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 #include <linux/rculist.h> 49 50 extern struct bug_entry __start___bug_table[], __stop___bug_table[]; 51 52 static inline unsigned long bug_addr(const struct bug_entry *bug) 53 { 54 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 55 return bug->bug_addr; 56 #else 57 return (unsigned long)bug + bug->bug_addr_disp; 58 #endif 59 } 60 61 #ifdef CONFIG_MODULES 62 /* Updates are protected by module mutex */ 63 static LIST_HEAD(module_bug_list); 64 65 static struct bug_entry *module_find_bug(unsigned long bugaddr) 66 { 67 struct module *mod; 68 struct bug_entry *bug = NULL; 69 70 rcu_read_lock_sched(); 71 list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { 72 unsigned i; 73 74 bug = mod->bug_table; 75 for (i = 0; i < mod->num_bugs; ++i, ++bug) 76 if (bugaddr == bug_addr(bug)) 77 goto out; 78 } 79 bug = NULL; 80 out: 81 rcu_read_unlock_sched(); 82 83 return bug; 84 } 85 86 void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 87 struct module *mod) 88 { 89 char *secstrings; 90 unsigned int i; 91 92 lockdep_assert_held(&module_mutex); 93 94 mod->bug_table = NULL; 95 mod->num_bugs = 0; 96 97 /* Find the __bug_table section, if present */ 98 secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 99 for (i = 1; i < hdr->e_shnum; i++) { 100 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 101 continue; 102 mod->bug_table = (void *) sechdrs[i].sh_addr; 103 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 104 break; 105 } 106 107 /* 108 * Strictly speaking this should have a spinlock to protect against 109 * traversals, but since we only traverse on BUG()s, a spinlock 110 * could potentially lead to deadlock and thus be counter-productive. 111 * Thus, this uses RCU to safely manipulate the bug list, since BUG 112 * must run in non-interruptive state. 113 */ 114 list_add_rcu(&mod->bug_list, &module_bug_list); 115 } 116 117 void module_bug_cleanup(struct module *mod) 118 { 119 lockdep_assert_held(&module_mutex); 120 list_del_rcu(&mod->bug_list); 121 } 122 123 #else 124 125 static inline struct bug_entry *module_find_bug(unsigned long bugaddr) 126 { 127 return NULL; 128 } 129 #endif 130 131 struct bug_entry *find_bug(unsigned long bugaddr) 132 { 133 struct bug_entry *bug; 134 135 for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 136 if (bugaddr == bug_addr(bug)) 137 return bug; 138 139 return module_find_bug(bugaddr); 140 } 141 142 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 143 { 144 struct bug_entry *bug; 145 const char *file; 146 unsigned line, warning, once, done; 147 148 if (!is_valid_bugaddr(bugaddr)) 149 return BUG_TRAP_TYPE_NONE; 150 151 bug = find_bug(bugaddr); 152 153 file = NULL; 154 line = 0; 155 warning = 0; 156 157 if (bug) { 158 #ifdef CONFIG_DEBUG_BUGVERBOSE 159 #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 160 file = bug->file; 161 #else 162 file = (const char *)bug + bug->file_disp; 163 #endif 164 line = bug->line; 165 #endif 166 warning = (bug->flags & BUGFLAG_WARNING) != 0; 167 once = (bug->flags & BUGFLAG_ONCE) != 0; 168 done = (bug->flags & BUGFLAG_DONE) != 0; 169 170 if (warning && once) { 171 if (done) 172 return BUG_TRAP_TYPE_WARN; 173 174 /* 175 * Since this is the only store, concurrency is not an issue. 176 */ 177 bug->flags |= BUGFLAG_DONE; 178 } 179 } 180 181 if (warning) { 182 /* this is a WARN_ON rather than BUG/BUG_ON */ 183 __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs, 184 NULL); 185 return BUG_TRAP_TYPE_WARN; 186 } 187 188 printk(KERN_DEFAULT "------------[ cut here ]------------\n"); 189 190 if (file) 191 pr_crit("kernel BUG at %s:%u!\n", file, line); 192 else 193 pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n", 194 (void *)bugaddr); 195 196 return BUG_TRAP_TYPE_BUG; 197 } 198