uboot启动文件start.s和main.c解析

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Ubooti启动文件解析

start.S

#include <config.h>

#include <version.h>

#if defined(CONFIG_OMAP1610)

#include <./configs/omap1510.h>

#elif defined(CONFIG_OMAP730)

#include <./configs/omap730.h>

#elif defined(CONFIG_HISILICON)

#include <asm/arch/platform.h>

#endif

*************************************************************************

*Jump vector table as in table 3.1 in [1]

*************************************************************************

/*******.globl声明一个符号可以被外部使用，相当于声明一个全局变量******/

.globl _start

_start:

/*******该部分为处理器的异常向量表，地址0x0000 0000 ~ 0x0000 0020******/

b reset

ldr pc, _undefined_instruction

ldr pc, _software_interrupt

ldr pc, _prefetch_abort

ldr pc, _data_abort

ldr pc, _not_used

ldr pc, _irq

ldr pc, _fiq

/*******.word伪操作是分配第一段子内存单元，并用expr初始化，此处即为存放中断函数地址******/

_undefined_instruction:

.wordundefined_instruction

_software_interrupt:

.wordsoftware_interrupt

_prefetch_abort:

.wordprefetch_abort

_data_abort:

.worddata_abort

_not_used:

.wordnot_used

_irq:

.wordirq

_fiq:

.wordfiq

/*******.align等同于balign******/

.balignl16,0xdeadbeef

*************************************************************************

*Startup Code (reset vector)

* doimportant init only if we don't start from memory!

*setup Memory and board specific bits prior to relocation.

*relocate armboot to ram

*setup stack

*************************************************************************

/******定义在/board/hi3515v100/config.mk中*******/

_TEXT_BASE:

.word TEXT_BASE

.globl _armboot_start

_armboot_start:

.word_start

.globl _img_end

_img_end:

.word__img_end

*These are defined in the board-specific linker script.

.globl _bss_start

_bss_start:

.word__bss_start

.globl _bss_end

_bss_end:

.word_end

#ifdef CONFIG_USE_IRQ

/* IRQ stack memory (calculated atrun-time) */

.globl IRQ_STACK_START

IRQ_STACK_START:

.word 0x0badc0de

/* IRQ stack memory (calculated atrun-time) */

.globl FIQ_STACK_START

FIQ_STACK_START:

.word0x0badc0de

#endif

#ifdef CONFIG_HISILICON

_clr_remap_rom_entry:

.word ROM_TEXT_ADRS + do_clr_remap - TEXT_BASE

_clr_remap_nand_entry:

.word NAND_TEXT_ADRS + do_clr_remap - TEXT_BASE

#endif

*the actual reset code

/*******实际的处理代码从这里开始******/

reset:

* set the cpu to SVC32 mode

mrs r0,cpsr /******将CPRS寄存器中的值传送给R0*******/

bic r0,r0,#0x1f /******清楚指定位r0 = r0&(!0x1f)*******/

orr r0,r0,#0xd3 /******或操作r0 = r0|0xd3*******/

msr cpsr,r0 /******将R0的值送回CPRS寄存器中*******/

* we do sys-critical inits only at reboot,

* not when booting from ram!

#ifndef CONFIG_SKIP_LOWLEVEL_INIT

* flush v4 I/D caches

mov r0, #0

mcr p15, 0, r0, c7, c7, 0 /* flush v3/v4 cache */

mcr p15, 0, r0, c8, c7, 0 /* flush v4 TLB <input type="text" >*/

* disable MMU stuff and caches

mrc p15, 0, r0, c1, c0, 0

bic r0, r0, #0x00002300 /* clear bits 13, 9:8 (--V- --RS) */

bic r0, r0, #0x00000087 /* clear bits 7, 2:0 (B--- -CAM) */

orr r0, r0, #0x00000002 /* set bit 2 (A) Align */

mcr p15, 0, r0, c1, c0, 0

ldr r0, =REG_BASE_SCTL

ldr r1, [r0, #0x8c]

