1/* Standard debugging hooks for `malloc'.
2 Copyright (C) 1990-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Written May 1989 by Mike Haertel.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20#ifndef _MALLOC_INTERNAL
21# define _MALLOC_INTERNAL
22# include <malloc.h>
23# include <mcheck.h>
24# include <stdint.h>
25# include <stdio.h>
26# include <libintl.h>
27# include <errno.h>
28#endif
29
30/* Old hook values. */
31static void (*old_free_hook)(void *ptr, const void *);
32static void *(*old_malloc_hook) (size_t size, const void *);
33static void *(*old_memalign_hook) (size_t alignment, size_t size,
34 const void *);
35static void *(*old_realloc_hook) (void *ptr, size_t size,
36 const void *);
37
38/* Function to call when something awful happens. */
39static void (*abortfunc) (enum mcheck_status);
40
41/* Arbitrary magical numbers. */
42#define MAGICWORD 0xfedabeeb
43#define MAGICFREE 0xd8675309
44#define MAGICBYTE ((char) 0xd7)
45#define MALLOCFLOOD ((char) 0x93)
46#define FREEFLOOD ((char) 0x95)
47
48struct hdr
49{
50 size_t size; /* Exact size requested by user. */
51 unsigned long int magic; /* Magic number to check header integrity. */
52 struct hdr *prev;
53 struct hdr *next;
54 void *block; /* Real block allocated, for memalign. */
55 unsigned long int magic2; /* Extra, keeps us doubleword aligned. */
56};
57
58/* This is the beginning of the list of all memory blocks allocated.
59 It is only constructed if the pedantic testing is requested. */
60static struct hdr *root;
61
62static int mcheck_used;
63
64/* Nonzero if pedentic checking of all blocks is requested. */
65static int pedantic;
66
67#if defined _LIBC || defined STDC_HEADERS || defined USG
68# include <string.h>
69# define flood memset
70#else
71static void flood (void *, int, size_t);
72static void
73flood (void *ptr, int val, size_t size)
74{
75 char *cp = ptr;
76 while (size--)
77 *cp++ = val;
78}
79#endif
80
81static enum mcheck_status
82checkhdr (const struct hdr *hdr)
83{
84 enum mcheck_status status;
85
86 if (!mcheck_used)
87 /* Maybe the mcheck used is disabled? This happens when we find
88 an error and report it. */
89 return MCHECK_OK;
90
91 switch (hdr->magic ^ ((uintptr_t) hdr->prev + (uintptr_t) hdr->next))
92 {
93 default:
94 status = MCHECK_HEAD;
95 break;
96 case MAGICFREE:
97 status = MCHECK_FREE;
98 break;
99 case MAGICWORD:
100 if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
101 status = MCHECK_TAIL;
102 else if ((hdr->magic2 ^ (uintptr_t) hdr->block) != MAGICWORD)
103 status = MCHECK_HEAD;
104 else
105 status = MCHECK_OK;
106 break;
107 }
108 if (status != MCHECK_OK)
109 {
110 mcheck_used = 0;
111 (*abortfunc) (status);
112 mcheck_used = 1;
113 }
114 return status;
115}
116
117void
118mcheck_check_all (void)
119{
120 /* Walk through all the active blocks and test whether they were tampered
121 with. */
122 struct hdr *runp = root;
123
124 /* Temporarily turn off the checks. */
125 pedantic = 0;
126
127 while (runp != NULL)
128 {
129 (void) checkhdr (runp);
130
131 runp = runp->next;
132 }
133
134 /* Turn checks on again. */
135 pedantic = 1;
136}
137#ifdef _LIBC
138libc_hidden_def (mcheck_check_all)
139#endif
140
141static void
142unlink_blk (struct hdr *ptr)
143{
144 if (ptr->next != NULL)
145 {
