UBOOT stage2 board_init_r();函数到引导内核流程
转载 ： http://blog.csdn.net/u014381531/article/details/52062257
本人用的是friendlyarm smart4418的板子，用的也是从其github clone下来的uboot-nanopi2的源码，感觉这个uboot特别的复杂，跟网上很多其余板子的教程有很多地方不同，此篇博客是学习的一点记录，欢迎广大网友指正。
上面的一篇博客给了很大帮助，也有别的很多优秀的博客，就没有一一列举。
UBOOT分为两个阶段，第一个阶段主要是汇编代码在START.S文件中实现。在stage1的最后初始化堆栈等操作为stage2C语言的运行提供了环境，最后程序跳入C语言。
ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
sub sp, #GD_SIZE /* allocate one GD above SP */
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
mov r9, sp /* GD is above SP */
mov r0, #0
bl board_init_f
mov sp, r9 /* SP is GD's base address */
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
sub sp, #GENERATED_BD_INFO_SIZE /* allocate one BD above SP */
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
mov r0, r9 /* gd_t *gd */
ldr r1, TEXT_BASE /* ulong text */
mov r2, sp /* ulong sp */
bl gdt_reset
/* call board_init_r(gd_t *id, ulong dest_addr) */
mov r0, r9 /* gd_t */
ldr r1, =(CONFIG_SYS_MALLOC_END) /* dest_addr for malloc heap end */
/* call board_init_r */
ldr pc, =board_init_r /* this is auto-relocated! */
#else /* CONFIG_RELOC_TO_TEXT_BASE */
bl _main
#endif上图是我所用的uboot-nanopi2下arch/arm/cpu/slsip/s5p4418/start.s文件，跟网上的很多教程相比很相似，但是细究起来差别也蛮大的，就上面的代码来说，在擦除了bss后设置可sp指针，然后就跳入board_init_f();函数，在board_init.f函数里面，完成了一系列初始化后再调回来。gdt_reset进行gd结构体的初始化，最后进入到了board_init_r();函数，这个函数就是最后载入内核或者开始uboot命令行的操作。
board_init_f();board_init_r();函数在arch/arm/lib/目录下，board_init_r();函数的一系列初始化操作就不说了，因为我也还没有弄懂具体的初始化机制和原由，直奔主题-------怎么进去的内核。
下图是我粘贴的board_init_r();的完整内容，可以直接略过。
/************************************************************************
*
* This is the next part if the initialization sequence: we are now
* running from RAM and have a "normal" C environment, i. e. global
* data can be written, BSS has been cleared, the stack size in not
* that critical any more, etc.
*
************************************************************************
*/
void board_init_r(gd_t *id, ulong dest_addr)
{
ulong malloc_start;
#if !defined(CONFIG_SYS_NO_FLASH)
ulong flash_size;
#endif
gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */
bootstage_mark_name(BOOTSTAGE_ID_START_UBOOT_R, "board_init_r");
monitor_flash_len = (ulong)&__rel_dyn_end - (ulong)_start;
/* Enable caches */
enable_caches();
debug("monitor flash len: %08lX\n", monitor_flash_len);
board_init(); /* Setup chipselects */
/*
* TODO: printing of the clock inforamtion of the board is now
* implemented as part of bdinfo command. Currently only support for
* davinci SOC's is added. Remove this check once all the board
* implement this.
