BL2的最后通过汇编调用了board_init_r函数，此时进入BL3的阶段，此时的主要工作：
这一阶段涉及的文件及任务如下
arch/arm/lib/board.c
1. board_init_r()是进入定制板目录的入口
common/main.c
2. main_loop()中关闭中断，执行命令以及加载引导内核
下面分析一下board_init_r函数：
/*
************************************************************************
*
* 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)
{
...
bd_t *bd;
...
gd = id;
bd = gd->bd;
gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */
monitor_flash_len = _end_ofs;
...
debug("monitor flash len: %08lX\n", monitor_flash_len);
board_init(); /* Setup chipselects */
上述代码的作用是对gd和bd进行赋值，其中monitor_flash_len为整个U-Boot的长度。
malloc_start = dest_addr - TOTAL_MALLOC_LEN - sizeof(struct spare_boot_head_t);
...
/* The Malloc area is immediately below the monitor copy in DRAM */
mem_malloc_init (malloc_start, TOTAL_MALLOC_LEN);
对SDRAM中的malloc空间进行清零初始化。
#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
*/
s = getenv("flashchecksum");
if (s && (*s == ‘y‘)) {
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
上述代码的作用是计算FLASH的大小，并把它通过串口显示在控制台上。由于没有定义CONFIG_SYS_FLASH_CHECKSUM，所以没有执行CRC的校验和。其中flash_init函数是在drivers/mtd目录下的cfi_flash.c文件内（因为include/configs/smdk2410.h中定义了CONFIG_FLASH_CFI_DRIVER）。
/* set up exceptions */
interrupt_init();
/* enable exceptions */
enable_interrupts();
interrupt_init函数是建立IRQ中断堆栈，enable_interrupts函数是使能IRQ中断，它们都是在arch/arm/lib目录下的interrupts.c文件中定义的。
...
/* initialize environment */
env_relocate();
初始化环境变量，由于gd->env_valid等于0，所以在这里设置的是缺省环境变量。env_relocate函数是在common目录下的env_common.c文件中定义的。
#if defined(CONFIG_CMD_PCI) || defined(CONFIG_PCI)
arm_pci_init();
#endif
初始化PCI。
/* IP Address */
gd->bd->bi_ip_addr = getenv_IPaddr("ipaddr");
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 */
上面代码的作用分别对应：
设置IP地址。
初始化各类外设，如IIC、LCD、键盘、USB等，当然只有在定义了这些外设的前提下，才对这些外设进行初始化。该函数是在common目录下的stdio.c文件中定义的。
初始化跳转表gd->jt，该跳转表是一个函数指针数组，它定义了U-Boot中基本的常用函数库。该函数是在common目录下的exports.c文件中定义的。
初始化API。
初始化控制台，即标准输入、标准输出和标准错误，在这里都是串口。该函数是在common目录下的console.c文件中定义的。
/* Initialize from environment */
s = getenv("loadaddr");
if (s != NULL)
load_addr = simple_strtoul(s, NULL, 16);
从环境变量中获取loadaddr参数，得到需要加载的地址。
#if defined(CONFIG_CMD_NET)
s = getenv("bootfile");
if (s != NULL)
copy_filename(BootFile, s, sizeof(BootFile));
#endif
从环境变量中获取bootfile参数，得到通过TFTP加载的镜像文件名。
#if defined(CONFIG_CMD_NET)
#if defined(CONFIG_NET_MULTI)
puts("Net: ");
#endif
eth_initialize(gd->bd);
#if defined(CONFIG_RESET_PHY_R)
debug("Reset Ethernet PHY\n");
reset_phy();
#endif
#endif
初始化以太网，其中eth_initialize函数是在net目录下的eth.c文件中定义的。
...
