iTop4412 支持内核调试-uboot篇

4412 官方的uboot 镜像很简单，少了很多的command,既没有printenv,也没有setenv,我们没法通过它的镜像来添加对内核调试的支持，还好它提供了uboot源码，我们只需要在include的environment.h加上：

#define CONFIG_BOOTARGS "kgdboc=ttySAC2,115200 kgdbwait"

它在Env_common.c会引用到这个宏：

uchar default_environment[] = {
#ifdef	CONFIG_BOOTARGS
	"bootargs="	CONFIG_BOOTARGS			"\0"
#endif
#ifdef	CONFIG_BOOTCOMMAND
	"bootcmd="	CONFIG_BOOTCOMMAND		"\0"
#endif
#ifdef	CONFIG_RAMBOOTCOMMAND
	"ramboot="	CONFIG_RAMBOOTCOMMAND		"\0"
#endif
#ifdef	CONFIG_NFSBOOTCOMMAND
	"nfsboot="	CONFIG_NFSBOOTCOMMAND		"\0"
#endif
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
	"bootdelay="	MK_STR(CONFIG_BOOTDELAY)	"\0"
#endif
#if defined(CONFIG_BAUDRATE) && (CONFIG_BAUDRATE >= 0)
	"baudrate="	MK_STR(CONFIG_BAUDRATE)		"\0"
#endif
#ifdef	CONFIG_LOADS_ECHO
	"loads_echo="	MK_STR(CONFIG_LOADS_ECHO)	"\0"
#endif
#ifdef	CONFIG_ETHADDR
	"ethaddr="	MK_STR(CONFIG_ETHADDR)		"\0"
#endif
#ifdef	CONFIG_ETH1ADDR
	"eth1addr="	MK_STR(CONFIG_ETH1ADDR)		"\0"
#endif
#ifdef	CONFIG_ETH2ADDR
	"eth2addr="	MK_STR(CONFIG_ETH2ADDR)		"\0"
#endif
#ifdef	CONFIG_ETH3ADDR
	"eth3addr="	MK_STR(CONFIG_ETH3ADDR)		"\0"
#endif
#ifdef	CONFIG_ETH4ADDR
	"eth4addr="	MK_STR(CONFIG_ETH4ADDR)		"\0"
#endif
#ifdef	CONFIG_ETH5ADDR
	"eth5addr="	MK_STR(CONFIG_ETH5ADDR)		"\0"
#endif
#ifdef	CONFIG_IPADDR
	"ipaddr="	MK_STR(CONFIG_IPADDR)		"\0"
#endif
#ifdef	CONFIG_SERVERIP
	"serverip="	MK_STR(CONFIG_SERVERIP)		"\0"
#endif
#ifdef	CONFIG_SYS_AUTOLOAD
	"autoload="	CONFIG_SYS_AUTOLOAD			"\0"
#endif
#ifdef	CONFIG_PREBOOT
	"preboot="	CONFIG_PREBOOT			"\0"
#endif
#ifdef	CONFIG_ROOTPATH
	"rootpath="	MK_STR(CONFIG_ROOTPATH)		"\0"
#endif
#ifdef	CONFIG_GATEWAYIP
	"gatewayip="	MK_STR(CONFIG_GATEWAYIP)	"\0"
#endif
#ifdef	CONFIG_NETMASK
	"netmask="	MK_STR(CONFIG_NETMASK)		"\0"
#endif
#ifdef	CONFIG_HOSTNAME
	"hostname="	MK_STR(CONFIG_HOSTNAME)		"\0"
#endif
#ifdef	CONFIG_BOOTFILE
	"bootfile="	MK_STR(CONFIG_BOOTFILE)		"\0"
#endif
#ifdef	CONFIG_LOADADDR
	"loadaddr="	MK_STR(CONFIG_LOADADDR)		"\0"
#endif
#ifdef  CONFIG_CLOCKS_IN_MHZ
	"clocks_in_mhz=1\0"
#endif
#if defined(CONFIG_PCI_BOOTDELAY) && (CONFIG_PCI_BOOTDELAY > 0)
	"pcidelay="	MK_STR(CONFIG_PCI_BOOTDELAY)	"\0"
#endif
#ifdef  CONFIG_EXTRA_ENV_SETTINGS
	CONFIG_EXTRA_ENV_SETTINGS
#endif
	"\0"
};

这样生成的uboot在启动时就会带上：bootargs= "kgdboc=ttySAC2,115200 kgdbwait"