*/
#ifdef CONFIG_CLOCKS
set_cpu_clk_info(); /* Setup clock information */
#endif
serial_initialize();
debug("Now running in RAM - U-Boot at: %08lx\n", dest_addr);
#ifdef CONFIG_LOGBUFFER
logbuff_init_ptrs();
#endif
#ifdef CONFIG_POST
post_output_backlog();
#endif
/* The Malloc area is immediately below the monitor copy in DRAM */
malloc_start = dest_addr - TOTAL_MALLOC_LEN;
mem_malloc_init (malloc_start, TOTAL_MALLOC_LEN);
#ifdef CONFIG_ARCH_EARLY_INIT_R
arch_early_init_r();
#endif
#ifndef CONFIG_PMIC_REG_DUMP
power_init_board();
#endif
#if !defined(CONFIG_SYS_NO_FLASH)
puts("Flash: ");
flash_size = flash_init();
if (flash_size > 0) {
# ifdef CONFIG_SYS_FLASH_CHECKSUM
print_size(flash_size, "");
/*
* Compute and print flash CRC if flashchecksum is set to 'y'
*
* NOTE: Maybe we should add some WATCHDOG_RESET()? XXX
*/
if (getenv_yesno("flashchecksum") == 1) {
printf(" CRC: %08X", crc32(0,
(const unsigned char *) CONFIG_SYS_FLASH_BASE,
flash_size));
}
putc('\n');
# else /* !CONFIG_SYS_FLASH_CHECKSUM */
print_size(flash_size, "\n");
# endif /* CONFIG_SYS_FLASH_CHECKSUM */
} else {
puts(failed);
hang();
}
#endif
#if defined(CONFIG_CMD_NAND)
#if defined(CONFIG_NAND_MTD)
puts("NAND: ");
nand_init(); /* go init the NAND */
#elif defined(CONFIG_NAND_FTL)
#include
puts("NAND FTL: ");
nand_ftl_init(); /* go init the NAND */
#endif
#endif /* CONFIG_CMD_NAND */
#if defined(CONFIG_CMD_ONENAND)
onenand_init();
#endif
#ifdef CONFIG_GENERIC_MMC
puts("MMC: ");
mmc_initialize(gd->bd);
#endif
#ifdef CONFIG_CMD_SCSI
puts("SCSI: ");
scsi_init();
#endif
#ifdef CONFIG_HAS_DATAFLASH
AT91F_DataflashInit();
dataflash_print_info();
#endif
/* initialize environment */
if (should_load_env())
env_relocate();
else
set_default_env(NULL);
#if defined(CONFIG_CMD_PCI) || defined(CONFIG_PCI)
arm_pci_init();
#endif
stdio_init(); /* get the devices list going. */
jumptable_init();
#if defined(CONFIG_API)
/* Initialize API */
api_init();
#endif
console_init_r(); /* fully init console as a device */
#ifdef CONFIG_PMIC_REG_DUMP
power_init_board();
#endif
#ifdef CONFIG_DISPLAY_BOARDINFO_LATE
# ifdef CONFIG_OF_CONTROL
/* Put this here so it appears on the LCD, now it is ready */
display_fdt_model(gd->fdt_blob);
# else
checkboard();
# endif
#endif
#if defined(CONFIG_ARCH_MISC_INIT)
/* miscellaneous arch dependent initialisations */
arch_misc_init();
#endif
#if defined(CONFIG_MISC_INIT_R)
/* miscellaneous platform dependent initialisations */
misc_init_r();
#endif
/* set up exceptions */
interrupt_init();
/* enable exceptions */
enable_interrupts();
/* Initialize from environment */
load_addr = getenv_ulong("loadaddr", 16, load_addr);
#ifdef CONFIG_BOARD_LATE_INIT
board_late_init();
#endif
#ifdef CONFIG_BITBANGMII
bb_miiphy_init();
#endif
#if defined(CONFIG_CMD_NET)
puts("Net: ");
eth_initialize(gd->bd);
#if defined(CONFIG_RESET_PHY_R)
debug("Reset Ethernet PHY\n");
reset_phy();
#endif
#endif
#ifdef CONFIG_POST
post_run(NULL, POST_RAM | post_bootmode_get(0));
#endif
#if defined(CONFIG_PRAM) || defined(CONFIG_LOGBUFFER)
/*
* Export available size of memory for Linux,
* taking into account the protected RAM at top of memory
