17664c5a1SJeremy Fitzhardinge /* 27664c5a1SJeremy Fitzhardinge Generic support for BUG() 37664c5a1SJeremy Fitzhardinge 47664c5a1SJeremy Fitzhardinge This respects the following config options: 57664c5a1SJeremy Fitzhardinge 67664c5a1SJeremy Fitzhardinge CONFIG_BUG - emit BUG traps. Nothing happens without this. 77664c5a1SJeremy Fitzhardinge CONFIG_GENERIC_BUG - enable this code. 8b93a531eSJan Beulich CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to 9b93a531eSJan Beulich the containing struct bug_entry for bug_addr and file. 107664c5a1SJeremy Fitzhardinge CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG 117664c5a1SJeremy Fitzhardinge 127664c5a1SJeremy Fitzhardinge CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable 137664c5a1SJeremy Fitzhardinge (though they're generally always on). 147664c5a1SJeremy Fitzhardinge 157664c5a1SJeremy Fitzhardinge CONFIG_GENERIC_BUG is set by each architecture using this code. 167664c5a1SJeremy Fitzhardinge 177664c5a1SJeremy Fitzhardinge To use this, your architecture must: 187664c5a1SJeremy Fitzhardinge 197664c5a1SJeremy Fitzhardinge 1. Set up the config options: 207664c5a1SJeremy Fitzhardinge - Enable CONFIG_GENERIC_BUG if CONFIG_BUG 217664c5a1SJeremy Fitzhardinge 227664c5a1SJeremy Fitzhardinge 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON) 237664c5a1SJeremy Fitzhardinge - Define HAVE_ARCH_BUG 247664c5a1SJeremy Fitzhardinge - Implement BUG() to generate a faulting instruction 257664c5a1SJeremy Fitzhardinge - NOTE: struct bug_entry does not have "file" or "line" entries 267664c5a1SJeremy Fitzhardinge when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate 277664c5a1SJeremy Fitzhardinge the values accordingly. 287664c5a1SJeremy Fitzhardinge 297664c5a1SJeremy Fitzhardinge 3. Implement the trap 307664c5a1SJeremy Fitzhardinge - In the illegal instruction trap handler (typically), verify 317664c5a1SJeremy Fitzhardinge that the fault was in kernel mode, and call report_bug() 327664c5a1SJeremy Fitzhardinge - report_bug() will return whether it was a false alarm, a warning, 337664c5a1SJeremy Fitzhardinge or an actual bug. 347664c5a1SJeremy Fitzhardinge - You must implement the is_valid_bugaddr(bugaddr) callback which 357664c5a1SJeremy Fitzhardinge returns true if the eip is a real kernel address, and it points 367664c5a1SJeremy Fitzhardinge to the expected BUG trap instruction. 377664c5a1SJeremy Fitzhardinge 387664c5a1SJeremy Fitzhardinge Jeremy Fitzhardinge <jeremy@goop.org> 2006 397664c5a1SJeremy Fitzhardinge */ 40c56ba703SFabian Frederick 41c56ba703SFabian Frederick #define pr_fmt(fmt) fmt 42c56ba703SFabian Frederick 437664c5a1SJeremy Fitzhardinge #include <linux/list.h> 447664c5a1SJeremy Fitzhardinge #include <linux/module.h> 45da9eac89SPaul Mundt #include <linux/kernel.h> 467664c5a1SJeremy Fitzhardinge #include <linux/bug.h> 47608e2619SHeiko Carstens #include <linux/sched.h> 48*b2d09103SIngo Molnar #include <linux/rculist.h> 497664c5a1SJeremy Fitzhardinge 507664c5a1SJeremy Fitzhardinge extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; 517664c5a1SJeremy Fitzhardinge 52b93a531eSJan Beulich static inline unsigned long bug_addr(const struct bug_entry *bug) 53b93a531eSJan Beulich { 54b93a531eSJan Beulich #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 55b93a531eSJan Beulich return bug->bug_addr; 