summaryrefslogtreecommitdiffstats
path: root/ksym_mod.c
blob: d84140e057511dec5a039fd90243d8e8774a2918 (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
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
#include "config.h"

#ifdef FEATURE_KLOGD
/*
    ksym_mod.c - functions for building symbol lookup tables for klogd
    Copyright (c) 1995, 1996  Dr. G.W. Wettstein <greg@wind.rmcc.com>
    Copyright (c) 1996 Enjellic Systems Development

    This file is part of the sysklogd package, a kernel and system log daemon.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
 * This file implements functions which are useful for building
 * a symbol lookup table based on the in kernel symbol table
 * maintained by the Linux kernel.
 *
 * Proper logging of kernel panics generated by loadable modules
 * tends to be difficult.  Since the modules are loaded dynamically
 * their addresses are not known at kernel load time.  A general
 * protection fault (Oops) cannot be properly deciphered with 
 * classic methods using the static symbol map produced at link time.
 *
 * One solution to this problem is to have klogd attempt to translate
 * addresses from module when the fault occurs.  By referencing the
 * the kernel symbol table proper resolution of these symbols is made
 * possible.
 *
 * At least that is the plan.
 *
 * Wed Aug 21 09:20:09 CDT 1996:  Dr. Wettstein
 *	The situation where no module support has been compiled into a
 *	kernel is now detected.  An informative message is output indicating
 *	that the kernel has no loadable module support whenever kernel
 *	module symbols are loaded.
 *
 *	An informative message is printed indicating the number of kernel
 *	modules and the number of symbols loaded from these modules.
 *
 * Sun Jun 15 16:23:29 MET DST 1997: Michael Alan Dorman
 *	Some more glibc patches made by <mdorman@debian.org>.
 *
 * Sat Jan 10 15:00:18 CET 1998: Martin Schulze <joey@infodrom.north.de>
 *	Fixed problem with klogd not being able to be built on a kernel
 *	newer than 2.1.18.  It was caused by modified structures
 *	inside the kernel that were included.  I have worked in a
 *	patch from Alessandro Suardi <asuardi@uninetcom.it>.
 *
 * Sun Jan 25 20:57:34 CET 1998: Martin Schulze <joey@infodrom.north.de>
 *	Another patch for Linux/alpha by Christopher C Chimelis
 *	<chris@classnet.med.miami.edu>.
 *
 * Thu Mar 19 23:39:29 CET 1998: Manuel Rodrigues <pmanuel@cindy.fe.up.pt>
 *	Changed lseek() to llseek() in order to support > 2GB address
 *	space which provided by kernels > 2.1.70.
 *
 * Mon Apr 13 18:18:45 CEST 1998: Martin Schulze <joey@infodrom.north.de>
 *	Removed <sys/module.h> as it's no longer part of recent glibc
 *	versions.  Added prototyp for llseek() which has been
 *	forgotton in <unistd.h> from glibc.  Added more log
 *	information if problems occurred while reading a system map
 *	file, by submission from Mark Simon Phillips <M.S.Phillips@nortel.co.uk>.
 *
 * Sun Jan  3 18:38:03 CET 1999: Martin Schulze <joey@infodrom.north.de>
 *	Corrected return value of AddModule if /dev/kmem can't be
 *	loaded.  This will prevent klogd from segfaulting if /dev/kmem
 *	is not available.  Patch from Topi Miettinen <tom@medialab.sonera.net>.
 *
 * Tue Sep 12 23:11:13 CEST 2000: Martin Schulze <joey@infodrom.ffis.de>
 *	Changed llseek() to lseek64() in order to skip a libc warning.
 */


/* Includes. */
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#if !defined(__GLIBC__)
#include <linux/time.h>
#include <linux/module.h>
#else /* __GLIBC__ */
#include "module.h"
extern __off64_t lseek64 __P ((int __fd, __off64_t __offset, int __whence));
extern int get_kernel_syms __P ((struct kernel_sym *__table));
#endif /* __GLIBC__ */
#include <stdarg.h>
#include <paths.h>
#include <linux/version.h>