146 ptr->next->prev = ptr->prev;
147 ptr->next->magic = MAGICWORD ^ ((uintptr_t) ptr->next->prev
148 + (uintptr_t) ptr->next->next);
149 }
150 if (ptr->prev != NULL)
151 {
152 ptr->prev->next = ptr->next;
153 ptr->prev->magic = MAGICWORD ^ ((uintptr_t) ptr->prev->prev
154 + (uintptr_t) ptr->prev->next);
155 }
156 else
157 root = ptr->next;
158}
159
160static void
161link_blk (struct hdr *hdr)
162{
163 hdr->prev = NULL;
164 hdr->next = root;
165 root = hdr;
166 hdr->magic = MAGICWORD ^ (uintptr_t) hdr->next;
167
168 /* And the next block. */
169 if (hdr->next != NULL)
170 {
171 hdr->next->prev = hdr;
172 hdr->next->magic = MAGICWORD ^ ((uintptr_t) hdr
173 + (uintptr_t) hdr->next->next);
174 }
175}
176static void
177freehook (void *ptr, const void *caller)
178{
179 if (pedantic)
180 mcheck_check_all ();
181 if (ptr)
182 {
183 struct hdr *hdr = ((struct hdr *) ptr) - 1;
184 checkhdr (hdr);
185 hdr->magic = MAGICFREE;
186 hdr->magic2 = MAGICFREE;
187 unlink_blk (hdr);
188 hdr->prev = hdr->next = NULL;
189 flood (ptr, FREEFLOOD, hdr->size);
190 ptr = hdr->block;
191 }
192 __free_hook = old_free_hook;
193 if (old_free_hook != NULL)
194 (*old_free_hook)(ptr, caller);
195 else
196 free (ptr);
197 __free_hook = freehook;
198}
199
200static void *
201mallochook (size_t size, const void *caller)
202{
203 struct hdr *hdr;
204
205 if (pedantic)
206 mcheck_check_all ();
207
208 if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
209 {
210 __set_errno (ENOMEM);
211 return NULL;
212 }
213
214 __malloc_hook = old_malloc_hook;
215 if (old_malloc_hook != NULL)
216 hdr = (struct hdr *) (*old_malloc_hook)(sizeof (struct hdr) + size + 1,
217 caller);
218 else
219 hdr = (struct hdr *) malloc (sizeof (struct hdr) + size + 1);
220 __malloc_hook = mallochook;
221 if (hdr == NULL)
222 return NULL;
223
224 hdr->size = size;
225 link_blk (hdr);
226 hdr->block = hdr;
227 hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
228 ((char *) &hdr[1])[size] = MAGICBYTE;
229 flood ((void *) (hdr + 1), MALLOCFLOOD, size);
230 return (void *) (hdr + 1);
231}
232
233static void *
234memalignhook (size_t alignment, size_t size,
235 const void *caller)
236{
237 struct hdr *hdr;
238 size_t slop;
239 char *block;
240
241 if (pedantic)
242 mcheck_check_all ();
243
244 slop = (sizeof *hdr + alignment - 1) & - alignment;
245
246 if (size > ~((size_t) 0) - (slop + 1))
247 {
248 __set_errno (ENOMEM);
249 return NULL;
250 }
251
252 __memalign_hook = old_memalign_hook;
253 if (old_memalign_hook != NULL)
254 block = (*old_memalign_hook)(alignment, slop + size + 1, caller);
255 else
256 block = memalign (alignment, slop + size + 1);
257 __memalign_hook = memalignhook;
258 if (block == NULL)
259 return NULL;
260
261 hdr = ((struct hdr *) (block + slop)) - 1;
262
263 hdr->size = size;
264 link_blk (hdr);
265 hdr->block = (void *) block;
266 hdr->magic2 = (uintptr_t) block ^ MAGICWORD;
267 ((char *) &hdr[1])[size] = MAGICBYTE;
268 flood ((void *) (hdr + 1), MALLOCFLOOD, size);
269 return (void *) (hdr + 1);
270}
271
272static void *
273reallochook (void *ptr, size_t size, const void *caller)
274{
275 if (size == 0)
276 {
277 freehook (ptr, caller);
278 return NULL;
279 }
280
281 struct hdr *hdr;
282 size_t osize;
283
284 if (pedantic)
285 mcheck_check_all ();
286
