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/kernel.h> 41 #include <linux/bug.h> 42 #include <linux/sched.h> 43 44 extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; 45 46 #ifdef CONFIG_MODULES 47 static LIST_HEAD(module_bug_list); 48 49 static const struct bug_entry *module_find_bug(unsigned long bugaddr) 50 { 51 struct module *mod; 52 53 list_for_each_entry(mod, &module_bug_list, bug_list) { 54 const struct bug_entry *bug = mod->bug_table; 55 unsigned i; 56 57 for (i = 0; i < mod->num_bugs; ++i, ++bug) 58 if (bugaddr == bug->bug_addr) 59 return bug; 60 } 61 return NULL; 62 } 63 64 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 65 struct module *mod) 66 { 67 char *secstrings; 68 unsigned int i; 69 70 mod->bug_table = NULL; 71 mod->num_bugs = 0; 72 73 /* Find the __bug_table section, if present */ 74 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 75 for (i = 1; i < hdr->e_shnum; i++) { 76 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 77 continue; 78 mod->bug_table = (void *) sechdrs[i].sh_addr; 79 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 80 break; 81 } 82 83 /* 84 * Strictly speaking this should have a spinlock to protect against 85 * traversals, but since we only traverse on BUG()s, a spinlock 86 * could potentially lead to deadlock and thus be counter-productive. 87 */ 88 list_add(&mod->bug_list, &module_bug_list); 89 90 return 0; 91 } 92 93 void module_bug_cleanup(struct module *mod) 94 { 95 list_del(&mod->bug_list); 96 } 97 98 #else 99 100 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 101 { 102 return NULL; 103 } 104 #endif 105 106 const struct bug_entry *find_bug(unsigned long bugaddr) 107 { 108 const struct bug_entry *bug; 109 110 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 111 if (bugaddr == bug->bug_addr) 112 return bug; 113 114 return module_find_bug(bugaddr); 115 } 116 117 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 118 { 119 const struct bug_entry *bug; 120 const char *file; 121 unsigned line, warning; 122 123 if (!is_valid_bugaddr(bugaddr)) 124 return BUG_TRAP_TYPE_NONE; 125 126 bug = find_bug(bugaddr); 127 128 printk(KERN_EMERG "------------[ cut here ]------------\n"); 129 130 file = NULL; 131 line = 0; 132 warning = 0; 133 134 if (bug) { 135 #ifdef CONFIG_DEBUG_BUGVERBOSE 136 file = bug->file; 137 line = bug->line; 138 #endif 139 warning = (bug->flags & BUGFLAG_WARNING) != 0; 140 } 141 142 if (warning) { 143 /* this is a WARN_ON rather than BUG/BUG_ON */ 144 if (file) 145 printk(KERN_ERR "Badness at %s:%u\n", 146 file, line); 147 else 148 printk(KERN_ERR "Badness at %p " 149 "[verbose debug info unavailable]\n", 150 (void *)bugaddr); 151 152 show_regs(regs); 153 add_taint(TAINT_WARN); 154 return BUG_TRAP_TYPE_WARN; 155 } 156 157 if (file) 158 printk(KERN_CRIT "kernel BUG at %s:%u!\n", 159 file, line); 160 else 161 printk(KERN_CRIT "Kernel BUG at %p " 162 "[verbose debug info unavailable]\n", 163 (void *)bugaddr); 164 165 return BUG_TRAP_TYPE_BUG; 166 } 167