projects/linux·blob v5.16-rc4 · refs

234 lines · 5.9 KiB

1// SPDX-License-Identifier: GPL-2.0
2/*
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.
9 CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
10 the containing struct bug_entry for bug_addr and file.
11 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 <[email protected]> 2006
40 */
41
42#define pr_fmt(fmt) fmt
43
44#include <linux/list.h>
45#include <linux/module.h>
46#include <linux/kernel.h>
47#include <linux/bug.h>
48#include <linux/sched.h>
49#include <linux/rculist.h>
50#include <linux/ftrace.h>
51
52extern struct bug_entry __start___bug_table[], __stop___bug_table[];
53
54static inline unsigned long bug_addr(const struct bug_entry *bug)
55{
56#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
57 return bug->bug_addr;
58#else
59 return (unsigned long)bug + bug->bug_addr_disp;
60#endif
61}
62
63#ifdef CONFIG_MODULES
64/* Updates are protected by module mutex */
65static LIST_HEAD(module_bug_list);
66
67static struct bug_entry *module_find_bug(unsigned long bugaddr)
68{
69 struct module *mod;
70 struct bug_entry *bug = NULL;
71
72 rcu_read_lock_sched();
73 list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
74 unsigned i;
75
76 bug = mod->bug_table;
77 for (i = 0; i < mod->num_bugs; ++i, ++bug)
78 if (bugaddr == bug_addr(bug))
79 goto out;
80 }
81 bug = NULL;
82out:
83 rcu_read_unlock_sched();
84
85 return bug;
86}
87
88void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
89 struct module *mod)
90{
91 char *secstrings;
92 unsigned int i;
93
94 mod->bug_table = NULL;
95 mod->num_bugs = 0;
96
97 /* Find the __bug_table section, if present */
98 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
99 for (i = 1; i < hdr->e_shnum; i++) {
100 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
101 continue;
102 mod->bug_table = (void *) sechdrs[i].sh_addr;
103 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
104 break;
105 }
106
107 /*
108 * Strictly speaking this should have a spinlock to protect against
109 * traversals, but since we only traverse on BUG()s, a spinlock
110 * could potentially lead to deadlock and thus be counter-productive.
111 * Thus, this uses RCU to safely manipulate the bug list, since BUG
112 * must run in non-interruptive state.
113 */
114 list_add_rcu(&mod->bug_list, &module_bug_list);
115}
116
117void module_bug_cleanup(struct module *mod)
118{
119 list_del_rcu(&mod->bug_list);
120}
121
122#else
123
124static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
125{
126 return NULL;
127}
128#endif
129
130void bug_get_file_line(struct bug_entry *bug, const char **file,
131 unsigned int *line)
132{
133#ifdef CONFIG_DEBUG_BUGVERBOSE
134#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
135 *file = bug->file;
136#else
137 *file = (const char *)bug + bug->file_disp;
138#endif
139 *line = bug->line;
140#else
141 *file = NULL;
142 *line = 0;
143#endif
144}
145
146struct bug_entry *find_bug(unsigned long bugaddr)
147{
148 struct bug_entry *bug;
149
150 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
151 if (bugaddr == bug_addr(bug))
152 return bug;
153
154 return module_find_bug(bugaddr);
155}
156
157enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
158{
159 struct bug_entry *bug;
160 const char *file;
161 unsigned line, warning, once, done;
162
163 if (!is_valid_bugaddr(bugaddr))
164 return BUG_TRAP_TYPE_NONE;
165
166 bug = find_bug(bugaddr);
167 if (!bug)
168 return BUG_TRAP_TYPE_NONE;
169
170 disable_trace_on_warning();
171
172 bug_get_file_line(bug, &file, &line);
173
174 warning = (bug->flags & BUGFLAG_WARNING) != 0;
175 once = (bug->flags & BUGFLAG_ONCE) != 0;
176 done = (bug->flags & BUGFLAG_DONE) != 0;
177
178 if (warning && once) {
179 if (done)
180 return BUG_TRAP_TYPE_WARN;
181
182 /*
183 * Since this is the only store, concurrency is not an issue.
184 */
185 bug->flags |= BUGFLAG_DONE;
186 }
187
188 /*
189 * BUG() and WARN_ON() families don't print a custom debug message
190 * before triggering the exception handler, so we must add the
191 * "cut here" line now. WARN() issues its own "cut here" before the
192 * extra debugging message it writes before triggering the handler.
193 */
194 if ((bug->flags & BUGFLAG_NO_CUT_HERE) == 0)
195 printk(KERN_DEFAULT CUT_HERE);
196
197 if (warning) {
198 /* this is a WARN_ON rather than BUG/BUG_ON */
199 __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
200 NULL);
201 return BUG_TRAP_TYPE_WARN;
202 }
203
204 if (file)
205 pr_crit("kernel BUG at %s:%u!\n", file, line);
206 else
207 pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n",
208 (void *)bugaddr);
209
210 return BUG_TRAP_TYPE_BUG;
211}
212
213static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
214{
215 struct bug_entry *bug;
216
217 for (bug = start; bug < end; bug++)
218 bug->flags &= ~BUGFLAG_DONE;
219}
220
221void generic_bug_clear_once(void)
222{
223#ifdef CONFIG_MODULES
224 struct module *mod;
225
226 rcu_read_lock_sched();
227 list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
228 clear_once_table(mod->bug_table,
229 mod->bug_table + mod->num_bugs);
230 rcu_read_unlock_sched();
231#endif
232
233 clear_once_table(__start___bug_table, __stop___bug_table);
234}