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v5.4
  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 <jeremy@goop.org> 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
 51extern struct bug_entry __start___bug_table[], __stop___bug_table[];
 52
 53static 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
 62#ifdef CONFIG_MODULES
 63/* Updates are protected by module mutex */
 64static LIST_HEAD(module_bug_list);
 65
 66static struct bug_entry *module_find_bug(unsigned long bugaddr)
 67{
 68	struct module *mod;
 69	struct bug_entry *bug = NULL;
 70
 71	rcu_read_lock_sched();
 72	list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
 73		unsigned i;
 74
 75		bug = mod->bug_table;
 76		for (i = 0; i < mod->num_bugs; ++i, ++bug)
 77			if (bugaddr == bug_addr(bug))
 78				goto out;
 79	}
 80	bug = NULL;
 81out:
 82	rcu_read_unlock_sched();
 83
 84	return bug;
 85}
 86
 87void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 88			 struct module *mod)
 89{
 90	char *secstrings;
 91	unsigned int i;
 92
 93	lockdep_assert_held(&module_mutex);
 94
 95	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.
112	 * Thus, this uses RCU to safely manipulate the bug list, since BUG
113	 * must run in non-interruptive state.
114	 */
115	list_add_rcu(&mod->bug_list, &module_bug_list);
116}
117
118void module_bug_cleanup(struct module *mod)
119{
120	lockdep_assert_held(&module_mutex);
121	list_del_rcu(&mod->bug_list);
122}
123
124#else
125
126static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
127{
128	return NULL;
129}
130#endif
131
132struct bug_entry *find_bug(unsigned long bugaddr)
133{
134	struct bug_entry *bug;
135
136	for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
137		if (bugaddr == bug_addr(bug))
138			return bug;
139
140	return module_find_bug(bugaddr);
141}
142
143enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
144{
145	struct bug_entry *bug;
146	const char *file;
147	unsigned line, warning, once, done;
148
149	if (!is_valid_bugaddr(bugaddr))
150		return BUG_TRAP_TYPE_NONE;
151
152	bug = find_bug(bugaddr);
153	if (!bug)
154		return BUG_TRAP_TYPE_NONE;
155
156	file = NULL;
157	line = 0;
158	warning = 0;
159
160	if (bug) {
161#ifdef CONFIG_DEBUG_BUGVERBOSE
162#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
163		file = bug->file;
164#else
165		file = (const char *)bug + bug->file_disp;
166#endif
167		line = bug->line;
168#endif
169		warning = (bug->flags & BUGFLAG_WARNING) != 0;
170		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		}
182	}
183
184	/*
185	 * BUG() and WARN_ON() families don't print a custom debug message
186	 * before triggering the exception handler, so we must add the
187	 * "cut here" line now. WARN() issues its own "cut here" before the
188	 * extra debugging message it writes before triggering the handler.
189	 */
190	if ((bug->flags & BUGFLAG_NO_CUT_HERE) == 0)
191		printk(KERN_DEFAULT CUT_HERE);
192
193	if (warning) {
194		/* this is a WARN_ON rather than BUG/BUG_ON */
195		__warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
196		       NULL);
 
 
 
 
 
 
 
 
 
 
 
 
197		return BUG_TRAP_TYPE_WARN;
198	}
199
 
 
200	if (file)
201		pr_crit("kernel BUG at %s:%u!\n", file, line);
 
202	else
203		pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n",
204			(void *)bugaddr);
 
205
206	return BUG_TRAP_TYPE_BUG;
207}
208
209static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
210{
211	struct bug_entry *bug;
212
213	for (bug = start; bug < end; bug++)
214		bug->flags &= ~BUGFLAG_DONE;
215}
216
217void generic_bug_clear_once(void)
218{
219#ifdef CONFIG_MODULES
220	struct module *mod;
221
222	rcu_read_lock_sched();
223	list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
224		clear_once_table(mod->bug_table,
225				 mod->bug_table + mod->num_bugs);
226	rcu_read_unlock_sched();
227#endif
228
229	clear_once_table(__start___bug_table, __stop___bug_table);
230}
v3.1
 
