// SPDX-License-Identifier: GPL-2.0 /* 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> #include <linux/rculist.h> #include <linux/ftrace.h> extern 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 struct bug_entry *module_find_bug(unsigned long bugaddr) { struct module *mod; 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 struct bug_entry *module_find_bug(unsigned long bugaddr) { return NULL; } #endif struct bug_entry *find_bug(unsigned long bugaddr) { 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) { struct bug_entry *bug; const char *file; unsigned line, warning, once, done; if (!is_valid_bugaddr(bugaddr)) return BUG_TRAP_TYPE_NONE; bug = find_bug(bugaddr); if (!bug) return BUG_TRAP_TYPE_NONE; disable_trace_on_warning(); 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; once = (bug->flags & BUGFLAG_ONCE) != 0; done = (bug->flags & BUGFLAG_DONE) != 0; if (warning && once) { if (done) return BUG_TRAP_TYPE_WARN; /* * Since this is the only store, concurrency is not an issue. */ bug->flags |= BUGFLAG_DONE; } } /* * BUG() and WARN_ON() families don't print a custom debug message * before triggering the exception handler, so we must add the * "cut here" line now. WARN() issues its own "cut here" before the * extra debugging message it writes before triggering the handler. */ if ((bug->flags & BUGFLAG_NO_CUT_HERE) == 0) printk(KERN_DEFAULT CUT_HERE); if (warning) { /* this is a WARN_ON rather than BUG/BUG_ON */ __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs, NULL); return BUG_TRAP_TYPE_WARN; } if (file) pr_crit("kernel BUG at %s:%u!\n", file, line); else pr_crit("Kernel BUG at %pB [verbose debug info unavailable]\n", (void *)bugaddr); return BUG_TRAP_TYPE_BUG; } static void clear_once_table(struct bug_entry *start, struct bug_entry *end) { struct bug_entry *bug; for (bug = start; bug < end; bug++) bug->flags &= ~BUGFLAG_DONE; } void generic_bug_clear_once(void) { #ifdef CONFIG_MODULES struct module *mod; rcu_read_lock_sched(); list_for_each_entry_rcu(mod, &module_bug_list, bug_list) clear_once_table(mod->bug_table, mod->bug_table + mod->num_bugs); rcu_read_unlock_sched(); #endif clear_once_table(__start___bug_table, __stop___bug_table); }