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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
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
49extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
50
51static 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 */
62static LIST_HEAD(module_bug_list);
63
64static 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;
79out:
80 rcu_read_unlock_sched();
81
82 return bug;
83}
84
85void 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
116void 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
124static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
125{
126 return NULL;
127}
128#endif
129
130const 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
141enum 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 %p [verbose debug info unavailable]\n",
181 (void *)bugaddr);
182
183 return BUG_TRAP_TYPE_BUG;
184}
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
46extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
47
48static 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 */
59static LIST_HEAD(module_bug_list);
60
61static 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
76void 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
103void module_bug_cleanup(struct module *mod)
104{
105 list_del(&mod->bug_list);
106}
107
108#else
109
110static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
111{
112 return NULL;
113}
114#endif
115
116const 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
127enum 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}