aboutsummaryrefslogtreecommitdiff
path: root/kernel/kallsyms.c
blob: d086c91d44edb8a0c89e95b5b0ebd1ea4005a52d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
/*
 * 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/err.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>	/* for cond_resched */
#include <linux/mm.h>
#include <linux/ctype.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 unsigned long kallsyms_num_syms __attribute__((weak));
extern const u8 kallsyms_names[] __attribute__((weak));

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_extratext(unsigned long addr)
{
	if (addr >= (unsigned long)_sextratext
	    && addr <= (unsigned long)_eextratext)
		return 1;
	return 0;
}

static inline int is_kernel_text(unsigned long addr)
{
	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
		return 1;
	return in_gate_area_no_task(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_task(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) ||
		is_kernel_extratext(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
 * begining 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+1];
	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);
}

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) / 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;
	}

	*symbolsize = symbol_end - symbol_start;
	*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)
{
	if (is_ksym_addr(addr))
		return !!get_symbol_pos(addr, symbolsize, offset);

	return !!module_address_lookup(addr, symbolsize, offset, NULL);
}

/*
 * 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)
{
	const char *msym;

	namebuf[KSYM_NAME_LEN] = 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);
		*modname = NULL;
		return namebuf;
	}

	/* see if it's in a module */
	msym = module_address_lookup(addr, symbolsize, offset, modname);
	if (msym)
		return strncpy(namebuf, msym, KSYM_NAME_LEN);

	return NULL;
}

/* Look up a kernel symbol and return it in a text buffer. */
int sprint_symbol(char *buffer, unsigned long address)
{
	char *modname;
	const char *name;
	unsigned long offset, size;
	char namebuf[KSYM_NAME_LEN+1];

	name = kallsyms_lookup(address, &size, &offset, &modname, namebuf);
	if (!name)
		return sprintf(buffer, "0x%lx", address);
	else {
		if (modname)
			return sprintf(buffer, "%s+%#lx/%#lx [%s]", name, offset,
				size, modname);
		else
			return sprintf(buffer, "%s+%#lx/%#lx", name, offset, size);
	}
}

/* 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);
}

/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
struct kallsym_iter
{
	loff_t pos;
	struct module *owner;
	unsigned long value;
	unsigned int nameoff; /* If iterating in core kernel symbols */
	char type;
	char name[KSYM_NAME_LEN+1];
};

static int get_ksymbol_mod(struct kallsym_iter *iter)
{
	iter->owner = module_get_kallsym(iter->pos - kallsyms_num_syms,
					 &iter->value, &iter->type,
					 iter->name);
	if (iter->owner == NULL)
		return 0;

	/* Label it "global" if it is exported, "local" if not exported. */
	iter->type = is_exported(iter->name, iter->owner)
		? toupper(iter->type) : tolower(iter->type);

	return 1;
}

/* Returns space to next name. */
static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
{
	unsigned off = iter->nameoff;

	iter->owner = NULL;
	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->owner)
		seq_printf(m, "%0*lx %c %s\t[%s]\n",
			   (int)(2*sizeof(void*)),
			   iter->value, iter->type, iter->name,
			   module_name(iter->owner));
	else
		seq_printf(m, "%0*lx %c %s\n",
			   (int)(2*sizeof(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;
}

static int kallsyms_release(struct inode *inode, struct file *file)
{
	struct seq_file *m = (struct seq_file *)file->private_data;
	kfree(m->private);
	return seq_release(inode, file);
}

static const struct file_operations kallsyms_operations = {
	.open = kallsyms_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = kallsyms_release,
};

static int __init kallsyms_init(void)
{
	struct proc_dir_entry *entry;

	entry = create_proc_entry("kallsyms", 0444, NULL);
	if (entry)
		entry->proc_fops = &kallsyms_operations;
	return 0;
}
__initcall(kallsyms_init);

EXPORT_SYMBOL(__print_symbol);
EXPORT_SYMBOL_GPL(sprint_symbol);