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 #include <linux/sched.h> 42 43 extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; 44 45 #ifdef CONFIG_MODULES 46 static LIST_HEAD(module_bug_list); 47 48 static const struct bug_entry *module_find_bug(unsigned long bugaddr) 49 { 50 struct module *mod; 51 52 list_for_each_entry(mod, &module_bug_list, bug_list) { 53 const struct bug_entry *bug = mod->bug_table; 54 unsigned i; 55 56 for (i = 0; i < mod->num_bugs; ++i, ++bug) 57 if (bugaddr == bug->bug_addr) 58 return bug; 59 } 60 return NULL; 61 } 62 63 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 64 struct module *mod) 65 { 66 char *secstrings; 67 unsigned int i; 68 69 mod->bug_table = NULL; 70 mod->num_bugs = 0; 71 72 /* Find the __bug_table section, if present */ 73 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 74 for (i = 1; i < hdr->e_shnum; i++) { 75 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 76 continue; 77 mod->bug_table = (void *) sechdrs[i].sh_addr; 78 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 79 break; 80 } 81 82 /* 83 * Strictly speaking this should have a spinlock to protect against 84 * traversals, but since we only traverse on BUG()s, a spinlock 85 * could potentially lead to deadlock and thus be counter-productive. 86 */ 87 list_add(&mod->bug_list, &module_bug_list); 88 89 return 0; 90 } 91 92 void module_bug_cleanup(struct module *mod) 93 { 94 list_del(&mod->bug_list); 95 } 96 97 #else 98 99 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 100 { 101 return NULL; 102 } 103 #endif 104 105 const struct bug_entry *find_bug(unsigned long bugaddr) 106 { 107 const struct bug_entry *bug; 108 109 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 110 if (bugaddr == bug->bug_addr) 111 return bug; 112 113 return module_find_bug(bugaddr); 114 } 115 116 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 117 { 118 const struct bug_entry *bug; 119 const char *file; 120 unsigned line, warning; 121 122 if (!is_valid_bugaddr(bugaddr)) 123 return BUG_TRAP_TYPE_NONE; 124 125 bug = find_bug(bugaddr); 126 127 printk(KERN_EMERG "------------[ cut here ]------------\n"); 128 129 file = NULL; 130 line = 0; 131 warning = 0; 132 133 if (bug) { 134 #ifdef CONFIG_DEBUG_BUGVERBOSE 135 file = bug->file; 136 line = bug->line; 137 #endif 138 warning = (bug->flags & BUGFLAG_WARNING) != 0; 139 } 140 141 if (warning) { 142 /* this is a WARN_ON rather than BUG/BUG_ON */ 143 if (file) 144 printk(KERN_ERR "Badness at %s:%u\n", 145 file, line); 146 else 147 printk(KERN_ERR "Badness at %p " 148 "[verbose debug info unavailable]\n", 149 (void *)bugaddr); 150 151 show_regs(regs); 152 return BUG_TRAP_TYPE_WARN; 153 } 154 155 if (file) 156 printk(KERN_CRIT "kernel BUG at %s:%u!\n", 157 file, line); 158 else 159 printk(KERN_CRIT "Kernel BUG at %p " 160 "[verbose debug info unavailable]\n", 161 (void *)bugaddr); 162 163 return BUG_TRAP_TYPE_BUG; 164 } 165