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Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -08002/*
3 Generic support for BUG()
4
5 This respects the following config options:
6
7 CONFIG_BUG - emit BUG traps. Nothing happens without this.
8 CONFIG_GENERIC_BUG - enable this code.
Jan Beulichb93a5312008-12-16 11:40:27 +00009 CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
10 the containing struct bug_entry for bug_addr and file.
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080011 CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
12
13 CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
14 (though they're generally always on).
15
16 CONFIG_GENERIC_BUG is set by each architecture using this code.
17
18 To use this, your architecture must:
19
20 1. Set up the config options:
21 - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
22
23 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
24 - Define HAVE_ARCH_BUG
25 - Implement BUG() to generate a faulting instruction
26 - NOTE: struct bug_entry does not have "file" or "line" entries
27 when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
28 the values accordingly.
29
30 3. Implement the trap
31 - In the illegal instruction trap handler (typically), verify
32 that the fault was in kernel mode, and call report_bug()
33 - report_bug() will return whether it was a false alarm, a warning,
34 or an actual bug.
35 - You must implement the is_valid_bugaddr(bugaddr) callback which
36 returns true if the eip is a real kernel address, and it points
37 to the expected BUG trap instruction.
38
39 Jeremy Fitzhardinge <jeremy@goop.org> 2006
40 */
Fabian Frederickc56ba702014-06-04 16:11:59 -070041
42#define pr_fmt(fmt) fmt
43
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080044#include <linux/list.h>
45#include <linux/module.h>
Paul Mundtda9eac82008-07-04 09:59:36 -070046#include <linux/kernel.h>
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080047#include <linux/bug.h>
Heiko Carstens608e2612007-07-15 23:41:39 -070048#include <linux/sched.h>
Ingo Molnarb2d09102017-02-04 01:27:20 +010049#include <linux/rculist.h>
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080050
Peter Zijlstra19d43622017-02-25 08:56:53 +010051extern struct bug_entry __start___bug_table[], __stop___bug_table[];
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080052
Jan Beulichb93a5312008-12-16 11:40:27 +000053static inline unsigned long bug_addr(const struct bug_entry *bug)
54{
55#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
56 return bug->bug_addr;
57#else
58 return (unsigned long)bug + bug->bug_addr_disp;
59#endif
60}
61
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080062#ifdef CONFIG_MODULES
Rusty Russell1fb93412013-01-12 13:27:34 +103063/* Updates are protected by module mutex */
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080064static LIST_HEAD(module_bug_list);
65
Peter Zijlstra19d43622017-02-25 08:56:53 +010066static struct bug_entry *module_find_bug(unsigned long bugaddr)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080067{
68 struct module *mod;
Peter Zijlstra19d43622017-02-25 08:56:53 +010069 struct bug_entry *bug = NULL;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080070
Peter Zijlstra0be964b2015-05-27 11:09:35 +093071 rcu_read_lock_sched();
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +103072 list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080073 unsigned i;
74
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +103075 bug = mod->bug_table;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080076 for (i = 0; i < mod->num_bugs; ++i, ++bug)
Jan Beulichb93a5312008-12-16 11:40:27 +000077 if (bugaddr == bug_addr(bug))
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +103078 goto out;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080079 }
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +103080 bug = NULL;
81out:
Peter Zijlstra0be964b2015-05-27 11:09:35 +093082 rcu_read_unlock_sched();
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +103083
84 return bug;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080085}
86
Linus Torvalds53363772010-10-05 11:29:27 -070087void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
88 struct module *mod)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080089{
90 char *secstrings;
91 unsigned int i;
92
Peter Zijlstra0be964b2015-05-27 11:09:35 +093093 lockdep_assert_held(&module_mutex);
94
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -080095 mod->bug_table = NULL;
96 mod->num_bugs = 0;
97
98 /* Find the __bug_table section, if present */
99 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
100 for (i = 1; i < hdr->e_shnum; i++) {
101 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
102 continue;
103 mod->bug_table = (void *) sechdrs[i].sh_addr;
104 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
105 break;
106 }
107
108 /*
109 * Strictly speaking this should have a spinlock to protect against
110 * traversals, but since we only traverse on BUG()s, a spinlock
111 * could potentially lead to deadlock and thus be counter-productive.
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +1030112 * Thus, this uses RCU to safely manipulate the bug list, since BUG
113 * must run in non-interruptive state.
