early_param和_setup宏

early_param和__setup宏

一.宏的定义

在/include/linux/Init.h中

#define __setup(str, fn)     \ __setup_param(str, fn, fn, 0)

#define early_param(str, fn)\__setup_param(str, fn, fn, 1)

两个宏都会调用__setup_param

跟踪进__setup_param宏的定义

#define __setup_param(str, unique_id, fn, early)\static const char __setup_str_##unique_id[] __initconst\__aligned(1) = str; \static struct obs_kernel_param __setup_##unique_id\__used __section(.init.setup)\__attribute__((aligned((sizeof(long)))))\= { __setup_str_##unique_id, fn, early }

 这个宏里面有个结构体obs_kernel_param

struct obs_kernel_param {const char *str;int (*setup_func)(char *);int early;};

结合上面两个宏和一个结构体展开__setup

__setup(str, fn)宏定义了

一个static const char  __setup_str_fn[]变量=str

接着定义了

一个static struct obs_kernel_param __setup_fn结构体,并赋值(标记编译进.init.setup段)

{

    str;

    fn(char *); 

    0,或1

}

二.宏的作用

1.编译相关

在/include/asm-generic/Vmlinux.lds.h文件中定义了__setup_start.....__setup_end段

#define INIT_SETUP(initsetup_align)\. = ALIGN(initsetup_align);\VMLINUX_SYMBOL(__setup_start) = .;\*(.init.setup)\VMLINUX_SYMBOL(__setup_end) = .;

标记了.init.setup的函数会被编译进该段

2.内核启动的相关调用关系

在start_kernel中调用parse_early_param()

void __init parse_early_param(void){static __initdata int done = 0;static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];if (done)return;strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);//复制启动命令行数据parse_early_options(tmp_cmdline);//调用parse_early_options函数done = 1;}

parse_early_options函数

void __init parse_early_options(char *cmdline){parse_args("early options", cmdline, NULL, 0, do_early_param);}

接着调用parse_args函数

int parse_args(const char *name,char *args,const struct kernel_param *params,unsigned num,int (*unknown)(char *param, char *val)){char *param, *val;DEBUGP("Parsing ARGS: %s\n", args);args = skip_spaces(args);while (*args) {//遍历启动命令行int ret;int irq_was_disabled;args = next_arg(args, &param, &val);//获取下一个参数,填充param和val参数(例如:param--console;val--tty2,115200n8)irq_was_disabled = irqs_disabled();ret = parse_one(param, val, params, num, unknown);//解析一个命令行参数if (irq_was_disabled && !irqs_disabled()) {printk(KERN_WARNING "parse_args(): option '%s' enabled ""irq's!\n", param);}switch (ret) {case -ENOENT:printk(KERN_ERR "%s: Unknown parameter `%s'\n",name, param);return ret;case -ENOSPC:printk(KERN_ERR "%s: `%s' too large for parameter `%s'\n",name, val ?: "", param);return ret;case 0:break;default:printk(KERN_ERR"%s: `%s' invalid for parameter `%s'\n",name, val ?: "", param);return ret;}}/* All parsed OK. */return 0;}

命令行参数的解析parse_one

static int parse_one(char *param,char *val,const struct kernel_param *params,unsigned num_params,int (*handle_unknown)(char *param, char *val)){unsigned int i;int err;/* Find parameter */for (i = 0; i < num_params; i++) {//num_params=0if (parameq(param, params[i].name)) {if (!val && params[i].ops->set != param_set_bool)return -EINVAL;DEBUGP("They are equal!  Calling %p\n",params[i].ops->set);mutex_lock(&param_lock);err = params[i].ops->set(val, &params[i]);mutex_unlock(&param_lock);return err;}}if (handle_unknown) {//若handle_unknown函数存在DEBUGP("Unknown argument: calling %p\n", handle_unknown);return handle_unknown(param, val);//则调用handle_unknown函数,参数为param,val}DEBUGP("Unknown argument `%s'\n", param);return -ENOENT;}

回溯回去handle_unknow函数就是do_early_param

static int __init do_early_param(char *param, char *val){const struct obs_kernel_param *p;for (p = __setup_start; p < __setup_end; p++) {if ((p->early && strcmp(param, p->str) == 0) || (strcmp(param, "console") == 0 && strcmp(p->str, "earlycon") == 0)) {if (p->setup_func(val) != 0)printk(KERN_WARNING"Malformed early option '%s'\n", param);}}/* We accept everything at this stage. */return 0;}

do_early_param函数从__setup_start遍历到__setup_end段,

判断参数,进入if函数体里面

if (p->setup_func(val) != 0)这句调用了对应setup_func或early_param成员的函数,并将val作为其参数,val其实便是__setup(str, fn)或__early_param中的str

其实就是调用了fn(str)
这里的第一条if会刷选掉__setup定义的情况(除了console和earlycon参数的),因为__setup定义的obs_kernel_param结构体p->early=0

__setup定义的fn会在start_kernel->parse_args("Booting kernel", static_command_line, __start___param,__stop___param - __start___param,&unknown_bootoption);

unknown_bootoption->obsolete_checksetup函数给调用
看start_kernel中调用顺序

parse_early_param();parse_args("Booting kernel", static_command_line, __start___param, __stop___param - __start___param,&unknown_bootoption);

可见先调用__early_param定义的解析参数函数及__setup定义的(console及earlycon)的参数解析函数

接着再调用__setup定义的其他解析参数函数