1 /* mtrace implementation for `malloc'.
2 Copyright (C) 1991-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19
20 #include <malloc.h>
21 #include <mcheck.h>
22
23 #include <dlfcn.h>
24 #include <fcntl.h>
25 #include <stdio.h>
26 #include <string.h>
27 #include <stdlib.h>
28 #include <inttypes.h>
29
30 #include <libc-internal.h>
31 #include <dso_handle.h>
32
33 #include <kernel-features.h>
34
35 static FILE *mallstream;
36 static const char mallenv[] = "MALLOC_TRACE";
37
38 static void
39 tr_where (const void *caller, Dl_info *info)
40 {
41 if (caller != NULL)
42 {
43 if (info != NULL)
44 {
45 char *buf = (char *) "";
46 if (info->dli_sname != NULL)
47 {
48 size_t len = strlen (info->dli_sname);
49 buf = alloca (len + 6 + 2 * sizeof (void *));
50 char sign;
51 ptrdiff_t offset =
52 (ptrdiff_t) info->dli_saddr - (ptrdiff_t) caller;
53
54 if (caller >= (const void *) info->dli_saddr)
55 {
56 sign = '+';
57 offset = -offset;
58 }
59 else
60 sign = '-';
61
62 sprintf (buf, "(%s%c%" PRIxPTR ")", info->dli_sname, sign,
63 offset);
64 }
65
66 fprintf (mallstream, "@ %s%s%s[0x%" PRIxPTR "] ",
67 info->dli_fname ? : "", info->dli_fname ? ":" : "", buf,
68 caller - info->dli_fbase);
69 }
70 else
71 fprintf (mallstream, "@ [%p] ", caller);
72 }
73 }
74
75 static Dl_info *
76 lock_and_info (const void *caller, Dl_info *mem)
77 {
78 if (caller == NULL)
79 return NULL;
80
81 Dl_info *res = dladdr (caller, mem) ? mem : NULL;
82
83 flockfile (mallstream);
84
85 return res;
86 }
87
88 static void
89 free_mtrace (void *ptr, const void *caller)
90 {
91 if (ptr == NULL)
92 return;
93
94 Dl_info mem;
95 Dl_info *info = lock_and_info (caller, &mem);
96 tr_where (caller, info);
97 /* Be sure to print it first. */
98 fprintf (mallstream, "- %p\n", ptr);
99 funlockfile (mallstream);
100 }
101
102 static void
103 malloc_mtrace_after (void *block, size_t size, const void *caller)
104 {
105 Dl_info mem;
106 Dl_info *info = lock_and_info (caller, &mem);
107
108 tr_where (caller, info);
109 /* We could be printing a NULL here; that's OK. */
110 fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
111
112 funlockfile (mallstream);
113 }
114
115 static void
116 realloc_mtrace_after (void *block, const void *oldptr, size_t size,
117 const void *caller)
118 {
119 Dl_info mem;
120 Dl_info *info = lock_and_info (caller, &mem);
121
122 tr_where (caller, info);
123 if (block == NULL)
124 {
125 if (size != 0)
126 /* Failed realloc. */
127 fprintf (mallstream, "! %p %#lx\n", oldptr, (unsigned long int) size);
128 else
129 fprintf (mallstream, "- %p\n", oldptr);
130 }
131 else if (oldptr == NULL)
132 fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
133 else
134 {
135 fprintf (mallstream, "< %p\n", oldptr);
136 tr_where (caller, info);
137 fprintf (mallstream, "> %p %#lx\n", block, (unsigned long int) size);
138 }
139
140 funlockfile (mallstream);
141 }
142
143 static void
144 memalign_mtrace_after (void *block, size_t size, const void *caller)
145 {
146 Dl_info mem;
147 Dl_info *info = lock_and_info (caller, &mem);
148
149 tr_where (caller, info);
150 /* We could be printing a NULL here; that's OK. */
151 fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
152
153 funlockfile (mallstream);
154 }
155
156 /* This function gets called to make sure all memory the library
157 allocates get freed and so does not irritate the user when studying
158 the mtrace output. */
159 static void
160 release_libc_mem (void)
161 {
162 /* Only call the free function if we still are running in mtrace mode. */
163 if (mallstream != NULL)
164 __libc_freeres ();
165 }
166
167 /* We enable tracing if the environment variable MALLOC_TRACE is set. */
168
169 static void
170 do_mtrace (void)
171 {
172 static int added_atexit_handler;
173 char *mallfile;
174
175 /* Don't panic if we're called more than once. */
176 if (mallstream != NULL)
177 return;
178
179 mallfile = secure_getenv (mallenv);
180 if (mallfile != NULL)
181 {
182 mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
183 if (mallstream != NULL)
184 {
185 /* Be sure it doesn't malloc its buffer! */
186 static char tracebuf [512];
187
188 setvbuf (mallstream, tracebuf, _IOFBF, sizeof (tracebuf));
189 fprintf (mallstream, "= Start\n");
190 if (!added_atexit_handler)
191 {
192 added_atexit_handler = 1;
193 __cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
194 __dso_handle);
195 }
196 __malloc_debug_enable (MALLOC_MTRACE_HOOK);
197 }
198 }
199 }
200
201 static void
202 do_muntrace (void)
203 {
204 __malloc_debug_disable (MALLOC_MTRACE_HOOK);
205 if (mallstream == NULL)
206 return;
207
208 /* Do the reverse of what done in mtrace: first reset the hooks and
209 MALLSTREAM, and only after that write the trailer and close the
210 file. */
211 FILE *f = mallstream;
212 mallstream = NULL;
213
214 fprintf (f, "= End\n");
215 fclose (f);
216 }