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 #include <asm/desc.h> 20 21 /* 22 * this changes the io permissions bitmap in the current task. 23 */ 24 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) 25 { 26 struct thread_struct *t = ¤t->thread; 27 struct tss_struct *tss; 28 unsigned int i, max_long, bytes, bytes_updated; 29 30 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 31 return -EINVAL; 32 if (turn_on && !capable(CAP_SYS_RAWIO)) 33 return -EPERM; 34 35 /* 36 * If it's the first ioperm() call in this thread's lifetime, set the 37 * IO bitmap up. ioperm() is much less timing critical than clone(), 38 * this is why we delay this operation until now: 39 */ 40 if (!t->io_bitmap_ptr) { 41 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 42 43 if (!bitmap) 44 return -ENOMEM; 45 46 memset(bitmap, 0xff, IO_BITMAP_BYTES); 47 t->io_bitmap_ptr = bitmap; 48 set_thread_flag(TIF_IO_BITMAP); 49 50 preempt_disable(); 51 refresh_TR(); 52 preempt_enable(); 53 } 54 55 /* 56 * do it in the per-thread copy and in the TSS ... 57 * 58 * Disable preemption via get_cpu() - we must not switch away 59 * because the ->io_bitmap_max value must match the bitmap 60 * contents: 61 */ 62 tss = &per_cpu(cpu_tss, get_cpu()); 63 64 if (turn_on) 65 bitmap_clear(t->io_bitmap_ptr, from, num); 66 else 67 bitmap_set(t->io_bitmap_ptr, from, num); 68 69 /* 70 * Search for a (possibly new) maximum. This is simple and stupid, 71 * to keep it obviously correct: 72 */ 73 max_long = 0; 74 for (i = 0; i < IO_BITMAP_LONGS; i++) 75 if (t->io_bitmap_ptr[i] != ~0UL) 76 max_long = i; 77 78 bytes = (max_long + 1) * sizeof(unsigned long); 79 bytes_updated = max(bytes, t->io_bitmap_max); 80 81 t->io_bitmap_max = bytes; 82 83 /* Update the TSS: */ 84 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 85 86 put_cpu(); 87 88 return 0; 89 } 90 91 /* 92 * sys_iopl has to be used when you want to access the IO ports 93 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 94 * you'd need 8kB of bitmaps/process, which is a bit excessive. 95 * 96 * Here we just change the flags value on the stack: we allow 97 * only the super-user to do it. This depends on the stack-layout 98 * on system-call entry - see also fork() and the signal handling 99 * code. 100 */ 101 SYSCALL_DEFINE1(iopl, unsigned int, level) 102 { 103 struct pt_regs *regs = current_pt_regs(); 104 struct thread_struct *t = ¤t->thread; 105 106 /* 107 * Careful: the IOPL bits in regs->flags are undefined under Xen PV 108 * and changing them has no effect. 109 */ 110 unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT; 111 112 if (level > 3) 113 return -EINVAL; 114 /* Trying to gain more privileges? */ 115 if (level > old) { 116 if (!capable(CAP_SYS_RAWIO)) 117 return -EPERM; 118 } 119 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | 120 (level << X86_EFLAGS_IOPL_BIT); 121 t->iopl = level << X86_EFLAGS_IOPL_BIT; 122 set_iopl_mask(t->iopl); 123 124 return 0; 125 } 126