// 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 relative pointers 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>#include <linux/context_tracking.h> extern struct bug_entry __start___bug_table[], __stop___bug_table[]; static inline unsigned long bug_addr(const struct bug_entry *bug){#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS	return (unsigned long)&bug->bug_addr_disp + bug->bug_addr_disp;#else	return bug->bug_addr;#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 bug_entry *bug;	struct module *mod; 	guard(rcu)();	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))				return bug;	}	return NULL;} void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,			 struct module *mod){	char *secstrings;	unsigned int i; 	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){	list_del_rcu(&mod->bug_list);} #else static inline struct bug_entry *module_find_bug(unsigned long bugaddr){	return NULL;}#endif void bug_get_file_line(struct bug_entry *bug, const char **file,		       unsigned int *line){#ifdef CONFIG_DEBUG_BUGVERBOSE#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS	*file = (const char *)&bug->file_disp + bug->file_disp;#else	*file = bug->file;#endif	*line = bug->line;#else	*file = NULL;	*line = 0;#endif} static const char *bug_get_format(struct bug_entry *bug){	const char *format = NULL;#ifdef HAVE_ARCH_BUG_FORMAT#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS	/*	 * Allow an architecture to:	 *  - relative encode NULL (difficult vs KASLR);	 *  - use a literal 0 (there are no valid objects inside	 *    the __bug_table itself to refer to after all);	 *  - use an empty string.	 */	if (bug->format_disp)		format = (const char *)&bug->format_disp + bug->format_disp;	if (format && format[0] == '\0')		format = NULL;#else	format = bug->format;#endif#endif	return format;} 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);} __diag_push();__diag_ignore(GCC, all, "-Wsuggest-attribute=format",	      "Not a valid __printf() conversion candidate.");static void __warn_printf(const char *fmt, struct pt_regs *regs){	if (!fmt)		return; #ifdef HAVE_ARCH_BUG_FORMAT_ARGS	if (regs) {		struct arch_va_list _args;		va_list *args = __warn_args(&_args, regs); 		if (args) {			vprintk(fmt, *args);			return;		}	}#endif 	printk("%s", fmt);}__diag_pop(); static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long bugaddr, struct pt_regs *regs){	bool warning, once, done, no_cut, has_args;	const char *file, *fmt;	unsigned line; 	if (!bug) {		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(); 	bug_get_file_line(bug, &file, &line);	fmt = bug_get_format(bug); 	warning  = bug->flags & BUGFLAG_WARNING;	once     = bug->flags & BUGFLAG_ONCE;	done     = bug->flags & BUGFLAG_DONE;	no_cut   = bug->flags & BUGFLAG_NO_CUT_HERE;	has_args = bug->flags & BUGFLAG_ARGS; 	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 (!no_cut) {		printk(KERN_DEFAULT CUT_HERE);		__warn_printf(fmt, has_args ? regs : NULL);	} 	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;} enum bug_trap_type report_bug_entry(struct bug_entry *bug, struct pt_regs *regs){	enum bug_trap_type ret;	bool rcu = false; 	rcu = warn_rcu_enter();	ret = __report_bug(bug, bug_addr(bug), regs);	warn_rcu_exit(rcu); 	return ret;} enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs){	enum bug_trap_type ret;	bool rcu = false; 	rcu = warn_rcu_enter();	ret = __report_bug(NULL, bugaddr, regs);	warn_rcu_exit(rcu); 	return ret;} 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; 	scoped_guard(rcu) {		list_for_each_entry_rcu(mod, &module_bug_list, bug_list)			clear_once_table(mod->bug_table,					 mod->bug_table + mod->num_bugs);	}#endif 	clear_once_table(__start___bug_table, __stop___bug_table);}