kernel/kallsyms.c

   1 /*
   2  * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
   3  *
   4  * Rewritten and vastly simplified by Rusty Russell for in-kernel
   5  * module loader:
   6  *   Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
   7  * Stem compression by Andi Kleen.
   8  */
   9 #include <linux/kallsyms.h>
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/seq_file.h>
  13 #include <linux/fs.h>
  14 #include <linux/err.h>
  15 #include <linux/proc_fs.h>
  16
  17 /* These will be re-linked against their real values during the second link stage */
  18 extern unsigned long kallsyms_addresses[] __attribute__((weak));
  19 extern unsigned long kallsyms_num_syms __attribute__((weak));
  20 extern char kallsyms_names[] __attribute__((weak));
  21
  22 /* Defined by the linker script. */
  23 extern char _stext[], _etext[], _sinittext[], _einittext[];
  24
  25 static inline int is_kernel_inittext(unsigned long addr)
  26 {
  27         if (addr >= (unsigned long)_sinittext
  28             && addr <= (unsigned long)_einittext)
  29                 return 1;
  30         return 0;
  31 }
  32
  33 static inline int is_kernel_text(unsigned long addr)
  34 {
  35         if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
  36                 return 1;
  37         return 0;
  38 }
  39
  40 /* Lookup the address for this symbol. Returns 0 if not found. */
  41 unsigned long kallsyms_lookup_name(const char *name)
  42 {
  43         char namebuf[KSYM_NAME_LEN+1];
  44         unsigned long i;
  45         char *knames;
  46
  47         for (i = 0, knames = kallsyms_names; i < kallsyms_num_syms; i++) {
  48                 unsigned prefix = *knames++;
  49
  50                 strlcpy(namebuf + prefix, knames, KSYM_NAME_LEN - prefix);
  51                 if (strcmp(namebuf, name) == 0)
  52                         return kallsyms_addresses[i];
  53
  54                 knames += strlen(knames) + 1;
  55         }
  56         return module_kallsyms_lookup_name(name);
  57 }
  58
  59 /* Lookup an address.  modname is set to NULL if it's in the kernel. */
  60 const char *kallsyms_lookup(unsigned long addr,
  61                             unsigned long *symbolsize,
  62                             unsigned long *offset,
  63                             char **modname, char *namebuf)
  64 {
  65         unsigned long i, best = 0;
  66
  67         /* This kernel should never had been booted. */
  68         BUG_ON(!kallsyms_addresses);
  69
  70         namebuf[KSYM_NAME_LEN] = 0;
  71         namebuf[0] = 0;
  72
  73         if (is_kernel_text(addr) || is_kernel_inittext(addr)) {
  74                 unsigned long symbol_end;
  75                 char *name = kallsyms_names;
  76
  77                 /* They're sorted, we could be clever here, but who cares? */
  78                 for (i = 0; i < kallsyms_num_syms; i++) {
  79                         if (kallsyms_addresses[i] > kallsyms_addresses[best] &&
  80                             kallsyms_addresses[i] <= addr)
  81                                 best = i;
  82                 }
  83
  84                 /* Grab name */
  85                 for (i = 0; i <= best; i++) {
  86                         unsigned prefix = *name++;
  87                         strncpy(namebuf + prefix, name, KSYM_NAME_LEN - prefix);
  88                         name += strlen(name) + 1;
  89                 }
  90
  91                 /* At worst, symbol ends at end of section. */
  92                 if (is_kernel_inittext(addr))
  93                         symbol_end = (unsigned long)_einittext;
  94                 else
  95                         symbol_end = (unsigned long)_etext;
  96
  97                 /* Search for next non-aliased symbol */
  98                 for (i = best+1; i < kallsyms_num_syms; i++) {
  99                         if (kallsyms_addresses[i] > kallsyms_addresses[best]) {
 100                                 symbol_end = kallsyms_addresses[i];
 101                                 break;
 102                         }
 103                 }
 104
 105                 *symbolsize = symbol_end - kallsyms_addresses[best];
 106                 *modname = NULL;
 107                 *offset = addr - kallsyms_addresses[best];
 108                 return namebuf;
 109         }
 110
 111         return module_address_lookup(addr, symbolsize, offset, modname);
 112 }
 113
 114 /* Replace "%s" in format with address, or returns -errno. */
 115 void __print_symbol(const char *fmt, unsigned long address)
 116 {
 117         char *modname;
 118         const char *name;
 119         unsigned long offset, size;
 120         char namebuf[KSYM_NAME_LEN+1];
 121         char buffer[sizeof("%s+%#lx/%#lx [%s]") + KSYM_NAME_LEN +
 122                     2*(BITS_PER_LONG*3/10) + MODULE_NAME_LEN + 1];
 123
 124         name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
 125
 126         if (!name)
 127                 sprintf(buffer, "0x%lx", address);
 128         else {
 129                 if (modname)
 130                         sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
 131                                 size, modname);
 132                 else
 133                         sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
 134         }
 135         printk(fmt, buffer);
 136 }
 137
 138 /* To avoid O(n^2) iteration, we carry prefix along. */
 139 struct kallsym_iter
 140 {
 141         loff_t pos;
 142         struct module *owner;
 143         unsigned long value;
