1 /*
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_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
9 the containing struct bug_entry for bug_addr and file.
10 CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
11
12 CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
13 (though they're generally always on).
14
15 CONFIG_GENERIC_BUG is set by each architecture using this code.
16
17 To use this, your architecture must:
18
19 1. Set up the config options:
20 - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
21
22 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
23 - Define HAVE_ARCH_BUG
24 - Implement BUG() to generate a faulting instruction
25 - NOTE: struct bug_entry does not have "file" or "line" entries
26 when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
27 the values accordingly.
28
29 3. Implement the trap
30 - In the illegal instruction trap handler (typically), verify
31 that the fault was in kernel mode, and call report_bug()
32 - report_bug() will return whether it was a false alarm, a warning,
33 or an actual bug.
34 - You must implement the is_valid_bugaddr(bugaddr) callback which
35 returns true if the eip is a real kernel address, and it points
36 to the expected BUG trap instruction.
37
38 Jeremy Fitzhardinge <jeremy@goop.org> 2006
39 */
40 #include <linux/list.h>
41 #include <linux/module.h>
42 #include <linux/kernel.h>
43 #include <linux/bug.h>
44 #include <linux/sched.h>
45
46 extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
47
48 static inline unsigned long bug_addr(const struct bug_entry *bug)
49 {
50 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
51 return bug->bug_addr;
52 #else
53 return (unsigned long)bug + bug->bug_addr_disp;
54 #endif
55 }
56
57 #ifdef CONFIG_MODULES
58 static LIST_HEAD(module_bug_list);
59
60 static const struct bug_entry *module_find_bug(unsigned long bugaddr)
61 {
62 struct module *mod;
63
64 list_for_each_entry(mod, &module_bug_list, bug_list) {
65 const struct bug_entry *bug = mod->bug_table;
66 unsigned i;
67
68 for (i = 0; i < mod->num_bugs; ++i, ++bug)
69 if (bugaddr == bug_addr(bug))
70 return bug;
71 }
72 return NULL;
73 }
74
75 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
76 struct module *mod)
77 {
78 char *secstrings;
79 unsigned int i;
80
81 mod->bug_table = NULL;
82 mod->num_bugs = 0;
83
84 /* Find the __bug_table section, if present */
85 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
86 for (i = 1; i < hdr->e_shnum; i++) {
87 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
88 continue;
89 mod->bug_table = (void *) sechdrs[i].sh_addr;
90 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
91 break;
92 }
93
94 /*
95 * Strictly speaking this should have a spinlock to protect against
96 * traversals, but since we only traverse on BUG()s, a spinlock
97 * could potentially lead to deadlock and thus be counter-productive.
98 */
99 list_add(&mod->bug_list, &module_bug_list);
100
101 return 0;
102 }
103
104 void module_bug_cleanup(struct module *mod)
105 {
106 list_del(&mod->bug_list);
107 }
108
109 #else
110
111 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
112 {
113 return NULL;
114 }
115 #endif
116
117 const struct bug_entry *find_bug(unsigned long bugaddr)
118 {
119 const struct bug_entry *bug;
120
121 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
122 if (bugaddr == bug_addr(bug))
123 return bug;
124
125 return module_find_bug(bugaddr);
126 }
127
128 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
129 {
130 const struct bug_entry *bug;
131 const char *file;
132 unsigned line, warning;
133
134 if (!is_valid_bugaddr(bugaddr))
135 return BUG_TRAP_TYPE_NONE;
136
137 bug = find_bug(bugaddr);
138
139 printk(KERN_EMERG "------------[ cut here ]------------\n");
140
141 file = NULL;
142 line = 0;
143 warning = 0;
144
145 if (bug) {
146 #ifdef CONFIG_DEBUG_BUGVERBOSE
147 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
148 file = bug->file;
149 #else
150 file = (const char *)bug + bug->file_disp;
151 #endif
152 line = bug->line;
153 #endif
154 warning = (bug->flags & BUGFLAG_WARNING) != 0;
155 }
156
157 if (warning) {
158 /* this is a WARN_ON rather than BUG/BUG_ON */
159 if (file)
160 printk(KERN_ERR "Badness at %s:%u\n",
161 file, line);
162 else
163 printk(KERN_ERR "Badness at %p "
164 "[verbose debug info unavailable]\n",
165 (void *)bugaddr);
166
167 show_regs(regs);
168 add_taint(TAINT_WARN);
169 return BUG_TRAP_TYPE_WARN;
170 }
171
172 if (file)
173 printk(KERN_CRIT "kernel BUG at %s:%u!\n",
174 file, line);
175 else
176 printk(KERN_CRIT "Kernel BUG at %p "
177 "[verbose debug info unavailable]\n",
178 (void *)bugaddr);
179
180 return BUG_TRAP_TYPE_BUG;
181 }
182
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