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 <linux/bitmap.h> 18 #include <asm/syscalls.h> 19 20 /* 21 * this changes the io permissions bitmap in the current task. 22 */ 23 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) 24 { 25 struct thread_struct *t = ¤t->thread; 26 struct tss_struct *tss; 27 unsigned int i, max_long, bytes, bytes_updated; 28 29 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 30 return -EINVAL; 31 if (turn_on && !capable(CAP_SYS_RAWIO)) 32 return -EPERM; 33 34 /* 35 * If it's the first ioperm() call in this thread's lifetime, set the 36 * IO bitmap up. ioperm() is much less timing critical than clone(), 37 * this is why we delay this operation until now: 38 */ 39 if (!t->io_bitmap_ptr) { 40 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 41 42 if (!bitmap) 43 return -ENOMEM; 44 45 memset(bitmap, 0xff, IO_BITMAP_BYTES); 46 t->io_bitmap_ptr = bitmap; 47 set_thread_flag(TIF_IO_BITMAP); 48 } 49 50 /* 51 * do it in the per-thread copy and in the TSS ... 52 * 53 * Disable preemption via get_cpu() - we must not switch away 54 * because the ->io_bitmap_max value must match the bitmap 55 * contents: 56 */ 57 tss = &per_cpu(init_tss, get_cpu()); 58 59 if (turn_on) 60 bitmap_clear(t->io_bitmap_ptr, from, num); 61 else 62 bitmap_set(t->io_bitmap_ptr, from, num); 63 64 /* 65 * Search for a (possibly new) maximum. This is simple and stupid, 66 * to keep it obviously correct: 67 */ 68 max_long = 0; 69 for (i = 0; i < IO_BITMAP_LONGS; i++) 70 if (t->io_bitmap_ptr[i] != ~0UL) 71 max_long = i; 72 73 bytes = (max_long + 1) * sizeof(unsigned long); 74 bytes_updated = max(bytes, t->io_bitmap_max); 75 76 t->io_bitmap_max = bytes; 77 78 /* Update the TSS: */ 79 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 80 81 put_cpu(); 82 83 return 0; 84 } 85 86 /* 87 * sys_iopl has to be used when you want to access the IO ports 88 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 89 * you'd need 8kB of bitmaps/process, which is a bit excessive. 90 * 91 * Here we just change the flags value on the stack: we allow 92 * only the super-user to do it. This depends on the stack-layout 93 * on system-call entry - see also fork() and the signal handling 94 * code. 95 */ 96 SYSCALL_DEFINE1(iopl, unsigned int, level) 97 { 98 struct pt_regs *regs = current_pt_regs(); 99 unsigned int old = (regs->flags >> 12) & 3; 100 struct thread_struct *t = ¤t->thread; 101 102 if (level > 3) 103 return -EINVAL; 104 /* Trying to gain more privileges? */ 105 if (level > old) { 106 if (!capable(CAP_SYS_RAWIO)) 107 return -EPERM; 108 } 109 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); 110 t->iopl = level << 12; 111 set_iopl_mask(t->iopl); 112 113 return 0; 114 } 115