c语言堆栈
- and sp, sp, #~7 @ 8 byte alinged for (ldr/str)d
- /* Clear BSS (if any). Is below tx (watch load addr - need space) */
- clear_bss:
- ldr r0, _bss_start @ find start of bss segment //清除bss段
- ldr r1, _bss_end @ stop here
- mov r2, #0x00000000 @ clear value
- clbss_l:
- str r2, [r0] @ clear BSS location
- cmp r0, r1 @ are we at the end yet
- add r0, r0, #4 @ increment clear index pointer
- bne clbss_l @ keep clearing till at end
- #ifdef CONFIG_ARCH_MMU
- bl board_mmu_init //初始化mmu
- #endif
- ldr pc, _start_armboot @ jump to C code以上所有的初始化就已经完成了,接下类正式执行c语言代码了。这才是我们的重点
- _start_armboot: .word start_armboot
接下来正式看C代码,也就是start_armboot这个函数代码在androidootableootloaderuboot-imxlib_armoard.c中
- void start_armboot (void)
- {
- init_fnc_t **init_fnc_ptr;
- char *s;
- #if defined(CONFIG_VFD) || defined(CONFIG_LCD)
- unsigned long addr;
- #endif
- /* Pointer is writable since we allocated a register for it */
- gd = (gd_t*)(_armboot_start - CONFIG_SYS_MALLOC_LEN - sizeof(gd_t));
- //分配一段内存.在cpu存储控制器初始化之前,是不能访问外部ram的,因此需要一小段
- //内存来运行最初的初始化函数,这段内存一般是cpu内部ram
- /* compiler optimization barrier needed for GCC >= 3.4 */
- __asm__ __volatile__("": : :"memory");
- memset ((void*)gd, 0, sizeof (gd_t));
- gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
- memset (gd->bd, 0, sizeof (bd_t));
- gd->flags |= GD_FLG_RELOC;
- monitor_flash_len = _bss_start - _armboot_start;
- for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
- if ((*init_fnc_ptr)() != 0) {
- hang ();
- }
- }
注意看这里init_sequence的定义
- init_fnc_t *init_sequence[] = {
- #if defined(CONFIG_ARCH_CPU_INIT)
- arch_cpu_init, /* basic arch cpu dependent setup */
- #endif
- board_init, /* basic board dependent setup */
- #if defined(CONFIG_USE_IRQ)
- interrupt_init, /* set up exceptions */
- #endif
- timer_init, /* initialize timer */
- env_init, /* initialize environment */
- init_baudrate, /* initialze baudrate settings */
- serial_init, /* serial communications setup */
- console_init_f, /* stage 1 init of console */
- display_banner, /* say that we are here */
- #if defined(CONFIG_DISPLAY_CPUINFO)
- print_cpuinfo, /* display cpu info (and speed) */
- #endif
- #if defined(CONFIG_DISPLAY_BOARDINFO)
- checkboard, /* display board info */
- #endif
- #if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
- init_func_i2c,
- #endif
- dram_init, /* configure available RAM banks */
- #if defined(CONFIG_CMD_PCI) || defined (CONFIG_PCI)
- arm_pci_init,
- #endif
- display_dram_config,
- NULL,
- };
这个是一个函数指针的数组,涉及到cpu的最后的一些初始化。到了这里cpu的所有初始化都完成了
我们继续看板子的其他配置
- #ifdef CONFIG_LCD //lcd缓存设置
- /* board init may have inited fb_base */
- if (!gd->fb_base) {
- # ifndef PAGE_SIZE
- # define PAGE_SIZE 4096
- # endif
- /*
- * reserve memory for LCD display (always full pages)
- */
- /* bss_end is defined in the board-specific linker script */
- addr = (_bss_end + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
