root/lib/bug.c

DEFINITIONS

1. module_find_bug
2. module_bug_finalize
3. module_bug_cleanup
4. module_find_bug
5. find_bug
6. report_bug

/*
  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/kernel.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);
                add_taint(TAINT_WARN);
                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;
}