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_DEBUG_BUGVERBOSE - emit full file+line information for each BUG 9 10 CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable 11 (though they're generally always on). 12 13 CONFIG_GENERIC_BUG is set by each architecture using this code. 14 15 To use this, your architecture must: 16 17 1. Set up the config options: 18 - Enable CONFIG_GENERIC_BUG if CONFIG_BUG 19 20 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON) 21 - Define HAVE_ARCH_BUG 22 - Implement BUG() to generate a faulting instruction 23 - NOTE: struct bug_entry does not have "file" or "line" entries 24 when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate 25 the values accordingly. 26 27 3. Implement the trap 28 - In the illegal instruction trap handler (typically), verify 29 that the fault was in kernel mode, and call report_bug() 30 - report_bug() will return whether it was a false alarm, a warning, 31 or an actual bug. 32 - You must implement the is_valid_bugaddr(bugaddr) callback which 33 returns true if the eip is a real kernel address, and it points 34 to the expected BUG trap instruction. 35 36 Jeremy Fitzhardinge <jeremy@goop.org> 2006 37 */ 38 #include <linux/list.h> 39 #include <linux/module.h> 40 #include <linux/bug.h> 41 42 extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; 43 44 #ifdef CONFIG_MODULES 45 static LIST_HEAD(module_bug_list); 46 47 static const struct bug_entry *module_find_bug(unsigned long bugaddr) 48 { 49 struct module *mod; 50 51 list_for_each_entry(mod, &module_bug_list, bug_list) { 52 const struct bug_entry *bug = mod->bug_table; 53 unsigned i; 54 55 for (i = 0; i < mod->num_bugs; ++i, ++bug) 56 if (bugaddr == bug->bug_addr) 57 return bug; 58 } 59 return NULL; 60 } 61 62 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 63 struct module *mod) 64 { 65 char *secstrings; 66 unsigned int i; 67 68 mod->bug_table = NULL; 69 mod->num_bugs = 0; 70 71 /* Find the __bug_table section, if present */ 72 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 73 for (i = 1; i < hdr->e_shnum; i++) { 74 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 75 continue; 76 mod->bug_table = (void *) sechdrs[i].sh_addr; 77 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 78 break; 79 } 80 81 /* 82 * Strictly speaking this should have a spinlock to protect against 83 * traversals, but since we only traverse on BUG()s, a spinlock 84 * could potentially lead to deadlock and thus be counter-productive. 85 */ 86 list_add(&mod->bug_list, &module_bug_list); 87 88 return 0; 89 } 90 91 void module_bug_cleanup(struct module *mod) 92 { 93 list_del(&mod->bug_list); 94 } 95 96 #else 97 98 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 99 { 100 return NULL; 101 } 102 #endif 103 104 const struct bug_entry *find_bug(unsigned long bugaddr) 105 { 106 const struct bug_entry *bug; 107 108 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 109 if (bugaddr == bug->bug_addr) 110 return bug; 111 112 return module_find_bug(bugaddr); 113 } 114 115 enum bug_trap_type report_bug(unsigned long bugaddr) 116 { 117 const struct bug_entry *bug; 118 const char *file; 119 unsigned line, warning; 120 121 if (!is_valid_bugaddr(bugaddr)) 122 return BUG_TRAP_TYPE_NONE; 123 124 bug = find_bug(bugaddr); 125 126 printk(KERN_EMERG "------------[ cut here ]------------\n"); 127 128 file = NULL; 129 line = 0; 130 warning = 0; 131 132 if (bug) { 133 #ifdef CONFIG_DEBUG_BUGVERBOSE 134 file = bug->file; 135 line = bug->line; 136 #endif 137 warning = (bug->flags & BUGFLAG_WARNING) != 0; 138 } 139 140 if (warning) { 141 /* this is a WARN_ON rather than BUG/BUG_ON */ 142 if (file) 143 printk(KERN_ERR "Badness at %s:%u\n", 144 file, line); 145 else 146 printk(KERN_ERR "Badness at %p " 147 "[verbose debug info unavailable]\n", 148 (void *)bugaddr); 149 150 dump_stack(); 151 return BUG_TRAP_TYPE_WARN; 152 } 153 154 if (file) 155 printk(KERN_CRIT "kernel BUG at %s:%u!\n", 156 file, line); 157 else 158 printk(KERN_CRIT "Kernel BUG at %p " 159 "[verbose debug info unavailable]\n", 160 (void *)bugaddr); 161 162 return BUG_TRAP_TYPE_BUG; 163 } 164