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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 | } |
186 |
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