1b2441318SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0 27664c5a1SJeremy Fitzhardinge /* 37664c5a1SJeremy Fitzhardinge Generic support for BUG() 47664c5a1SJeremy Fitzhardinge 57664c5a1SJeremy Fitzhardinge This respects the following config options: 67664c5a1SJeremy Fitzhardinge 77664c5a1SJeremy Fitzhardinge CONFIG_BUG - emit BUG traps. Nothing happens without this. 87664c5a1SJeremy Fitzhardinge CONFIG_GENERIC_BUG - enable this code. 9b93a531eSJan Beulich CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to 10b93a531eSJan Beulich the containing struct bug_entry for bug_addr and file. 117664c5a1SJeremy Fitzhardinge CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG 127664c5a1SJeremy Fitzhardinge 137664c5a1SJeremy Fitzhardinge CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable 147664c5a1SJeremy Fitzhardinge (though they're generally always on). 157664c5a1SJeremy Fitzhardinge 167664c5a1SJeremy Fitzhardinge CONFIG_GENERIC_BUG is set by each architecture using this code. 177664c5a1SJeremy Fitzhardinge 187664c5a1SJeremy Fitzhardinge To use this, your architecture must: 197664c5a1SJeremy Fitzhardinge 207664c5a1SJeremy Fitzhardinge 1. Set up the config options: 217664c5a1SJeremy Fitzhardinge - Enable CONFIG_GENERIC_BUG if CONFIG_BUG 227664c5a1SJeremy Fitzhardinge 237664c5a1SJeremy Fitzhardinge 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON) 247664c5a1SJeremy Fitzhardinge - Define HAVE_ARCH_BUG 257664c5a1SJeremy Fitzhardinge - Implement BUG() to generate a faulting instruction 267664c5a1SJeremy Fitzhardinge - NOTE: struct bug_entry does not have "file" or "line" entries 277664c5a1SJeremy Fitzhardinge when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate 287664c5a1SJeremy Fitzhardinge the values accordingly. 297664c5a1SJeremy Fitzhardinge 307664c5a1SJeremy Fitzhardinge 3. Implement the trap 317664c5a1SJeremy Fitzhardinge - In the illegal instruction trap handler (typically), verify 327664c5a1SJeremy Fitzhardinge that the fault was in kernel mode, and call report_bug() 337664c5a1SJeremy Fitzhardinge - report_bug() will return whether it was a false alarm, a warning, 347664c5a1SJeremy Fitzhardinge or an actual bug. 357664c5a1SJeremy Fitzhardinge - You must implement the is_valid_bugaddr(bugaddr) callback which 367664c5a1SJeremy Fitzhardinge returns true if the eip is a real kernel address, and it points 377664c5a1SJeremy Fitzhardinge to the expected BUG trap instruction. 387664c5a1SJeremy Fitzhardinge 397664c5a1SJeremy Fitzhardinge Jeremy Fitzhardinge <jeremy@goop.org> 2006 407664c5a1SJeremy Fitzhardinge */ 41c56ba703SFabian Frederick 42c56ba703SFabian Frederick #define pr_fmt(fmt) fmt 43c56ba703SFabian Frederick 447664c5a1SJeremy Fitzhardinge #include <linux/list.h> 457664c5a1SJeremy Fitzhardinge #include <linux/module.h> 46da9eac89SPaul Mundt #include <linux/kernel.h> 477664c5a1SJeremy Fitzhardinge #include <linux/bug.h> 