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
42extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
43
44#ifdef CONFIG_MODULES
45static LIST_HEAD(module_bug_list);
46
47static 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
62int 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
91void module_bug_cleanup(struct module *mod)
92{
93	list_del(&mod->bug_list);
94}
95
96#else
97
98static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
99{
100	return NULL;
101}
102#endif
103
104const 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
115enum 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