Root/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 *
8 * ChangeLog:
9 *
10 * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
11 * Changed the compression method from stem compression to "table lookup"
12 * compression (see scripts/kallsyms.c for a more complete description)
13 */
14#include <linux/kallsyms.h>
15#include <linux/module.h>
16#include <linux/init.h>
17#include <linux/seq_file.h>
18#include <linux/fs.h>
19#include <linux/kdb.h>
20#include <linux/err.h>
21#include <linux/proc_fs.h>
22#include <linux/sched.h> /* for cond_resched */
23#include <linux/mm.h>
24#include <linux/ctype.h>
25#include <linux/slab.h>
26
27#include <asm/sections.h>
28
29#ifdef CONFIG_KALLSYMS_ALL
30#define all_var 1
31#else
32#define all_var 0
33#endif
34
35/*
36 * These will be re-linked against their real values
37 * during the second link stage.
38 */
39extern const unsigned long kallsyms_addresses[] __attribute__((weak));
40extern const u8 kallsyms_names[] __attribute__((weak));
41
42/*
43 * Tell the compiler that the count isn't in the small data section if the arch
44 * has one (eg: FRV).
45 */
46extern const unsigned long kallsyms_num_syms
47__attribute__((weak, section(".rodata")));
48
49extern const u8 kallsyms_token_table[] __attribute__((weak));
50extern const u16 kallsyms_token_index[] __attribute__((weak));
51
52extern const unsigned long kallsyms_markers[] __attribute__((weak));
53
54static inline int is_kernel_inittext(unsigned long addr)
55{
56    if (addr >= (unsigned long)_sinittext
57        && addr <= (unsigned long)_einittext)
58        return 1;
59    return 0;
60}
61
62static inline int is_kernel_text(unsigned long addr)
63{
64    if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
65        arch_is_kernel_text(addr))
66        return 1;
67    return in_gate_area_no_mm(addr);
68}
69
70static inline int is_kernel(unsigned long addr)
71{
72    if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
73        return 1;
74    return in_gate_area_no_mm(addr);
75}
76
77static int is_ksym_addr(unsigned long addr)
78{
79    if (all_var)
80        return is_kernel(addr);
81
82    return is_kernel_text(addr) || is_kernel_inittext(addr);
83}
84
85/*
86 * Expand a compressed symbol data into the resulting uncompressed string,
87 * given the offset to where the symbol is in the compressed stream.
88 */
89static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
90{
91    int len, skipped_first = 0;
92    const u8 *tptr, *data;
93
94    /* Get the compressed symbol length from the first symbol byte. */
95    data = &kallsyms_names[off];
96    len = *data;
97    data++;
98
99    /*
100     * Update the offset to return the offset for the next symbol on
101     * the compressed stream.
102     */
103    off += len + 1;
104
105    /*
106     * For every byte on the compressed symbol data, copy the table
107     * entry for that byte.
108     */
109    while (len) {
110        tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
111        data++;
112        len--;
113
114        while (*tptr) {
115            if (skipped_first) {
116                *result = *tptr;
117                result++;
118            } else
119                skipped_first = 1;
120            tptr++;
121        }
122    }
123
124    *result = '\0';
125
126    /* Return to offset to the next symbol. */
127    return off;
128}
129
130/*
131 * Get symbol type information. This is encoded as a single char at the
132 * beginning of the symbol name.
133 */
134static char kallsyms_get_symbol_type(unsigned int off)
135{
136    /*
137     * Get just the first code, look it up in the token table,
138     * and return the first char from this token.
139     */
140    return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
141}
142
143
144/*
145 * Find the offset on the compressed stream given and index in the
146 * kallsyms array.
147 */
148static unsigned int get_symbol_offset(unsigned long pos)
149{
150    const u8 *name;
151    int i;
152
153    /*
154     * Use the closest marker we have. We have markers every 256 positions,
155     * so that should be close enough.
156     */
157    name = &kallsyms_names[kallsyms_markers[pos >> 8]];
158
159    /*
160     * Sequentially scan all the symbols up to the point we're searching
161     * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
162     * so we just need to add the len to the current pointer for every
163     * symbol we wish to skip.
