FreeBSD/Linux Kernel Cross Reference
sys/kernel/kallsyms.c

     /*
      * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
      *
      * Rewritten and vastly simplified by Rusty Russell for in-kernel
      * module loader:
      *   Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
      *
      * ChangeLog:
      *
     * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
     *      Changed the compression method from stem compression to "table lookup"
     *      compression (see scripts/kallsyms.c for a more complete description)
     */
    #include <linux/kallsyms.h>
    #include <linux/module.h>
    #include <linux/init.h>
    #include <linux/seq_file.h>
    #include <linux/fs.h>
    #include <linux/kdb.h>
    #include <linux/err.h>
    #include <linux/proc_fs.h>
    #include <linux/sched.h>        /* for cond_resched */
    #include <linux/mm.h>
    #include <linux/ctype.h>
    #include <linux/slab.h>
    
    #include <asm/sections.h>
    
    #ifdef CONFIG_KALLSYMS_ALL
    #define all_var 1
    #else
    #define all_var 0
    #endif
    
    /*
     * These will be re-linked against their real values
     * during the second link stage.
     */
    extern const unsigned long kallsyms_addresses[] __attribute__((weak));
    extern const u8 kallsyms_names[] __attribute__((weak));
    
    /*
     * Tell the compiler that the count isn't in the small data section if the arch
     * has one (eg: FRV).
     */
    extern const unsigned long kallsyms_num_syms
    __attribute__((weak, section(".rodata")));
    
    extern const u8 kallsyms_token_table[] __attribute__((weak));
    extern const u16 kallsyms_token_index[] __attribute__((weak));
    
    extern const unsigned long kallsyms_markers[] __attribute__((weak));
    
    static inline int is_kernel_inittext(unsigned long addr)
    {
            if (addr >= (unsigned long)_sinittext
                && addr <= (unsigned long)_einittext)
                    return 1;
            return 0;
    }
    
    static inline int is_kernel_text(unsigned long addr)
    {
            if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
                arch_is_kernel_text(addr))
                    return 1;
            return in_gate_area_no_mm(addr);
    }
    
    static inline int is_kernel(unsigned long addr)
    {
            if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
                    return 1;
            return in_gate_area_no_mm(addr);
    }
    
    static int is_ksym_addr(unsigned long addr)
    {
            if (all_var)
                    return is_kernel(addr);
    
            return is_kernel_text(addr) || is_kernel_inittext(addr);
    }
    
    /*
     * Expand a compressed symbol data into the resulting uncompressed string,
     * given the offset to where the symbol is in the compressed stream.
     */
    static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
    {
            int len, skipped_first = 0;
            const u8 *tptr, *data;
    
            /* Get the compressed symbol length from the first symbol byte. */
            data = &kallsyms_names[off];
            len = *data;
            data++;
    
            /*
            * Update the offset to return the offset for the next symbol on
            * the compressed stream.
            */
           off += len + 1;
   
           /*
            * For every byte on the compressed symbol data, copy the table
            * entry for that byte.
            */
           while (len) {
                   tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
                   data++;
                   len--;
   
                   while (*tptr) {
                           if (skipped_first) {
                                   *result = *tptr;
                                   result++;
                           } else
                                   skipped_first = 1;
                           tptr++;
                   }
           }
   
           *result = '\0';
   
           /* Return to offset to the next symbol. */
           return off;
   }
   
   /*
    * Get symbol type information. This is encoded as a single char at the
    * beginning of the symbol name.
    */
   static char kallsyms_get_symbol_type(unsigned int off)
   {
           /*
            * Get just the first code, look it up in the token table,
            * and return the first char from this token.
            */
           return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
   }
   
   
   /*
    * Find the offset on the compressed stream given and index in the
    * kallsyms array.
    */
   static unsigned int get_symbol_offset(unsigned long pos)
   {
           const u8 *name;
           int i;
   
           /*
            * Use the closest marker we have. We have markers every 256 positions,
            * so that should be close enough.
            */
           name = &kallsyms_names[kallsyms_markers[pos >> 8]];
   