- lcd_setmem (addr);
- gd->fb_base = addr;
- }
- #endif /* CONFIG_LCD */
- env_relocate ();//设置环境变量 也就是printenv 打印出来的那些
- #ifdef CONFIG_VFD
- /* must do this after the framebuffer is allocated */
- drv_vfd_init(); //空函数
- #endif /* CONFIG_VFD */
- #ifdef CONFIG_SERIAL_MULTI
- serial_initialize();//串口初始化
- #endif
- /* IP Address */
- gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr");
- #if defined CONFIG_SPLASH_SCREEN && defined CONFIG_VIDEO_MX5
- setup_splash_image();//lcd显示log
- #endif
- //重新定义stdio的位置,在本环境中被定义到了串口上
- stdio_init (); /* get the devices list going. */
- jumptable_init ();//把一些初始化函数的指针放到gd中,为以后调用
- #if defined(CONFIG_API)
- /* Initialize API */
- api_init ();
- #endif
- console_init_r (); /* fully init console as a device 控制台初始化*/
- #if defined(CONFIG_ARCH_MISC_INIT)
- /* miscellaneous arch dependent initialisations */
- arch_misc_init ();//空函数
- #endif
- #if defined(CONFIG_MISC_INIT_R)
- /* miscellaneous platform dependent initialisations */
- misc_init_r ();//空函数
- #endif
- /* enable exceptions */
- enable_interrupts ();//使能中断
- /* Perform network card initialisation if necessary */
- #ifdef CONFIG_DRIVER_TI_EMAC
- /* XXX: this needs to be moved to board init */
- extern void davinci_eth_set_mac_addr (const u_int8_t *addr);//不编译
- if (getenv ("ethaddr")) {
- uchar enetaddr[6];
- eth_getenv_enetaddr("ethaddr", enetaddr);
- davinci_eth_set_mac_addr(enetaddr);
- }
- #endif
- #ifdef CONFIG_DRIVER_CS8900
- /* XXX: this needs to be moved to board init */
- cs8900_get_enetaddr ();//不编译
- #endif
- #if defined(CONFIG_DRIVER_SMC91111) || defined (CONFIG_DRIVER_LAN91C96)
- /* XXX: this needs to be moved to board init */
- if (getenv ("ethaddr")) {
- uchar enetaddr[6];
- eth_getenv_enetaddr("ethaddr", enetaddr);//不编译
- smc_set_mac_addr(enetaddr);
- }
- #endif /* CONFIG_DRIVER_SMC91111 || CONFIG_DRIVER_LAN91C96 */
- #if defined(CONFIG_ENC28J60_ETH) && !defined(CONFIG_ETHADDR)
- extern void enc_set_mac_addr (void);//不编译
- enc_set_mac_addr ();
- #endif /* CONFIG_ENC28J60_ETH && !CONFIG_ETHADDR*/
- /* Initialize from environment */
- if ((s = getenv ("loadaddr")) != NULL) {
- load_addr = simple_strtoul (s, NULL, 16);
- }
- #if defined(CONFIG_CMD_NET)
- if ((s = getenv ("bootfile")) != NULL) {
- copy_filename (BootFile, s, sizeof (BootFile));
- }
- #endif
- #ifdef BOARD_LATE_INIT
- board_late_init (); //初始化i2c,pmic等
- #endif
接下来涉及到了我们最关心的地方,启动模式和按键响应
- #ifdef CONFIG_ANDROID_RECOVERY
- check_recovery_mode(); //检测是否进入recovery
- #endif
- #if defined(CONFIG_CMD_NET)
- #if defined(CONFIG_NET_MULTI)
- puts ("Net: ");
- #endif
- eth_initialize(gd->bd); //根据gd的配置初始化以太网
- #if defined(CONFIG_RESET_PHY_R)
- debug ("Reset Ethernet PHY ");
- reset_phy();
- #endif
- #endif
- #ifdef CONFIG_FASTBOOT
- check_fastboot_mode(); //检测是否进入fastboot
- #endif
从代码里可以看出我们是首先检测recovery,然后才检测fastboot模式。