164     */
165    for (i = 0; i < (pos & 0xFF); i++)
166        name = name + (*name) + 1;
167
168    return name - kallsyms_names;
169}
170
171/* Lookup the address for this symbol. Returns 0 if not found. */
172unsigned long kallsyms_lookup_name(const char *name)
173{
174    char namebuf[KSYM_NAME_LEN];
175    unsigned long i;
176    unsigned int off;
177
178    for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
179        off = kallsyms_expand_symbol(off, namebuf);
180
181        if (strcmp(namebuf, name) == 0)
182            return kallsyms_addresses[i];
183    }
184    return module_kallsyms_lookup_name(name);
185}
186EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
187
188int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
189                      unsigned long),
190                void *data)
191{
192    char namebuf[KSYM_NAME_LEN];
193    unsigned long i;
194    unsigned int off;
195    int ret;
196
197    for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
198        off = kallsyms_expand_symbol(off, namebuf);
199        ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
200        if (ret != 0)
201            return ret;
202    }
203    return module_kallsyms_on_each_symbol(fn, data);
204}
205EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
206
207static unsigned long get_symbol_pos(unsigned long addr,
208                    unsigned long *symbolsize,
209                    unsigned long *offset)
210{
211    unsigned long symbol_start = 0, symbol_end = 0;
212    unsigned long i, low, high, mid;
213
214    /* This kernel should never had been booted. */
215    BUG_ON(!kallsyms_addresses);
216
217    /* Do a binary search on the sorted kallsyms_addresses array. */
218    low = 0;
219    high = kallsyms_num_syms;
220
221    while (high - low > 1) {
222        mid = low + (high - low) / 2;
223        if (kallsyms_addresses[mid] <= addr)
224            low = mid;
225        else
226            high = mid;
227    }
228
229    /*
230     * Search for the first aliased symbol. Aliased
231     * symbols are symbols with the same address.
232     */
233    while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
234        --low;
235
236    symbol_start = kallsyms_addresses[low];
237
238    /* Search for next non-aliased symbol. */
239    for (i = low + 1; i < kallsyms_num_syms; i++) {
240        if (kallsyms_addresses[i] > symbol_start) {
241            symbol_end = kallsyms_addresses[i];
242            break;
243        }
244    }
245
246    /* If we found no next symbol, we use the end of the section. */
247    if (!symbol_end) {
248        if (is_kernel_inittext(addr))
249            symbol_end = (unsigned long)_einittext;
250        else if (all_var)
251            symbol_end = (unsigned long)_end;
252        else
253            symbol_end = (unsigned long)_etext;
254    }
255
256    if (symbolsize)
257        *symbolsize = symbol_end - symbol_start;
258    if (offset)
259        *offset = addr - symbol_start;
260
261    return low;
262}
263
264/*
265 * Lookup an address but don't bother to find any names.
266 */
267int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
268                unsigned long *offset)
269{
270    char namebuf[KSYM_NAME_LEN];
271    if (is_ksym_addr(addr))
272        return !!get_symbol_pos(addr, symbolsize, offset);
273
274    return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
275}
276
277/*
278 * Lookup an address
279 * - modname is set to NULL if it's in the kernel.
280 * - We guarantee that the returned name is valid until we reschedule even if.
281 * It resides in a module.
282 * - We also guarantee that modname will be valid until rescheduled.
