uboot分析のstart.s
最近、Mini 6410には、起動画面とOSが起動していない場合の充電管理画面が追加されました.使用するプラットフォームはフレンドリーなmini 6410です.OSが起動していないため、ほとんどの作業はUBOotで完了します.現在、充電管理と起動アニメーションは基本的に実現されています.ほほほ、途中でN多磨難を経験しました.今、やった仕事を記録します.前の2つの文章はUBOotのmakefileを紹介しています.makefileからコンパイル生成の最初のターゲットファイルがstartであることがわかります.o、今からstart.s分析を行う.システムが起動したばかりでC実行のスタックが用意されていないのでstart.sはアセンブリとして実現される.
start.s主な仕事はARMがlowlevelを初期化することです.Init下節分析.nandflahのコードをSDRAMに読み込み、スタックを設定してBSSセグメントを初期化します.ldrpc,start_Armboot SDRAMにジャンプしてCコードstart_を実行armboot . 次のセクションでは、主にlowlevelを分析します.init、copy_uboot_to_ラムおよびstart_armbootはどんな仕事をしましたか.参照先:http://blog.csdn.net/ecbtnrt/article/details/6630085
#include <config.h>
#include <version.h>
#ifdef CONFIG_ENABLE_MMU
#include <asm/proc/domain.h>
#endif
#include <regs.h>
#ifndef CONFIG_ENABLE_MMU
#ifndef CFG_PHY_UBOOT_BASE
#define CFG_PHY_UBOOT_BASE CFG_UBOOT_BASE // MMU 0xc7e00000
#endif
#endif
/*
*************************************************************************
*
* Jump vector table as in table 3.1 in [1]
*
*************************************************************************
*/
/* */
.globl _start
_start: 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
/* _undefined_instruction , undefined_instruction
/* . _undefined_instruction undefined_instruction
/*word （ ）， expr 。.long .int 。
_undefined_instruction:
.word undefined_instruction
_software_interrupt:
.word software_interrupt
_prefetch_abort:
.word prefetch_abort
_data_abort:
.word data_abort
_not_used:
.word not_used
_irq:
.word irq
_fiq:
.word fiq
_pad:
.word 0x12345678 /* now 16*4=64 */
.global _end_vect
_end_vect:
.balignl 16,0xdeadbeef
/*
*************************************************************************
*
* Startup Code (reset vector)
*
* do important init only if we don't start from memory!
* setup Memory and board specific bits prior to relocation.
* relocate armboot to ram
* setup stack
*
*************************************************************************
*/
/*TEXT_BASE /board/config.mk , , _TEXT_BASE
_TEXT_BASE:
.word TEXT_BASE
/*
* Below variable is very important because we use MMU in U-Boot.
* Without it, we cannot run code correctly before MMU is ON.
* by scsuh.
*/
_TEXT_PHY_BASE:
.word CFG_PHY_UBOOT_BASE /* MMU 0xc7e00000*/
.globl _armboot_start/* . _armboot_start */
_armboot_start:
.word _start
/*
* These are defined in the board-specific linker script.
*/
/*
BSS
： ， 。
BSS ： ，BSS （bsssegment） 。BSS Block Started by Symbol 。BSS 。
： ， （datasegment） 。 。
： ， （codesegment / text segment） 。 ， , ， 。 ， ， 。
（heap）： ， ， 。 malloc ， （ ）； free ， （ ）
(stack)： ， ， “{}” （ static ，static ）。 ， ， ， ， 。 ， / 。 ， 、 。
*/
.globl _bss_start //bss
_bss_start:
.word __bss_start
.globl _bss_end //bss
_bss_end:
.word _end
#ifdef CONFIG_USE_IRQ
/* IRQ stack memory (calculated at run-time) */
.globl IRQ_STACK_START/* : IRQ_STACK_START 0x0badc0de( )*/
IRQ_STACK_START:
.word 0x0badc0de
/* IRQ stack memory (calculated at run-time) */
.globl FIQ_STACK_START
FIQ_STACK_START:
.word 0x0badc0de
#endif
/*
* the actual reset code
*/
/*
reset:/* * set the cpu to SVC32 mode
*/
/*EC: *//*bic (Bit Clear) ， r0 Bit[4:0] ( 0x1F )， r0 。*/
/*EC: 10011, ,irq fiq 1, */
/*orr ， r0 Bit7,Bit6,Bit4,Bit1,Bit0 1， 。*/
/* ，cpsr I=1, F=1, T ( 0)，M[4:0]=10011， IRQ， FIQ，/* ，cpsr I=1, F=1, T ( 0)，M[4:0]=10011， IRQ， FIQ， ARM ， SVC32 。*/
mrs r0,cpsr
bic r0,r0,#0x1f
orr r0,r0,#0xd3
msr cpsr,r0
/*
*************************************************************************
*
* CPU_init_critical registers
*
* setup important registers
* setup memory timing
*
*************************************************************************
*/
/*
* we do sys-critical inits only at reboot,
* not when booting from ram!
