xref: /openbmc/linux/lib/bug.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
9 
10   CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
11   (though they're generally always on).
12 
13   CONFIG_GENERIC_BUG is set by each architecture using this code.
14 
15   To use this, your architecture must:
16 
17   1. Set up the config options:
18      - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
19 
20   2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
21      - Define HAVE_ARCH_BUG
22      - Implement BUG() to generate a faulting instruction
23      - NOTE: struct bug_entry does not have "file" or "line" entries
24        when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
25        the values accordingly.
26 
27   3. Implement the trap
28      - In the illegal instruction trap handler (typically), verify
29        that the fault was in kernel mode, and call report_bug()
30      - report_bug() will return whether it was a false alarm, a warning,
31        or an actual bug.
32      - You must implement the is_valid_bugaddr(bugaddr) callback which
33        returns true if the eip is a real kernel address, and it points
34        to the expected BUG trap instruction.
35 
36     Jeremy Fitzhardinge <jeremy@goop.org> 2006
37  */
38 #include <linux/list.h>
39 #include <linux/module.h>
40 #include <linux/bug.h>
41 
42 extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
43 
44 #ifdef CONFIG_MODULES
45 static LIST_HEAD(module_bug_list);
46 
47 static const struct bug_entry *module_find_bug(unsigned long bugaddr)
48 {
49 	struct module *mod;
50 
51 	list_for_each_entry(mod, &module_bug_list, bug_list) {
52 		const struct bug_entry *bug = mod->bug_table;
53 		unsigned i;
54 
55 		for (i = 0; i < mod->num_bugs; ++i, ++bug)
56 			if (bugaddr == bug->bug_addr)
57 				return bug;
58 	}
59 	return NULL;
60 }
61 
62 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
63 			struct module *mod)
64 {
65 	char *secstrings;
66 	unsigned int i;
67 
68 	mod->bug_table = NULL;
69 	mod->num_bugs = 0;
70 
71 	/* Find the __bug_table section, if present */
72 	secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
73 	for (i = 1; i < hdr->e_shnum; i++) {
74 		if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
75 			continue;
76 		mod->bug_table = (void *) sechdrs[i].sh_addr;
77 		mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
78 		break;
79 	}
80 
81 	/*
82 	 * Strictly speaking this should have a spinlock to protect against
83 	 * traversals, but since we only traverse on BUG()s, a spinlock
84 	 * could potentially lead to deadlock and thus be counter-productive.
85 	 */
86 	list_add(&mod->bug_list, &module_bug_list);
87 
88 	return 0;
89 }
90 
91 void module_bug_cleanup(struct module *mod)
92 {
93 	list_del(&mod->bug_list);
94 }
95 
96 #else
97 
98 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
99 {
100 	return NULL;
101 }
102 #endif
103 
104 const struct bug_entry *find_bug(unsigned long bugaddr)
105 {
106 	const struct bug_entry *bug;
107 
108 	for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
109 		if (bugaddr == bug->bug_addr)
110 			return bug;
111 
112 	return module_find_bug(bugaddr);
113 }
114 
115 enum bug_trap_type report_bug(unsigned long bugaddr)
116 {
117 	const struct bug_entry *bug;
118 	const char *file;
119 	unsigned line, warning;
120 
121 	if (!is_valid_bugaddr(bugaddr))
122 		return BUG_TRAP_TYPE_NONE;
123 
124 	bug = find_bug(bugaddr);
125 
126 	printk(KERN_EMERG "------------[ cut here ]------------\n");
127 
128 	file = NULL;
129 	line = 0;
130 	warning = 0;
131 
132 	if (bug) {
133 #ifdef CONFIG_DEBUG_BUGVERBOSE
134 		file = bug->file;
135 		line = bug->line;
136 #endif
137 		warning = (bug->flags & BUGFLAG_WARNING) != 0;
138 	}
139 
140 	if (warning) {
141 		/* this is a WARN_ON rather than BUG/BUG_ON */
142 		if (file)
143 			printk(KERN_ERR "Badness at %s:%u\n",
144 			       file, line);
145 		else
146 			printk(KERN_ERR "Badness at %p "
147 			       "[verbose debug info unavailable]\n",
148 			       (void *)bugaddr);
149 
150 		dump_stack();
151 		return BUG_TRAP_TYPE_WARN;
152 	}
153 
154 	if (file)
155 		printk(KERN_CRIT "kernel BUG at %s:%u!\n",
156 		       file, line);
157 	else
158 		printk(KERN_CRIT "Kernel BUG at %p "
159 		       "[verbose debug info unavailable]\n",
160 		       (void *)bugaddr);
161 
162 	return BUG_TRAP_TYPE_BUG;
163 }
164