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Commit | Line | Data |
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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 | #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 | /* Updates are protected by module mutex */ | |
59 | static LIST_HEAD(module_bug_list); | |
60 | ||
61 | static const struct bug_entry *module_find_bug(unsigned long bugaddr) | |
62 | { | |
63 | struct module *mod; | |
64 | ||
65 | list_for_each_entry(mod, &module_bug_list, bug_list) { | |
66 | const struct bug_entry *bug = mod->bug_table; | |
67 | unsigned i; | |
68 | ||
69 | for (i = 0; i < mod->num_bugs; ++i, ++bug) | |
70 | if (bugaddr == bug_addr(bug)) | |
71 | return bug; | |
72 | } | |
73 | return NULL; | |
74 | } | |
75 | ||
76 | void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, | |
77 | struct module *mod) | |
78 | { | |
79 | char *secstrings; | |
80 | unsigned int i; | |
81 | ||
82 | mod->bug_table = NULL; | |
83 | mod->num_bugs = 0; | |
84 | ||
85 | /* Find the __bug_table section, if present */ | |
86 | secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; | |
87 | for (i = 1; i < hdr->e_shnum; i++) { | |
88 | if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) | |
89 | continue; | |
90 | mod->bug_table = (void *) sechdrs[i].sh_addr; | |
91 | mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); | |
92 | break; | |
93 | } | |
94 | ||
95 | /* | |
96 | * Strictly speaking this should have a spinlock to protect against | |
97 | * traversals, but since we only traverse on BUG()s, a spinlock | |
98 | * could potentially lead to deadlock and thus be counter-productive. | |
99 | */ | |
100 | list_add(&mod->bug_list, &module_bug_list); | |
101 | } | |
102 | ||
103 | void module_bug_cleanup(struct module *mod) | |
104 | { | |
105 | list_del(&mod->bug_list); | |
106 | } | |
107 | ||
108 | #else | |
109 | ||
110 | static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) | |
111 | { | |
112 | return NULL; | |
113 | } | |
114 | #endif | |
115 | ||
116 | const struct bug_entry *find_bug(unsigned long bugaddr) | |
117 | { | |
118 | const struct bug_entry *bug; | |
119 | ||
120 | for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) | |
121 | if (bugaddr == bug_addr(bug)) | |
122 | return bug; | |
123 | ||
124 | return module_find_bug(bugaddr); | |
125 | } | |
126 | ||
127 | enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) | |
128 | { | |
129 | const struct bug_entry *bug; | |
130 | const char *file; | |
131 | unsigned line, warning; | |
132 | ||
133 | if (!is_valid_bugaddr(bugaddr)) | |
134 | return BUG_TRAP_TYPE_NONE; | |
135 | ||
136 | bug = find_bug(bugaddr); | |
137 | ||
138 | file = NULL; | |
139 | line = 0; | |
140 | warning = 0; | |
141 | ||
142 | if (bug) { | |
143 | #ifdef CONFIG_DEBUG_BUGVERBOSE | |
144 | #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS | |
145 | file = bug->file; | |
146 | #else | |
147 | file = (const char *)bug + bug->file_disp; | |
148 | #endif | |
149 | line = bug->line; | |
150 | #endif | |
151 | warning = (bug->flags & BUGFLAG_WARNING) != 0; | |
152 | } | |
153 | ||
154 | if (warning) { | |
155 | /* this is a WARN_ON rather than BUG/BUG_ON */ | |
156 | printk(KERN_WARNING "------------[ cut here ]------------\n"); | |
157 | ||
158 | if (file) | |
159 | printk(KERN_WARNING "WARNING: at %s:%u\n", | |
160 | file, line); | |
161 | else | |
162 | printk(KERN_WARNING "WARNING: at %p " | |
163 | "[verbose debug info unavailable]\n", | |
164 | (void *)bugaddr); | |
165 | ||
166 | print_modules(); | |
167 | show_regs(regs); | |
168 | print_oops_end_marker(); | |
169 | /* Just a warning, don't kill lockdep. */ | |
170 | add_taint(BUG_GET_TAINT(bug), LOCKDEP_STILL_OK); | |
171 | return BUG_TRAP_TYPE_WARN; | |
172 | } | |
173 | ||
174 | printk(KERN_DEFAULT "------------[ cut here ]------------\n"); | |
175 | ||
176 | if (file) | |
177 | printk(KERN_CRIT "kernel BUG at %s:%u!\n", | |
178 | file, line); | |
179 | else | |
180 | printk(KERN_CRIT "Kernel BUG at %p " | |
181 | "[verbose debug info unavailable]\n", | |
182 | (void *)bugaddr); | |
183 | ||
184 | return BUG_TRAP_TYPE_BUG; | |
185 | } |