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
  42 extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
  43
  44 #ifdef CONFIG_MODULES
  45 static LIST_HEAD(module_bug_list);
  46
  47 static const struct bug_entry *module_find_bug(unsigned long bugaddr)
  48 {
  49         struct module *mod;
  50
  51         list_for_each_entry(mod, &module_bug_list, bug_list) {
  52                 const struct bug_entry *bug = mod->bug_table;
  53                 unsigned i;
  54
  55                 for (i = 0; i < mod->num_bugs; ++i, ++bug)
  56                         if (bugaddr == bug->bug_addr)
  57                                 return bug;
  58         }
  59         return NULL;
  60 }
  61
  62 int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
  63                         struct module *mod)
  64 {
  65         char *secstrings;
  66         unsigned int i;
  67
  68         mod->bug_table = NULL;
  69         mod->num_bugs = 0;
  70
  71         /* Find the __bug_table section, if present */
  72         secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
  73         for (i = 1; i < hdr->e_shnum; i++) {
  74                 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
  75                         continue;
  76                 mod->bug_table = (void *) sechdrs[i].sh_addr;
  77                 mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
  78                 break;
  79         }
  80
  81         /*
  82          * Strictly speaking this should have a spinlock to protect against
  83          * traversals, but since we only traverse on BUG()s, a spinlock
  84          * could potentially lead to deadlock and thus be counter-productive.
  85          */
  86         list_add(&mod->bug_list, &module_bug_list);
  87
  88         return 0;
  89 }
  90
  91 void module_bug_cleanup(struct module *mod)
  92 {
  93         list_del(&mod->bug_list);
  94 }
  95
  96 #else
  97
  98 static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
  99 {
 100         return NULL;
 101 }
 102 #endif
 103
 104 const struct bug_entry *find_bug(unsigned long bugaddr)
 105 {
 106         const struct bug_entry *bug;
 107
 108         for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
 109                 if (bugaddr == bug->bug_addr)
 110                         return bug;
 111
 112         return module_find_bug(bugaddr);
 113 }
 114
 115 enum bug_trap_type report_bug(unsigned long bugaddr)
 116 {
 117         const struct bug_entry *bug;
 118         const char *file;
 119         unsigned line, warning;
 120
 121         if (!is_valid_bugaddr(bugaddr))
 122                 return BUG_TRAP_TYPE_NONE;
 123
 124         bug = find_bug(bugaddr);
 125
 126         printk(KERN_EMERG "------------[ cut here ]------------\n");
 127
 128         file = NULL;
 129         line = 0;
 130         warning = 0;
 131
 132         if (bug) {
 133 #ifdef CONFIG_DEBUG_BUGVERBOSE
 134                 file = bug->file;
 135                 line = bug->line;
 136 #endif
 137                 warning = (bug->flags & BUGFLAG_WARNING) != 0;
 138         }
 139
 140         if (warning) {
 141                 /* this is a WARN_ON rather than BUG/BUG_ON */
 142                 if (file)
 143                         printk(KERN_ERR "Badness at %s:%u\n",
 144                                file, line);
 145                 else
 146                         printk(KERN_ERR "Badness at %p "
 147                                "[verbose debug info unavailable]\n",
 148                                (void *)bugaddr);
 149
 150                 dump_stack();
 151                 return BUG_TRAP_TYPE_WARN;
 152         }
 153
 154         if (file)
 155                 printk(KERN_CRIT "kernel BUG at %s:%u!\n",
 156                        file, line);
 157         else
 158                 printk(KERN_CRIT "Kernel BUG at %p "
 159                        "[verbose debug info unavailable]\n",
 160                        (void *)bugaddr);
 161
 162         return BUG_TRAP_TYPE_BUG;
 163 }