2 Generic support for BUG()
4 This respects the following config options:
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
12 CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
13 (though they're generally always on).
15 CONFIG_GENERIC_BUG is set by each architecture using this code.
17 To use this, your architecture must:
19 1. Set up the config options:
20 - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
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.
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,
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.
38 Jeremy Fitzhardinge <jeremy@goop.org> 2006
41 #define pr_fmt(fmt) fmt
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 #include <linux/rculist.h>
50 extern struct bug_entry __start___bug_table[], __stop___bug_table[];
52 static inline unsigned long bug_addr(const struct bug_entry *bug)
54 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
57 return (unsigned long)bug + bug->bug_addr_disp;
62 /* Updates are protected by module mutex */
63 static LIST_HEAD(module_bug_list);
65 static struct bug_entry *module_find_bug(unsigned long bugaddr)
68 struct bug_entry *bug = NULL;
70 rcu_read_lock_sched();
71 list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
75 for (i = 0; i < mod->num_bugs; ++i, ++bug)
76 if (bugaddr == bug_addr(bug))
81 rcu_read_unlock_sched();
86 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
92 lockdep_assert_held(&module_mutex);
94 mod->bug_table = NULL;
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"))
102 mod->bug_table = (void *) sechdrs[i].sh_addr;
103 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
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.
114 list_add_rcu(&mod->bug_list, &module_bug_list);
117 void module_bug_cleanup(struct module *mod)
119 lockdep_assert_held(&module_mutex);
120 list_del_rcu(&mod->bug_list);
125 static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
131 struct bug_entry *find_bug(unsigned long bugaddr)
133 struct bug_entry *bug;
135 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
136 if (bugaddr == bug_addr(bug))
139 return module_find_bug(bugaddr);
142 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
144 struct bug_entry *bug;
146 unsigned line, warning, once, done;
148 if (!is_valid_bugaddr(bugaddr))
149 return BUG_TRAP_TYPE_NONE;
151 bug = find_bug(bugaddr);
158 #ifdef CONFIG_DEBUG_BUGVERBOSE
159 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
162 file = (const char *)bug + bug->file_disp;
166 warning = (bug->flags & BUGFLAG_WARNING) != 0;
167 once = (bug->flags & BUGFLAG_ONCE) != 0;
168 done = (bug->flags & BUGFLAG_DONE) != 0;
170 if (warning && once) {
172 return BUG_TRAP_TYPE_WARN;
175 * Since this is the only store, concurrency is not an issue.
177 bug->flags |= BUGFLAG_DONE;
182 /* this is a WARN_ON rather than BUG/BUG_ON */
183 __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
185 return BUG_TRAP_TYPE_WARN;
188 printk(KERN_DEFAULT "------------[ cut here ]------------\n");
191 pr_crit("kernel BUG at %s:%u!\n", file, line);
193 pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n",
196 return BUG_TRAP_TYPE_BUG;