and r1, r1, #0x60

lsr r4, r1, #5

@Checkif I need jump to rom

@movs r0, pc, lsr#24 /* Z flag if r0 == 0 then 1 else 0 */

@bne do_clr_remap

mov r0, pc, lsr#24

cmp r0, #0x0

bne do_clr_remap

cmp r4, #2 /*boot from nand flash*/

ldreq pc, _clr_remap_nand_entry

cmp r4, #0 /* boot from nor flash */

ldreq pc, _clr_remap_rom_entry

do_clr_remap:

ldr r4, =REG_BASE_SCTL

@ldr r0, =REG_VALUE_SC_NOLOCK

@str r0, [r4, #REG_VALUE_SC_LOCKED]

ldr r0, [r4, #REG_SC_CTRL]

@Setclear remap bit.

orr r0, #(1<<8)

str r0, [r4, #REG_SC_CTRL]

@SetupITCM (ENABLED, 2KB)

ldr r0, =( 1 | (MEM_CONF_ITCM_SIZE<<2) |MEM_BASE_ITCM)

mcr p15, 0, r0, c9, c1, 1

@enableI-Cache now

mrc p15, 0, r0, c1, c0, 0

orr r0, r0, #0x00001000 /* set bit 12 (I) I-Cache */

mcr p15, 0, r0, c1, c0, 0

@Setuplowlevel sp

ldr sp, =(MEM_BASE_ITCM + MEM_SIZE_ITCM)

@Checkif I'm running in static mem bank

mov r0, pc, lsr#28

cmp r0, #(TEXT_BASE>>28)

* Go setup Memory and board specific bitsprior to relocation.

beq relocate

/******跳转到lowlevel_init,该函数在board/hi3515v100/lowlevel_init.c*******/

bl lowlevel_init /* go setup pll,mux,memory */

#endif

#ifndef CONFIG_SKIP_RELOCATE_UBOOT

/******重定向代码，也就是uboot将自己从flash复制到RAM中*******/

relocate: /*relocate U-Boot to RAM */

ldr r0, =REG_BASE_SCTL

ldr r6, [r0, #0x8c]

and r6, #0x60

lsr r4, r6, #5

adr r0, _start /*r0 <- current position of code */

/******获取_TEXT_BASE地址,定义在/board/hi3515v100/config.mk中*******/

ldr r1, _TEXT_BASE /* test if we run from flash or RAM */

cmp r0, r1 /* don't reloc duringdebug */

beq stack_setup

ldr r2, _armboot_start

/******_img_end定义在/board/hi3515v100/u-boot.lds中*******/

ldr r3, _img_end

sub r2, r3, r2 /*r2 <- size of armboot */

cmp r4, #2

ldreq r2, =(CFG_NAND_U_BOOT_ONE_PART)

add r2, r0, r2 /*r2 <- source end address */

copy_loop:

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 */

//初始化堆栈

stack_setup:

ldr r0, _TEXT_BASE /* upper 128 KiB: relocated uboot */

sub r0, r0, #CFG_MALLOC_LEN /* malloc area */

sub r0, r0, #CFG_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 */

clear_bss:

ldr r0, _bss_start /* find start of bss segment */

ldr r1, _bss_end /*stop here */

mov r2, #0x00000000 /*clear */

clbss_l:str r2,[r0] /* clear loop... */

add r0, r0, #4

cmp r0, r1

ble clbss_l

/******跳转到start_armboot函数，该函数在/lib_arm/board.c*******/

ldr pc, _start_armboot

_start_armboot:

.wordstart_armboot

*************************************************************************

*Interrupt handling

*************************************************************************

@ IRQ stack frame.

#define S_FRAME_SIZE 72

#define S_OLD_R0 68

#define S_PSR 64

#define S_PC 60

#define S_LR 56

#define S_SP 52

#define S_IP 48

#define S_FP 44

#define S_R10 40

#define S_R9 36

#define S_R8 32

#define S_R7 28

#define S_R6 24

#define S_R5 20

#define S_R4 16

#define S_R3 12

#define S_R2 8

#define S_R1 4

#define S_R0 0

#define MODE_SVC 0x13

#define I_BIT 0x80

*use bad_save_user_regs for abort/prefetch/undef/swi ...