/* main_loop() can return to retry autoboot, if so just run it again. */
for (;;)
{
main_loop();
}
hang();
/* NOTREACHED - no way out of command loop except booting */
}
board_init_r函数的最后就是执行一个死循环，调用main_loop函数。该函数是在common目录下的main.c文件内定义的。
总结：
3.接下来分析main_loop函数：
void main_loop (void)
{
#ifndef CONFIG_SYS_HUSH_PARSER
static char lastcommand[CONFIG_SYS_CBSIZE] = { 0, };
int len;
int rc = 1;
int flag;
#endif
声明一些hush参数。关于hush后面会讲到。
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
char *s;
int bootdelay;
#endif
声明启动延时需要的参数。
#ifdef CONFIG_SYS_HUSH_PARSER
u_boot_hush_start ();
#endif
初始化hush功能。稍后再说。
1 #if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
2 s = getenv ("bootdelay");
3 bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;
4
5 debug ("### main_loop entered: bootdelay=%d\n\n", bootdelay);
6
7 # ifdef CONFIG_BOOT_RETRY_TIME
8 init_cmd_timeout ();
9 # endif /* CONFIG_BOOT_RETRY_TIME */
10
11 #ifdef CONFIG_POST
12 if (gd->flags & GD_FLG_POSTFAIL) {
13 s = getenv("failbootcmd");
14 }
15 else
16 #endif /* CONFIG_POST */
17 #ifdef CONFIG_BOOTCOUNT_LIMIT
18 if (bootlimit && (bootcount > bootlimit)) {
19 printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd.\n",
20 (unsigned)bootlimit);
21 s = getenv ("altbootcmd");
22 }
23 else
24 #endif /* CONFIG_BOOTCOUNT_LIMIT */
25 s = getenv ("bootcmd");
26
27 debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");
28
29 if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
30 # ifdef CONFIG_AUTOBOOT_KEYED
31 int prev = disable_ctrlc(1); /* disable Control C checking */
32 # endif
33
34 # ifndef CONFIG_SYS_HUSH_PARSER
35 run_command (s, 0);
36 # else
37 parse_string_outer(s, FLAG_PARSE_SEMICOLON |
38 FLAG_EXIT_FROM_LOOP);
39 # endif
40
41 # ifdef CONFIG_AUTOBOOT_KEYED
42 disable_ctrlc(prev); /* restore Control C checking */
43 # endif
44 }
45
46 # ifdef CONFIG_MENUKEY
47 if (menukey == CONFIG_MENUKEY) {
48 s = getenv("menucmd");
49 if (s) {
50 # ifndef CONFIG_SYS_HUSH_PARSER
51 run_command(s, 0);
52 # else
53 parse_string_outer(s, FLAG_PARSE_SEMICOLON |
54 FLAG_EXIT_FROM_LOOP);
55 # endif
56 }
57 }
58 #endif /* CONFIG_MENUKEY */
59 #endif /* CONFIG_BOOTDELAY */
第2行和第3行的含义是从环境变量中获取bootdelay参数，得到自动启动缺省镜像文件的延时（单位是秒）。
其中bootdelay的作用是：uboot正常启动后，会调用main_loop(void)函数，进入main_loop()之后，如果在规定的时间（CONFIG_BOOTDELAY）内，没有检查到任何按键事件的发生，就会去加载OS，并启动系统。
第8行的含义是初始化命令行超时机制。
第25行的含义是从环境变量中获取bootcmd参数，得到在启动延时过程中自动执行的命令。当我们得到了bootcmd参数，bootdelay参数也是大于等于0，并且在启动延时过程中没有按下任意键时，执行第37行的parse_string_outer函数，该函数的作用是解释bootcmd参数
并执行，它是在common目录下的hush.c文件内定义的。
1 /*
2 * Main Loop for Monitor Command Processing
3 */
4 #ifdef CONFIG_SYS_HUSH_PARSER
5 parse_file_outer();
6 /* This point is never reached */
7 for (;;);
8 #else
9 for (;;) {
10 #ifdef CONFIG_BOOT_RETRY_TIME
11 if (rc >= 0) {
12 /* Saw enough of a valid command to
13 * restart the timeout.
