日期:2014-05-16  浏览次数:20981 次

linux 3.12内核里系统调用常见的问题
01)系统调用信息保存在哪儿?
      保存在sys_call_table当中。以X86为例,sys_call_table的初始化如下:
    arch/x86/kernel/syscall_32.c
#define __SYSCALL_I386(nr, sym, compat) [nr] = sym,
 
typedef asmlinkage void (*sys_call_ptr_t)(void);
 
extern asmlinkage void sys_ni_syscall(void);
 
__visible const sys_call_ptr_t sys_call_table[__NR_syscall_max+1] = {
    /*
     * Smells like a compiler bug -- it doesn't work
     * when the & below is removed.
     */
    [0 ... __NR_syscall_max] = &sys_ni_syscall,
#include <asm/syscalls_32.h>
};
    
其中sys_call_table数组的初始化使用GCC的扩展语法,语句[0 ... __NR_syscall_max] = &sys_ni_syscall将数组内容全部初始化为未实现版本,然后包含asm/syscalls_32.h当中逐项初始化的内容进行初始化。
asm/syscalls_32.h为编译期间生成的一个头文件,该内容由/include/uapi/asm-generic/unistd.h等头文件共同生成,其内容如下:
__SYSCALL_I386(0, sys_restart_syscall, sys_restart_syscall)
__SYSCALL_I386(1, sys_exit, sys_exit)
__SYSCALL_I386(2, sys_fork, stub32_fork)
__SYSCALL_I386(3, sys_read, sys_read)
__SYSCALL_I386(4, sys_write, sys_write)
__SYSCALL_I386(5, sys_open, compat_sys_open)
__SYSCALL_I386(6, sys_close, sys_close)
__SYSCALL_I386(7, sys_waitpid, sys32_waitpid)
__SYSCALL_I386(8, sys_creat, sys_creat)
__SYSCALL_I386(9, sys_link, sys_link)
__SYSCALL_I386(10, sys_unlink, sys_unlink)
__SYSCALL_I386(11, sys_execve, stub32_execve)
__SYSCALL_I386(12, sys_chdir, sys_chdir)
__SYSCALL_I386(13, sys_time, compat_sys_time)
__SYSCALL_I386(14, sys_mknod, sys_mknod)
__SYSCALL_I386(15, sys_chmod, sys_chmod)
__SYSCALL_I386(16, sys_lchown16, sys_lchown16)
__SYSCALL_I386(18, sys_stat, sys_stat)
__SYSCALL_I386(19, sys_lseek, compat_sys_lseek)
__SYSCALL_I386(20, sys_getpid, sys_getpid)
__SYSCALL_I386(21, sys_mount, compat_sys_mount)
__SYSCALL_I386(22, sys_oldumount, sys_oldumount)
__SYSCALL_I386(23, sys_setuid16, sys_setuid16)
__SYSCALL_I386(24, sys_getuid16, sys_getuid16)
__SYSCALL_I386(25, sys_stime, compat_sys_stime)
__SYSCALL_I386(26, sys_ptrace, compat_sys_ptrace)
__SYSCALL_I386(27, sys_alarm, sys_alarm)
__SYSCALL_I386(28, sys_fstat, sys_fstat)
__SYSCALL_I386(29, sys_pause, sys_p