a.out.h 头文件分析 \linux-1.0\linux\include\linux\a.out.h

最新推荐文章于 2025-01-09 16:34:15 发布

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最新推荐文章于 2025-01-09 16:34:15 发布 · 1.9k 阅读

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本文详细介绍了Linux内核中a.out头文件的结构，包括执行文件的结构定义、机器类型枚举、魔法值宏定义等，以及如何设置和获取这些信息的方法，是理解Linux可执行文件格式的重要参考资料。

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#ifndef __A_OUT_GNU_H__
#define __A_OUT_GNU_H__

#define __GNU_EXEC_MACROS__

#ifndef __STRUCT_EXEC_OVERRIDE__

//定义执行文件结构
struct exec
{
  unsigned long a_info;		/* Use macros N_MAGIC, etc for access */
  unsigned a_text;		/* length of text, in bytes */
  unsigned a_data;		/* length of data, in bytes */
  unsigned a_bss;		/* length of uninitialized data area for file, in bytes */
  unsigned a_syms;		/* length of symbol table data in file, in bytes */
  unsigned a_entry;		/* start address */
  unsigned a_trsize;		/* length of relocation info for text, in bytes */
  unsigned a_drsize;		/* length of relocation info for data, in bytes */
};

#endif /* __STRUCT_EXEC_OVERRIDE__ */

//机器类型设定
/* these go in the N_MACHTYPE field */
enum machine_type {
#if defined (M_OLDSUN2)
  M__OLDSUN2 = M_OLDSUN2,
#else
  M_OLDSUN2 = 0,
#endif
#if defined (M_68010)
  M__68010 = M_68010,
#else
  M_68010 = 1,
#endif
#if defined (M_68020)
  M__68020 = M_68020,
#else
  M_68020 = 2,
#endif
#if defined (M_SPARC)
  M__SPARC = M_SPARC,
#else
  M_SPARC = 3,
#endif
  /* skip a bunch so we don't run into any of sun's numbers */
  M_386 = 100,
};

//定义MAGIC地址为32位的有效值。0-16位
#if !defined (N_MAGIC)
#define N_MAGIC(exec) ((exec).a_info & 0xffff)
#endif

//获取机器类型 16-23位
#define N_MACHTYPE(exec) ((enum machine_type)(((exec).a_info >> 16) & 0xff))

//标记 24－31位
#define N_FLAGS(exec) (((exec).a_info >> 24) & 0xff)

//设定Magic，机器类型，标记
#define N_SET_INFO(exec, magic, type, flags) \
	((exec).a_info = ((magic) & 0xffff) \
	 | (((int)(type) & 0xff) << 16) \
	 | (((flags) & 0xff) << 24))

//单独设定Magic值
#define N_SET_MAGIC(exec, magic) \
	((exec).a_info = (((exec).a_info & 0x