LXR linux/lib/bug.c

   1/*
   2  Generic support for BUG()
   3
   4  This respects the following config options:
   5
   6  CONFIG_BUG - emit BUG traps.  Nothing happens without this.
   7  CONFIG_GENERIC_BUG - enable this code.
   8  CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
   9
  10  CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
  11  (though they're generally always on).
  12
  13  CONFIG_GENERIC_BUG is set by each architecture using this code.
  14
  15  To use this, your architecture must:
  16
  17  1. Set up the config options:
  18     - Enable CONFIG_GENERIC_BUG if CONFIG_BUG
  19
  20  2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
  21     - Define HAVE_ARCH_BUG
  22     - Implement BUG() to generate a faulting instruction
  23     - NOTE: struct bug_entry does not have "file" or "line" entries
  24       when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
  25       the values accordingly.
  26
  27  3. Implement the trap
  28     - In the illegal instruction trap handler (typically), verify
  29       that the fault was in kernel mode, and call report_bug()
  30     - report_bug() will return whether it was a false alarm, a warning,
  31       or an actual bug.
  32     - You must implement the is_valid_bugaddr(bugaddr) callback which
  33       returns true if the eip is a real kernel address, and it points
  34       to the expected BUG trap instruction.
  35
  36    Jeremy Fitzhardinge <jeremy@goop.org> 2006
  37 */
  38#include <linux/list.h>
  39#include <linux/module.h>
  40#include <linux/bug.h>
  41#include <linux/sched.h>
  42
  43extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
  44
  45#ifdef CONFIG_MODULES
  46static LIST_HEAD(module_bug_list);
  47
  48static const struct bug_entry *module_find_bug(unsigned long bugaddr)
  49{
  50        struct module *mod;
  51
  52        list_for_each_entry(mod, &module_bug_list, bug_list) {
  53                const struct bug_entry *bug = mod->bug_table;
  54                unsigned i;
  55
  56                for (i = 0; i < mod->num_bugs; ++i, ++bug)
  57                        if (bugaddr == bug->bug_addr)
  58                                return bug;
  59        }
  60        return NULL;
  61}
  62
  63int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
  64                        struct module *mod)
  65{
  66        char *secstrings;
  67        unsigned int i;
  68
  69        mod->bug_table = NULL;
  70        mod->num_bugs = 0;
  71
  72        /* Find the __bug_table section, if present */
  73        secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
  74        for (i = 1; i < hdr->e_shnum; i++) {
  75                if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
  76                        continue;
  77                mod->bug_table = (void *) sechdrs[i].sh_addr;
  78                mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
  79                break;
  80        }
  81
  82        /*
  83         * Strictly speaking this should have a spinlock to protect against
  84         * traversals, but since we only traverse on BUG()s, a spinlock
  85         * could potentially lead to deadlock and thus be counter-productive.
  86         */
  87        list_add(&mod->bug_list, &module_bug_list);
  88
  89        return 0;
  90}
  91
  92void module_bug_cleanup(struct module *mod)
  93{
  94        list_del(&mod->bug_list);
  95}
  96
  97#else
  98
  99static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
 100{
 101        return NULL;
 102}
 103#endif
 104
 105const struct bug_entry *find_bug(unsigned long bugaddr)
 106{
 107        const struct bug_entry *bug;
 108
 109        for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
 110                if (bugaddr == bug->bug_addr)
 111                        return bug;
 112
 113        return module_find_bug(bugaddr);
 114}
 115
 116enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 117{
 118        const struct bug_entry *bug;
 119        const char *file;
 120        unsigned line, warning;
 121
 122        if (!is_valid_bugaddr(bugaddr))
 123                return BUG_TRAP_TYPE_NONE;
 124
 125        bug = find_bug(bugaddr);
 126
 127        printk(KERN_EMERG "------------[ cut here ]------------\n");
 128
 129        file = NULL;
 130        line = 0;
 131        warning = 0;
 132
 133        if (bug) {
 134#ifdef CONFIG_DEBUG_BUGVERBOSE
 135                file = bug->file;
 136                line = bug->line;
 137#endif
 138                warning = (bug->flags & BUGFLAG_WARNING) != 0;
 139        }
 140
 141        if (warning) {
 142                /* this is a WARN_ON rather than BUG/BUG_ON */
 143                if (file)
 144                        printk(KERN_ERR "Badness at %s:%u\n",
 145                               file, line);
 146                else
 147                        printk(KERN_ERR "Badness at %p "
 148                               "[verbose debug info unavailable]\n",
 149                               (void *)bugaddr);
 150
 151                show_regs(regs);
 152                return BUG_TRAP_TYPE_WARN;
 153        }
 154
 155        if (file)
 156                printk(KERN_CRIT "kernel BUG at %s:%u!\n",
 157                       file, line);
 158        else
 159                printk(KERN_CRIT "Kernel BUG at %p "
 160                       "[verbose debug info unavailable]\n",
 161                       (void *)bugaddr);
 162
 163        return BUG_TRAP_TYPE_BUG;
 164}
 165