// 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!
  ", file, line);

  	else

  		pr_crit("Kernel BUG at %pB [verbose debug info unavailable]
  ",

  			(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);
  }