我们先来看原版是怎么做的,首先是recovery
- void check_recovery_mode(void)
- {
- if (check_key_pressing())
- setup_recovery_env();
- else if (check_recovery_cmd_file()) {
- puts("Recovery command file founded! ");
- setup_recovery_env();
- }
- }
这里首先检测是否有合法的按键按下,如果有的话就配置环境变量进入recovery
没有按键就检测uboot命令文件,看是不是主系统要求进入recovery
因此我们这里的重点是check_key_pressing()这个函数,仔细研究发现这个函数用的是uboot
标准的gpio驱动,官方给我们移植的uboot里面并没有初始化这个驱动,而是自己另外写的。也就是说
我们调用check_key_pressing()这个函数永远都返回0值而执行else if (check_recovery_cmd_file())这一句
我们来看 check_recovery_cmd_file()
- int check_recovery_cmd_file(void)
- {
- int button_pressed = 0;
- int recovery_mode = 0;
- recovery_mode = check_and_clean_recovery_flag();//读取kernel的recovery标志位,如果有的话就要进入recovery
- /* Check Recovery Combo Button press or not. */
- mxc_iomux_v3_setup_pad(MX6X_IOMUX(PAD_GPIO_5__GPIO_1_5)); //初始化vol down的gpio
- gpio_direction_input(GPIO_VOL_DN_KEY);
- if (gpio_get_value(GPIO_VOL_DN_KEY) == 0) { /* VOL_DN key is low assert *///如果vol down已经按下
- button_pressed = 1;
- printf("Recovery key pressed ");
- }
- return recovery_mode || button_pressed; //返回进入recovery
- }
也就是说官方修改的uboot走了偷懒的方法,直接在check_recovery_cmd_file()增加了一个按键的盘定。很不正规
因此我们下一步要修改它,从官方的基础上走,我们也不走标准uboot 按键驱动,而是自己写。
修改之前先来看原版fastboot怎么进入的
- /* export to lib_arm/board.c */
- void check_fastboot_mode(void)
- {
- if (fastboot_check_and_clean_flag())
- do_fastboot(NULL, 0, 0, 0);
- }
这里调用fastboot_check_and_clean_flag()来判定是否进入fastboot
- /* check if the recovery bit is set by kernel, it can be set by kernel
- * issue a command '# reboot fastboot' */
- int fastboot_check_and_clean_flag(void)
- {
- int flag_set = 0;
- u32 reg;
- reg = readl(SRC_BASE_ADDR + SRC_GPR10);
- flag_set = !!(reg & ANDROID_FASTBOOT_BOOT);
- /* clean it in case looping infinite here.... */
- if (flag_set) {
- reg &= ~ANDROID_FASTBOOT_BOOT;
- writel(reg, SRC_BASE_ADDR + SRC_GPR10);
- }
- return flag_set;
- }
从这里看出,要进入进入fastboot,只能检测(SRC_BASE_ADDR + SRC_GPR10)寄存器的
ANDROID_FASTBOOT_BOOT位是否被kernel置位,并没有按键,因此我们的板子不可能靠
按键进入fastboot的实际情况也确实这样。因此我们要修改这一块,由于我们的cpu在power键按住5s
以后会强制关机。因此开机后我们必须松开power键,我们板子检测的按键只能是1个。开机时vol up键进入
recovery,按住vol down进入fastboot模式。我们修改代码如下
新建个按键检测函数check_key()
- int check_key(void)
- {
- #define PRESSED_VOLUP 1
- #define PRESSED_VOLDOWN 2
- #define KEY_MASK (PRESSED_VOLUP|PRESSED_VOLDOWN)
- #define RECOVERY_KEY_MASK (PRESSED_VOLUP)
- #define FASTBOOT_KEY_MASK (PRESSED_VOLDOWN)
- int state = 0;
- mxc_iomux_v3_setup_pad(MX6X_IOMUX(PAD_GPIO_5__GPIO_1_5));//vol down
- mxc_iomux_v3_setup_pad(MX6X_IOMUX(PAD_GPIO_5__GPIO_1_4));//vol up
- gpio_direction_input(GPIO_VOL_DN_KEY);
- gpio_direction_input(GPIO_VOL_UP_KEY);
- if (gpio_get_value(GPIO_VOL_UP_KEY) == 0)
- state |= PRESSED_VOLUP;
- if (gpio_get_value(GPIO_VOL_DN_KEY) == 0)
- state |= PRESSED_VOLDOWN;
- //如果摁下power+voldown就进入fastboot 这个的优先级要比recovery高。
- //就算同时按下power+volup+voldown三个键也要进入fastboot模式
