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 18 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */ 19 static void set_bitmap(unsigned long *bitmap, unsigned int base, 20 unsigned int extent, int new_value) 21 { 22 unsigned int i; 23 24 for (i = base; i < base + extent; i++) { 25 if (new_value) 26 __set_bit(i, bitmap); 27 else 28 __clear_bit(i, bitmap); 29 } 30 } 31 32 /* 33 * this changes the io permissions bitmap in the current task. 34 */ 35 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) 36 { 37 struct thread_struct * t = ¤t->thread; 38 struct tss_struct * tss; 39 unsigned int i, max_long, bytes, bytes_updated; 40 41 if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) 42 return -EINVAL; 43 if (turn_on && !capable(CAP_SYS_RAWIO)) 44 return -EPERM; 45 46 /* 47 * If it's the first ioperm() call in this thread's lifetime, set the 48 * IO bitmap up. ioperm() is much less timing critical than clone(), 49 * this is why we delay this operation until now: 50 */ 51 if (!t->io_bitmap_ptr) { 52 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); 53 54 if (!bitmap) 55 return -ENOMEM; 56 57 memset(bitmap, 0xff, IO_BITMAP_BYTES); 58 t->io_bitmap_ptr = bitmap; 59 set_thread_flag(TIF_IO_BITMAP); 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(init_tss, get_cpu()); 70 71 set_bitmap(t->io_bitmap_ptr, from, num, !turn_on); 72 73 /* 74 * Search for a (possibly new) maximum. This is simple and stupid, 75 * to keep it obviously correct: 76 */ 77 max_long = 0; 78 for (i = 0; i < IO_BITMAP_LONGS; i++) 79 if (t->io_bitmap_ptr[i] != ~0UL) 80 max_long = i; 81 82 bytes = (max_long + 1) * sizeof(unsigned long); 83 bytes_updated = max(bytes, t->io_bitmap_max); 84 85 t->io_bitmap_max = bytes; 86 87 #ifdef CONFIG_X86_32 88 /* 89 * Sets the lazy trigger so that the next I/O operation will 90 * reload the correct bitmap. 91 * Reset the owner so that a process switch will not set 92 * tss->io_bitmap_base to IO_BITMAP_OFFSET. 93 */ 94 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY; 95 tss->io_bitmap_owner = NULL; 96 #else 97 /* Update the TSS: */ 98 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated); 99 #endif 100 101 put_cpu(); 102 103 return 0; 104 } 105 106 /* 107 * sys_iopl has to be used when you want to access the IO ports 108 * beyond the 0x3ff range: to get the full 65536 ports bitmapped 109 * you'd need 8kB of bitmaps/process, which is a bit excessive. 110 * 111 * Here we just change the flags value on the stack: we allow 112 * only the super-user to do it. This depends on the stack-layout 113 * on system-call entry - see also fork() and the signal handling 114 * code. 115 */ 116 static int do_iopl(unsigned int level, struct pt_regs *regs) 117 { 118 unsigned int old = (regs->flags >> 12) & 3; 119 120 if (level > 3) 121 return -EINVAL; 122 /* Trying to gain more privileges? */ 123 if (level > old) { 124 if (!capable(CAP_SYS_RAWIO)) 125 return -EPERM; 126 } 127 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); 128 129 return 0; 130 } 131 132 #ifdef CONFIG_X86_32 133 asmlinkage long sys_iopl(unsigned long regsp) 134 { 135 struct pt_regs *regs = (struct pt_regs *)®sp; 136 unsigned int level = regs->bx; 137 struct thread_struct *t = ¤t->thread; 138 int rc; 139 140 rc = do_iopl(level, regs); 141 if (rc < 0) 142 goto out; 143 144 t->iopl = level << 12; 145 set_iopl_mask(t->iopl); 146 out: 147 return rc; 148 } 149 #else 150 asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs) 151 { 152 return do_iopl(level, regs); 153 } 154 #endif 155