48608e2619SHeiko Carstens #include <linux/sched.h> 49b2d09103SIngo Molnar #include <linux/rculist.h> 507664c5a1SJeremy Fitzhardinge 5119d43626SPeter Zijlstra extern struct bug_entry __start___bug_table[], __stop___bug_table[]; 527664c5a1SJeremy Fitzhardinge 53b93a531eSJan Beulich static inline unsigned long bug_addr(const struct bug_entry *bug) 54b93a531eSJan Beulich { 55b93a531eSJan Beulich #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 56b93a531eSJan Beulich return bug->bug_addr; 57b93a531eSJan Beulich #else 58b93a531eSJan Beulich return (unsigned long)bug + bug->bug_addr_disp; 59b93a531eSJan Beulich #endif 60b93a531eSJan Beulich } 61b93a531eSJan Beulich 627664c5a1SJeremy Fitzhardinge #ifdef CONFIG_MODULES 631fb9341aSRusty Russell /* Updates are protected by module mutex */ 647664c5a1SJeremy Fitzhardinge static LIST_HEAD(module_bug_list); 657664c5a1SJeremy Fitzhardinge 6619d43626SPeter Zijlstra static struct bug_entry *module_find_bug(unsigned long bugaddr) 677664c5a1SJeremy Fitzhardinge { 687664c5a1SJeremy Fitzhardinge struct module *mod; 6919d43626SPeter Zijlstra struct bug_entry *bug = NULL; 707664c5a1SJeremy Fitzhardinge 710be964beSPeter Zijlstra rcu_read_lock_sched(); 720286b5eaSMasami Hiramatsu list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { 737664c5a1SJeremy Fitzhardinge unsigned i; 747664c5a1SJeremy Fitzhardinge 750286b5eaSMasami Hiramatsu bug = mod->bug_table; 767664c5a1SJeremy Fitzhardinge for (i = 0; i < mod->num_bugs; ++i, ++bug) 77b93a531eSJan Beulich if (bugaddr == bug_addr(bug)) 780286b5eaSMasami Hiramatsu goto out; 797664c5a1SJeremy Fitzhardinge } 800286b5eaSMasami Hiramatsu bug = NULL; 810286b5eaSMasami Hiramatsu out: 820be964beSPeter Zijlstra rcu_read_unlock_sched(); 830286b5eaSMasami Hiramatsu 840286b5eaSMasami Hiramatsu return bug; 857664c5a1SJeremy Fitzhardinge } 867664c5a1SJeremy Fitzhardinge 875336377dSLinus Torvalds void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, 887664c5a1SJeremy Fitzhardinge struct module *mod) 897664c5a1SJeremy Fitzhardinge { 907664c5a1SJeremy Fitzhardinge char *secstrings; 917664c5a1SJeremy Fitzhardinge unsigned int i; 927664c5a1SJeremy Fitzhardinge 930be964beSPeter Zijlstra lockdep_assert_held(&module_mutex); 940be964beSPeter Zijlstra 957664c5a1SJeremy Fitzhardinge mod->bug_table = NULL; 967664c5a1SJeremy Fitzhardinge mod->num_bugs = 0; 977664c5a1SJeremy Fitzhardinge 987664c5a1SJeremy Fitzhardinge /* Find the __bug_table section, if present */ 997664c5a1SJeremy Fitzhardinge secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 1007664c5a1SJeremy Fitzhardinge for (i = 1; i < hdr->e_shnum; i++) { 1017664c5a1SJeremy Fitzhardinge if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) 1027664c5a1SJeremy Fitzhardinge continue; 1037664c5a1SJeremy Fitzhardinge mod->bug_table = (void *) sechdrs[i].sh_addr; 1047664c5a1SJeremy Fitzhardinge mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); 