1 /* 2 * This contains the io-permission bitmap code - written by obz, with changes 3 * by Linus. 32/64 bits code unification by Miguel Botón. 4 */ 5 6 #include <linux/sched.h> 7 #include <linux/kernel.h> 8 #include <linux/capability.h> 9 #include <linux/errno.h> 10 #include <linux/types.h> 11 #include <linux/ioport.h> 12 #include <linux/smp.h> 13 #include <linux/stddef.h> 14 #include <linux/slab.h> 15 #include <linux/thread_info.h> 16 #include <linux/syscalls.h> 17 #include <asm/syscalls.h> 18 19 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */ 20 static void set_bitmap(unsigned long *bitmap, unsigned int base, 21 unsigned int extent, int new_value) 22 { 23 unsigned int i; 24 25 for (i = base; i < base + extent; i++) { 26 if (new_value) 27 __set_bit(i, bitmap); 28 else 29 __clear_bit(i, bitmap); 30 } 31 } 32 33 /* 34 * this changes the io permissions bitmap in the current task. 35 */ 36 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) 37 { 38 struct thread_struct *t = ¤t->thread; 39 struct tss_struct *tss; 40 unsigned int i, max_long, bytes, bytes_updated; 41 42 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 43 return -EINVAL; 44 if (turn_on && !capable(CAP_SYS_RAWIO)) 45 return -EPERM; 46 47 /* 48 * If it's the first ioperm() call in this thread's lifetime, set the 49 * IO bitmap up. ioperm() is much less timing critical than clone(), 50 * this is why we delay this operation until now: 51 */ 52 if (!t->io_bitmap_ptr) { 53 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 54 55 if (!bitmap) 56 return -ENOMEM; 57 58 memset(bitmap, 0xff, IO_BITMAP_BYTES); 59 t->io_bitmap_ptr = bitmap; 60 set_thread_flag(TIF_IO_BITMAP); 61 } 62 63 /* 64 * do it in the per-thread copy and in the TSS ... 65 * 66 * Disable preemption via get_cpu() - we must not switch away 67 * because the ->io_bitmap_max value must match the bitmap 68 * contents: 69 */ 70 tss = &per_cpu(init_tss, get_cpu()); 71 72 set_bitmap(t->io_bitmap_ptr, from, num, !turn_on); 73 74 /* 75 * Search for a (possibly new) maximum. This is simple and stupid, 76 * to keep it obviously correct: 77 */ 78 max_long = 0; 79 for (i = 0; i < IO_BITMAP_LONGS; i++) 80 if (t->io_bitmap_ptr[i] != ~0UL) 81 max_long = i; 82 83 bytes = (max_long + 1) * sizeof(unsigned long); 84 bytes_updated = max(bytes, t->io_bitmap_max); 85 86 t->io_bitmap_max = bytes; 87 88 /* Update the TSS: */ 89 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 90 91 put_cpu(); 92 93 return 0; 94 } 95 96 /* 97 * sys_iopl has to be used when you want to access the IO ports 98 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 99 * you'd need 8kB of bitmaps/process, which is a bit excessive. 100 * 101 * Here we just change the flags value on the stack: we allow 102 * only the super-user to do it. This depends on the stack-layout 103 * on system-call entry - see also fork() and the signal handling 104 * code. 105 */ 106 long sys_iopl(unsigned int level, struct pt_regs *regs) 107 { 108 unsigned int old = (regs->flags >> 12) & 3; 109 struct thread_struct *t = ¤t->thread; 110 111 if (level > 3) 112 return -EINVAL; 113 /* Trying to gain more privileges? */ 114 if (level > old) { 115 if (!capable(CAP_SYS_RAWIO)) 116 return -EPERM; 117 } 118 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); 119 t->iopl = level << 12; 120 set_iopl_mask(t->iopl); 121 122 return 0; 123 } 124