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 /* Updates are protected by module mutex */ 59 static LIST_HEAD(module_bug_list); 60 61 static const struct bug_entry *module_find_bug(unsigned long bugaddr) 62 { 63 struct module *mod; 64 65 list_for_each_entry(mod, &module_bug_list, bug_list) { 66 const struct bug_entry *bug = mod->bug_table; 67 unsigned i; 68 69 for (i = 0; i < mod->num_bugs; ++i, ++bug) 70 if (bugaddr == bug_addr(bug)) 71 return bug; 72 } 73 return NULL; 74 } 75 76 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 77 struct module *mod) 78 { 79 char *secstrings; 80 unsigned int i; 81 82 mod->bug_table = NULL; 83 mod->num_bugs = 0; 84 85 /* Find the __bug_table section, if present */ 86 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 87 for (i = 1; i < hdr->e_shnum; i++) { 88 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 89 continue; 90 mod->bug_table = (void *) sechdrs[i].sh_addr; 91 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 92 break; 93 } 94 95 /* 96 * Strictly speaking this should have a spinlock to protect against 97 * traversals, but since we only traverse on BUG()s, a spinlock 98 * could potentially lead to deadlock and thus be counter-productive. 99 */ 100 list_add(&mod->bug_list, &module_bug_list); 101 } 102 103 void module_bug_cleanup(struct module *mod) 104 { 105 list_del(&mod->bug_list); 106 } 107 108 #else 109 110 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 111 { 112 return NULL; 113 } 114 #endif 115 116 const struct bug_entry *find_bug(unsigned long bugaddr) 117 { 118 const struct bug_entry *bug; 119 120 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 121 if (bugaddr == bug_addr(bug)) 122 return bug; 123 124 return module_find_bug(bugaddr); 125 } 126 127 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 128 { 129 const struct bug_entry *bug; 130 const char *file; 131 unsigned line, warning; 132 133 if (!is_valid_bugaddr(bugaddr)) 134 return BUG_TRAP_TYPE_NONE; 135 136 bug = find_bug(bugaddr); 137 138 file = NULL; 139 line = 0; 140 warning = 0; 141 142 if (bug) { 143 #ifdef CONFIG_DEBUG_BUGVERBOSE 144 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 145 file = bug->file; 146 #else 147 file = (const char *)bug + bug->file_disp; 148 #endif 149 line = bug->line; 150 #endif 151 warning = (bug->flags & BUGFLAG_WARNING) != 0; 152 } 153 154 if (warning) { 155 /* this is a WARN_ON rather than BUG/BUG_ON */ 156 printk(KERN_WARNING "------------[ cut here ]------------\n"); 157 158 if (file) 159 printk(KERN_WARNING "WARNING: at %s:%u\n", 160 file, line); 161 else 162 printk(KERN_WARNING "WARNING: at %p " 163 "[verbose debug info unavailable]\n", 164 (void *)bugaddr); 165 166 print_modules(); 167 show_regs(regs); 168 print_oops_end_marker(); 169 /* Just a warning, don't kill lockdep. */ 170 add_taint(BUG_GET_TAINT(bug), LOCKDEP_STILL_OK); 171 return BUG_TRAP_TYPE_WARN; 172 } 173 174 printk(KERN_DEFAULT "------------[ cut here ]------------\n"); 175 176 if (file) 177 printk(KERN_CRIT "kernel BUG at %s:%u!\n", 178 file, line); 179 else 180 printk(KERN_CRIT "Kernel BUG at %p " 181 "[verbose debug info unavailable]\n", 182 (void *)bugaddr); 183 184 return BUG_TRAP_TYPE_BUG; 185 } 186