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#include <linux/mm.h> 14#include <linux/smp.h> 15#include <linux/smp_lock.h> 16#include <linux/stddef.h> 17 18/* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */ 19static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value) 20{ 21 int mask; 22 unsigned long *bitmap_base = bitmap + (base >> 5); 23 unsigned short low_index = base & 0x1f; 24 int length = low_index + extent; 25 26 if (low_index != 0) { 27 mask = (~0 << low_index); 28 if (length < 32) 29 mask &= ~(~0 << length); 30 if (new_value) 31 *bitmap_base++ |= mask; 32 else 33 *bitmap_base++ &= ~mask; 34 length -= 32; 35 } 36 37 mask = (new_value ? ~0 : 0); 38 while (length >= 32) { 39 *bitmap_base++ = mask; 40 length -= 32; 41 } 42 43 if (length > 0) { 44 mask = ~(~0 << length); 45 if (new_value) 46 *bitmap_base++ |= mask; 47 else 48 *bitmap_base++ &= ~mask; 49 } 50} 51 52/* 53 * this changes the io permissions bitmap in the current task. 54 */ 55asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on) 56{ 57 struct thread_struct * t = ¤t->thread; 58 struct tss_struct * tss = init_tss + smp_processor_id(); 59 60 if ((from + num <= from) || (from + num > IO_BITMAP_SIZE*32)) 61 return -EINVAL; 62 if (turn_on && !capable(CAP_SYS_RAWIO)) 63 return -EPERM; 64 /* 65 * If it's the first ioperm() call in this thread's lifetime, set the 66 * IO bitmap up. ioperm() is much less timing critical than clone(), 67 * this is why we delay this operation until now: 68 */ 69 if (!t->ioperm) { 70 /* 71 * just in case ... 72 */ 73 memset(t->io_bitmap,0xff,(IO_BITMAP_SIZE+1)*4); 74 t->ioperm = 1; 75 /* 76 * this activates it in the TSS 77 */ 78 tss->bitmap = IO_BITMAP_OFFSET; 79 } 80 81 /* 82 * do it in the per-thread copy and in the TSS ... 83 */ 84 set_bitmap(t->io_bitmap, from, num, !turn_on); 85 set_bitmap(tss->io_bitmap, from, num, !turn_on); 86 87 return 0; 88} 89 90/* 91 * sys_iopl has to be used when you want to access the IO ports 92 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 93 * you'd need 8kB of bitmaps/process, which is a bit excessive. 94 * 95 * Here we just change the eflags value on the stack: we allow 96 * only the super-user to do it. This depends on the stack-layout 97 * on system-call entry - see also fork() and the signal handling 98 * code. 99 */ 100 101asmlinkage int sys_iopl(unsigned long unused) 102{ 103 struct pt_regs * regs = (struct pt_regs *) &unused; 104 unsigned int level = regs->ebx; 105 unsigned int old = (regs->eflags >> 12) & 3; 106 107 if (level > 3) 108 return -EINVAL; 109 /* Trying to gain more privileges? */ 110 if (level > old) { 111 if (!capable(CAP_SYS_RAWIO)) 112 return -EPERM; 113 } 114 regs->eflags = (regs->eflags & 0xffffcfff) | (level << 12); 115 return 0; 116} 117