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 <asm/syscalls.h>
18
19 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
set_bitmap(unsigned long * bitmap,unsigned int base,unsigned int extent,int new_value)20 static void set_bitmap(unsigned long *bitmap, unsigned int base,
21 unsigned int extent, int new_value)
22 {
23 unsigned int i;
24
25 for (i = base; i < base + extent; i++) {
26 if (new_value)
27 __set_bit(i, bitmap);
28 else
29 __clear_bit(i, bitmap);
30 }
31 }
32
33 /*
34 * this changes the io permissions bitmap in the current task.
35 */
sys_ioperm(unsigned long from,unsigned long num,int turn_on)36 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
37 {
38 struct thread_struct *t = ¤t->thread;
39 struct tss_struct *tss;
40 unsigned int i, max_long, bytes, bytes_updated;
41
42 if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
43 return -EINVAL;
44 if (turn_on && !capable(CAP_SYS_RAWIO))
45 return -EPERM;
46
47 /*
48 * If it's the first ioperm() call in this thread's lifetime, set the
49 * IO bitmap up. ioperm() is much less timing critical than clone(),
50 * this is why we delay this operation until now:
51 */
52 if (!t->io_bitmap_ptr) {
53 unsigned long *bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
54
55 if (!bitmap)
56 return -ENOMEM;
57
58 memset(bitmap, 0xff, IO_BITMAP_BYTES);
59 t->io_bitmap_ptr = bitmap;
60 set_thread_flag(TIF_IO_BITMAP);
61 }
62
63 /*
64 * do it in the per-thread copy and in the TSS ...
65 *
66 * Disable preemption via get_cpu() - we must not switch away
67 * because the ->io_bitmap_max value must match the bitmap
68 * contents:
69 */
70 tss = &per_cpu(init_tss, get_cpu());
71
72 set_bitmap(t->io_bitmap_ptr, from, num, !turn_on);
73
74 /*
75 * Search for a (possibly new) maximum. This is simple and stupid,
76 * to keep it obviously correct:
77 */
78 max_long = 0;
79 for (i = 0; i < IO_BITMAP_LONGS; i++)
80 if (t->io_bitmap_ptr[i] != ~0UL)
81 max_long = i;
82
83 bytes = (max_long + 1) * sizeof(unsigned long);
84 bytes_updated = max(bytes, t->io_bitmap_max);
85
86 t->io_bitmap_max = bytes;
87
88 #ifdef CONFIG_X86_32
89 /*
90 * Sets the lazy trigger so that the next I/O operation will
91 * reload the correct bitmap.
92 * Reset the owner so that a process switch will not set
93 * tss->io_bitmap_base to IO_BITMAP_OFFSET.
94 */
95 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
96 tss->io_bitmap_owner = NULL;
97 #else
98 /* Update the TSS: */
99 memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
100 #endif
101
102 put_cpu();
103
104 return 0;
105 }
106
107 /*
108 * sys_iopl has to be used when you want to access the IO ports
109 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
110 * you'd need 8kB of bitmaps/process, which is a bit excessive.
111 *
112 * Here we just change the flags value on the stack: we allow
113 * only the super-user to do it. This depends on the stack-layout
114 * on system-call entry - see also fork() and the signal handling
115 * code.
116 */
do_iopl(unsigned int level,struct pt_regs * regs)117 static int do_iopl(unsigned int level, struct pt_regs *regs)
118 {
119 unsigned int old = (regs->flags >> 12) & 3;
120
121 if (level > 3)
122 return -EINVAL;
123 /* Trying to gain more privileges? */
124 if (level > old) {
125 if (!capable(CAP_SYS_RAWIO))
126 return -EPERM;
127 }
128 regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
129
130 return 0;
131 }
132
133 #ifdef CONFIG_X86_32
sys_iopl(unsigned long regsp)134 asmlinkage long sys_iopl(unsigned long regsp)
135 {
136 struct pt_regs *regs = (struct pt_regs *)®sp;
137 unsigned int level = regs->bx;
138 struct thread_struct *t = ¤t->thread;
139 int rc;
140
141 rc = do_iopl(level, regs);
142 if (rc < 0)
143 goto out;
144
145 t->iopl = level << 12;
146 set_iopl_mask(t->iopl);
147 out:
148 return rc;
149 }
150 #else
sys_iopl(unsigned int level,struct pt_regs * regs)151 asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs)
152 {
153 return do_iopl(level, regs);
154 }
155 #endif
156