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800114 */
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +1030115 list_add_rcu(&mod->bug_list, &module_bug_list);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800116}
117
118void module_bug_cleanup(struct module *mod)
119{
Peter Zijlstra0be964b2015-05-27 11:09:35 +0930120 lockdep_assert_held(&module_mutex);
Masami Hiramatsu0286b5e2014-11-10 09:28:29 +1030121 list_del_rcu(&mod->bug_list);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800122}
123
124#else
125
Peter Zijlstra19d43622017-02-25 08:56:53 +0100126static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800127{
128 return NULL;
129}
130#endif
131
Peter Zijlstra19d43622017-02-25 08:56:53 +0100132struct bug_entry *find_bug(unsigned long bugaddr)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800133{
Peter Zijlstra19d43622017-02-25 08:56:53 +0100134 struct bug_entry *bug;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800135
136 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
Jan Beulichb93a5312008-12-16 11:40:27 +0000137 if (bugaddr == bug_addr(bug))
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800138 return bug;
139
140 return module_find_bug(bugaddr);
141}
142
Heiko Carstens608e2612007-07-15 23:41:39 -0700143enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800144{
Peter Zijlstra19d43622017-02-25 08:56:53 +0100145 struct bug_entry *bug;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800146 const char *file;
Peter Zijlstra19d43622017-02-25 08:56:53 +0100147 unsigned line, warning, once, done;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800148
149 if (!is_valid_bugaddr(bugaddr))
150 return BUG_TRAP_TYPE_NONE;
151
152 bug = find_bug(bugaddr);
Kees Cook1b4cfe32018-03-09 15:51:02 -0800153 if (!bug)
154 return BUG_TRAP_TYPE_NONE;
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800155
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800156 file = NULL;
157 line = 0;
158 warning = 0;
159
160 if (bug) {
161#ifdef CONFIG_DEBUG_BUGVERBOSE
Jan Beulichb93a5312008-12-16 11:40:27 +0000162#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800163 file = bug->file;
Jan Beulichb93a5312008-12-16 11:40:27 +0000164#else
165 file = (const char *)bug + bug->file_disp;
166#endif
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800167 line = bug->line;
168#endif
169 warning = (bug->flags & BUGFLAG_WARNING) != 0;
Peter Zijlstra19d43622017-02-25 08:56:53 +0100170 once = (bug->flags & BUGFLAG_ONCE) != 0;
171 done = (bug->flags & BUGFLAG_DONE) != 0;
172
173 if (warning && once) {
174 if (done)
175 return BUG_TRAP_TYPE_WARN;
176
177 /*
178 * Since this is the only store, concurrency is not an issue.
179 */
180 bug->flags |= BUGFLAG_DONE;
181 }
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800182 }
183
184 if (warning) {
185 /* this is a WARN_ON rather than BUG/BUG_ON */
Josh Poimboeuf2553b672016-03-17 14:23:04 -0700186 __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
187 NULL);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800188 return BUG_TRAP_TYPE_WARN;
189 }
190
Kees Cook2a8358d2017-11-17 15:27:21 -0800191 printk(KERN_DEFAULT CUT_HERE);
Anton Blancharde2e7e092010-08-10 18:03:29 -0700192
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800193 if (file)
Fabian Frederickc56ba702014-06-04 16:11:59 -0700194 pr_crit("kernel BUG at %s:%u!\n", file, line);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800195 else
Kees Cook0862ca42018-03-09 15:50:59 -0800196 pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n",
Fabian Frederickc56ba702014-06-04 16:11:59 -0700197 (void *)bugaddr);
Jeremy Fitzhardinge7664c5a2006-12-08 02:36:19 -0800198
199 return BUG_TRAP_TYPE_BUG;
200}
Andi Kleenaaf5dcf2017-11-17 15:27:06 -0800201
202static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
203{
204 struct bug_entry *bug;
205
206 for (bug = start; bug < end; bug++)
207 bug->flags &= ~BUGFLAG_DONE;
208}
209
210void generic_bug_clear_once(void)
211{
212#ifdef CONFIG_MODULES
213 struct module *mod;
214
215 rcu_read_lock_sched();
216 list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
217 clear_once_table(mod->bug_table,
218 mod->bug_table + mod->num_bugs);
219 rcu_read_unlock_sched();
220#endif
221
222 clear_once_table(__start___bug_table, __stop___bug_table);
223}