56b93a531eSJan Beulich #else 57b93a531eSJan Beulich return (unsigned long)bug + bug->bug_addr_disp; 58b93a531eSJan Beulich #endif 59b93a531eSJan Beulich } 60b93a531eSJan Beulich 617664c5a1SJeremy Fitzhardinge #ifdef CONFIG_MODULES 621fb9341aSRusty Russell /* Updates are protected by module mutex */ 637664c5a1SJeremy Fitzhardinge static LIST_HEAD(module_bug_list); 647664c5a1SJeremy Fitzhardinge 657664c5a1SJeremy Fitzhardinge static const struct bug_entry *module_find_bug(unsigned long bugaddr) 667664c5a1SJeremy Fitzhardinge { 677664c5a1SJeremy Fitzhardinge struct module *mod; 680286b5eaSMasami Hiramatsu const struct bug_entry *bug = NULL; 697664c5a1SJeremy Fitzhardinge 700be964beSPeter Zijlstra rcu_read_lock_sched(); 710286b5eaSMasami Hiramatsu list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { 727664c5a1SJeremy Fitzhardinge unsigned i; 737664c5a1SJeremy Fitzhardinge 740286b5eaSMasami Hiramatsu bug = mod->bug_table; 757664c5a1SJeremy Fitzhardinge for (i = 0; i < mod->num_bugs; ++i, ++bug) 76b93a531eSJan Beulich if (bugaddr == bug_addr(bug)) 770286b5eaSMasami Hiramatsu goto out; 787664c5a1SJeremy Fitzhardinge } 790286b5eaSMasami Hiramatsu bug = NULL; 800286b5eaSMasami Hiramatsu out: 810be964beSPeter Zijlstra rcu_read_unlock_sched(); 820286b5eaSMasami Hiramatsu 830286b5eaSMasami Hiramatsu return bug; 847664c5a1SJeremy Fitzhardinge } 857664c5a1SJeremy Fitzhardinge 865336377dSLinus Torvalds void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 877664c5a1SJeremy Fitzhardinge struct module *mod) 887664c5a1SJeremy Fitzhardinge { 897664c5a1SJeremy Fitzhardinge char *secstrings; 907664c5a1SJeremy Fitzhardinge unsigned int i; 917664c5a1SJeremy Fitzhardinge 920be964beSPeter Zijlstra lockdep_assert_held(&module_mutex); 930be964beSPeter Zijlstra 947664c5a1SJeremy Fitzhardinge mod->bug_table = NULL; 957664c5a1SJeremy Fitzhardinge mod->num_bugs = 0; 967664c5a1SJeremy Fitzhardinge 977664c5a1SJeremy Fitzhardinge /* Find the __bug_table section, if present */ 987664c5a1SJeremy Fitzhardinge secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 997664c5a1SJeremy Fitzhardinge for (i = 1; i < hdr->e_shnum; i++) { 1007664c5a1SJeremy Fitzhardinge if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 1017664c5a1SJeremy Fitzhardinge continue; 1027664c5a1SJeremy Fitzhardinge mod->bug_table = (void *) sechdrs[i].sh_addr; 1037664c5a1SJeremy Fitzhardinge mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 1047664c5a1SJeremy Fitzhardinge break; 1057664c5a1SJeremy Fitzhardinge } 1067664c5a1SJeremy Fitzhardinge 1077664c5a1SJeremy Fitzhardinge /* 1087664c5a1SJeremy Fitzhardinge * Strictly speaking this should have a spinlock to protect against 1097664c5a1SJeremy Fitzhardinge * traversals, but since we only traverse on BUG()s, a spinlock 1107664c5a1SJeremy Fitzhardinge * could potentially lead to deadlock and thus be counter-productive. 1110286b5eaSMasami Hiramatsu * Thus, this uses RCU to safely manipulate the bug list, since BUG 1120286b5eaSMasami Hiramatsu * must run in non-interruptive state. 