生成asm-offset

因为不善于在Makefile中调用shell的相关工具，所以关于asm-offsets.h中的产生的16进制数并不知如何做到。

因此自己写了个脚本，可以生成同样的文件（再次造了轮子）。

参考：https://lkml.org/lkml/2001/10/6/3

#脚本offset.awk
1 /^->$/{printf("\n");next}
 /^->.*/{sym = $; val = $; $ = ""; $ = ""; sub(/^\->/,"",sym);sub(/^\$/,"", val);printf("#define %-15s  %3d\t/* 0x%x\t%s */\n", sym, val, val, $)}

//测试文件asm-offset.c
#include <stddef.h>

#ifndef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif

#define DEFINE(sym, val) \
    asm volatile("\n->" #sym " %0 " #val : : "i" (val))

#define BLANK() asm volatile("\n->" : : )

struct university
{
    int soochow;
    int seu;
    int tsing;
    int peking;
    int nju;
    int sjtu;
};

int main(void)
{
    BLANK();
    DEFINE(SOOCHOW, offsetof(struct university, soochow));
    BLANK();
    DEFINE(SEU,     offsetof(struct university, seu));
    BLANK();
    DEFINE(TSING,   offsetof(struct university, tsing));
    BLANK();
    DEFINE(PEKING,  offsetof(struct university, peking));
    BLANK();
    DEFINE(NJU,     offsetof(struct university, nju));
    BLANK();
    DEFINE(SJTU,    offsetof(struct university, sjtu));
    BLANK();
}

使用：

 gcc -S asm-offset.c; awk -f offset.awk asm-offset.s > asm-offset.h; rm asm-offset.s

输出：

//asm-offset.h                                                                                                                   

#define SOOCHOW            0    /* 0x0    offsetof(struct university, soochow) */

#define SEU                4    /* 0x4    offsetof(struct university, seu) */

#define TSING              8    /* 0x8    offsetof(struct university, tsing) */

#define PEKING            12    /* 0xc    offsetof(struct university, peking) */

#define NJU               16    /* 0x10   offsetof(struct university, nju) */

#define SJTU              20    /* 0x14   offsetof(struct university, sjtu) */