- if ((state & KEY_MASK) == FASTBOOT_KEY_MASK)
- return 1;
- if(((state & KEY_MASK) == FASTBOOT_KEY_MASK))
- return 2;
- return 0;
- }
主函数判定的代码段修改为
- if (check_key()==1)
- do_fastboot(NULL, 0, 0, 0);
- if (check_key()==2)
- setup_recovery_env();
- if (check_and_clean_recovery_flag()) {
- setup_recovery_env();
- }
- if (fastboot_check_and_clean_flag())
- do_fastboot(NULL, 0, 0, 0);
这样我们的启动模式按键就修改完成了,编译后测试成功。
下面我们还有代码没有分析完:uboot的主循环:main_loop()
代码在:ootableootloaderuboot-imxcommonmain.c
- void main_loop (void)
- {
- #ifndef CONFIG_SYS_HUSH_PARSER
- static char lastcommand[CONFIG_SYS_CBSIZE] = { 0, };
- int len;
- int rc = 1;
- int flag;
- #endif
- #if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
- char *s;
- int bootdelay;
- #endif
- #ifdef CONFIG_PREBOOT
- char *p;
- #endif
- #ifdef CONFIG_BOOTCOUNT_LIMIT
- unsigned long bootcount = 0;
- unsigned long bootlimit = 0;
- char *bcs;
- char bcs_set[16];
- #endif /* CONFIG_BOOTCOUNT_LIMIT */
- #if defined(CONFIG_VFD) && defined(VFD_TEST_LOGO)
- ulong bmp = 0; /* default bitmap */
- extern int trab_vfd (ulong bitmap);
- #ifdef CONFIG_MODEM_SUPPORT
- if (do_mdm_init)
- bmp = 1; /* alternate bitmap */
- #endif
- trab_vfd (bmp);
- #endif /* CONFIG_VFD && VFD_TEST_LOGO */
- #if defined(CONFIG_UPDATE_TFTP)
- update_tftp ();
- #endif /* CONFIG_UPDATE_TFTP */
- #ifdef CONFIG_BOOTCOUNT_LIMIT
- bootcount = bootcount_load();
- bootcount++;
- bootcount_store (bootcount);
- sprintf (bcs_set, "%lu", bootcount);
- setenv ("bootcount", bcs_set);
- bcs = getenv ("bootlimit");
- bootlimit = bcs ? simple_strtoul (bcs, NULL, 10) : 0;
- #endif /* CONFIG_BOOTCOUNT_LIMIT */
- #ifdef CONFIG_MODEM_SUPPORT
- debug ("DEBUG: main_loop: do_mdm_init=%d ", do_mdm_init);
- if (do_mdm_init) {
- char *str = strdup(getenv("mdm_cmd"));
- setenv ("preboot", str); /* set or delete definition */
- if (str != NULL)
- free (str);
- mdm_init(); /* wait for modem connection */
- }
- #endif /* CONFIG_MODEM_SUPPORT */
- #ifdef CONFIG_VERSION_VARIABLE
- {
- extern char version_string[];
- setenv ("ver", version_string); /* set version variable */
- }
- #endif /* CONFIG_VERSION_VARIABLE */
- #ifdef CONFIG_SYS_HUSH_PARSER
- u_boot_hush_start ();
- #endif
- #if defined(CONFIG_HUSH_INIT_VAR)
- hush_init_var ();
- #endif
- #ifdef CONFIG_AUTO_COMPLETE
- install_auto_complete();
- #endif
- #ifdef CONFIG_PREBOOT
- if ((p = getenv ("preboot")) != NULL) {
- # ifdef CONFIG_AUTOBOOT_KEYED
- int prev = disable_ctrlc(1); /* disable Control C checking */
- # endif
- # ifndef CONFIG_SYS_HUSH_PARSER
- run_command (p, 0);
- # else
- parse_string_outer(p, FLAG_PARSE_SEMICOLON |
- FLAG_EXIT_FROM_LOOP);
- # endif
- # ifdef CONFIG_AUTOBOOT_KEYED
- disable_ctrlc(prev); /* restore Control C checking */
- # endif
- }
- #endif /* CONFIG_PREBOOT */
- #if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
- s = getenv ("bootdelay");
- bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;//计算bootdelay
- debug ("### main_loop entered: bootdelay=%d ", bootdelay);
- # ifdef CONFIG_BOOT_RETRY_TIME
- init_cmd_timeout ();
- # endif /* CONFIG_BOOT_RETRY_TIME */
- #ifdef CONFIG_POST
- if (gd->flags & GD_FLG_POSTFAIL) {
- s = getenv("failbootcmd");
- }
- else
- #endif /* CONFIG_POST */
- #ifdef CONFIG_BOOTCOUNT_LIMIT
- if (bootlimit && (bootcount > bootlimit)) {
- printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd. ",
- (unsigned)bootlimit);
- s = getenv ("altbootcmd");
- }
- else
- #endif /* CONFIG_BOOTCOUNT_LIMIT */
- s = getenv ("bootcmd");//得到bootcmd命令
- debug ("### main_loop: bootcmd="%s" ", s ? s : "<UNDEFINED>");
- //每10ms从控制台读取一个字符,并且显示倒计时。如果读取成功的话就继续执行main_loop代码,
- //如果失败的话就执行下面的run_command(s,0)
- if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
- # ifdef CONFIG_AUTOBOOT_KEYED
- int prev = disable_ctrlc(1); /* disable Control C checking */
- # endif
- # ifndef CONFIG_SYS_HUSH_PARSER
- run_command (s, 0);//执行 bootcmd命令
- # else
- parse_string_outer(s, FLAG_PARSE_SEMICOLON |
- FLAG_EXIT_FROM_LOOP);
- # endif
- # ifdef CONFIG_AUTOBOOT_KEYED
- disable_ctrlc(prev); /* restore Control C checking */
- # endif
- }
- # ifdef CONFIG_MENUKEY
- if (menukey == CONFIG_MENUKEY) {
- s = getenv("menucmd");
- if (s) {
- # ifndef CONFIG_SYS_HUSH_PARSER
- run_command (s, 0);
- # else
- parse_string_outer(s, FLAG_PARSE_SEMICOLON |
- FLAG_EXIT_FROM_LOOP);
- # endif
- }
- }
- #endif /* CONFIG_MENUKEY */
- #endif /* CONFIG_BOOTDELAY */
- #ifdef CONFIG_AMIGAONEG3SE
- {
- extern void video_banner(void);
- video_banner();
- }
- #endif
- /*
- * Main Loop for Monitor Command Processing
- */
- #ifdef CONFIG_SYS_HUSH_PARSER
- parse_file_outer();
- /* This point is never reached */
- for (;;);
- #else
- for (;;) { //如果bootdelay时候有按键 就进入命令处理模式
- #ifdef CONFIG_BOOT_RETRY_TIME
- if (rc >= 0) {
- /* Saw enough of a valid command to
- * restart the timeout.
- */
- reset_cmd_timeout();
- }
- #endif
- len = readline (CONFIG_SYS_PROMPT);//从控制台读取一行数据,以回车为标志
- flag = 0; /* assume no special flags for now */
- if (len > 0)
- z (lastcommand, console_buffer);
- else if (len == 0)
- flag |= CMD_FLAG_REPEAT;
- #ifdef CONFIG_BOOT_RETRY_TIME
- else if (len == -2) {
- /* -2 means timed out, retry autoboot
- */
- puts (" Timed out waiting for command ");
- # ifdef CONFIG_RESET_TO_RETRY
- /* Reinit board to run initialization code again */
- do_reset (NULL, 0, 0, NULL);
- # else
- return; /* retry autoboot */
- # endif
- }
- #endif
- if (len == -1)
- puts ("<INTERRUPT> ");
- else
- rc = run_command (lastcommand, flag);//处理这条命令
- if (rc <= 0) {
- /* invalid command or not repeatable, forget it */
- lastcommand[0] = 0;
- }
- }
- #endif /*CONFIG_SYS_HUSH_PARSER*/
- }
到了这里整个的uboot流程已经走完了。从这里可以知道,uboot正式运行以后,实现的所有功能都是通过命令实现的,要继续分析的话,就要分析uboot的命令的实现了。
我们在下一篇文章里面讲述uboot命令是怎么实现的,kernel是怎么启动的。