1137664c5a1SJeremy Fitzhardinge */ 1140286b5eaSMasami Hiramatsu list_add_rcu(&mod->bug_list, &module_bug_list); 1157664c5a1SJeremy Fitzhardinge } 1167664c5a1SJeremy Fitzhardinge 1177664c5a1SJeremy Fitzhardinge void module_bug_cleanup(struct module *mod) 1187664c5a1SJeremy Fitzhardinge { 1190be964beSPeter Zijlstra lockdep_assert_held(&module_mutex); 1200286b5eaSMasami Hiramatsu list_del_rcu(&mod->bug_list); 1217664c5a1SJeremy Fitzhardinge } 1227664c5a1SJeremy Fitzhardinge 1237664c5a1SJeremy Fitzhardinge #else 1247664c5a1SJeremy Fitzhardinge 1257664c5a1SJeremy Fitzhardinge static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) 1267664c5a1SJeremy Fitzhardinge { 1277664c5a1SJeremy Fitzhardinge return NULL; 1287664c5a1SJeremy Fitzhardinge } 1297664c5a1SJeremy Fitzhardinge #endif 1307664c5a1SJeremy Fitzhardinge 1317664c5a1SJeremy Fitzhardinge const struct bug_entry *find_bug(unsigned long bugaddr) 1327664c5a1SJeremy Fitzhardinge { 1337664c5a1SJeremy Fitzhardinge const struct bug_entry *bug; 1347664c5a1SJeremy Fitzhardinge 1357664c5a1SJeremy Fitzhardinge for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 136b93a531eSJan Beulich if (bugaddr == bug_addr(bug)) 1377664c5a1SJeremy Fitzhardinge return bug; 1387664c5a1SJeremy Fitzhardinge 1397664c5a1SJeremy Fitzhardinge return module_find_bug(bugaddr); 1407664c5a1SJeremy Fitzhardinge } 1417664c5a1SJeremy Fitzhardinge 142608e2619SHeiko Carstens enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 1437664c5a1SJeremy Fitzhardinge { 1447664c5a1SJeremy Fitzhardinge const struct bug_entry *bug; 1457664c5a1SJeremy Fitzhardinge const char *file; 1467664c5a1SJeremy Fitzhardinge unsigned line, warning; 1477664c5a1SJeremy Fitzhardinge 1487664c5a1SJeremy Fitzhardinge if (!is_valid_bugaddr(bugaddr)) 1497664c5a1SJeremy Fitzhardinge return BUG_TRAP_TYPE_NONE; 1507664c5a1SJeremy Fitzhardinge 1517664c5a1SJeremy Fitzhardinge bug = find_bug(bugaddr); 1527664c5a1SJeremy Fitzhardinge 1537664c5a1SJeremy Fitzhardinge file = NULL; 1547664c5a1SJeremy Fitzhardinge line = 0; 1557664c5a1SJeremy Fitzhardinge warning = 0; 1567664c5a1SJeremy Fitzhardinge 1577664c5a1SJeremy Fitzhardinge if (bug) { 1587664c5a1SJeremy Fitzhardinge #ifdef CONFIG_DEBUG_BUGVERBOSE 159b93a531eSJan Beulich #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 1607664c5a1SJeremy Fitzhardinge file = bug->file; 161b93a531eSJan Beulich #else 162b93a531eSJan Beulich file = (const char *)bug + bug->file_disp; 163b93a531eSJan Beulich #endif 1647664c5a1SJeremy Fitzhardinge line = bug->line; 1657664c5a1SJeremy Fitzhardinge #endif 1667664c5a1SJeremy Fitzhardinge warning = (bug->flags & BUGFLAG_WARNING) != 0; 1677664c5a1SJeremy Fitzhardinge } 1687664c5a1SJeremy Fitzhardinge 1697664c5a1SJeremy Fitzhardinge if (warning) { 1707664c5a1SJeremy Fitzhardinge /* this is a WARN_ON rather than BUG/BUG_ON */ 1712553b67aSJosh Poimboeuf __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs, 1722553b67aSJosh Poimboeuf NULL); 1737664c5a1SJeremy Fitzhardinge return BUG_TRAP_TYPE_WARN; 1747664c5a1SJeremy Fitzhardinge } 1757664c5a1SJeremy Fitzhardinge 176b0f4c4b3SPrarit Bhargava printk(KERN_DEFAULT "------------[ cut here ]------------\n"); 177e2e7e093SAnton Blanchard 1787664c5a1SJeremy Fitzhardinge if (file) 179c56ba703SFabian Frederick pr_crit("kernel BUG at %s:%u!\n", file, line); 1807664c5a1SJeremy Fitzhardinge else 181c56ba703SFabian Frederick pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n", 1827664c5a1SJeremy Fitzhardinge (void *)bugaddr); 1837664c5a1SJeremy Fitzhardinge 1847664c5a1SJeremy Fitzhardinge return BUG_TRAP_TYPE_BUG; 1857664c5a1SJeremy Fitzhardinge } 186