*/
{
ulong pram = 0;
uchar memsz[32];
#ifdef CONFIG_PRAM
pram = getenv_ulong("pram", 10, CONFIG_PRAM);
#endif
#ifdef CONFIG_LOGBUFFER
#ifndef CONFIG_ALT_LB_ADDR
/* Also take the logbuffer into account (pram is in kB) */
pram += (LOGBUFF_LEN + LOGBUFF_OVERHEAD) / 1024;
#endif
#endif
sprintf((char *)memsz, "%ldk", (gd->ram_size / 1024) - pram);
setenv("mem", (char *)memsz);
}
#endif
/* main_loop() can return to retry autoboot, if so just run it again. */
for (;;) {
main_loop();
}
/* NOTREACHED - no way out of command loop except booting */
}
200多行其实有关的只有这个main_loop();循环。
main_loop();循环：
/* We come here after U-Boot is initialised and ready to process commands */
void main_loop(void)
{
const char *s;
bootstage_mark_name(BOOTSTAGE_ID_MAIN_LOOP, "main_loop");
#ifndef CONFIG_SYS_GENERIC_BOARD
puts("Warning: Your board does not use generic board. Please read\n");
puts("doc/README.generic-board and take action. Boards not\n");
puts("upgraded by the late 2014 may break or be removed.\n");
#endif
modem_init();
#ifdef CONFIG_VERSION_VARIABLE
setenv("ver", version_string); /* set version variable */
#endif /* CONFIG_VERSION_VARIABLE */
cli_init();
run_preboot_environment_command();
#if defined(CONFIG_UPDATE_TFTP)
update_tftp(0UL);
#endif /* CONFIG_UPDATE_TFTP */
s = bootdelay_process();
if (cli_process_fdt(&s))
cli_secure_boot_cmd(s);
autoboot_command(s);
cli_loop();
}autoboot_command(s);
void autoboot_command(const char *s)
{
debug("### main_loop: bootcmd=\"%s\"\n", s ? s : "");
if (stored_bootdelay != -1 && s && !abortboot(stored_bootdelay)) {
#if defined(CONFIG_AUTOBOOT_KEYED) && !defined(CONFIG_AUTOBOOT_KEYED_CTRLC)
int prev = disable_ctrlc(1); /* disable Control C checking */
#endif
run_command_list(s, -1, 0);
#if defined(CONFIG_AUTOBOOT_KEYED) && !defined(CONFIG_AUTOBOOT_KEYED_CTRLC)
disable_ctrlc(prev); /* restore Control C checking */
#endif
}
#ifdef CONFIG_MENUKEY
if (menukey == CONFIG_MENUKEY) {
s = getenv("menucmd");
if (s)
run_command_list(s, -1, 0);
}
#endif /* CONFIG_MENUKEY */
} 我把编译指令都用黄色去掉，发现剩下的就是一个abortboot();这个函数比较有用。
abortboot();
static int abortboot(int bootdelay)
{
#ifdef CONFIG_AUTOBOOT_KEYED
return abortboot_keyed(bootdelay);
#else
return abortboot_normal(bootdelay);
#endif
}abortboot_normal();
static int abortboot_normal(int bootdelay)
{
int abort = 0;
unsigned long ts;
#ifdef CONFIG_MENUPROMPT
printf(CONFIG_MENUPROMPT);
#else
if (bootdelay >= 0)
printf("Hit any key to stop autoboot: %2d ", bootdelay);
#endif
#if defined CONFIG_ZERO_BOOTDELAY_CHECK
/*
* Check if key already pressed
* Don't check if bootdelay < 0
*/
if (bootdelay >= 0) {
if (tstc()) { /* we got a key press */
(void) getc(); /* consume input */
puts("\b\b\b 0");
abort = 1; /* don't auto boot */
}
}
#endif
while ((bootdelay > 0) && (!abort)) {
--bootdelay;
/* delay 1000 ms */
ts = get_timer(0);
do {
if (tstc()) { /* we got a key press */
abort = 1; /* don't auto boot */
bootdelay = 0; /* no more delay */
# ifdef CONFIG_MENUKEY
menukey = getc();
# else
(void) getc(); /* consume input */
# endif
break;
}
udelay(10000);
} while (!abort && get_timer(ts) < 1000);