           /*
            * Sequentially scan all the symbols up to the point we're searching
            * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
            * so we just need to add the len to the current pointer for every
            * symbol we wish to skip.
            */
           for (i = 0; i < (pos & 0xFF); i++)
                   name = name + (*name) + 1;
   
           return name - kallsyms_names;
   }
   
   /* Lookup the address for this symbol. Returns 0 if not found. */
   unsigned long kallsyms_lookup_name(const char *name)
   {
           char namebuf[KSYM_NAME_LEN];
           unsigned long i;
           unsigned int off;
   
           for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
                   off = kallsyms_expand_symbol(off, namebuf);
   
                   if (strcmp(namebuf, name) == 0)
                           return kallsyms_addresses[i];
           }
           return module_kallsyms_lookup_name(name);
   }
   EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
   
   int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
                                         unsigned long),
                               void *data)
   {
           char namebuf[KSYM_NAME_LEN];
           unsigned long i;
           unsigned int off;
           int ret;
   
           for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
                   off = kallsyms_expand_symbol(off, namebuf);
                   ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
                   if (ret != 0)
                           return ret;
           }
           return module_kallsyms_on_each_symbol(fn, data);
   }
   EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
   
   static unsigned long get_symbol_pos(unsigned long addr,
                                       unsigned long *symbolsize,
                                       unsigned long *offset)
   {
           unsigned long symbol_start = 0, symbol_end = 0;
           unsigned long i, low, high, mid;
   
           /* This kernel should never had been booted. */
           BUG_ON(!kallsyms_addresses);
   
           /* Do a binary search on the sorted kallsyms_addresses array. */
           low = 0;
           high = kallsyms_num_syms;
   
           while (high - low > 1) {
                   mid = low + (high - low) / 2;
                   if (kallsyms_addresses[mid] <= addr)
                           low = mid;
                   else
                           high = mid;
           }
   
           /*
            * Search for the first aliased symbol. Aliased
            * symbols are symbols with the same address.
            */
           while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
                   --low;
   
           symbol_start = kallsyms_addresses[low];
   
           /* Search for next non-aliased symbol. */
           for (i = low + 1; i < kallsyms_num_syms; i++) {
                   if (kallsyms_addresses[i] > symbol_start) {
                           symbol_end = kallsyms_addresses[i];
                           break;
                   }
           }
   
           /* If we found no next symbol, we use the end of the section. */
           if (!symbol_end) {
                   if (is_kernel_inittext(addr))
                           symbol_end = (unsigned long)_einittext;
                   else if (all_var)
                           symbol_end = (unsigned long)_end;
                   else
                           symbol_end = (unsigned long)_etext;
           }
   
           if (symbolsize)
                   *symbolsize = symbol_end - symbol_start;
           if (offset)
                   *offset = addr - symbol_start;
   
           return low;
   }
   
   /*
    * Lookup an address but don't bother to find any names.
    */
   int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
                                   unsigned long *offset)
   {
           char namebuf[KSYM_NAME_LEN];
           if (is_ksym_addr(addr))
                   return !!get_symbol_pos(addr, symbolsize, offset);
   
           return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
   }
   
   /*
    * Lookup an address
    * - modname is set to NULL if it's in the kernel.
    * - We guarantee that the returned name is valid until we reschedule even if.
    *   It resides in a module.
    * - We also guarantee that modname will be valid until rescheduled.
    */
   const char *kallsyms_lookup(unsigned long addr,
                               unsigned long *symbolsize,
                               unsigned long *offset,
                               char **modname, char *namebuf)
   {
           namebuf[KSYM_NAME_LEN - 1] = 0;
           namebuf[0] = 0;
   
           if (is_ksym_addr(addr)) {
                   unsigned long pos;
   
                   pos = get_symbol_pos(addr, symbolsize, offset);
                   /* Grab name */
                   kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
                   if (modname)
                           *modname = NULL;
                   return namebuf;
           }
   