*/
cpu_init_crit:
/*
* 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 */
/* Ｐ ， cache
* 。 ， 。
* ARM 。
* CDP {<cond>} cp, opcode1, Cd, Cn{,opcode2} --
* <MRC/MCR> {<cond>} cp, opcode1, Rd, Cn, Cm{,opcode2} -- /
* <LDC/STC> {<cod>} cp, Cd, addressing -- /
* :cp ， p0~P15. opcode 。Cn, Cm Cd 。
* 15(CP15) ， ， ，cache 。
* MRC p15,0,r10,c0,c0,0 15 c0 r10 ，cp15 c0 ， r10
*/
/*
* 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
orr r0, r0, #0x00001000 @ set bit 12 (I) I-Cache
mcr p15, 0, r0, c1, c0, 0
/* Peri port setup */
ldr r0, =0x70000000
orr r0, r0, #0x13
mcr p15,0,r0,c15,c2,4 @ 256M(0x70000000-0x7fffffff)
/*
* Go setup Memory and board specific bits prior to relocation.
*/
bl lowlevel_init /* go setup pll,mux,memory */
/* when we already run in ram, we don't need to relocate U-Boot.
* and actually, memory controller must be configured before U-Boot
* is running in ram.
*//* */
ldr r0, =0xff000fff
bic r1, pc, r0 /* r0 <- current base addr of code */
ldr r2, _TEXT_BASE /* r1 <- original base addr in ram */
bic r2, r2, r0 /* r0 <- current base addr of code */
cmp r1, r2 /* compare r0, r1 */
beq after_copy /* r0 == r1 then skip flash copy */
#ifdef CONFIG_BOOT_NAND
mov r0, #0x1000
bl copy_from_nand /*copy uboot to ram from nand*/
#endif
after_copy: /* */
ldr r0, =ELFIN_GPIO_BASE
ldr r1, =0xC00
str r1, [r0, #GPPDAT_OFFSET]
ldr r1, [r0, #GPFPUD_OFFSET]
bic r1, r1, #0xc0000000
orr r1, r1, #0x80000000
str r1, [r0, #GPFPUD_OFFSET]
ldr r1, [r0, #GPFDAT_OFFSET]
orr r1, r1, #0x8000
str r1, [r0, #GPFDAT_OFFSET]
ldr r1, [r0, #GPFCON_OFFSET]
bic r1, r1, #0xc0000000
orr r1, r1, #0x40000000
str r1, [r0, #GPFCON_OFFSET]
#ifdef CONFIG_ENABLE_MMU
enable_mmu:
/* enable domain access */
ldr r5, =0x0000ffff
mcr p15, 0, r5, c3, c0, 0 @ load domain access register
/* Set the TTB register */
ldr r0, _mmu_table_base
ldr r1, =CFG_PHY_UBOOT_BASE
ldr r2, =0xfff00000
bic r0, r0, r2
orr r1, r0, r1
mcr p15, 0, r1, c2, c0, 0
/* Enable the MMU */
mmu_on:
mrc p15, 0, r0, c1, c0, 0
orr r0, r0, #1 /* Set CR_M to enable MMU */
mcr p15, 0, r0, c1, c0, 0
nop
nop
nop
nop
#endif
skip_hw_init:
/* Set up the stack */
stack_setup: //
#ifdef CONFIG_MEMORY_UPPER_CODE
ldr sp, =(CFG_UBOOT_BASE + CFG_UBOOT_SIZE - 0xc)
#endif
// BSS
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
ldr pc, _start_armboot /* SDRAM */
_start_armboot:
.word start_armboot
#ifdef CONFIG_ENABLE_MMU
_mmu_table_base:
.word mmu_table
#endif
/*
* copy U-Boot to SDRAM and jump to ram (from NAND or OneNAND)
* r0: size to be compared
* Load 1'st 2blocks to RAM because U-boot's size is larger than 1block(128k) size
*/
.globl copy_from_nand
copy_from_nand:
mov r10, lr /* save return address */
mov r9, r0
/* get ready to call C functions */
ldr sp, _TEXT_PHY_BASE /* setup temp stack pointer */
sub sp, sp, #12
mov fp, #0 /* no previous frame, so fp=0 */
mov r9, #0x1000
// ldr r0, =ELFIN_UART_BASE
// ldr r1, =0x4b4b4b4b
// str r1, [r0, #UTXH_OFFSET]
bl copy_uboot_to_ram
3: tst r0, #0x0 /*copy_uboot_to_ram 0 */
bne copy_failed
/*Stepping Stone start address 0x0c000000*/
ldr r0, =0x0c000000
ldr r1, _TEXT_PHY_BASE
1: ldr r3, [r0], #4
ldr r4, [r1], #4
teq r3, r4
bne compare_failed /* not matched */
subs r9, r9, #4
bne 1b /* 4k */
4: mov lr, r10 /* all is OK */
mov pc, lr
copy_failed:
nop /* copy from nand failed */
