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 46 extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; 47 48 static 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 58 static LIST_HEAD(module_bug_list); 59 60 static 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 75 int 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 return 0; 102 } 103 104 void module_bug_cleanup(struct module *mod) 105 { 106 list_del(&mod->bug_list); 107 } 108 109 #else 110 111 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 112 { 113 return NULL; 114 } 115 #endif 116 117 const struct bug_entry *find_bug(unsigned long bugaddr) 118 { 119 const struct bug_entry *bug; 120 121 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 122 if (bugaddr == bug_addr(bug)) 123 return bug; 124 125 return module_find_bug(bugaddr); 126 } 127 128 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 129 { 130 const struct bug_entry *bug; 131 const char *file; 132 unsigned line, warning; 133 134 if (!is_valid_bugaddr(bugaddr)) 135 return BUG_TRAP_TYPE_NONE; 136 137 bug = find_bug(bugaddr); 138 139 printk(KERN_EMERG "------------[ cut here ]------------\n"); 140 141 file = NULL; 142 line = 0; 143 warning = 0; 144 145 if (bug) { 146 #ifdef CONFIG_DEBUG_BUGVERBOSE 147 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 148 file = bug->file; 149 #else 150 file = (const char *)bug + bug->file_disp; 151 #endif 152 line = bug->line; 153 #endif 154 warning = (bug->flags & BUGFLAG_WARNING) != 0; 155 } 156 157 if (warning) { 158 /* this is a WARN_ON rather than BUG/BUG_ON */ 159 if (file) 160 printk(KERN_ERR "Badness at %s:%u\n", 161 file, line); 162 else 163 printk(KERN_ERR "Badness at %p " 164 "[verbose debug info unavailable]\n", 165 (void *)bugaddr); 166 167 show_regs(regs); 168 add_taint(TAINT_WARN); 169 return BUG_TRAP_TYPE_WARN; 170 } 171 172 if (file) 173 printk(KERN_CRIT "kernel BUG at %s:%u!\n", 174 file, line); 175 else 176 printk(KERN_CRIT "Kernel BUG at %p " 177 "[verbose debug info unavailable]\n", 178 (void *)bugaddr); 179 180 return BUG_TRAP_TYPE_BUG; 181 } 182