定义：<arch/arm/include/asm/u-boot.h>
其具体结构如下：
typedef struct bd_info {
unsigned int bi_baudrate; /* serial console baudrate */
ulong bi_arch_number; /* unique id for this board */
ulong bi_boot_params; /* where this board expects params */
unsigned long bi_arm_freq; /* arm frequency */
unsigned long bi_dsp_freq; /* dsp core frequency */
unsigned long bi_ddr_freq; /* ddr frequency */
struct /* RAM configuration */
{
ulong start;
ulong size;
} bi_dram[CONFIG_NR_DRAM_BANKS];
} bd_t;
2. gd_t
定义：<include/asm-generic/global_data.h>
其具体结构如下：
typedef struct global_data {
bd_t *bd;
unsigned long flags;
unsigned int baudrate;
unsigned long cpu_clk; /* CPU clock in Hz! */
unsigned long bus_clk;
/* We cannot bracket this with CONFIG_PCI due to mpc5xxx */
unsigned long pci_clk;
unsigned long mem_clk;
#if defined(CONFIG_LCD) || defined(CONFIG_VIDEO)
unsigned long fb_base; /* Base address of framebuffer mem */
#endif
#if defined(CONFIG_POST) || defined(CONFIG_LOGBUFFER)
unsigned long post_log_word; /* Record POST activities */
unsigned long post_log_res; /* success of POST test */
unsigned long post_init_f_time; /* When post_init_f started */
#endif
#ifdef CONFIG_BOARD_TYPES
unsigned long board_type;
#endif
unsigned long have_console; /* serial_init() was called */
#ifdef CONFIG_PRE_CONSOLE_BUFFER
unsigned long precon_buf_idx; /* Pre-Console buffer index */
#endif
#ifdef CONFIG_MODEM_SUPPORT
unsigned long do_mdm_init;
unsigned long be_quiet;
#endif
unsigned long env_addr; /* Address of Environment struct */
unsigned long env_valid; /* Checksum of Environment valid? */
/* TODO: is this the same as relocaddr, or something else? */
unsigned long dest_addr; /* Post-relocation address of U-Boot */
unsigned long dest_addr_sp;
unsigned long ram_top; /* Top address of RAM used by U-Boot */
unsigned long relocaddr; /* Start address of U-Boot in RAM */
phys_size_t ram_size; /* RAM size */
unsigned long mon_len; /* monitor len */
unsigned long irq_sp; /* irq stack pointer */
unsigned long start_addr_sp; /* start_addr_stackpointer */
unsigned long reloc_off;
struct global_data *new_gd; /* relocated global data */
const void *fdt_blob; /* Our device tree, NULL if none */
void *new_fdt; /* Relocated FDT */
unsigned long fdt_size; /* Space reserved for relocated FDT */
void **jt; /* jump table */
char env_buf[32]; /* buffer for getenv() before reloc. */
struct arch_global_data arch; /* architecture-specific data */
} gd_t;
这其中还包含了一个arch_global_data，对于ARM,这个结构体定义在：<arch/arm/include/asm/global_data.h>