287 if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
288 {
289 __set_errno (ENOMEM);
290 return NULL;
291 }
292
293 if (ptr)
294 {
295 hdr = ((struct hdr *) ptr) - 1;
296 osize = hdr->size;
297
298 checkhdr (hdr);
299 unlink_blk (hdr);
300 if (size < osize)
301 flood ((char *) ptr + size, FREEFLOOD, osize - size);
302 }
303 else
304 {
305 osize = 0;
306 hdr = NULL;
307 }
308 __free_hook = old_free_hook;
309 __malloc_hook = old_malloc_hook;
310 __memalign_hook = old_memalign_hook;
311 __realloc_hook = old_realloc_hook;
312 if (old_realloc_hook != NULL)
313 hdr = (struct hdr *) (*old_realloc_hook)((void *) hdr,
314 sizeof (struct hdr) + size + 1,
315 caller);
316 else
317 hdr = (struct hdr *) realloc ((void *) hdr,
318 sizeof (struct hdr) + size + 1);
319 __free_hook = freehook;
320 __malloc_hook = mallochook;
321 __memalign_hook = memalignhook;
322 __realloc_hook = reallochook;
323 if (hdr == NULL)
324 return NULL;
325
326 hdr->size = size;
327 link_blk (hdr);
328 hdr->block = hdr;
329 hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
330 ((char *) &hdr[1])[size] = MAGICBYTE;
331 if (size > osize)
332 flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
333 return (void *) (hdr + 1);
334}
335
336__attribute__ ((noreturn))
337static void
338mabort (enum mcheck_status status)
339{
340 const char *msg;
341 switch (status)
342 {
343 case MCHECK_OK:
344 msg = _ ("memory is consistent, library is buggy\n");
345 break;
346 case MCHECK_HEAD:
347 msg = _ ("memory clobbered before allocated block\n");
348 break;
349 case MCHECK_TAIL:
350 msg = _ ("memory clobbered past end of allocated block\n");
351 break;
352 case MCHECK_FREE:
353 msg = _ ("block freed twice\n");
354 break;
355 default:
356 msg = _ ("bogus mcheck_status, library is buggy\n");
357 break;
358 }
359#ifdef _LIBC
360 __libc_fatal (msg);
361#else
362 fprintf (stderr, "mcheck: %s", msg);
363 fflush (stderr);
364 abort ();
365#endif
366}
367
368/* Memory barrier so that GCC does not optimize out the argument. */
369#define malloc_opt_barrier(x) \
370 ({ __typeof (x) __x = x; __asm ("" : "+m" (__x)); __x; })
371
372int
373mcheck (void (*func) (enum mcheck_status))
374{
375 abortfunc = (func != NULL) ? func : &mabort;
376
377 /* These hooks may not be safely inserted if malloc is already in use. */
378 if (__malloc_initialized <= 0 && !mcheck_used)
379 {
380 /* We call malloc() once here to ensure it is initialized. */
381 void *p = malloc (0);
382 /* GCC might optimize out the malloc/free pair without a barrier. */
383 p = malloc_opt_barrier (p);
384 free (p);
385
386 old_free_hook = __free_hook;
387 __free_hook = freehook;
388 old_malloc_hook = __malloc_hook;
389 __malloc_hook = mallochook;
390 old_memalign_hook = __memalign_hook;
391 __memalign_hook = memalignhook;
392 old_realloc_hook = __realloc_hook;
393 __realloc_hook = reallochook;
394 mcheck_used = 1;
395 }
396
397 return mcheck_used ? 0 : -1;
398}
399#ifdef _LIBC
400libc_hidden_def (mcheck)
401#endif
402
403int
404mcheck_pedantic (void (*func) (enum mcheck_status))
405{
406 int res = mcheck (func);
407 if (res == 0)
408 pedantic = 1;
409 return res;
410}
411
412enum mcheck_status
413mprobe (void *ptr)
414{
415 return mcheck_used ? checkhdr (((struct hdr *) ptr) - 1) : MCHECK_DISABLED;
416}
417