// 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);}