14 */
15 reset_cmd_timeout();
16 }
17 #endif
18 len = readline (CONFIG_SYS_PROMPT);
19
20 flag = 0; /* assume no special flags for now */
21 if (len > 0)
22 strcpy (lastcommand, console_buffer);
23 else if (len == 0)
24 flag |= CMD_FLAG_REPEAT;
25 #ifdef CONFIG_BOOT_RETRY_TIME
26 else if (len == -2) {
27 /* -2 means timed out, retry autoboot
28 */
29 puts ("\nTimed out waiting for command\n");
30 # ifdef CONFIG_RESET_TO_RETRY
31 /* Reinit board to run initialization code again */
32 do_reset (NULL, 0, 0, NULL);
33 # else
34 return; /* retry autoboot */
35 # endif
36 }
37 #endif
38
39 if (len == -1)
40 puts ("<INTERRUPT>\n");
41 else
42 rc = run_command (lastcommand, flag);
43
44 if (rc <= 0) {
45 /* invalid command or not repeatable, forget it */
46 lastcommand[0] = 0;
47 }
48 }
49 #endif /*CONFIG_SYS_HUSH_PARSER*/
50 }
由于在include/configs/smdk2410.h文件中定义了CONFIG_SYS_HUSH_PARSER，所以上面的代码仅仅执行的是第5行至第7行的内容。第5行的parse_file_outer函数是在common目录下的hush.c文件中定义的，它的含义是依次读取命令序列中的命令并执行之，其中在该
函数还调用了parse_stream_outer函数，这个函数体内有一个do-while循环，只有发生语法错误的时候才会跳出该循环，因此一般情况下永远也不会执行上面代码中的第7行内容，而是始终在那个do-while循环体内。
上面说到过如果在CONFIG_BOOTDELAY时间内，用户按下键盘上的任意一个按键，uboot就会进入与用户交互的状态。如果用户在配置文件中定义了CONFIG_SYS_HUSH_PARSER，就会通过parse_file_outer()，去接收并解析用户命令，否则进入一个for（;;）循环，
通过 readline (CONFIG_SYS_PROMPT)接收用户命令，然后调用run_command(cmd,flag)去解析并执行命令。
当在配置文件中定义了CONFIG_SYS_HUSH_PARSER，main_loop会调用parse_file_outer()，进入hush中。其中parse_file_outer()在u-boot\common\hush.c下。
#ifndef __U_BOOT__
static int parse_file_outer(FILE *f)
#else
int parse_file_outer(void)
#endif
{
int rcode;
struct in_str input;
#ifndef __U_BOOT__
setup_file_in_str(&input, f);
#else
setup_file_in_str(&input);
#endif
rcode = parse_stream_outer(&input, FLAG_PARSE_SEMICOLON);
return rcode;
}
/* most recursion does not come through here, the exeception is
* from builtin_source() */
int parse_stream_outer(struct in_str *inp, int flag)
{
struct p_context ctx;
o_string temp=NULL_O_STRING;
int rcode;
#ifdef __U_BOOT__
int code = 0;
#endif
do {
ctx.type = flag;
initialize_context(&ctx);
update_ifs_map();
if (!(flag & FLAG_PARSE_SEMICOLON) || (flag & FLAG_REPARSING)) mapset((uchar *)";$&|", 0);
inp->promptmode=1;
rcode = parse_stream(&temp, &ctx, inp, ‘\n‘);
#ifdef __U_BOOT__
if (rcode == 1) flag_repeat = 0;
#endif
if (rcode != 1 && ctx.old_flag != 0) {
syntax();
#ifdef __U_BOOT__
flag_repeat = 0;
#endif
}
if (rcode != 1 && ctx.old_flag == 0) {
done_word(&temp, &ctx);
done_pipe(&ctx,PIPE_SEQ);
#ifndef __U_BOOT__
run_list(ctx.list_head);
#else
code = run_list(ctx.list_head);
if (code == -2) { /* exit */
b_free(&temp);
code = 0;
/* XXX hackish way to not allow exit from main loop */
if (inp->peek == file_peek) {
printf("exit not allowed from main input shell.\n");
continue;
}
break;
}
if (code == -1)
flag_repeat = 0;
#endif
} else {
if (ctx.old_flag != 0) {
free(ctx.stack);
b_reset(&temp);
}
#ifdef __U_BOOT__
if (inp->__promptme == 0) printf("<INTERRUPT>\n");
inp->__promptme = 1;
#endif
temp.nonnull = 0;
temp.quote = 0;
inp->p = NULL;
free_pipe_list(ctx.list_head,0);
}
b_free(&temp);
} while (rcode != -1 && !(flag & FLAG_EXIT_FROM_LOOP)); /* loop on syntax errors, return on EOF */
#ifndef __U_BOOT__
return 0;
#else
return (code != 0) ? 1 : 0;
#endif /* __U_BOOT__ */
}
hush是uboot中命令接收和解析的工具，与uboot原始的命令解析方法相比，该工具更加智能。
这里会在run_list中调用到hush中的run_pipe_real(struct pipe *pi)，在该函数中经过一些列解析，最终会调用到对应的命令执行函数。
/* run_pipe_real() starts all the jobs, but doesn‘t wait for anything
* to finish. See checkjobs().
*
* return code is normally -1, when the caller has to wait for children
* to finish to determine the exit status of the pipe. If the pipe
* is a simple builtin command, however, the action is done by the
* time run_pipe_real returns, and the exit code is provided as the
* return value.