283 */
284const char *kallsyms_lookup(unsigned long addr,
285                unsigned long *symbolsize,
286                unsigned long *offset,
287                char **modname, char *namebuf)
288{
289    namebuf[KSYM_NAME_LEN - 1] = 0;
290    namebuf[0] = 0;
291
292    if (is_ksym_addr(addr)) {
293        unsigned long pos;
294
295        pos = get_symbol_pos(addr, symbolsize, offset);
296        /* Grab name */
297        kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
298        if (modname)
299            *modname = NULL;
300        return namebuf;
301    }
302
303    /* See if it's in a module. */
304    return module_address_lookup(addr, symbolsize, offset, modname,
305                     namebuf);
306}
307
308int lookup_symbol_name(unsigned long addr, char *symname)
309{
310    symname[0] = '\0';
311    symname[KSYM_NAME_LEN - 1] = '\0';
312
313    if (is_ksym_addr(addr)) {
314        unsigned long pos;
315
316        pos = get_symbol_pos(addr, NULL, NULL);
317        /* Grab name */
318        kallsyms_expand_symbol(get_symbol_offset(pos), symname);
319        return 0;
320    }
321    /* See if it's in a module. */
322    return lookup_module_symbol_name(addr, symname);
323}
324
325int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
326            unsigned long *offset, char *modname, char *name)
327{
328    name[0] = '\0';
329    name[KSYM_NAME_LEN - 1] = '\0';
330
331    if (is_ksym_addr(addr)) {
332        unsigned long pos;
333
334        pos = get_symbol_pos(addr, size, offset);
335        /* Grab name */
336        kallsyms_expand_symbol(get_symbol_offset(pos), name);
337        modname[0] = '\0';
338        return 0;
339    }
340    /* See if it's in a module. */
341    return lookup_module_symbol_attrs(addr, size, offset, modname, name);
342}
343
344/* Look up a kernel symbol and return it in a text buffer. */
345static int __sprint_symbol(char *buffer, unsigned long address,
346               int symbol_offset)
347{
348    char *modname;
349    const char *name;
350    unsigned long offset, size;
351    int len;
352
353    address += symbol_offset;
354    name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
355    if (!name)
356        return sprintf(buffer, "0x%lx", address);
357
358    if (name != buffer)
359        strcpy(buffer, name);
360    len = strlen(buffer);
361    buffer += len;
362    offset -= symbol_offset;
363
364    if (modname)
365        len += sprintf(buffer, "+%#lx/%#lx [%s]", offset, size, modname);
366    else
367        len += sprintf(buffer, "+%#lx/%#lx", offset, size);
368
369    return len;
370}
371
372/**
373 * sprint_symbol - Look up a kernel symbol and return it in a text buffer
374 * @buffer: buffer to be stored
375 * @address: address to lookup
376 *
377 * This function looks up a kernel symbol with @address and stores its name,
378 * offset, size and module name to @buffer if possible. If no symbol was found,
379 * just saves its @address as is.
380 *
381 * This function returns the number of bytes stored in @buffer.
382 */
383int sprint_symbol(char *buffer, unsigned long address)
384{
385    return __sprint_symbol(buffer, address, 0);
386}
387
388EXPORT_SYMBOL_GPL(sprint_symbol);
389
390/**
391 * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
392 * @buffer: buffer to be stored
393 * @address: address to lookup
394 *
395 * This function is for stack backtrace and does the same thing as
396 * sprint_symbol() but with modified/decreased @address. If there is a
397 * tail-call to the function marked "noreturn", gcc optimized out code after
398 * the call so that the stack-saved return address could point outside of the
399 * caller. This function ensures that kallsyms will find the original caller
400 * by decreasing @address.
401 *
402 * This function returns the number of bytes stored in @buffer.