b copy_failed
compare_failed:
nop /* compare failed */
b compare_failed
/*
* we assume that cache operation is done before. (eg. cleanup_before_linux())
* actually, we don't need to do anything about cache if not use d-cache in U-Boot
* So, in this function we clean only MMU. by scsuh
*
* void theLastJump(void *kernel, int arch_num, uint boot_params);
*/
#ifdef CONFIG_ENABLE_MMU
.globl theLastJump
theLastJump:
mov r9, r0
ldr r3, =0xfff00000
ldr r4, _TEXT_PHY_BASE
adr r5, phy_last_jump
bic r5, r5, r3
orr r5, r5, r4
mov pc, r5
phy_last_jump:
/*
* disable MMU stuff
*/
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 */
orr r0, r0, #0x00001000 /* set bit 12 (I) I-Cache */
mcr p15, 0, r0, c1, c0, 0
mcr p15, 0, r0, c8, c7, 0 /* flush v4 TLB */
mov r0, #0
mov pc, r9
#endif
/*
*************************************************************************
*
* 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
sub sp, sp, #S_FRAME_SIZE @ carve out a frame on current user stack
stmia sp, {r0 - r12} @ Save user registers (now in svc mode) r0-r12
ldr r2, _armboot_start
sub r2, r2, #(CFG_MALLOC_LEN)
sub r2, r2, #(CFG_GBL_DATA_SIZE+8) @ set base 2 words into abort stack
ldmia r2, {r2 - r3} @ get values for "aborted" pc and cpsr (into parm regs)
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
add r8, sp, #S_PC @ !!!! R8 NEEDS to be saved !!!! a reserved stack spot would be good.
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
.macro get_bad_stack
ldr r13, _armboot_start @ setup our mode stack (enter in banked mode)
sub r13, r13, #(CFG_MALLOC_LEN) @ move past malloc pool
sub r13, r13, #(CFG_GBL_DATA_SIZE+8) @ move to reserved a couple spots for 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
.macro get_bad_stack_swi
sub r13, r13, #4 @ space on current stack for scratch reg.
str r0, [r13] @ save R0's value.
ldr r0, _armboot_start @ get data regions start
sub r0, r0, #(CFG_MALLOC_LEN) @ move past malloc pool
sub r0, r0, #(CFG_GBL_DATA_SIZE+8) @ move past gbl and a couple spots for abort stack
str lr, [r0] @ save caller lr in position 0 of saved stack
mrs r0, spsr @ get the spsr
str lr, [r0, #4] @ save spsr in position 1 of saved stack
ldr r0, [r13] @ restore r0
add r13, r13, #4 @ pop stack entry
.endm
.macro get_irq_stack @ setup IRQ stack
ldr sp, IRQ_STACK_START
.endm
.macro get_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_swi
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
.align 5
.global arm1136_cache_flush
arm1136_cache_flush:
mcr p15, 0, r1, c7, c5, 0 @ invalidate I cache
mov pc, lr @ back to caller
#if defined(CONFIG_INTEGRATOR) && defined(CONFIG_ARCH_CINTEGRATOR)
/* Use the IntegratorCP function from board/integratorcp/platform.S */
#elif defined(CONFIG_S3C64XX)
/* For future usage of S3C64XX*/
#else
.align 5
.globl reset_cpu
reset_cpu:
ldr r1, rstctl /* get addr for global reset reg */
mov r3, #0x2 /* full reset pll+mpu */
str r3, [r1] /* force reset */
mov r0, r0
_loop_forever:
b _loop_forever
rstctl:
.word PM_RSTCTRL_WKUP
#endif start.s主な仕事はARMがlowlevelを初期化することです.Init下節分析.nandflahのコードをSDRAMに読み込み、スタックを設定してBSSセグメントを初期化します.ldrpc,start_Armboot SDRAMにジャンプしてCコードstart_を実行armboot . 次のセクションでは、主にlowlevelを分析します.init、copy_uboot_to_ラムおよびstart_armbootはどんな仕事をしましたか.参照先:http://blog.csdn.net/ecbtnrt/article/details/6630085