/* Generic support for BUG() This respects the following config options: CONFIG_BUG - emit BUG traps. Nothing happens without this. CONFIG_GENERIC_BUG - enable this code. CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to the containing struct bug_entry for bug_addr and file. CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable (though they're generally always on). CONFIG_GENERIC_BUG is set by each architecture using this code. To use this, your architecture must: 1. Set up the config options: - Enable CONFIG_GENERIC_BUG if CONFIG_BUG 2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON) - Define HAVE_ARCH_BUG - Implement BUG() to generate a faulting instruction - NOTE: struct bug_entry does not have "file" or "line" entries when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate the values accordingly. 3. Implement the trap - In the illegal instruction trap handler (typically), verify that the fault was in kernel mode, and call report_bug() - report_bug() will return whether it was a false alarm, a warning, or an actual bug. - You must implement the is_valid_bugaddr(bugaddr) callback which returns true if the eip is a real kernel address, and it points to the expected BUG trap instruction. Jeremy Fitzhardinge <jeremy@goop.org> 2006 */ #define pr_fmt(fmt) fmt #include <linux/list.h> #include <linux/module.h> #include <linux/kernel.h> #include <linux/bug.h> #include <linux/sched.h> extern const struct bug_entry __start___bug_table[], __stop___bug_table[]; static inline unsigned long bug_addr(const struct bug_entry *bug) { #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS return bug->bug_addr; #else return (unsigned long)bug + bug->bug_addr_disp; #endif } #ifdef CONFIG_MODULES /* Updates are protected by module mutex */ static LIST_HEAD(module_bug_list); static const struct bug_entry *module_find_bug(unsigned long bugaddr) { struct module *mod; const struct bug_entry *bug = NULL; rcu_read_lock_sched(); list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { unsigned i; bug = mod->bug_table; for (i = 0; i < mod->num_bugs; ++i, ++bug) if (bugaddr == bug_addr(bug)) goto out; } bug = NULL; out: rcu_read_unlock_sched(); return bug; } void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *mod) { char *secstrings; unsigned int i; lockdep_assert_held(&module_mutex); mod->bug_table = NULL; mod->num_bugs = 0; /* Find the __bug_table section, if present */ secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; for (i = 1; i < hdr->e_shnum; i++) { if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table")) continue; mod->bug_table = (void *) sechdrs[i].sh_addr; mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry); break; } /* * Strictly speaking this should have a spinlock to protect against * traversals, but since we only traverse on BUG()s, a spinlock * could potentially lead to deadlock and thus be counter-productive. * Thus, this uses RCU to safely manipulate the bug list, since BUG * must run in non-interruptive state. */ list_add_rcu(&mod->bug_list, &module_bug_list); } void module_bug_cleanup(struct module *mod) { lockdep_assert_held(&module_mutex); list_del_rcu(&mod->bug_list); } #else static inline const struct bug_entry *module_find_bug(unsigned long bugaddr) { return NULL; } #endif const struct bug_entry *find_bug(unsigned long bugaddr) { const struct bug_entry *bug; for (bug = __start___bug_table; bug < __stop___bug_table; ++bug) if (bugaddr == bug_addr(bug)) return bug; return module_find_bug(bugaddr); } enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) { const struct bug_entry *bug; const char *file; unsigned line, warning; if (!is_valid_bugaddr(bugaddr)) return BUG_TRAP_TYPE_NONE; bug = find_bug(bugaddr); file = NULL; line = 0; warning = 0; if (bug) { #ifdef CONFIG_DEBUG_BUGVERBOSE #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS file = bug->file; #else file = (const char *)bug + bug->file_disp; #endif line = bug->line; #endif warning = (bug->flags & BUGFLAG_WARNING) != 0; } if (warning) { /* this is a WARN_ON rather than BUG/BUG_ON */ pr_warn("------------[ cut here ]------------\n"); if (file) pr_warn("WARNING: at %s:%u\n", file, line); else pr_warn("WARNING: at %p [verbose debug info unavailable]\n", (void *)bugaddr); print_modules(); show_regs(regs); print_oops_end_marker(); /* Just a warning, don't kill lockdep. */ add_taint(BUG_GET_TAINT(bug), LOCKDEP_STILL_OK); return BUG_TRAP_TYPE_WARN; } printk(KERN_DEFAULT "------------[ cut here ]------------\n"); if (file) pr_crit("kernel BUG at %s:%u!\n", file, line); else pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n", (void *)bugaddr); return BUG_TRAP_TYPE_BUG; }