 144         unsigned int nameoff; /* If iterating in core kernel symbols */
 145         char type;
 146         char name[KSYM_NAME_LEN+1];
 147 };
 148
 149 /* Only label it "global" if it is exported. */
 150 static void upcase_if_global(struct kallsym_iter *iter)
 151 {
 152         if (is_exported(iter->name, iter->owner))
 153                 iter->type += 'A' - 'a';
 154 }
 155
 156 static int get_ksymbol_mod(struct kallsym_iter *iter)
 157 {
 158         iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
 159                                          &iter->value,
 160                                          &iter->type, iter->name);
 161         if (iter->owner == NULL)
 162                 return 0;
 163
 164         upcase_if_global(iter);
 165         return 1;
 166 }
 167
 168 /* Returns space to next name. */
 169 static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
 170 {
 171         unsigned stemlen, off = iter->nameoff;
 172
 173         /* First char of each symbol name indicates prefix length
 174            shared with previous name (stem compression). */
 175         stemlen = kallsyms_names[off++];
 176
 177         strlcpy(iter->name+stemlen, kallsyms_names + off,
 178                 KSYM_NAME_LEN+1-stemlen);
 179         off += strlen(kallsyms_names + off) + 1;
 180         iter->owner = NULL;
 181         iter->value = kallsyms_addresses[iter->pos];
 182         if (is_kernel_text(iter->value) || is_kernel_inittext(iter->value))
 183                 iter->type = 't';
 184         else
 185                 iter->type = 'd';
 186
 187         upcase_if_global(iter);
 188         return off - iter->nameoff;
 189 }
 190
 191 static void reset_iter(struct kallsym_iter *iter)
 192 {
 193         iter->name[0] = '\0';
 194         iter->nameoff = 0;
 195         iter->pos = 0;
 196 }
 197
 198 /* Returns false if pos at or past end of file. */
 199 static int update_iter(struct kallsym_iter *iter, loff_t pos)
 200 {
 201         /* Module symbols can be accessed randomly. */
 202         if (pos >= kallsyms_num_syms) {
 203                 iter->pos = pos;
 204                 return get_ksymbol_mod(iter);
 205         }
 206
 207         /* If we're past the desired position, reset to start. */
 208         if (pos < iter->pos)
 209                 reset_iter(iter);
 210
 211         /* We need to iterate through the previous symbols: can be slow */
 212         for (; iter->pos != pos; iter->pos++) {
 213                 iter->nameoff += get_ksymbol_core(iter);
 214                 cond_resched();
 215         }
 216         get_ksymbol_core(iter);
 217         return 1;
 218 }
 219
 220 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 221 {
 222         (*pos)++;
 223
 224         if (!update_iter(m->private, *pos))
 225                 return NULL;
 226         return p;
 227 }
 228
 229 static void *s_start(struct seq_file *m, loff_t *pos)
 230 {
 231         if (!update_iter(m->private, *pos))
 232                 return NULL;
 233         return m->private;
 234 }
 235
 236 static void s_stop(struct seq_file *m, void *p)
 237 {
 238 }
 239
 240 static int s_show(struct seq_file *m, void *p)
 241 {
 242         struct kallsym_iter *iter = m->private;
 243
 244         /* Some debugging symbols have no name.  Ignore them. */
 245         if (!iter->name[0])
 246                 return 0;
 247
 248         if (iter->owner)
 249                 seq_printf(m, "%0*lx %c %s\t[%s]\n",
 250                            (int)(2*sizeof(void*)),
 251                            iter->value, iter->type, iter->name,
 252                            module_name(iter->owner));
 253         else
 254                 seq_printf(m, "%0*lx %c %s\n",
 255                            (int)(2*sizeof(void*)),
 256                            iter->value, iter->type, iter->name);
 257         return 0;
 258 }
 259
 260 struct seq_operations kallsyms_op = {
 261         .start = s_start,
 262         .next = s_next,
 263         .stop = s_stop,
 264         .show = s_show
 265 };
 266
 267 static int kallsyms_open(struct inode *inode, struct file *file)
 268 {
 269         /* We keep iterator in m->private, since normal case is to
 270          * s_start from where we left off, so we avoid O(N^2). */
 271         struct kallsym_iter *iter;
 272         int ret;
 273
 274         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 275         if (!iter)
 276                 return -ENOMEM;
 277         reset_iter(iter);
 278
 279         ret = seq_open(file, &kallsyms_op);
 280         if (ret == 0)
 281                 ((struct seq_file *)file->private_data)->private = iter;
 282         else
 283                 kfree(iter);
 284         return ret;
 285 }
 286
 287 static int kallsyms_release(struct inode *inode, struct file *file)
 288 {
 289         struct seq_file *m = (struct seq_file *)file->private_data;
 290         kfree(m->private);
 291         return seq_release(inode, file);
 292 }
 293
 294 static struct file_operations kallsyms_operations = {
 295         .open = kallsyms_open,
 296         .read = seq_read,
 297         .llseek = seq_lseek,
 298         .release = kallsyms_release,
 299 };
 300
 301 int __init kallsyms_init(void)
 302 {
 303         struct proc_dir_entry *entry;
 304
 305         entry = create_proc_entry("kallsyms", 0444, NULL);
 306         if (entry)
 307                 entry->proc_fops = &kallsyms_operations;
 308         return 0;
 309 }
 310 __initcall(kallsyms_init);
 311
 312 EXPORT_SYMBOL(__print_symbol);