#include "klogd.h"
#include "ksyms.h"


#if !defined(__GLIBC__)
/*
 * The following bit uses some kernel/library magic to product what
 * looks like a function call to user level code.  This function is
 * actually a system call in disguise.  The purpose of the getsyms
 * call is to return a current copy of the in-kernel symbol table.
 */
#define __LIBRARY__
#include <linux/unistd.h>
#define __NR_getsyms __NR_get_kernel_syms
_syscall1(int, getsyms, struct kernel_sym *, syms);
#undef __LIBRARY__
extern int getsyms(struct kernel_sym *);
#else /* __GLIBC__ */
#define getsyms get_kernel_syms
#endif /* __GLIBC__ */

/* Variables static to this module. */
struct sym_table
{
	unsigned long value;
	char *name;
};

struct Module
{
	struct sym_table *sym_array;
	int num_syms;

	char *name;
	struct module module;
#if LINUX_VERSION_CODE >= 0x20112
	struct module_info module_info;
#endif
};

static int num_modules = 0;
struct Module *sym_array_modules = (struct Module *) 0;

static int have_modules = 0;

#if defined(TEST)
static int debugging = 1;
#else
extern int debugging;
#endif


/* Function prototypes. */
static void FreeModules(void);
static int AddSymbol(struct Module *mp, unsigned long, char *);
static int AddModule(unsigned long, char *);
static int symsort(const void *, const void *);


/**************************************************************************
 * Function:	InitMsyms
 *
 * Purpose:	This function is responsible for building a symbol
 *		table which can be used to resolve addresses for
 *		loadable modules.
 *
 * Arguements:	Void
 *
 * Return:	A boolean return value is assumed.
 *
 *		A false value indicates that something went wrong.
 *
 *		True if loading is successful.
 **************************************************************************/

extern int InitMsyms()

{
	auto int	rtn,
			tmp;

	auto struct kernel_sym	*ksym_table,
				*p;


	/* Initialize the kernel module symbol table. */
	FreeModules();


	/*
	 * The system call which returns the kernel symbol table has
	 * essentialy two modes of operation.  Called with a null pointer
	 * the system call returns the number of symbols defined in the
	 * the table.
	 *
	 * The second mode of operation is to pass a valid pointer to
	 * the call which will then load the current symbol table into
	 * the memory provided.
	 *
	 * Returning the symbol table is essentially an all or nothing
	 * proposition so we need to pre-allocate enough memory for the
	 * complete table regardless of how many symbols we need.
	 *
	 * Bummer.
	 */
	if ( (rtn = getsyms((struct kernel_sym *) 0)) < 0 )
	{
		if ( errno == ENOSYS )
			Syslog(LOG_INFO, "No module symbols loaded - "
			       "kernel modules not enabled.\n");
		else
			Syslog(LOG_ERR, "Error loading kernel symbols " \
			       "- %s\n", strerror(errno));
		return(0);
	}
	if ( debugging )
		fprintf(stderr, "Loading kernel module symbols - "
			"Size of table: %d\n", rtn);

	ksym_table = (struct kernel_sym *) malloc(rtn * \
						  sizeof(struct kernel_sym));
	if ( ksym_table == (struct kernel_sym *) 0 )
	{
		Syslog(LOG_WARNING, " Failed memory allocation for kernel " \
		       "symbol table.\n");
		return(0);
	}
	if ( (rtn = getsyms(ksym_table)) < 0 )
	{
		Syslog(LOG_WARNING, "Error reading kernel symbols - %s\n", \
		       strerror(errno));
		return(0);
	}


	/*
	 * Build a symbol table compatible with the other one used by
	 * klogd.
	 */
	tmp = rtn;
	p = ksym_table;
	while ( tmp-- )
	{
 		if ( !AddModule(p->value, p->name) )
		{
			Syslog(LOG_WARNING, "Error adding kernel module table "
				"entry.\n");
			free(ksym_table);
			return(0);
		}
		++p;
	}