403 */
404int sprint_backtrace(char *buffer, unsigned long address)
405{
406    return __sprint_symbol(buffer, address, -1);
407}
408
409/* Look up a kernel symbol and print it to the kernel messages. */
410void __print_symbol(const char *fmt, unsigned long address)
411{
412    char buffer[KSYM_SYMBOL_LEN];
413
414    sprint_symbol(buffer, address);
415
416    printk(fmt, buffer);
417}
418EXPORT_SYMBOL(__print_symbol);
419
420/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
421struct kallsym_iter {
422    loff_t pos;
423    unsigned long value;
424    unsigned int nameoff; /* If iterating in core kernel symbols. */
425    char type;
426    char name[KSYM_NAME_LEN];
427    char module_name[MODULE_NAME_LEN];
428    int exported;
429};
430
431static int get_ksymbol_mod(struct kallsym_iter *iter)
432{
433    if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
434                &iter->type, iter->name, iter->module_name,
435                &iter->exported) < 0)
436        return 0;
437    return 1;
438}
439
440/* Returns space to next name. */
441static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
442{
443    unsigned off = iter->nameoff;
444
445    iter->module_name[0] = '\0';
446    iter->value = kallsyms_addresses[iter->pos];
447
448    iter->type = kallsyms_get_symbol_type(off);
449
450    off = kallsyms_expand_symbol(off, iter->name);
451
452    return off - iter->nameoff;
453}
454
455static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
456{
457    iter->name[0] = '\0';
458    iter->nameoff = get_symbol_offset(new_pos);
459    iter->pos = new_pos;
460}
461
462/* Returns false if pos at or past end of file. */
463static int update_iter(struct kallsym_iter *iter, loff_t pos)
464{
465    /* Module symbols can be accessed randomly. */
466    if (pos >= kallsyms_num_syms) {
467        iter->pos = pos;
468        return get_ksymbol_mod(iter);
469    }
470
471    /* If we're not on the desired position, reset to new position. */
472    if (pos != iter->pos)
473        reset_iter(iter, pos);
474
475    iter->nameoff += get_ksymbol_core(iter);
476    iter->pos++;
477
478    return 1;
479}
480
481static void *s_next(struct seq_file *m, void *p, loff_t *pos)
482{
483    (*pos)++;
484
485    if (!update_iter(m->private, *pos))
486        return NULL;
487    return p;
488}
489
490static void *s_start(struct seq_file *m, loff_t *pos)
491{
492    if (!update_iter(m->private, *pos))
493        return NULL;
494    return m->private;
495}
496
497static void s_stop(struct seq_file *m, void *p)
498{
499}
500
501static int s_show(struct seq_file *m, void *p)
502{
503    struct kallsym_iter *iter = m->private;
504
505    /* Some debugging symbols have no name. Ignore them. */
506    if (!iter->name[0])
507        return 0;
508
509    if (iter->module_name[0]) {
510        char type;
511
512        /*
513         * Label it "global" if it is exported,
514         * "local" if not exported.
515         */
516        type = iter->exported ? toupper(iter->type) :
517                    tolower(iter->type);
518        seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
519               type, iter->name, iter->module_name);
520    } else
521        seq_printf(m, "%pK %c %s\n", (void *)iter->value,
522               iter->type, iter->name);
523    return 0;
524}
525
526static const struct seq_operations kallsyms_op = {
527    .start = s_start,
528    .next = s_next,
529    .stop = s_stop,
530    .show = s_show
531};
532
533static int kallsyms_open(struct inode *inode, struct file *file)
534{
535    /*
536     * We keep iterator in m->private, since normal case is to
537     * s_start from where we left off, so we avoid doing
538     * using get_symbol_offset for every symbol.
539     */
540    struct kallsym_iter *iter;
541    int ret;
542
543    iter = kmalloc(sizeof(*iter), GFP_KERNEL);
544    if (!iter)
545        return -ENOMEM;
546    reset_iter(iter, 0);
547
548    ret = seq_open(file, &kallsyms_op);
549    if (ret == 0)
550        ((struct seq_file *)file->private_data)->private = iter;
551    else
552        kfree(iter);
553    return ret;
554}
555
556#ifdef CONFIG_KGDB_KDB
557const char *kdb_walk_kallsyms(loff_t *pos)
558{
559    static struct kallsym_iter kdb_walk_kallsyms_iter;
560    if (*pos == 0) {
561        memset(&kdb_walk_kallsyms_iter, 0,
562               sizeof(kdb_walk_kallsyms_iter));
563        reset_iter(&kdb_walk_kallsyms_iter, 0);
564    }
565    while (1) {
566        if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
567            return NULL;
568        ++*pos;
569        /* Some debugging symbols have no name. Ignore them. */
570        if (kdb_walk_kallsyms_iter.name[0])
571            return kdb_walk_kallsyms_iter.name;
572    }
573}
574#endif /* CONFIG_KGDB_KDB */
575
576static const struct file_operations kallsyms_operations = {
577    .open = kallsyms_open,
578    .read = seq_read,
579    .llseek = seq_lseek,
580    .release = seq_release_private,
581};
582
583static int __init kallsyms_init(void)
584{
585    proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
586    return 0;
587}
588device_initcall(kallsyms_init);
589

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