*
* The input of the pipe is always stdin, the output is always
* stdout. The outpipe[] mechanism in BusyBox-0.48 lash is bogus,
* because it tries to avoid running the command substitution in
* subshell, when that is in fact necessary. The subshell process
* now has its stdout directed to the input of the appropriate pipe,
* so this routine is noticeably simpler.
*/
static int run_pipe_real(struct pipe *pi)
{
int i;
#ifndef __U_BOOT__
int nextin, nextout;
int pipefds[2]; /* pipefds[0] is for reading */
struct child_prog *child;
struct built_in_command *x;
char *p;
# if __GNUC__
/* Avoid longjmp clobbering */
(void) &i;
(void) &nextin;
(void) &nextout;
(void) &child;
# endif
#else
int nextin;
int flag = do_repeat ? CMD_FLAG_REPEAT : 0;
struct child_prog *child;
cmd_tbl_t *cmdtp;
char *p;
# if __GNUC__
/* Avoid longjmp clobbering */
(void) &i;
(void) &nextin;
(void) &child;
# endif
#endif /* __U_BOOT__ */
nextin = 0;
#ifndef __U_BOOT__
pi->pgrp = -1;
#endif
/* Check if this is a simple builtin (not part of a pipe).
* Builtins within pipes have to fork anyway, and are handled in
* pseudo_exec. "echo foo | read bar" doesn‘t work on bash, either.
*/
if (pi->num_progs == 1) child = & (pi->progs[0]);
#ifndef __U_BOOT__
if (pi->num_progs == 1 && child->group && child->subshell == 0) {
int squirrel[] = {-1, -1, -1};
int rcode;
debug_printf("non-subshell grouping\n");
setup_redirects(child, squirrel);
/* XXX could we merge code with following builtin case,
* by creating a pseudo builtin that calls run_list_real? */
rcode = run_list_real(child->group);
restore_redirects(squirrel);
#else
if (pi->num_progs == 1 && child->group) {
int rcode;
debug_printf("non-subshell grouping\n");
rcode = run_list_real(child->group);
#endif
return rcode;
} else if (pi->num_progs == 1 && pi->progs[0].argv != NULL) {
for (i=0; is_assignment(child->argv[i]); i++) { /* nothing */ }
if (i!=0 && child->argv[i]==NULL) {
/* assignments, but no command: set the local environment */
for (i=0; child->argv[i]!=NULL; i++) {
/* Ok, this case is tricky. We have to decide if this is a
* local variable, or an already exported variable. If it is
* already exported, we have to export the new value. If it is
* not exported, we need only set this as a local variable.
* This junk is all to decide whether or not to export this
* variable. */
int export_me=0;
char *name, *value;
name = xstrdup(child->argv[i]);
debug_printf("Local environment set: %s\n", name);
value = strchr(name, ‘=‘);
if (value)
*value=0;
#ifndef __U_BOOT__
if ( get_local_var(name)) {
export_me=1;
}
#endif
free(name);
p = insert_var_value(child->argv[i]);
set_local_var(p, export_me);
if (p != child->argv[i]) free(p);
}
return EXIT_SUCCESS; /* don‘t worry about errors in set_local_var() yet */
}
for (i = 0; is_assignment(child->argv[i]); i++) {
p = insert_var_value(child->argv[i]);
#ifndef __U_BOOT__
putenv(strdup(p));
#else
set_local_var(p, 0);
#endif
if (p != child->argv[i]) {
child->sp--;
free(p);
}
}
if (child->sp) {
char * str = NULL;
str = make_string((child->argv + i));
parse_string_outer(str, FLAG_EXIT_FROM_LOOP | FLAG_REPARSING);
free(str);
return last_return_code;
}
#ifndef __U_BOOT__
for (x = bltins; x->cmd; x++) {
if (strcmp(child->argv[i], x->cmd) == 0 ) {
int squirrel[] = {-1, -1, -1};
int rcode;
if (x->function == builtin_exec && child->argv[i+1]==NULL) {
debug_printf("magic exec\n");
setup_redirects(child,NULL);
return EXIT_SUCCESS;
}
debug_printf("builtin inline %s\n", child->argv[0]);
/* XXX setup_redirects acts on file descriptors, not FILEs.
* This is perfect for work that comes after exec().