	/* Sort the symbol tables in each module. */
	for (rtn = tmp= 0; tmp < num_modules; ++tmp)
	{
		rtn += sym_array_modules[tmp].num_syms;
		if ( sym_array_modules[tmp].num_syms < 2 )
			continue;
		qsort(sym_array_modules[tmp].sym_array, \
		      sym_array_modules[tmp].num_syms, \
		      sizeof(struct sym_table), symsort);
	}

	if ( rtn == 0 )
		Syslog(LOG_INFO, "No module symbols loaded.");
	else
		Syslog(LOG_INFO, "Loaded %d %s from %d module%s", rtn, \
		       (rtn == 1) ? "symbol" : "symbols", \
		       num_modules, (num_modules == 1) ? "." : "s.");
	free(ksym_table);
	return(1);
}


static int symsort(p1, p2)

     const void *p1;

     const void *p2;

{
	auto const struct sym_table	*sym1 = p1,
					*sym2 = p2;

	if ( sym1->value < sym2->value )
		return(-1);
	if ( sym1->value == sym2->value )
		return(0);
	return(1);
}


/**************************************************************************
 * Function:	FreeModules
 *
 * Purpose:	This function is used to free all memory which has been
 *		allocated for the modules and their symbols.
 *
 * Arguements:	None specified.
 *
 * Return:	void
 **************************************************************************/

static void FreeModules()

{
	auto int	nmods,
			nsyms;

	auto struct Module *mp;


	/* Check to see if the module symbol tables need to be cleared. */
	have_modules = 0;
	if ( num_modules == 0 )
		return;


	for (nmods= 0; nmods < num_modules; ++nmods)
	{
		mp = &sym_array_modules[nmods];
		if ( mp->num_syms == 0 )
			continue;
	       
		for (nsyms= 0; nsyms < mp->num_syms; ++nsyms)
			free(mp->sym_array[nsyms].name);
		free(mp->sym_array);
	}

	free(sym_array_modules);
	sym_array_modules = (struct Module *) 0;
	num_modules = 0;
	return;
}


/**************************************************************************
 * Function:	AddModule
 *
 * Purpose:	This function is responsible for adding a module to
 *		the list of currently loaded modules.
 *
 * Arguements:	(unsigned long) address, (char *) symbol
 *
 *		address:->	The address of the module.
 *
 *		symbol:->	The name of the module.
 *
 * Return:	int
 **************************************************************************/

static int AddModule(address, symbol)

     unsigned long address;

     char *symbol;

{
	auto int memfd;

	auto struct Module *mp;


	/* Return if we have loaded the modules. */
	if ( have_modules )
		return(1);

	/*
	 * The following section of code is responsible for determining
	 * whether or not we are done reading the list of modules.
	 */
	if ( symbol[0] == '#' )
	{

		if ( symbol[1] == '\0' )
		{
			/*
			 * A symbol which consists of a # sign only
			 * signifies a a resident kernel segment.  When we
			 * hit one of these we are done reading the
			 * module list.
			 */
			have_modules = 1;
			return(1);
		}
		/* Allocate space for the module. */
		sym_array_modules = (struct Module *) \
			realloc(sym_array_modules, \
				(num_modules+1) * sizeof(struct Module));
		if ( sym_array_modules == (struct Module *) 0 )
		{
			Syslog(LOG_WARNING, "Cannot allocate Module array.\n");
			return(0);
		}
		mp = &sym_array_modules[num_modules];

		if ( (memfd = open("/dev/kmem", O_RDONLY)) < 0 )
		{
			Syslog(LOG_WARNING, "Error opening /dev/kmem\n");
			return(0);
		}
		if ( lseek64(memfd, address, SEEK_SET) < 0 )
		{
			Syslog(LOG_WARNING, "Error seeking in /dev/kmem\n");
			Syslog(LOG_WARNING, "Symbol %s, value %08x\n", symbol, address);
			return(0);
		}
		if ( read(memfd, \
			  (char *)&sym_array_modules[num_modules].module,  \
			  sizeof(struct module)) < 0 )
		{
			Syslog(LOG_WARNING, "Error reading module "
			       "descriptor.\n");
			return(0);
		}
		close(memfd);