           /* See if it's in a module. */
           return module_address_lookup(addr, symbolsize, offset, modname,
                                        namebuf);
   }
   
   int lookup_symbol_name(unsigned long addr, char *symname)
   {
           symname[0] = '\0';
           symname[KSYM_NAME_LEN - 1] = '\0';
   
           if (is_ksym_addr(addr)) {
                   unsigned long pos;
   
                   pos = get_symbol_pos(addr, NULL, NULL);
                   /* Grab name */
                   kallsyms_expand_symbol(get_symbol_offset(pos), symname);
                   return 0;
           }
           /* See if it's in a module. */
           return lookup_module_symbol_name(addr, symname);
   }
   
   int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
                           unsigned long *offset, char *modname, char *name)
   {
           name[0] = '\0';
           name[KSYM_NAME_LEN - 1] = '\0';
   
           if (is_ksym_addr(addr)) {
                   unsigned long pos;
   
                   pos = get_symbol_pos(addr, size, offset);
                   /* Grab name */
                   kallsyms_expand_symbol(get_symbol_offset(pos), name);
                   modname[0] = '\0';
                   return 0;
           }
           /* See if it's in a module. */
           return lookup_module_symbol_attrs(addr, size, offset, modname, name);
   }
   
   /* Look up a kernel symbol and return it in a text buffer. */
   static int __sprint_symbol(char *buffer, unsigned long address,
                              int symbol_offset, int add_offset)
   {
           char *modname;
           const char *name;
           unsigned long offset, size;
           int len;
   
           address += symbol_offset;
           name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
           if (!name)
                   return sprintf(buffer, "0x%lx", address);
   
           if (name != buffer)
                   strcpy(buffer, name);
           len = strlen(buffer);
           offset -= symbol_offset;
   
           if (add_offset)
                   len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
   
           if (modname)
                   len += sprintf(buffer + len, " [%s]", modname);
   
           return len;
   }
   
   /**
    * sprint_symbol - Look up a kernel symbol and return it in a text buffer
    * @buffer: buffer to be stored
    * @address: address to lookup
    *
    * This function looks up a kernel symbol with @address and stores its name,
    * offset, size and module name to @buffer if possible. If no symbol was found,
    * just saves its @address as is.
    *
    * This function returns the number of bytes stored in @buffer.
    */
   int sprint_symbol(char *buffer, unsigned long address)
   {
           return __sprint_symbol(buffer, address, 0, 1);
   }
   EXPORT_SYMBOL_GPL(sprint_symbol);
   
   /**
    * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
    * @buffer: buffer to be stored
    * @address: address to lookup
    *
    * This function looks up a kernel symbol with @address and stores its name
    * and module name to @buffer if possible. If no symbol was found, just saves
    * its @address as is.
    *
    * This function returns the number of bytes stored in @buffer.
    */
   int sprint_symbol_no_offset(char *buffer, unsigned long address)
   {
           return __sprint_symbol(buffer, address, 0, 0);
   }
   EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
   
   /**
    * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
    * @buffer: buffer to be stored
    * @address: address to lookup
    *
    * This function is for stack backtrace and does the same thing as
    * sprint_symbol() but with modified/decreased @address. If there is a
    * tail-call to the function marked "noreturn", gcc optimized out code after
    * the call so that the stack-saved return address could point outside of the
    * caller. This function ensures that kallsyms will find the original caller
    * by decreasing @address.
    *
    * This function returns the number of bytes stored in @buffer.
    */
   int sprint_backtrace(char *buffer, unsigned long address)
   {
           return __sprint_symbol(buffer, address, -1, 1);
   }
   
   /* Look up a kernel symbol and print it to the kernel messages. */
   void __print_symbol(const char *fmt, unsigned long address)
   {
           char buffer[KSYM_SYMBOL_LEN];
   
           sprint_symbol(buffer, address);
   
           printk(fmt, buffer);
   }
   EXPORT_SYMBOL(__print_symbol);
   
   /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
   struct kallsym_iter {
           loff_t pos;
           unsigned long value;
           unsigned int nameoff; /* If iterating in core kernel symbols. */
           char type;
           char name[KSYM_NAME_LEN];
           char module_name[MODULE_NAME_LEN];
           int exported;
   };
   
   static int get_ksymbol_mod(struct kallsym_iter *iter)
   {
           if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
                                   &iter->type, iter->name, iter->module_name,
                                   &iter->exported) < 0)
                   return 0;
           return 1;
   }
   