*use irq_save_user_regs / irq_restore_user_regs for IRQ/FIQ handling

.macro bad_save_user_regs

@carve out a frame on current user stack

sub sp, sp, #S_FRAME_SIZE

stmia sp, {r0 - r12} @ Save user registers (now in svc mode) r0-r12

ldr r2, _armboot_start

sub r2, r2, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)

sub r2, r2, #(CFG_GBL_DATA_SIZE+8) @ set base 2 words into abort stack

@get values for "aborted" pc and cpsr (into parm regs)

ldmia r2, {r2 - r3}

add r0, sp, #S_FRAME_SIZE @ grab pointer to old stack

add r5, sp, #S_SP

mov r1, lr

stmia r5, {r0 - r3} @ save sp_SVC, lr_SVC, pc, cpsr

mov r0, sp @save current stack into r0 (param register)

.endm

.macro irq_save_user_regs

sub sp, sp, #S_FRAME_SIZE

stmia sp, {r0 - r12} @ Calling r0-r12

@!!!! R8 NEEDS to be saved !!!! a reserved stack spot would be good.

add r8, sp, #S_PC

stmdb r8, {sp, lr}^ @ Calling SP, LR

str lr, [r8, #0] @Save calling PC

mrs r6, spsr

str r6, [r8, #4] @Save CPSR

str r0, [r8, #8] @Save OLD_R0

mov r0, sp

.endm

.macro irq_restore_user_regs

ldmia sp, {r0 - lr}^ @ Calling r0 - lr

mov r0, r0

ldr lr, [sp, #S_PC] @ Get PC

add sp, sp, #S_FRAME_SIZE

subs pc, lr, #4 @return & move spsr_svc into cpsr

.endm

.macroget_bad_stack

ldr r13, _armboot_start @ setup our mode stack

sub r13, r13, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)

sub r13, r13, #(CFG_GBL_DATA_SIZE+8) @ reserved acouple spots in abort stack

str lr, [r13] @save caller lr in position 0 of saved stack

mrs lr, spsr @get the spsr

str lr, [r13, #4] @ save spsr in position 1 of saved stack

mov r13, #MODE_SVC @prepare SVC-Mode

@msr spsr_c, r13

msr spsr, r13 @switch modes, make sure moves will execute

mov lr, pc @capture return pc

movs pc, lr @jump to next instruction & switch modes.

.endm

.macroget_irq_stack @setup IRQ stack

ldr sp, IRQ_STACK_START

.endm

.macroget_fiq_stack @setup FIQ stack

ldr sp, FIQ_STACK_START

.endm

*exception handlers

.align 5

undefined_instruction:

get_bad_stack

bad_save_user_regs

bl do_undefined_instruction

.align 5

software_interrupt:

get_bad_stack

bad_save_user_regs

bl do_software_interrupt

.align 5

prefetch_abort:

get_bad_stack

bad_save_user_regs

bl do_prefetch_abort

.align 5

data_abort:

get_bad_stack

bad_save_user_regs

bl do_data_abort

.align 5

not_used:

get_bad_stack

bad_save_user_regs

bl do_not_used

#ifdef CONFIG_USE_IRQ

.align 5

irq:

get_irq_stack

irq_save_user_regs

bl do_irq

irq_restore_user_regs

.align 5

fiq:

get_fiq_stack

/*someone ought to write a more effiction fiq_save_user_regs */

irq_save_user_regs

bl do_fiq

irq_restore_user_regs

#else

.align 5

irq:

get_bad_stack

bad_save_user_regs

bl do_irq

.align 5

fiq:

get_bad_stack

bad_save_user_regs

bl do_fiq

#endif

main.c

void mian_loop(void)

{

#ifndef CFG_HUSH_PARSER

staticchar lastcommand[CFG_CBSIZE] = { 0, };

intlen;

intrc = 1;

intflag;