* Is it really safe for inline use? Experimentally,
* things seem to work with glibc. */
setup_redirects(child, squirrel);
#else
/* check ";", because ,example , argv consist from
* "help;flinfo" must not execute
*/
if (strchr(child->argv[i], ‘;‘)) {
printf ("Unknown command ‘%s‘ - try ‘help‘ or use ‘run‘ command\n",
child->argv[i]);
return -1;
}
/* Look up command in command table */
if ((cmdtp = find_cmd(child->argv[i])) == NULL) {
printf ("Unknown command ‘%s‘ - try ‘help‘\n", child->argv[i]);
return -1; /* give up after bad command */
} else {
int rcode;
#if defined(CONFIG_CMD_BOOTD)
/* avoid "bootd" recursion */
if (cmdtp->cmd == do_bootd) {
if (flag & CMD_FLAG_BOOTD) {
printf ("‘bootd‘ recursion detected\n");
return -1;
}
else
flag |= CMD_FLAG_BOOTD;
}
#endif
/* found - check max args */
if ((child->argc - i) > cmdtp->maxargs)
return cmd_usage(cmdtp);
#endif
child->argv+=i; /* XXX horrible hack */
#ifndef __U_BOOT__
rcode = x->function(child);
#else
/* OK - call function to do the command */
rcode = (cmdtp->cmd)
(cmdtp, flag,child->argc-i,&child->argv[i]);
if ( !cmdtp->repeatable )
flag_repeat = 0;
#endif
child->argv-=i; /* XXX restore hack so free() can work right */
#ifndef __U_BOOT__
restore_redirects(squirrel);
#endif
return rcode;
}
}
#ifndef __U_BOOT__
}
for (i = 0; i < pi->num_progs; i++) {
child = & (pi->progs[i]);
/* pipes are inserted between pairs of commands */
if ((i + 1) < pi->num_progs) {
if (pipe(pipefds)<0) perror_msg_and_die("pipe");
nextout = pipefds[1];
} else {
nextout=1;
pipefds[0] = -1;
}
/* XXX test for failed fork()? */
if (!(child->pid = fork())) {
/* Set the handling for job control signals back to the default. */
signal(SIGINT, SIG_DFL);
signal(SIGQUIT, SIG_DFL);
signal(SIGTERM, SIG_DFL);
signal(SIGTSTP, SIG_DFL);
signal(SIGTTIN, SIG_DFL);
signal(SIGTTOU, SIG_DFL);
signal(SIGCHLD, SIG_DFL);
close_all();
if (nextin != 0) {
dup2(nextin, 0);
close(nextin);
}
if (nextout != 1) {
dup2(nextout, 1);
close(nextout);
}
if (pipefds[0]!=-1) {
close(pipefds[0]); /* opposite end of our output pipe */
}
/* Like bash, explicit redirects override pipes,
* and the pipe fd is available for dup‘ing. */
setup_redirects(child,NULL);
if (interactive && pi->followup!=PIPE_BG) {
/* If we (the child) win the race, put ourselves in the process
* group whose leader is the first process in this pipe. */
if (pi->pgrp < 0) {
pi->pgrp = getpid();
}
if (setpgid(0, pi->pgrp) == 0) {
tcsetpgrp(2, pi->pgrp);
}
}
pseudo_exec(child);
}
/* put our child in the process group whose leader is the
first process in this pipe */
if (pi->pgrp < 0) {
pi->pgrp = child->pid;
}
/* Don‘t check for errors. The child may be dead already,
* in which case setpgid returns error code EACCES. */
setpgid(child->pid, pi->pgrp);
if (nextin != 0)
close(nextin);
if (nextout != 1)
close(nextout);
/* If there isn‘t another process, nextin is garbage
but it doesn‘t matter */
nextin = pipefds[0];
}
#endif
return -1;
}
上面关键是这段：
/* OK - call function to do the command */
rcode = (cmdtp->cmd)
(cmdtp, flag,child->argc-i,&child->argv[i]);
if ( !cmdtp->repeatable )
flag_repeat = 0;
通过这段代码调用对应的命令执行函数。cmd_tbl_t的结构如下：
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;
对于uboot支持的每一个命令，是通过U_BOOT_CMD宏定义的，他定义了该命令对应的名称name，支持的最大参数rep，重复次数，实现函数cmd，以及输入help命令时，显示的帮助信息usage。
在执行函数cmd中，第一个参数对应该命令结构本身的指针，第二个参数对应flag标记，第三个参数对应参数数目，第四个参数是指针数组，里面存储的是对应参数的指针。
时间： 2024-11-10 07:17:49