1#include <linux/module.h>
2#include <linux/spinlock.h>
3#include <linux/sort.h>
4#include <asm/uaccess.h>
5
6static inline unsigned long
7ex_insn_addr(const struct exception_table_entry *x)
8{
9	return (unsigned long)&x->insn + x->insn;
10}
11static inline unsigned long
12ex_fixup_addr(const struct exception_table_entry *x)
13{
14	return (unsigned long)&x->fixup + x->fixup;
15}
16
17int fixup_exception(struct pt_regs *regs)
18{
19	const struct exception_table_entry *fixup;
20	unsigned long new_ip;
21
22#ifdef CONFIG_PNPBIOS
23	if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
24		extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
25		extern u32 pnp_bios_is_utter_crap;
26		pnp_bios_is_utter_crap = 1;
27		printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
28		__asm__ volatile(
29			"movl %0, %%esp\n\t"
30			"jmp *%1\n\t"
31			: : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
32		panic("do_trap: can't hit this");
33	}
34#endif
35
36	fixup = search_exception_tables(regs->ip);
37	if (fixup) {
38		new_ip = ex_fixup_addr(fixup);
39
40		if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
41			/* Special hack for uaccess_err */
42			current_thread_info()->uaccess_err = 1;
43			new_ip -= 0x7ffffff0;
44		}
45		regs->ip = new_ip;
46		return 1;
47	}
48
49	return 0;
50}
51
52/* Restricted version used during very early boot */
53int __init early_fixup_exception(unsigned long *ip)
54{
55	const struct exception_table_entry *fixup;
56	unsigned long new_ip;
57
58	fixup = search_exception_tables(*ip);
59	if (fixup) {
60		new_ip = ex_fixup_addr(fixup);
61
62		if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
63			/* uaccess handling not supported during early boot */
64			return 0;
65		}
66
67		*ip = new_ip;
68		return 1;
69	}
70
71	return 0;
72}
73
74/*
75 * Search one exception table for an entry corresponding to the
76 * given instruction address, and return the address of the entry,
77 * or NULL if none is found.
78 * We use a binary search, and thus we assume that the table is
79 * already sorted.
80 */
81const struct exception_table_entry *
82search_extable(const struct exception_table_entry *first,
83	       const struct exception_table_entry *last,
84	       unsigned long value)
85{
86	while (first <= last) {
87		const struct exception_table_entry *mid;
88		unsigned long addr;
89
90		mid = ((last - first) >> 1) + first;
91		addr = ex_insn_addr(mid);
92		if (addr < value)
93			first = mid + 1;
94		else if (addr > value)
95			last = mid - 1;
96		else
97			return mid;
98        }
99        return NULL;
100}
101
102/*
103 * The exception table needs to be sorted so that the binary
104 * search that we use to find entries in it works properly.
105 * This is used both for the kernel exception table and for
106 * the exception tables of modules that get loaded.
107 *
108 */
109static int cmp_ex(const void *a, const void *b)
110{
111	const struct exception_table_entry *x = a, *y = b;
112
113	/*
114	 * This value will always end up fittin in an int, because on
115	 * both i386 and x86-64 the kernel symbol-reachable address
116	 * space is < 2 GiB.
117	 *
118	 * This compare is only valid after normalization.
119	 */
120	return x->insn - y->insn;
121}
122
123void sort_extable(struct exception_table_entry *start,
124		  struct exception_table_entry *finish)
125{
126	struct exception_table_entry *p;
127	int i;
128
129	/* Convert all entries to being relative to the start of the section */
130	i = 0;
131	for (p = start; p < finish; p++) {
132		p->insn += i;
133		i += 4;
134		p->fixup += i;
135		i += 4;
136	}
137
138	sort(start, finish - start, sizeof(struct exception_table_entry),
139	     cmp_ex, NULL);
140
141	/* Denormalize all entries */
142	i = 0;
143	for (p = start; p < finish; p++) {
144		p->insn -= i;
145		i += 4;
146		p->fixup -= i;
147		i += 4;
148	}
149}
150
151#ifdef CONFIG_MODULES
152/*
153 * If the exception table is sorted, any referring to the module init
154 * will be at the beginning or the end.
155 */
156void trim_init_extable(struct module *m)
157{
158	/*trim the beginning*/
159	while (m->num_exentries &&
160	       within_module_init(ex_insn_addr(&m->extable[0]), m)) {
161		m->extable++;
162		m->num_exentries--;
163	}
164	/*trim the end*/
165	while (m->num_exentries &&
166	       within_module_init(ex_insn_addr(&m->extable[m->num_exentries-1]), m))
167		m->num_exentries--;
168}
169#endif /* CONFIG_MODULES */
170