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1da177e4 LT |
1 | /* |
2 | * linux/arch/i386/kernel/ioport.c | |
3 | * | |
4 | * This contains the io-permission bitmap code - written by obz, with changes | |
5 | * by Linus. | |
6 | */ | |
7 | ||
8 | #include <linux/sched.h> | |
9 | #include <linux/kernel.h> | |
10 | #include <linux/errno.h> | |
11 | #include <linux/types.h> | |
12 | #include <linux/ioport.h> | |
13 | #include <linux/smp.h> | |
14 | #include <linux/smp_lock.h> | |
15 | #include <linux/stddef.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/thread_info.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, unsigned int extent, int new_value) | |
21 | { | |
22 | unsigned long mask; | |
23 | unsigned long *bitmap_base = bitmap + (base / BITS_PER_LONG); | |
24 | unsigned int low_index = base & (BITS_PER_LONG-1); | |
25 | int length = low_index + extent; | |
26 | ||
27 | if (low_index != 0) { | |
28 | mask = (~0UL << low_index); | |
29 | if (length < BITS_PER_LONG) | |
30 | mask &= ~(~0UL << length); | |
31 | if (new_value) | |
32 | *bitmap_base++ |= mask; | |
33 | else | |
34 | *bitmap_base++ &= ~mask; | |
35 | length -= BITS_PER_LONG; | |
36 | } | |
37 | ||
38 | mask = (new_value ? ~0UL : 0UL); | |
39 | while (length >= BITS_PER_LONG) { | |
40 | *bitmap_base++ = mask; | |
41 | length -= BITS_PER_LONG; | |
42 | } | |
43 | ||
44 | if (length > 0) { | |
45 | mask = ~(~0UL << length); | |
46 | if (new_value) | |
47 | *bitmap_base++ |= mask; | |
48 | else | |
49 | *bitmap_base++ &= ~mask; | |
50 | } | |
51 | } | |
52 | ||
53 | ||
54 | /* | |
55 | * this changes the io permissions bitmap in the current task. | |
56 | */ | |
57 | asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) | |
58 | { | |
59 | unsigned long i, max_long, bytes, bytes_updated; | |
60 | struct thread_struct * t = ¤t->thread; | |
61 | struct tss_struct * tss; | |
62 | unsigned long *bitmap; | |
63 | ||
64 | if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) | |
65 | return -EINVAL; | |
66 | if (turn_on && !capable(CAP_SYS_RAWIO)) | |
67 | return -EPERM; | |
68 | ||
69 | /* | |
70 | * If it's the first ioperm() call in this thread's lifetime, set the | |
71 | * IO bitmap up. ioperm() is much less timing critical than clone(), | |
72 | * this is why we delay this operation until now: | |
73 | */ | |
74 | if (!t->io_bitmap_ptr) { | |
75 | bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); | |
76 | if (!bitmap) | |
77 | return -ENOMEM; | |
78 | ||
79 | memset(bitmap, 0xff, IO_BITMAP_BYTES); | |
80 | t->io_bitmap_ptr = bitmap; | |
81 | } | |
82 | ||
83 | /* | |
84 | * do it in the per-thread copy and in the TSS ... | |
85 | * | |
86 | * Disable preemption via get_cpu() - we must not switch away | |
87 | * because the ->io_bitmap_max value must match the bitmap | |
88 | * contents: | |
89 | */ | |
90 | tss = &per_cpu(init_tss, get_cpu()); | |
91 | ||
92 | set_bitmap(t->io_bitmap_ptr, from, num, !turn_on); | |
93 | ||
94 | /* | |
95 | * Search for a (possibly new) maximum. This is simple and stupid, | |
96 | * to keep it obviously correct: | |
97 | */ | |
98 | max_long = 0; | |
99 | for (i = 0; i < IO_BITMAP_LONGS; i++) | |
100 | if (t->io_bitmap_ptr[i] != ~0UL) | |
101 | max_long = i; | |
102 | ||
103 | bytes = (max_long + 1) * sizeof(long); | |
104 | bytes_updated = max(bytes, t->io_bitmap_max); | |
105 | ||
106 | t->io_bitmap_max = bytes; | |
107 | ||
108 | /* | |
109 | * Sets the lazy trigger so that the next I/O operation will | |
110 | * reload the correct bitmap. | |
111 | */ | |
112 | tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY; | |
113 | ||
114 | put_cpu(); | |
115 | ||
116 | return 0; | |
117 | } | |
118 | ||
119 | /* | |
120 | * sys_iopl has to be used when you want to access the IO ports | |
121 | * beyond the 0x3ff range: to get the full 65536 ports bitmapped | |
122 | * you'd need 8kB of bitmaps/process, which is a bit excessive. | |
123 | * | |
124 | * Here we just change the eflags value on the stack: we allow | |
125 | * only the super-user to do it. This depends on the stack-layout | |
126 | * on system-call entry - see also fork() and the signal handling | |
127 | * code. | |
128 | */ | |
129 | ||
130 | asmlinkage long sys_iopl(unsigned long unused) | |
131 | { | |
132 | volatile struct pt_regs * regs = (struct pt_regs *) &unused; | |
133 | unsigned int level = regs->ebx; | |
134 | unsigned int old = (regs->eflags >> 12) & 3; | |
135 | ||
136 | if (level > 3) | |
137 | return -EINVAL; | |
138 | /* Trying to gain more privileges? */ | |
139 | if (level > old) { | |
140 | if (!capable(CAP_SYS_RAWIO)) | |
141 | return -EPERM; | |
142 | } | |
143 | regs->eflags = (regs->eflags &~ 0x3000UL) | (level << 12); | |
144 | /* Make sure we return the long way (not sysenter) */ | |
145 | set_thread_flag(TIF_IRET); | |
146 | return 0; | |
147 | } |