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/*
  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_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
 */
#include <linux/list.h>
#include <linux/module.h>
#include <linux/bug.h>
#include <linux/sched.h>
 
extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
 
#ifdef CONFIG_MODULES
static LIST_HEAD(module_bug_list);
 
static const struct bug_entry *module_find_bug(unsigned long bugaddr)
{
	struct module *mod;
 
	list_for_each_entry(mod, &module_bug_list, bug_list) {
		const struct bug_entry *bug = mod->bug_table;
		unsigned i;
 
		for (i = 0; i < mod->num_bugs; ++i, ++bug)
			if (bugaddr == bug->bug_addr)
				return bug;
	}
	return NULL;
}
 
int 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.
	 */
	list_add(&mod->bug_list, &module_bug_list);
 
	return 0;
}
 
void module_bug_cleanup(struct module *mod)
{
	list_del(&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->bug_addr)
			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);
 
	printk(KERN_EMERG "------------[ cut here ]------------\n");
 
	file = NULL;
	line = 0;
	warning = 0;
 
	if (bug) {
#ifdef CONFIG_DEBUG_BUGVERBOSE
		file = bug->file;
		line = bug->line;
#endif
		warning = (bug->flags & BUGFLAG_WARNING) != 0;
	}
 
	if (warning) {
		/* this is a WARN_ON rather than BUG/BUG_ON */
		if (file)
			printk(KERN_ERR "Badness at %s:%u\n",
			       file, line);
		else
			printk(KERN_ERR "Badness at %p "
			       "[verbose debug info unavailable]\n",
			       (void *)bugaddr);
 
		show_regs(regs);
		return BUG_TRAP_TYPE_WARN;
	}
 
	if (file)
		printk(KERN_CRIT "kernel BUG at %s:%u!\n",
		       file, line);
	else
		printk(KERN_CRIT "Kernel BUG at %p "
		       "[verbose debug info unavailable]\n",
		       (void *)bugaddr);
 
	return BUG_TRAP_TYPE_BUG;
}