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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
41 #define pr_fmt(fmt) fmt
42
43 #include <linux/list.h>
44 #include <linux/module.h>
45 #include <linux/kernel.h>
46 #include <linux/bug.h>
47 #include <linux/sched.h>
48
49 extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
50
51 static inline unsigned long bug_addr(const struct bug_entry *bug)
52 {
53 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
54 return bug->bug_addr;
55 #else
56 return (unsigned long)bug + bug->bug_addr_disp;
57 #endif
58 }
59
60 #ifdef CONFIG_MODULES
61 /* Updates are protected by module mutex */
62 static LIST_HEAD(module_bug_list);
63
64 static const struct bug_entry *module_find_bug(unsigned long bugaddr)
65 {
66 struct module *mod;
67
68 list_for_each_entry(mod, &module_bug_list, bug_list) {
69 const struct bug_entry *bug = mod->bug_table;
70 unsigned i;
71
72 for (i = 0; i < mod->num_bugs; ++i, ++bug)
73 if (bugaddr == bug_addr(bug))
74 return bug;
75 }
76 return NULL;
77 }
78
79 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
80 struct module *mod)
81 {
82 char *secstrings;
83 unsigned int i;
84
85 mod->bug_table = NULL;
86 mod->num_bugs = 0;
87
88 /* Find the __bug_table section, if present */
89 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
90 for (i = 1; i < hdr->e_shnum; i++) {
91 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
92 continue;
93 mod->bug_table = (void *) sechdrs[i].sh_addr;
94 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
95 break;
96 }
97
98 /*
99 * Strictly speaking this should have a spinlock to protect against
100 * traversals, but since we only traverse on BUG()s, a spinlock
101 * could potentially lead to deadlock and thus be counter-productive.
102 */
103 list_add(&mod->bug_list, &module_bug_list);
104 }
105
106 void module_bug_cleanup(struct module *mod)
107 {
108 list_del(&mod->bug_list);
109 }
110
111 #else
112
113 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
114 {
115 return NULL;
116 }
117 #endif
118
119 const struct bug_entry *find_bug(unsigned long bugaddr)
120 {
121 const struct bug_entry *bug;
122
123 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
124 if (bugaddr == bug_addr(bug))
125 return bug;
126
127 return module_find_bug(bugaddr);
128 }
129
130 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
131 {
132 const struct bug_entry *bug;
133 const char *file;
134 unsigned line, warning;
135
136 if (!is_valid_bugaddr(bugaddr))
137 return BUG_TRAP_TYPE_NONE;
138
139 bug = find_bug(bugaddr);
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 pr_warn("------------[ cut here ]------------\n");
160
161 if (file)
162 pr_warn("WARNING: at %s:%u\n", file, line);
163 else
164 pr_warn("WARNING: at %p [verbose debug info unavailable]\n",
165 (void *)bugaddr);
166
167 print_modules();
168 show_regs(regs);
169 print_oops_end_marker();
170 /* Just a warning, don't kill lockdep. */
171 add_taint(BUG_GET_TAINT(bug), LOCKDEP_STILL_OK);
172 return BUG_TRAP_TYPE_WARN;
173 }
174
175 printk(KERN_DEFAULT "------------[ cut here ]------------\n");
176
177 if (file)
178 pr_crit("kernel BUG at %s:%u!\n", file, line);
179 else
180 pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n",
181 (void *)bugaddr);
182
183 return BUG_TRAP_TYPE_BUG;
184 }