blob: dc7aa6bfad15be6a8ba41bb80afe3e30a771ba96
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 | const struct bug_entry *bug = NULL; |
68 | |
69 | rcu_read_lock_sched(); |
70 | list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { |
71 | unsigned i; |
72 | |
73 | bug = mod->bug_table; |
74 | for (i = 0; i < mod->num_bugs; ++i, ++bug) |
75 | if (bugaddr == bug_addr(bug)) |
76 | goto out; |
77 | } |
78 | bug = NULL; |
79 | out: |
80 | rcu_read_unlock_sched(); |
81 | |
82 | return bug; |
83 | } |
84 | |
85 | void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, |
86 | struct module *mod) |
87 | { |
88 | char *secstrings; |
89 | unsigned int i; |
90 | |
91 | lockdep_assert_held(&module_mutex); |
92 | |
93 | mod->bug_table = NULL; |
94 | mod->num_bugs = 0; |
95 | |
96 | /* Find the __bug_table section, if present */ |
97 | secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; |
98 | for (i = 1; i < hdr->e_shnum; i++) { |
99 | if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) |
100 | continue; |
101 | mod->bug_table = (void *) sechdrs[i].sh_addr; |
102 | mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); |
103 | break; |
104 | } |
105 | |
106 | /* |
107 | * Strictly speaking this should have a spinlock to protect against |
108 | * traversals, but since we only traverse on BUG()s, a spinlock |
109 | * could potentially lead to deadlock and thus be counter-productive. |
110 | * Thus, this uses RCU to safely manipulate the bug list, since BUG |
111 | * must run in non-interruptive state. |
112 | */ |
113 | list_add_rcu(&mod->bug_list, &module_bug_list); |
114 | } |
115 | |
116 | void module_bug_cleanup(struct module *mod) |
117 | { |
118 | lockdep_assert_held(&module_mutex); |
119 | list_del_rcu(&mod->bug_list); |
120 | } |
121 | |
122 | #else |
123 | |
124 | static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) |
125 | { |
126 | return NULL; |
127 | } |
128 | #endif |
129 | |
130 | const struct bug_entry *find_bug(unsigned long bugaddr) |
131 | { |
132 | const struct bug_entry *bug; |
133 | |
134 | for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) |
135 | if (bugaddr == bug_addr(bug)) |
136 | return bug; |
137 | |
138 | return module_find_bug(bugaddr); |
139 | } |
140 | |
141 | enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) |
142 | { |
143 | const struct bug_entry *bug; |
144 | const char *file; |
145 | unsigned line, warning; |
146 | |
147 | if (!is_valid_bugaddr(bugaddr)) |
148 | return BUG_TRAP_TYPE_NONE; |
149 | |
150 | bug = find_bug(bugaddr); |
151 | |
152 | file = NULL; |
153 | line = 0; |
154 | warning = 0; |
155 | |
156 | if (bug) { |
157 | #ifdef CONFIG_DEBUG_BUGVERBOSE |
158 | #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS |
159 | file = bug->file; |
160 | #else |
161 | file = (const char *)bug + bug->file_disp; |
162 | #endif |
163 | line = bug->line; |
164 | #endif |
165 | warning = (bug->flags & BUGFLAG_WARNING) != 0; |
166 | } |
167 | |
168 | if (warning) { |
169 | /* this is a WARN_ON rather than BUG/BUG_ON */ |
170 | __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs, |
171 | NULL); |
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 %pB [verbose debug info unavailable]\n", |
181 | (void *)bugaddr); |
182 | |
183 | return BUG_TRAP_TYPE_BUG; |
184 | } |
185 |