FreeBSD/Linux Kernel Cross Reference
sys/lib/bug.c

     /*
       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
     */
    #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[];
    
    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 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_addr(bug))
                                    return bug;
            }
            return NULL;
    }
    
    void 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);
   }
   
   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_addr(bug))
                           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);
   
           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;
           }
   
           if (warning) {
                   /* this is a WARN_ON rather than BUG/BUG_ON */
                   printk(KERN_WARNING "------------[ cut here ]------------\n");
   
                   if (file)
                           printk(KERN_WARNING "WARNING: at %s:%u\n",
                                  file, line);
                   else
                           printk(KERN_WARNING "WARNING: at %p "
                                  "[verbose debug info unavailable]\n",
                                  (void *)bugaddr);
   
                   print_modules();
                   show_regs(regs);
                   print_oops_end_marker();
                   add_taint(BUG_GET_TAINT(bug));
                   return BUG_TRAP_TYPE_WARN;
           }
   
           printk(KERN_DEFAULT "------------[ cut here ]------------\n");
   
           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;
   }

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