root/arch/i386/kernel/ioport.c

/* */

DEFINITIONS

1. set_bitmap
2. sys_ioperm
3. sys_iopl

   1 /*
   2  *      linux/arch/i386/kernel/ioport.c
   3  *
   4  * This contains the io-permission bitmap code - written by obz, with changes
   5  * by Linus.
   6  */
   7 
   8 #include <linux/sched.h>
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/types.h>
  12 #include <linux/ioport.h>
  13 
  14 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
  15 static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value)
     /*  */
  16 {
  17         int mask;
  18         unsigned long *bitmap_base = bitmap + (base >> 5);
  19         unsigned short low_index = base & 0x1f;
  20         int length = low_index + extent;
  21 
  22         if (low_index != 0) {
  23                 mask = (~0 << low_index);
  24                 if (length < 32)
  25                                 mask &= ~(~0 << length);
  26                 if (new_value)
  27                         *bitmap_base++ |= mask;
  28                 else
  29                         *bitmap_base++ &= ~mask;
  30                 length -= 32;
  31         }
  32 
  33         mask = (new_value ? ~0 : 0);
  34         while (length >= 32) {
  35                 *bitmap_base++ = mask;
  36                 length -= 32;
  37         }
  38 
  39         if (length > 0) {
  40                 mask = ~(~0 << length);
  41                 if (new_value)
  42                         *bitmap_base++ |= mask;
  43                 else
  44                         *bitmap_base++ &= ~mask;
  45         }
  46 }
  47 
  48 /*
  49  * this changes the io permissions bitmap in the current task.
  50  */
  51 asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)
     /*  */
  52 {
  53         if (from + num <= from)
  54                 return -EINVAL;
  55         if (from + num > IO_BITMAP_SIZE*32)
  56                 return -EINVAL;
  57         if (!suser())
  58                 return -EPERM;
  59 
  60         set_bitmap((unsigned long *)current->tss.io_bitmap, from, num, !turn_on);
  61         return 0;
  62 }
  63 
  64 unsigned int *stack;
  65 
  66 /*
  67  * sys_iopl has to be used when you want to access the IO ports
  68  * beyond the 0x3ff range: to get the full 65536 ports bitmapped
  69  * you'd need 8kB of bitmaps/process, which is a bit excessive.
  70  *
  71  * Here we just change the eflags value on the stack: we allow
  72  * only the super-user to do it. This depends on the stack-layout
  73  * on system-call entry - see also fork() and the signal handling
  74  * code.
  75  */
  76 asmlinkage int sys_iopl(long ebx,long ecx,long edx,
     /*  */
  77              long esi, long edi, long ebp, long eax, long ds,
  78              long es, long fs, long gs, long orig_eax,
  79              long eip,long cs,long eflags,long esp,long ss)
  80 {
  81         unsigned int level = ebx;
  82 
  83         if (level > 3)
  84                 return -EINVAL;
  85         if (!suser())
  86                 return -EPERM;
  87         *(&eflags) = (eflags & 0xffffcfff) | (level << 12);
  88         return 0;
  89 }

/* */