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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.
Jan Beulichb93a5312008-12-16 11:40:27 +00008 CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
9 the containing struct bug_entry for bug_addr and file.
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080010 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>
Paul Mundtda9eac82008-07-04 09:59:36 -070042#include <linux/kernel.h>
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080043#include <linux/bug.h>
Heiko Carstens608e2612007-07-15 23:41:39 -070044#include <linux/sched.h>
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080045
46extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
47
Jan Beulichb93a5312008-12-16 11:40:27 +000048static 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
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080057#ifdef CONFIG_MODULES
58static LIST_HEAD(module_bug_list);
59
60static 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)
Jan Beulichb93a5312008-12-16 11:40:27 +000069 if (bugaddr == bug_addr(bug))
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080070 return bug;
71 }
72 return NULL;
73}
74
75int 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
104void module_bug_cleanup(struct module *mod)
105{
106 list_del(&mod->bug_list);
107}
108
109#else
110
111static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
112{
113 return NULL;
114}
115#endif
116
117const 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)
Jan Beulichb93a5312008-12-16 11:40:27 +0000122 if (bugaddr == bug_addr(bug))
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800123 return bug;
124
125 return module_find_bug(bugaddr);
126}
127
Heiko Carstens608e2612007-07-15 23:41:39 -0700128enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800129{
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
Jan Beulichb93a5312008-12-16 11:40:27 +0000147#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800148 file = bug->file;
Jan Beulichb93a5312008-12-16 11:40:27 +0000149#else
150 file = (const char *)bug + bug->file_disp;
151#endif
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800152 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
Heiko Carstens608e2612007-07-15 23:41:39 -0700167 show_regs(regs);
Paul Mundtda9eac82008-07-04 09:59:36 -0700168 add_taint(TAINT_WARN);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800169 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}