  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
 
 58static LIST_HEAD(module_bug_list);
 59
 60static const struct bug_entry *module_find_bug(unsigned long bugaddr)
 61{
 62	struct module *mod;
 
 63
 64	list_for_each_entry(mod, &module_bug_list, bug_list) {
 65		const struct bug_entry *bug = mod->bug_table;
 66		unsigned i;
 67
 
 68		for (i = 0; i < mod->num_bugs; ++i, ++bug)
 69			if (bugaddr == bug_addr(bug))
 70				return bug;
 71	}
 72	return NULL;
 
 
 
 
 73}
 74
 75void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 76			 struct module *mod)
 77{
 78	char *secstrings;
 79	unsigned int i;
 80
 
 
 81	mod->bug_table = NULL;
 82	mod->num_bugs = 0;
 83
 84	/* Find the __bug_table section, if present */
 85	secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 86	for (i = 1; i < hdr->e_shnum; i++) {
 87		if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
 88			continue;
 89		mod->bug_table = (void *) sechdrs[i].sh_addr;
 90		mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
 91		break;
 92	}
 93
 94	/*
 95	 * Strictly speaking this should have a spinlock to protect against
 96	 * traversals, but since we only traverse on BUG()s, a spinlock
 97	 * could potentially lead to deadlock and thus be counter-productive.
 
 
 98	 */
 99	list_add(&mod->bug_list, &module_bug_list);
100}
101
102void module_bug_cleanup(struct module *mod)
103{
104	list_del(&mod->bug_list);
 
105}
106
107#else
108
109static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
110{
111	return NULL;
112}
113#endif
114
115const struct bug_entry *find_bug(unsigned long bugaddr)
116{
117	const struct bug_entry *bug;
118
119	for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
120		if (bugaddr == bug_addr(bug))
121			return bug;
122
123	return module_find_bug(bugaddr);
124}
125
126enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
127{
128	const struct bug_entry *bug;
129	const char *file;
130	unsigned line, warning;
131
132	if (!is_valid_bugaddr(bugaddr))
133		return BUG_TRAP_TYPE_NONE;
134
135	bug = find_bug(bugaddr);
 
 
136
137	file = NULL;
138	line = 0;
139	warning = 0;
140
141	if (bug) {
142#ifdef CONFIG_DEBUG_BUGVERBOSE
143#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
144		file = bug->file;
145#else
146		file = (const char *)bug + bug->file_disp;
147#endif
148		line = bug->line;
149#endif
150		warning = (bug->flags & BUGFLAG_WARNING) != 0;
 
 
 
 
 
 
 
 
 
 
 
 
151	}
152
 
 
 
 
 
 
 
 
 
153	if (warning) {
154		/* this is a WARN_ON rather than BUG/BUG_ON */
155		printk(KERN_WARNING "------------[ cut here ]------------\n");
156
157		if (file)
158			printk(KERN_WARNING "WARNING: at %s:%u\n",
159			       file, line);
160		else
161			printk(KERN_WARNING "WARNING: at %p "
162			       "[verbose debug info unavailable]\n",
163			       (void *)bugaddr);
164
165		print_modules();
166		show_regs(regs);
167		print_oops_end_marker();
168		add_taint(BUG_GET_TAINT(bug));
169		return BUG_TRAP_TYPE_WARN;
170	}
171
172	printk(KERN_EMERG "------------[ cut here ]------------\n");
173
174	if (file)
175		printk(KERN_CRIT "kernel BUG at %s:%u!\n",
176		       file, line);
177	else
178		printk(KERN_CRIT "Kernel BUG at %p "
179		       "[verbose debug info unavailable]\n",
180		       (void *)bugaddr);
181
182	return BUG_TRAP_TYPE_BUG;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
183}