linux 1.0 内核注解 linux/kernel/ioport.c

时间：2009-03-09 来源：taozhijiangscu

/********************************************
*Created By: 陶治江
*Date:       2009-3-7
********************************************/
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/ioport.h> static unsigned long ioport_registrar[IO_BITMAP_SIZE] = {0, /* ... */}; #define _IODEBUG #ifdef IODEBUG //将l实际的位图数字转换为字符串形式
static char * ios(unsigned long l)
{
static char str[33] = { '\0' };
int i;
unsigned long mask; for (i = 0, mask = 0x80000000; i < 32; ++i, mask >>= 1)
  str[i] = (l & mask) ? '1' : '0';
return str;
} //显示当前进程的IO位图
static void dump_io_bitmap(void)
{
int i, j;
//unsigned long io_bitmap[IO_BITMAP_SIZE+1];
//IO_BITMAP_SIZE=32

int numl = sizeof(current->tss.io_bitmap) >> 2; for (i = j = 0; j < numl; ++i)
{
  printk("%4d [%3x]: ", 64*i, 64*i);  //64位一显示
  printk("%s ", ios(current->tss.io_bitmap[j++]));
  if (j < numl)
   printk("%s", ios(current->tss.io_bitmap[j++]));
  printk("\n");
}
}
#endif asmlinkage void set_bitmap(unsigned long *bitmap,
         short base, short extent, int new_value)
{
int mask;
unsigned long *bitmap_base = bitmap + (base >> 5);
   //>>5就是*8变成比特，*4变成long类型
unsigned short low_index = base & 0x1f;  //就是获得long对其后的低位
int length = low_index + extent; if (low_index != 0) {
  mask = (~0 << low_index);   //将低位的32位转换为位图模式
  if (length < 32)
    mask &= ~(~0 << length);

  if (new_value)  //1表示设置，0表示取消
   *bitmap_base++ |= mask;
  else
   *bitmap_base++ &= ~mask;
  length -= 32;
} //呃，下面都是32为单位操作了

mask = (new_value ? ~0 : 0);
while (length >= 32) {
  *bitmap_base++ = mask;
  length -= 32;
} if (length > 0) {
  mask = ~(~0 << length);  //剩下的零碎的位
  if (new_value)
   *bitmap_base++ |= mask;
  else
   *bitmap_base++ &= ~mask;
}
} //呃，基本的操作的原理是同上面相类似的，检测的范围只要有
//置位就返回1，否则如果全部复位就返回0
asmlinkage int check_bitmap(unsigned long *bitmap, short base, short extent)
{
int mask;
unsigned long *bitmap_base = bitmap + (base >> 5);
unsigned short low_index = base & 0x1f;
int length = low_index + extent; if (low_index != 0) {
  mask = (~0 << low_index);
  if (length < 32)
    mask &= ~(~0 << length);
  if (*bitmap_base++ & mask)
   return 1;
  length -= 32;
}
while (length >= 32) {
  if (*bitmap_base++ != 0)
   return 1;
  length -= 32;
} if (length > 0) {
  mask = ~(~0 << length);
  if (*bitmap_base++ & mask)
   return 1;
}
return 0;
} //从from开始设置连续num个端口的状态，内核的手册上说
//使用fork是不会继承端口设置的，但是使用execv是会继承的
asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)
{
if (from + num <= from)
  return -EINVAL;
if (from + num > IO_BITMAP_SIZE*32)  //只能对0x3ff以下的端口进行设置
  return -EINVAL;
if (!suser())
  return -EPERM; #ifdef IODEBUG
printk("io: from=%d num=%d %s\n", from, num, (turn_on ? "on" : "off"));
#endif
set_bitmap((unsigned long *)current->tss.io_bitmap, from, num, !turn_on);
return 0;
} unsigned int *stack; //这个是通过系统调用设置eflags的io特权级来设置的
//设置当前进程的io特权级到level指定的值
//如果使得CPL<=IOPL成立就不用检查IO位图了，同时这对于
//0x3ff以上的65536全端口是唯一的控制了
asmlinkage int sys_iopl(long ebx,long ecx,long edx,
      long esi, long edi, long ebp, long eax, long ds,
      long es, long fs, long gs, long orig_eax,
      long eip,long cs,long eflags,long esp,long ss)
{
unsigned int level = ebx; if (level > 3)
  return -EINVAL;
if (!suser())
  return -EPERM;
*(&eflags) = (eflags & 0xffffcfff) | (level << 12);
return 0;
} //实际的被外部调用的函数
void snarf_region(unsigned int from, unsigned int num)
{
if (from > IO_BITMAP_SIZE*32)
  return;
if (from + num > IO_BITMAP_SIZE*32)
  num = IO_BITMAP_SIZE*32 - from;
set_bitmap(ioport_registrar, from, num, 1);
return;
} int check_region(unsigned int from, unsigned int num)
{
if (from > IO_BITMAP_SIZE*32)
  return 0;
if (from + num > IO_BITMAP_SIZE*32)
  num = IO_BITMAP_SIZE*32 - from;
return check_bitmap(ioport_registrar, from, num);
} // Called from init/main.c to reserve IO ports. 设置保留的IO端口
void reserve_setup(char *str, int *ints)
{
int i; for (i = 1; i < ints[0]; i += 2)
  snarf_region(ints[i], ints[i+1]);
}
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