1057664c5a1SJeremy Fitzhardinge break; 1067664c5a1SJeremy Fitzhardinge } 1077664c5a1SJeremy Fitzhardinge 1087664c5a1SJeremy Fitzhardinge /* 1097664c5a1SJeremy Fitzhardinge * Strictly speaking this should have a spinlock to protect against 1107664c5a1SJeremy Fitzhardinge * traversals, but since we only traverse on BUG()s, a spinlock 1117664c5a1SJeremy Fitzhardinge * could potentially lead to deadlock and thus be counter-productive. 1120286b5eaSMasami Hiramatsu * Thus, this uses RCU to safely manipulate the bug list, since BUG 1130286b5eaSMasami Hiramatsu * must run in non-interruptive state. 1147664c5a1SJeremy Fitzhardinge */ 1150286b5eaSMasami Hiramatsu list_add_rcu(&mod->bug_list, &module_bug_list); 1167664c5a1SJeremy Fitzhardinge } 1177664c5a1SJeremy Fitzhardinge 1187664c5a1SJeremy Fitzhardinge void module_bug_cleanup(struct module *mod) 1197664c5a1SJeremy Fitzhardinge { 1200be964beSPeter Zijlstra lockdep_assert_held(&module_mutex); 1210286b5eaSMasami Hiramatsu list_del_rcu(&mod->bug_list); 1227664c5a1SJeremy Fitzhardinge } 1237664c5a1SJeremy Fitzhardinge 1247664c5a1SJeremy Fitzhardinge #else 1257664c5a1SJeremy Fitzhardinge 12619d43626SPeter Zijlstra static inline struct bug_entry *module_find_bug(unsigned long bugaddr) 1277664c5a1SJeremy Fitzhardinge { 1287664c5a1SJeremy Fitzhardinge return NULL; 1297664c5a1SJeremy Fitzhardinge } 1307664c5a1SJeremy Fitzhardinge #endif 1317664c5a1SJeremy Fitzhardinge 13219d43626SPeter Zijlstra struct bug_entry *find_bug(unsigned long bugaddr) 1337664c5a1SJeremy Fitzhardinge { 13419d43626SPeter Zijlstra struct bug_entry *bug; 1357664c5a1SJeremy Fitzhardinge 1367664c5a1SJeremy Fitzhardinge for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) 137b93a531eSJan Beulich if (bugaddr == bug_addr(bug)) 1387664c5a1SJeremy Fitzhardinge return bug; 1397664c5a1SJeremy Fitzhardinge 1407664c5a1SJeremy Fitzhardinge return module_find_bug(bugaddr); 1417664c5a1SJeremy Fitzhardinge } 1427664c5a1SJeremy Fitzhardinge 143608e2619SHeiko Carstens enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) 1447664c5a1SJeremy Fitzhardinge { 14519d43626SPeter Zijlstra struct bug_entry *bug; 1467664c5a1SJeremy Fitzhardinge const char *file; 14719d43626SPeter Zijlstra unsigned line, warning, once, done; 1487664c5a1SJeremy Fitzhardinge 1497664c5a1SJeremy Fitzhardinge if (!is_valid_bugaddr(bugaddr)) 1507664c5a1SJeremy Fitzhardinge return BUG_TRAP_TYPE_NONE; 1517664c5a1SJeremy Fitzhardinge 1527664c5a1SJeremy Fitzhardinge bug = find_bug(bugaddr); 153*1b4cfe3cSKees Cook if (!bug) 154*1b4cfe3cSKees Cook return BUG_TRAP_TYPE_NONE; 1557664c5a1SJeremy Fitzhardinge 1567664c5a1SJeremy Fitzhardinge file = NULL; 1577664c5a1SJeremy Fitzhardinge line = 0; 1587664c5a1SJeremy Fitzhardinge warning = 0; 1597664c5a1SJeremy Fitzhardinge 1607664c5a1SJeremy Fitzhardinge if (bug) { 1617664c5a1SJeremy Fitzhardinge #ifdef CONFIG_DEBUG_BUGVERBOSE 162b93a531eSJan Beulich #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS 1637664c5a1SJeremy Fitzhardinge file = bug->file; 164b93a531eSJan Beulich #else 165b93a531eSJan Beulich file = (const char *)bug + bug->file_disp; 166b93a531eSJan Beulich #endif 1677664c5a1SJeremy Fitzhardinge line = bug->line; 1687664c5a1SJeremy Fitzhardinge #endif 1697664c5a1SJeremy Fitzhardinge warning = (bug->flags & BUGFLAG_WARNING) != 0; 17019d43626SPeter Zijlstra once = (bug->flags & BUGFLAG_ONCE) != 0; 17119d43626SPeter Zijlstra done = (bug->flags & BUGFLAG_DONE) != 0; 17219d43626SPeter Zijlstra 17319d43626SPeter Zijlstra if (warning && once) { 17419d43626SPeter Zijlstra if (done) 17519d43626SPeter Zijlstra return BUG_TRAP_TYPE_WARN; 17619d43626SPeter Zijlstra 17719d43626SPeter Zijlstra /* 17819d43626SPeter Zijlstra * Since this is the only store, concurrency is not an issue. 17919d43626SPeter Zijlstra */ 18019d43626SPeter Zijlstra bug->flags |= BUGFLAG_DONE; 18119d43626SPeter Zijlstra } 1827664c5a1SJeremy Fitzhardinge } 1837664c5a1SJeremy Fitzhardinge 1847664c5a1SJeremy Fitzhardinge if (warning) { 1857664c5a1SJeremy Fitzhardinge /* this is a WARN_ON rather than BUG/BUG_ON */ 1862553b67aSJosh Poimboeuf __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs, 1872553b67aSJosh Poimboeuf NULL); 1887664c5a1SJeremy Fitzhardinge return BUG_TRAP_TYPE_WARN; 1897664c5a1SJeremy Fitzhardinge } 1907664c5a1SJeremy Fitzhardinge 1912a8358d8SKees Cook printk(KERN_DEFAULT CUT_HERE); 192e2e7e093SAnton Blanchard 1937664c5a1SJeremy Fitzhardinge if (file) 194c56ba703SFabian Frederick pr_crit("kernel BUG at %s:%u!\n", file, line); 1957664c5a1SJeremy Fitzhardinge else 1960862ca42SKees Cook pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n", 1977664c5a1SJeremy Fitzhardinge (void *)bugaddr); 1987664c5a1SJeremy Fitzhardinge 1997664c5a1SJeremy Fitzhardinge return BUG_TRAP_TYPE_BUG; 2007664c5a1SJeremy Fitzhardinge } 201aaf5dcfbSAndi Kleen 202aaf5dcfbSAndi Kleen static void clear_once_table(struct bug_entry *start, struct bug_entry *end) 203aaf5dcfbSAndi Kleen { 204aaf5dcfbSAndi Kleen struct bug_entry *bug; 205aaf5dcfbSAndi Kleen 206aaf5dcfbSAndi Kleen for (bug = start; bug < end; bug++) 207aaf5dcfbSAndi Kleen bug->flags &= ~BUGFLAG_DONE; 208aaf5dcfbSAndi Kleen } 209aaf5dcfbSAndi Kleen 210aaf5dcfbSAndi Kleen void generic_bug_clear_once(void) 211aaf5dcfbSAndi Kleen { 212aaf5dcfbSAndi Kleen #ifdef CONFIG_MODULES 213aaf5dcfbSAndi Kleen struct module *mod; 214aaf5dcfbSAndi Kleen 215aaf5dcfbSAndi Kleen rcu_read_lock_sched(); 216aaf5dcfbSAndi Kleen list_for_each_entry_rcu(mod, &module_bug_list, bug_list) 217aaf5dcfbSAndi Kleen clear_once_table(mod->bug_table, 218aaf5dcfbSAndi Kleen mod->bug_table + mod->num_bugs); 219aaf5dcfbSAndi Kleen rcu_read_unlock_sched(); 220aaf5dcfbSAndi Kleen #endif 221aaf5dcfbSAndi Kleen 222aaf5dcfbSAndi Kleen clear_once_table(__start___bug_table, __stop___bug_table); 223aaf5dcfbSAndi Kleen } 224