		/* Save the module name. */
		mp->name = (char *) malloc(strlen(&symbol[1]) + 1);
		if ( mp->name == (char *) 0 )
			return(0);
		strcpy(mp->name, &symbol[1]);

		mp->num_syms = 0;
		mp->sym_array = (struct sym_table *) 0;
		++num_modules;
		return(1);
	}
	else
	{
	    if (num_modules > 0)
		mp = &sym_array_modules[num_modules - 1];
	    else
		mp = &sym_array_modules[0];
		AddSymbol(mp, address, symbol);
	}


	return(1);
}


/**************************************************************************
 * Function:	AddSymbol
 *
 * Purpose:	This function is responsible for adding a symbol name
 *		and its address to the symbol table.
 *
 * Arguements:	(struct Module *) mp, (unsigned long) address, (char *) symbol
 *
 *		mp:->	A pointer to the module which the symbol is
 *			to be added to.
 *
 *		address:->	The address of the symbol.
 *
 *		symbol:->	The name of the symbol.
 *
 * Return:	int
 *
 *		A boolean value is assumed.  True if the addition is
 *		successful.  False if not.
 **************************************************************************/

static int AddSymbol(mp, address, symbol)

	struct Module *mp;     

	unsigned long address;
	
	char *symbol;
	
{
	auto int tmp;


	/* Allocate space for the symbol table entry. */
	mp->sym_array = (struct sym_table *) realloc(mp->sym_array, \
        	(mp->num_syms+1) * sizeof(struct sym_table));
	if ( mp->sym_array == (struct sym_table *) 0 )
		return(0);

	/* Then the space for the symbol. */
	tmp = strlen(symbol);
	tmp += (strlen(mp->name) + 1);
	mp->sym_array[mp->num_syms].name = (char *) malloc(tmp + 1);
	if ( mp->sym_array[mp->num_syms].name == (char *) 0 )
		return(0);
	memset(mp->sym_array[mp->num_syms].name, '\0', tmp + 1);
	
	/* Stuff interesting information into the module. */
	mp->sym_array[mp->num_syms].value = address;
	strcpy(mp->sym_array[mp->num_syms].name, mp->name);
	strcat(mp->sym_array[mp->num_syms].name, ":");
	strcat(mp->sym_array[mp->num_syms].name, symbol);
	++mp->num_syms;

	return(1);
}


/**************************************************************************
 * Function:	LookupModuleSymbol
 *
 * Purpose:	Find the symbol which is related to the given address from
 *		a kernel module.
 *
 * Arguements:	(long int) value, (struct symbol *) sym
 *
 *		value:->	The address to be located.
 * 
 *		sym:->		A pointer to a structure which will be
 *				loaded with the symbol's parameters.
 *
 * Return:	(char *)
 *
 *		If a match cannot be found a diagnostic string is printed.
 *		If a match is found the pointer to the symbolic name most
 *		closely matching the address is returned.
 **************************************************************************/

extern char * LookupModuleSymbol(value, sym)

	unsigned long value;

	struct symbol *sym;
	
{
	auto int	nmod,
			nsym;

	auto struct sym_table *last;

	auto struct Module *mp;


	sym->size = 0;
	sym->offset = 0;
	if ( num_modules == 0 )
		return((char *) 0);
	
	for(nmod= 0; nmod < num_modules; ++nmod)
	{
		mp = &sym_array_modules[nmod];