printf("\b\b\b%2d ", bootdelay);
}
putc('\n');
#ifdef CONFIG_SILENT_CONSOLE
if (abort)
gd->flags &= ~GD_FLG_SILENT;
#endif
return abort;
}这个函数里面重要的都用红色标出，其中tstc();函数是查询串口的接收标志位，每次buf中收到数据（对应着如果你在这时候按下了某个按键）从而打断uboot自动加载内核从而进入command line模式。
假设没有按键，让其启动内核。这时候函数返回，执行run_command_list();函数。
int run_command_list(const char *cmd, int len, int flag)
{
int need_buff = 1;
char *buff = (char *)cmd; /* cast away const */
int rcode = 0;
if (len == -1) {
len = strlen(cmd);
#ifdef CONFIG_SYS_HUSH_PARSER
/* hush will never change our string */
need_buff = 0;
#else
/* the built-in parser will change our string if it sees \n */
need_buff = strchr(cmd, '\n') != NULL;
#endif
}
if (need_buff) {
buff = malloc(len + 1);
if (!buff)
return 1;
memcpy(buff, cmd, len);
buff[len] = '\0';
}
#ifdef CONFIG_SYS_HUSH_PARSER
rcode = parse_string_outer(buff, FLAG_PARSE_SEMICOLON);
#else
/*
* This function will overwrite any \n it sees with a \0, which
* is why it can't work with a const char *. Here we are making
* using of internal knowledge of this function, to avoid always
* doing a malloc() which is actually required only in a case that
* is pretty rare.
*/
rcode = cli_simple_run_command_list(buff, flag);
if (need_buff)
free(buff);
#endif
return rcode;
}cli_simple_run_command_list();
int cli_simple_run_command_list(char *cmd, int flag)
{
char *line, *next;
int rcode = 0;
/*
* Break into individual lines, and execute each line; terminate on
* error.
*/
next = cmd;
line = cmd;
while (*next) {
if (*next == '\n') {
*next = '\0';
/* run only non-empty commands */
if (*line) {
debug("** exec: \"%s\"\n", line);
if (cli_simple_run_command(line, 0) < 0) {
rcode = 1;
break;
}
}
line = next + 1;
}
++next;
}
if (rcode == 0 && *line)
rcode = (cli_simple_run_command(line, 0) < 0);
return rcode;
} cli_simple_run_command();/*
* WARNING:
*
* We must create a temporary copy of the command since the command we get
* may be the result from getenv(), which returns a pointer directly to
* the environment data, which may change magicly when the command we run
* creates or modifies environment variables (like "bootp" does).
*/
int cli_simple_run_command(const char *cmd, int flag)
{
char cmdbuf[CONFIG_SYS_CBSIZE]; /* working copy of cmd */
char *token; /* start of token in cmdbuf */
char *sep; /* end of token (separator) in cmdbuf */
char finaltoken[CONFIG_SYS_CBSIZE];
char *str = cmdbuf;
char *argv[CONFIG_SYS_MAXARGS + 1]; /* NULL terminated */
int argc, inquotes;
int repeatable = 1;
int rc = 0;
debug_parser("[RUN_COMMAND] cmd[%p]=\"", cmd);
if (DEBUG_PARSER) {
/* use puts - string may be loooong */
puts(cmd ? cmd : "NULL");
puts("\"\n");
}
clear_ctrlc(); /* forget any previous Control C */
if (!cmd || !*cmd)
return -1; /* empty command */
if (strlen(cmd) >= CONFIG_SYS_CBSIZE) {
puts("## Command too long!\n");
return -1;
}
strcpy(cmdbuf, cmd);
/* Process separators and check for invalid
* repeatable commands
*/
debug_parser("[PROCESS_SEPARATORS] %s\n", cmd);
while (*str) {
/*
* Find separator, or string end
* Allow simple escape of ';' by writing "\;"
*/
for (inquotes = 0, sep = str; *sep; sep++) {