#endif

#if defined(CONFIG_BOOTDELAY) &&(CONFIG_BOOTDELAY >= 0)

char*s;

intbootdelay;

#endif

#ifdef CONFIG_PREBOOT

char*p;

#endif

#ifdef CONFIG_BOOTCOUNT_LIMIT

unsignedlong bootcount = 0;

unsignedlong bootlimit = 0;

char*bcs;

charbcs_set[16];

#endif /* CONFIG_BOOTCOUNT_LIMIT */

#if defined(CONFIG_VFD) && defined(VFD_TEST_LOGO)

ulongbmp = 0; /* default bitmap */

externint 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 */

#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\n", do_mdm_init);

if(do_mdm_init) {

char*str = strdup(getenv("mdm_cmd"));

setenv("preboot", str); /* set ordelete definition */

if(str != NULL)

free(str);

mdm_init();/* wait for modem connection */

}

#endif /* CONFIG_MODEM_SUPPORT */

#ifdef CONFIG_VERSION_VARIABLE

{

externchar version_string[];

setenv("ver", version_string); /*set version variable */

}

#endif /* CONFIG_VERSION_VARIABLE */

#ifdef CFG_HUSH_PARSER

u_boot_hush_start();

#endif

#ifdef CONFIG_AUTO_COMPLETE

install_auto_complete();

#endif

#ifdef CONFIG_PREBOOT

if((p = getenv ("preboot")) != NULL) {

# ifdef CONFIG_AUTOBOOT_KEYED

intprev = disable_ctrlc(1); /* disableControl C checking */

# endif

# ifndef CFG_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;

debug("### main_loop entered: bootdelay=%d\n\n", 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.\n",

(unsigned)bootlimit);

s= getenv ("altbootcmd");

}

else

#endif /* CONFIG_BOOTCOUNT_LIMIT */

s= getenv ("bootcmd");

debug("### main_loop: bootcmd=\"%s\"\n", s ? s :"<UNDEFINED>");

/* abortboot (bootdelay)返回1则不启动boot，否则启动boot */

if(bootdelay >= 0 && s && !abortboot (bootdelay)) {

/*llz added to pass mac address from uboot to kernel by merge the valueof ethaddr to bootargs.*/

// extern void merge_mac_to_bootargs(void);

// merge_mac_to_bootargs();

# ifdef CONFIG_AUTOBOOT_KEYED

intprev = disable_ctrlc(1); /* disableControl C checking */

# endif

# ifndef CFG_HUSH_PARSER

run_command(s, 0);

# 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该部分代码不会调用 */

# ifdef CONFIG_MENUKEY

if(menukey == CONFIG_MENUKEY) {

/*add by heliangbin 2012-7-21 */

printf("main_loop#################trace2!\n");

s = getenv("menucmd");

if (s) {

# ifndef CFG_HUSH_PARSER

run_command(s, 0);

/*add by heliangbin 2012-7-21 */

printf("main_loop#################trace3!\n");

# 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 CFG_HUSH_PARSER

parse_file_outer();

/*This point is never reached */

for(;;);

#else

for(;;) {

#ifdef CONFIG_BOOT_RETRY_TIME

if(rc >= 0) {

/*Saw enough of a valid command to

* restart the timeout.

reset_cmd_timeout();

}

#endif

len = readline (CFG_PROMPT);

flag= 0; /* assume no special flags for now*/

if(len > 0)

strcpy (lastcommand, console_buffer);

elseif (len == 0)

flag|= CMD_FLAG_REPEAT;

#ifdef CONFIG_BOOT_RETRY_TIME

elseif (len == -2) {

/*-2 means timed out, retry autoboot

puts("\nTimed out waiting for command\n");

# 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>\n");

else

rc = run_command (lastcommand, flag);

/*add by heliangbin 2012-7-21 */

printf("main_looplastcommand = %s!\n", lastcommand);

//if(rc <= 0) {

/*invalid command or not repeatable, forget it */

lastcommand[0]= 0;

//}

}

#endif /*CFG_HUSH_PARSER*/

}

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