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/sched/task_stack.h> 8 #include <linux/kernel.h> 9 #include <linux/capability.h> 10 #include <linux/errno.h> 11 #include <linux/types.h> 12 #include <linux/ioport.h> 13 #include <linux/smp.h> 14 #include <linux/stddef.h> 15 #include <linux/slab.h> 16 #include <linux/thread_info.h> 17 #include <linux/syscalls.h> 18 #include <linux/bitmap.h> 19 #include <asm/syscalls.h> 20 #include <asm/desc.h> 21 22 /* 23 * this changes the io permissions bitmap in the current task. 24 */ 25 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) 26 { 27 struct thread_struct *t = ¤t->thread; 28 struct tss_struct *tss; 29 unsigned int i, max_long, bytes, bytes_updated; 30 31 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 32 return -EINVAL; 33 if (turn_on && !capable(CAP_SYS_RAWIO)) 34 return -EPERM; 35 36 /* 37 * If it's the first ioperm() call in this thread's lifetime, set the 38 * IO bitmap up. ioperm() is much less timing critical than clone(), 39 * this is why we delay this operation until now: 40 */ 41 if (!t->io_bitmap_ptr) { 42 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 43 44 if (!bitmap) 45 return -ENOMEM; 46 47 memset(bitmap, 0xff, IO_BITMAP_BYTES); 48 t->io_bitmap_ptr = bitmap; 49 set_thread_flag(TIF_IO_BITMAP); 50 51 /* 52 * Now that we have an IO bitmap, we need our TSS limit to be 53 * correct. It's fine if we are preempted after doing this: 54 * with TIF_IO_BITMAP set, context switches will keep our TSS 55 * limit correct. 56 */ 57 preempt_disable(); 58 refresh_tss_limit(); 59 preempt_enable(); 60 } 61 62 /* 63 * do it in the per-thread copy and in the TSS ... 64 * 65 * Disable preemption via get_cpu() - we must not switch away 66 * because the ->io_bitmap_max value must match the bitmap 67 * contents: 68 */ 69 tss = &per_cpu(cpu_tss, get_cpu()); 70 71 if (turn_on) 72 bitmap_clear(t->io_bitmap_ptr, from, num); 73 else 74 bitmap_set(t->io_bitmap_ptr, from, num); 75 76 /* 77 * Search for a (possibly new) maximum. This is simple and stupid, 78 * to keep it obviously correct: 79 */ 80 max_long = 0; 81 for (i = 0; i < IO_BITMAP_LONGS; i++) 82 if (t->io_bitmap_ptr[i] != ~0UL) 83 max_long = i; 84 85 bytes = (max_long + 1) * sizeof(unsigned long); 86 bytes_updated = max(bytes, t->io_bitmap_max); 87 88 t->io_bitmap_max = bytes; 89 90 /* Update the TSS: */ 91 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 92 93 put_cpu(); 94 95 return 0; 96 } 97 98 /* 99 * sys_iopl has to be used when you want to access the IO ports 100 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 101 * you'd need 8kB of bitmaps/process, which is a bit excessive. 102 * 103 * Here we just change the flags value on the stack: we allow 104 * only the super-user to do it. This depends on the stack-layout 105 * on system-call entry - see also fork() and the signal handling 106 * code. 107 */ 108 SYSCALL_DEFINE1(iopl, unsigned int, level) 109 { 110 struct pt_regs *regs = current_pt_regs(); 111 struct thread_struct *t = ¤t->thread; 112 113 /* 114 * Careful: the IOPL bits in regs->flags are undefined under Xen PV 115 * and changing them has no effect. 116 */ 117 unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT; 118 119 if (level > 3) 120 return -EINVAL; 121 /* Trying to gain more privileges? */ 122 if (level > old) { 123 if (!capable(CAP_SYS_RAWIO)) 124 return -EPERM; 125 } 126 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | 127 (level << X86_EFLAGS_IOPL_BIT); 128 t->iopl = level << X86_EFLAGS_IOPL_BIT; 129 set_iopl_mask(t->iopl); 130 131 return 0; 132 } 133