if ((*sep == '\'') &&
(*(sep - 1) != '\\'))
inquotes = !inquotes;
if (!inquotes &&
(*sep == ';') && /* separator */
(sep != str) && /* past string start */
(*(sep - 1) != '\\')) /* and NOT escaped */
break;
}
/*
* Limit the token to data between separators
*/
token = str;
if (*sep) {
str = sep + 1; /* start of command for next pass */
*sep = '\0';
} else {
str = sep; /* no more commands for next pass */
}
debug_parser("token: \"%s\"\n", token);
/* find macros in this token and replace them */
process_macros(token, finaltoken);
/* Extract arguments */
argc = cli_simple_parse_line(finaltoken, argv);
if (argc == 0) {
rc = -1; /* no command at all */
continue;
}
if (cmd_process(flag, argc, argv, &repeatable, NULL))
rc = -1;
/* Did the user stop this? */
if (had_ctrlc())
return -1; /* if stopped then not repeatable */
}
return rc ? rc : repeatable;
}cmd_process();
enum command_ret_t cmd_process(int flag, int argc, char * const argv[],
int *repeatable, ulong *ticks)
{
enum command_ret_t rc = CMD_RET_SUCCESS;
cmd_tbl_t *cmdtp;
/* Look up command in command table */
cmdtp = find_cmd(argv[0]);
if (cmdtp == NULL) {
printf("Unknown command '%s' - try 'help'\n", argv[0]);
return 1;
}
/* found - check max args */
if (argc > cmdtp->maxargs)
rc = CMD_RET_USAGE;
#if defined(CONFIG_CMD_BOOTD)
/* avoid "bootd" recursion */
else if (cmdtp->cmd == do_bootd) {
if (flag & CMD_FLAG_BOOTD) {
puts("'bootd' recursion detected\n");
rc = CMD_RET_FAILURE;
} else {
flag |= CMD_FLAG_BOOTD;
}
}
#endif
/* If OK so far, then do the command */
if (!rc) {
if (ticks)
*ticks = get_timer(0);
rc = cmd_call(cmdtp, flag, argc, argv);
if (ticks)
*ticks = get_timer(*ticks);
*repeatable &= cmdtp->repeatable;
}
if (rc == CMD_RET_USAGE)
rc = cmd_usage(cmdtp);
return rc;
}
cmd_call();
/**
* Call a command function. This should be the only route in U-Boot to call
* a command, so that we can track whether we are waiting for input or
* executing a command.
*
* @param cmdtp Pointer to the command to execute
* @param flag Some flags normally 0 (see CMD_FLAG_.. above)
* @param argc Number of arguments (arg 0 must be the command text)
* @param argv Arguments
* @return 0 if command succeeded, else non-zero (CMD_RET_...)
*/
static int cmd_call(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
int result;
result = (cmdtp->cmd)(cmdtp, flag, argc, argv);
if (result)
debug("Command failed, result=%d", result);
return result;
}到了这里应该算是结束了。。。下图就是cmd_tbl_s结构体，这个结构体定义了uboot能够识别并且执行的命令，其中包括了name,maxargs,(*cmd）其中cmd就是指令对应处理函数的指针。
struct cmd_tbl_s {
char *name; /* Command Name */
int maxargs; /* maximum number of arguments */
int repeatable; /* autorepeat allowed? */
/* Implementation function */
int (*cmd)(struct cmd_tbl_s *, int, int, char * const []);
char *usage; /* Usage message (short) */
#ifdef CONFIG_SYS_LONGHELP
char *help; /* Help message (long) */
#endif
#ifdef CONFIG_AUTO_COMPLETE
/* do auto completion on the arguments */
int (*complete)(int argc, char * const argv[], char last_char, int maxv, char *cmdv[]);
#endif
};
typedef struct cmd_tbl_s cmd_tbl_t;加载内核用的是do_bootm命令，可以查到对应的cmd_tbl_s结构。
到了这里就算是完成了这些工作。