   /* Returns space to next name. */
   static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
   {
           unsigned off = iter->nameoff;
   
           iter->module_name[0] = '\0';
           iter->value = kallsyms_addresses[iter->pos];
   
           iter->type = kallsyms_get_symbol_type(off);
   
           off = kallsyms_expand_symbol(off, iter->name);
   
           return off - iter->nameoff;
   }
   
   static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
   {
           iter->name[0] = '\0';
           iter->nameoff = get_symbol_offset(new_pos);
           iter->pos = new_pos;
   }
   
   /* Returns false if pos at or past end of file. */
   static int update_iter(struct kallsym_iter *iter, loff_t pos)
   {
           /* Module symbols can be accessed randomly. */
           if (pos >= kallsyms_num_syms) {
                   iter->pos = pos;
                   return get_ksymbol_mod(iter);
           }
   
           /* If we're not on the desired position, reset to new position. */
           if (pos != iter->pos)
                   reset_iter(iter, pos);
   
           iter->nameoff += get_ksymbol_core(iter);
           iter->pos++;
   
           return 1;
   }
   
   static void *s_next(struct seq_file *m, void *p, loff_t *pos)
   {
           (*pos)++;
   
           if (!update_iter(m->private, *pos))
                   return NULL;
           return p;
   }
   
   static void *s_start(struct seq_file *m, loff_t *pos)
   {
           if (!update_iter(m->private, *pos))
                   return NULL;
           return m->private;
   }
   
   static void s_stop(struct seq_file *m, void *p)
   {
   }
   
   static int s_show(struct seq_file *m, void *p)
   {
           struct kallsym_iter *iter = m->private;
   
           /* Some debugging symbols have no name.  Ignore them. */
           if (!iter->name[0])
                   return 0;
   
           if (iter->module_name[0]) {
                   char type;
   
                   /*
                    * Label it "global" if it is exported,
                    * "local" if not exported.
                    */
                   type = iter->exported ? toupper(iter->type) :
                                           tolower(iter->type);
                   seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
                              type, iter->name, iter->module_name);
           } else
                   seq_printf(m, "%pK %c %s\n", (void *)iter->value,
                              iter->type, iter->name);
           return 0;
   }
   
   static const struct seq_operations kallsyms_op = {
           .start = s_start,
           .next = s_next,
           .stop = s_stop,
           .show = s_show
   };
   
   static int kallsyms_open(struct inode *inode, struct file *file)
   {
           /*
            * We keep iterator in m->private, since normal case is to
            * s_start from where we left off, so we avoid doing
            * using get_symbol_offset for every symbol.
            */
           struct kallsym_iter *iter;
           int ret;
   
           iter = kmalloc(sizeof(*iter), GFP_KERNEL);
           if (!iter)
                   return -ENOMEM;
           reset_iter(iter, 0);
   
           ret = seq_open(file, &kallsyms_op);
           if (ret == 0)
                   ((struct seq_file *)file->private_data)->private = iter;
           else
                   kfree(iter);
           return ret;
   }
   
   #ifdef  CONFIG_KGDB_KDB
   const char *kdb_walk_kallsyms(loff_t *pos)
   {
           static struct kallsym_iter kdb_walk_kallsyms_iter;
           if (*pos == 0) {
                   memset(&kdb_walk_kallsyms_iter, 0,
                          sizeof(kdb_walk_kallsyms_iter));
                   reset_iter(&kdb_walk_kallsyms_iter, 0);
           }
           while (1) {
                   if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
                           return NULL;
                   ++*pos;
                   /* Some debugging symbols have no name.  Ignore them. */
                   if (kdb_walk_kallsyms_iter.name[0])
                           return kdb_walk_kallsyms_iter.name;
           }
   }
   #endif  /* CONFIG_KGDB_KDB */
   
   static const struct file_operations kallsyms_operations = {
           .open = kallsyms_open,
           .read = seq_read,
           .llseek = seq_lseek,
           .release = seq_release_private,
   };
   
   static int __init kallsyms_init(void)
   {
           proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
           return 0;
   }
   device_initcall(kallsyms_init);

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