c demo
#include <unistd.h>
#include <stdio.h>
struct mydyh_desc {
unsigned int nr;
const char *name;
unsigned long price;
void (*fun)(unsigned long, const char *);
};
extern struct mydyh_desc __dyh_info_begin[], __dyh_info_end[];
#define for_each_dyh_desc(p) \
for (p = __dyh_info_begin; p < __dyh_info_end; p++)
#define SECTION_START(_type,_name) \
static const struct mydyh_desc __mydyh_desc_##_type \
__attribute__((used, __section__(".dyh.info.init"))) = { \
.nr = MY_DYH_##_type, \
.name = _name,
#define SECTION_END \
};
#define MY_DYH_PHONE 0
#define MY_DYH_CAR 1
void huawei_phone(unsigned long price, const char *name)
{
printf("hello.\n");
printf("name=%s, price=%ld\n", name, price);
return;
}
void byd_phone(unsigned long price, const char *name)
{
printf("world.\n");
printf("name=%s, price=%ld\n", name, price);
return;
}
SECTION_START(PHONE, "huawei")
.price = 100,
.fun = huawei_phone,
SECTION_END
SECTION_START(CAR, "byd")
.price = 200,
.fun = byd_phone,
SECTION_END
int main()
{
struct mydyh_desc *p;
for_each_dyh_desc(p) {
p->fun(p->price, p->name);
}
return 0;
}以上代码是新增一个自定义的section，为了使用该section内的函数，需要定义一个起始的位置，这个是在.S链接脚本中实现的。demo中的section存储的数据格式为mydyh_desc结构体，因此sizeof(mydyh_desc) 大小为一个元素。
lds链接脚本
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}该链接脚本中主要增加了
.mydyh :
{
__dyh_info_begin = .;
*(.dyh.info.init)
__dyh_info_end = .;
} .dyh.info.init为段名， __dyh_info_begin为段的开始位置，__dyh_info_end为段的结束位置，gcc在编译代码时，会将一些指定的数据放到该段中，然后会计算出__dyh_info_end的位置。而demo中使用到的__dyh_info_end和 __dyh_info_begin则是gcc通过链接脚本连接后的出来的一些地址。
Makefile
CC ?= gcc
all:
$(CC) section.c -T section.lds -o section
clean:
rm -rf section执行时 ./section 即可运行
以上则是内核代码中 .initcall*.init 的执行原理