		/*
		 * Run through the list of symbols in this module and
		 * see if the address can be resolved.
		 */
		for(nsym= 1, last = &mp->sym_array[0];
		    nsym < mp->num_syms;
		    ++nsym)
		{
			if ( mp->sym_array[nsym].value > value )
			{		
				sym->offset = value - last->value;
				sym->size = mp->sym_array[nsym].value - \
					last->value;
				return(last->name);
			}
			last = &mp->sym_array[nsym];
		}


		/*
		 * At this stage of the game we still cannot give up the
		 * ghost.  There is the possibility that the address is
		 * from a module which has no symbols registered with
		 * the kernel.  The solution is to compare the address
		 * against the starting address and extant of the module
		 * If it is in this range we can at least return the
		 * name of the module.
		 */
#if LINUX_VERSION_CODE < 0x20112
		if ( (void *) value >= mp->module.addr &&
		     (void *) value <= (mp->module.addr + \
					mp->module.size * 4096) )
#else
		if ( value >= mp->module_info.addr &&
		     value <= (mp->module_info.addr + \
					mp->module.size * 4096) )
#endif
		{
			/*
			 * A special case needs to be checked for.  The above
			 * conditional tells us that we are within the
			 * extant of this module but symbol lookup has
			 * failed.
			 *
			 * We need to check to see if any symbols have
			 * been defined in this module.  If there have been
			 * symbols defined the assumption must be made that
			 * the faulting address lies somewhere beyond the
			 * last symbol.  About the only thing we can do
			 * at this point is use an offset from this
			 * symbol.
			 */
			if ( mp->num_syms > 0 )
			{
				last = &mp->sym_array[mp->num_syms - 1];
#if LINUX_VERSION_CODE < 0x20112
				sym->size = (int) mp->module.addr + \
					(mp->module.size * 4096) - value;
#else
				sym->size = (int) mp->module_info.addr + \
					(mp->module.size * 4096) - value;
#endif
				sym->offset = value - last->value;
				return(last->name);
			}

			/*
			 * There were no symbols defined for this module.
			 * Return the module name and the offset of the
			 * faulting address in the module.
			 */
			sym->size = mp->module.size * 4096;
#if LINUX_VERSION_CODE < 0x20112
			sym->offset = (void *) value - mp->module.addr;
#else
			sym->offset = value - mp->module_info.addr;
#endif
			return(mp->name);
		}
	}

	/* It has been a hopeless exercise. */
	return((char *) 0);
}


/*
 * Setting the -DTEST define enables the following code fragment to
 * be compiled.  This produces a small standalone program which will
 * dump the current kernel symbol table.
 */
#if defined(TEST)

#include <stdarg.h>


extern int main(int, char **);


int main(argc, argv)

	int argc;

	char *argv[];

{
	auto int lp, syms;


	if ( !InitMsyms() )
	{
		fprintf(stderr, "Cannot load module symbols.\n");
		return(1);
	}

	printf("Number of modules: %d\n\n", num_modules);

	for(lp= 0; lp < num_modules; ++lp)
	{
		printf("Module #%d = %s, Number of symbols = %d\n", lp + 1, \
		       sym_array_modules[lp].name, \
		       sym_array_modules[lp].num_syms);

		for (syms= 0; syms < sym_array_modules[lp].num_syms; ++syms)
		{
			printf("\tSymbol #%d\n", syms + 1);
			printf("\tName: %s\n", \
			       sym_array_modules[lp].sym_array[syms].name);
			printf("\tAddress: %lx\n\n", \
			       sym_array_modules[lp].sym_array[syms].value);
		}
	}

	FreeModules();
	return(0);
}

extern void Syslog(int priority, char *fmt, ...)

{
	va_list ap;

	va_start(ap, fmt);
	fprintf(stdout, "Pr: %d, ", priority);
	vfprintf(stdout, fmt, ap);
	va_end(ap);
	fputc('\n', stdout);

	return;
}

#endif
#endif /* #ifdef FEATURE_KLOGD */