Uboot中start.S源码的指令级的详尽解析

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typedef struct global_data {
bd_t *bd;
unsigned long flags;
unsigned long baudrate;
unsigned long have_console; /* serial_init() was called */
unsigned long reloc_off; /* Relocation Offset */
unsigned long env_addr; /* Address of Environment struct */
unsigned long env_valid; /* Checksum of Environment valid? */
unsigned long fb_base; /* base address of frame buffer */
#ifdef CONFIG_VFD
#endif
#if 0
#endif
} gd_t;
unsigned char vfd_type; /* display type */
unsigned long cpu_clk; /* CPU clock in Hz! */
unsigned long bus_clk;
unsigned long ram_size; /* RAM size */
unsigned long reset_status; /* reset status register at boot */
void **jt; /* jump table */
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而此全局变量gd_t *gd会被其他很多文件所引用,详情自己去代码中找。
.macro get_fiq_stack @ setup FIQ stack
ldr sp, FIQ_STACK_START
.endm
此处和上面类似,把地址为FIQ_STACK_START中的内容,给sp。
其中:
FIQ_STACK_START = IRQ_STACK_START - CONFIG_STACKSIZE_IRQ;
即FIQ的堆栈起始地址,是IRQ堆栈起始地址减去IRQ堆栈的大小。
/*
* exception handlers
*/
.align 5
undefined_instruction:
get_bad_stack
bad_save_user_regs
bl do_undefined_instruction
.align 5