uboot移植-内存分布
设置堆栈 uboot内存使用图
1、uboot第一阶段start.S
设置堆栈
stack_setup:
ldr r0, _TEXT_BASE /* upper 128 KiB: relocated uboot */
sub r0, r0, #CONFIG_SYS_MALLOC_LEN /* malloc area */
sub r0, r0, #CONFIG_SYS_GBL_DATA_SIZE /* 跳过全局数据区 */
#ifdef CONFIG_USE_IRQ
sub r0, r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
#endif
sub sp, r0, #12 /* leave 3 words for abort-stack */只要将sp指针指向一段没有被使用的内存就完成栈的设置了。
注：在配置文件tx244.h定义
#define CONFIG_SYS_MALLOC_LEN (CONFIG_ENV_SIZE + 128*1024)=192Kbyte
#define CONFIG_SYS_GBL_DATA_SIZE 128 /* size in bytes reserved for initial data */
#define CONFIG_ENV_SIZE 0x20000
2、uboot第二阶段 start_armboot()
设置全局变量gd
gd = (gd_t*)(_armboot_start - CONFIG_SYS_MALLOC_LEN - sizeof(gd_t));
__asm__ __volatile__("": : :"memory");
memset ((void*)gd, 0, sizeof (gd_t));//将gd所指向内存区域的前gd_t所需空间 置零
gd->bd = (bd_t*)((char*)gd - sizeof(bd_t)); //申请bd_t区间
memset (gd->bd, 0, sizeof (bd_t));
gd->flags |= GD_FLG_RELOC; //Code was relocated to RAM 表示代码已经搬运到RAM中
monitor_flash_len = _bss_start - _armboot_start;//计算uboot代码length
根据上面的代码可以知道U-Boot内存使用情况了，如下图所示：
注：1、用户堆区_bss_start、_end地址如何得到？根据uboot.lds链接脚本，知道分布位置。但具体地址由编译后得到。
uboot.lds内容：
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{
。。。。。。。。。。。。。。。。。
. = ALIGN(4);
__bss_start = .;
.bss (NOLOAD) : { *(.bss) . = ALIGN(4); }
_end = .;
}
2、查看uboot.map编译后地址
_bss_start地址
_end地址
其中1、gd_t结构说明：
typedef struct global_data {
bd_t *bd;
unsigned long flags;
unsigned long baudrate;
unsigned long have_console; /* serial_init() was called */
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
unsigned char vfd_type; /* display type */
#endif
#ifdef CONFIG_FSL_ESDHC
unsigned long sdhc_clk;
#endif
#if 0
unsigned long cpu_clk; /* CPU clock in Hz! */
unsigned long bus_clk;
phys_size_t ram_size; /* RAM size */
unsigned long reset_status; /* reset status register at boot */
#endif
void **jt; /* jump table */
} gd_t;
2、bd_t结构说明：
typedef struct bd_info {
int bi_baudrate; /* serial console baudrate */
unsigned long bi_ip_addr; /* IP Address */
struct environment_s *bi_env;
ulong bi_arch_number; /* unique id for this board */
ulong bi_boot_params; /* where this board expects params */
struct /* RAM configuration */
{
ulong start;
ulong size;
} bi_dram[CONFIG_NR_DRAM_BANKS];
} bd_t;