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Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -08001/*
2 Generic support for BUG()
3
4 This respects the following config options:
5
6 CONFIG_BUG - emit BUG traps. Nothing happens without this.
7 CONFIG_GENERIC_BUG - enable this code.
8 CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
9
10 CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
11 (though they're generally always on).
12
13 CONFIG_GENERIC_BUG is set by each architecture using this code.
14
15 To use this, your architecture must:
16
17 1. Set up the config options:
18 - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
19
20 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
21 - Define HAVE_ARCH_BUG
22 - Implement BUG() to generate a faulting instruction
23 - NOTE: struct bug_entry does not have "file" or "line" entries
24 when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
25 the values accordingly.
26
27 3. Implement the trap
28 - In the illegal instruction trap handler (typically), verify
29 that the fault was in kernel mode, and call report_bug()
30 - report_bug() will return whether it was a false alarm, a warning,
31 or an actual bug.
32 - You must implement the is_valid_bugaddr(bugaddr) callback which
33 returns true if the eip is a real kernel address, and it points
34 to the expected BUG trap instruction.
35
36 Jeremy Fitzhardinge <jeremy@goop.org> 2006
37 */
38#include <linux/list.h>
39#include <linux/module.h>
Paul Mundtda9eac82008-07-04 09:59:36 -070040#include <linux/kernel.h>
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080041#include <linux/bug.h>
Heiko Carstens608e2612007-07-15 23:41:39 -070042#include <linux/sched.h>
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080043
44extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
45
46#ifdef CONFIG_MODULES
47static LIST_HEAD(module_bug_list);
48
49static const struct bug_entry *module_find_bug(unsigned long bugaddr)
50{
51 struct module *mod;
52
53 list_for_each_entry(mod, &module_bug_list, bug_list) {
54 const struct bug_entry *bug = mod->bug_table;
55 unsigned i;
56
57 for (i = 0; i < mod->num_bugs; ++i, ++bug)
58 if (bugaddr == bug->bug_addr)
59 return bug;
60 }
61 return NULL;
62}
63
64int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
65 struct module *mod)
66{
67 char *secstrings;
68 unsigned int i;
69
70 mod->bug_table = NULL;
71 mod->num_bugs = 0;
72
73 /* Find the __bug_table section, if present */
74 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
75 for (i = 1; i < hdr->e_shnum; i++) {
76 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
77 continue;
78 mod->bug_table = (void *) sechdrs[i].sh_addr;
79 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
80 break;
81 }
82
83 /*
84 * Strictly speaking this should have a spinlock to protect against
85 * traversals, but since we only traverse on BUG()s, a spinlock
86 * could potentially lead to deadlock and thus be counter-productive.
87 */
88 list_add(&mod->bug_list, &module_bug_list);
89
90 return 0;
91}
92
93void module_bug_cleanup(struct module *mod)
94{
95 list_del(&mod->bug_list);
96}
97
98#else
99
100static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
101{
102 return NULL;
103}
104#endif
105
106const struct bug_entry *find_bug(unsigned long bugaddr)
107{
108 const struct bug_entry *bug;
109
110 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
111 if (bugaddr == bug->bug_addr)
112 return bug;
113
114 return module_find_bug(bugaddr);
115}
116
Heiko Carstens608e2612007-07-15 23:41:39 -0700117enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800118{
119 const struct bug_entry *bug;
120 const char *file;
121 unsigned line, warning;
122
123 if (!is_valid_bugaddr(bugaddr))
124 return BUG_TRAP_TYPE_NONE;
125
126 bug = find_bug(bugaddr);
127
128 printk(KERN_EMERG "------------[ cut here ]------------\n");
129
130 file = NULL;
131 line = 0;
132 warning = 0;
133
134 if (bug) {
135#ifdef CONFIG_DEBUG_BUGVERBOSE
136 file = bug->file;
137 line = bug->line;
138#endif
139 warning = (bug->flags & BUGFLAG_WARNING) != 0;
140 }
141
142 if (warning) {
143 /* this is a WARN_ON rather than BUG/BUG_ON */
144 if (file)
145 printk(KERN_ERR "Badness at %s:%u\n",
146 file, line);
147 else
148 printk(KERN_ERR "Badness at %p "
149 "[verbose debug info unavailable]\n",
150 (void *)bugaddr);
151
Heiko Carstens608e2612007-07-15 23:41:39 -0700152 show_regs(regs);
Paul Mundtda9eac82008-07-04 09:59:36 -0700153 add_taint(TAINT_WARN);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800154 return BUG_TRAP_TYPE_WARN;
155 }
156
157 if (file)
158 printk(KERN_CRIT "kernel BUG at %s:%u!\n",
159 file, line);
160 else
161 printk(KERN_CRIT "Kernel BUG at %p "
162 "[verbose debug info unavailable]\n",
163 (void *)bugaddr);
164
165 return BUG_TRAP_TYPE_BUG;
166}