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 41 #define pr_fmt(fmt) fmt 42 43 #include <linux/list.h> 44 #include <linux/module.h> 45 #include <linux/kernel.h> 46 #include <linux/bug.h> 47 #include <linux/sched.h> 48 49 extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; 50 51 static inline unsigned long bug_addr(const struct bug_entry *bug) 52 { 53 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 54 return bug->bug_addr; 55 #else 56 return (unsigned long)bug + bug->bug_addr_disp; 57 #endif 58 } 59 60 #ifdef CONFIG_MODULES 61 /* Updates are protected by module mutex */ 62 static LIST_HEAD(module_bug_list); 63 64 static const struct bug_entry *module_find_bug(unsigned long bugaddr) 65 { 66 struct module *mod; 67 const struct bug_entry *bug = NULL; 68 69 rcu_read_lock_sched(); 70 list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { 71 unsigned i; 72 73 bug = mod->bug_table; 74 for (i = 0; i < mod->num_bugs; ++i, ++bug) 75 if (bugaddr == bug_addr(bug)) 76 goto out; 77 } 78 bug = NULL; 79 out: 80 rcu_read_unlock_sched(); 81 82 return bug; 83 } 84 85 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 86 struct module *mod) 87 { 88 char *secstrings; 89 unsigned int i; 90 91 lockdep_assert_held(&module_mutex); 92 93 mod->bug_table = NULL; 94 mod->num_bugs = 0; 95 96 /* Find the __bug_table section, if present */ 97 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 98 for (i = 1; i < hdr->e_shnum; i++) { 99 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 100 continue; 101 mod->bug_table = (void *) sechdrs[i].sh_addr; 102 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 103 break; 104 } 105 106 /* 107 * Strictly speaking this should have a spinlock to protect against 108 * traversals, but since we only traverse on BUG()s, a spinlock 109 * could potentially lead to deadlock and thus be counter-productive. 110 * Thus, this uses RCU to safely manipulate the bug list, since BUG 111 * must run in non-interruptive state. 112 */ 113 list_add_rcu(&mod->bug_list, &module_bug_list); 114 } 115 116 void module_bug_cleanup(struct module *mod) 117 { 118 lockdep_assert_held(&module_mutex); 119 list_del_rcu(&mod->bug_list); 120 } 121 122 #else 123 124 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 125 { 126 return NULL; 127 } 128 #endif 129 130 const struct bug_entry *find_bug(unsigned long bugaddr) 131 { 132 const struct bug_entry *bug; 133 134 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 135 if (bugaddr == bug_addr(bug)) 136 return bug; 137 138 return module_find_bug(bugaddr); 139 } 140 141 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 142 { 143 const struct bug_entry *bug; 144 const char *file; 145 unsigned line, warning; 146 147 if (!is_valid_bugaddr(bugaddr)) 148 return BUG_TRAP_TYPE_NONE; 149 150 bug = find_bug(bugaddr); 151 152 file = NULL; 153 line = 0; 154 warning = 0; 155 156 if (bug) { 157 #ifdef CONFIG_DEBUG_BUGVERBOSE 158 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 159 file = bug->file; 160 #else 161 file = (const char *)bug + bug->file_disp; 162 #endif 163 line = bug->line; 164 #endif 165 warning = (bug->flags & BUGFLAG_WARNING) != 0; 166 } 167 168 if (warning) { 169 /* this is a WARN_ON rather than BUG/BUG_ON */ 170 pr_warn("------------[ cut here ]------------\n"); 171 172 if (file) 173 pr_warn("WARNING: at %s:%u\n", file, line); 174 else 175 pr_warn("WARNING: at %p [verbose debug info unavailable]\n", 176 (void *)bugaddr); 177 178 print_modules(); 179 show_regs(regs); 180 print_oops_end_marker(); 181 /* Just a warning, don't kill lockdep. */ 182 add_taint(BUG_GET_TAINT(bug), LOCKDEP_STILL_OK); 183 return BUG_TRAP_TYPE_WARN; 184 } 185 186 printk(KERN_DEFAULT "------------[ cut here ]------------\n"); 187 188 if (file) 189 pr_crit("kernel BUG at %s:%u!\n", file, line); 190 else 191 pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n", 192 (void *)bugaddr); 193 194 return BUG_TRAP_TYPE_BUG; 195 } 196