7 * My own versions of malloc, realloc and free. Because I want
8 * malloc and realloc to bomb out and exit the program if they run
9 * out of memory, realloc to reliably call malloc if passed a NULL
10 * pointer, and free to reliably do nothing if passed a NULL
11 * pointer. We can also put trace printouts in, if we need to; and
12 * we can also replace the allocator with an ElectricFence-like
18 * Minefield - a Windows equivalent for Electric Fence
26 * We start by reserving as much virtual address space as Windows
27 * will sensibly (or not sensibly) let us have. We flag it all as
30 * Any allocation attempt is satisfied by committing one or more
31 * pages, with an uncommitted page on either side. The returned
32 * memory region is jammed up against the _end_ of the pages.
34 * Freeing anything causes instantaneous decommitment of the pages
35 * involved, so stale pointers are caught as soon as possible.
38 static int minefield_initialised = 0;
39 static void *minefield_region = NULL;
40 static long minefield_size = 0;
41 static long minefield_npages = 0;
42 static long minefield_curpos = 0;
43 static unsigned short *minefield_admin = NULL;
44 static void *minefield_pages = NULL;
46 static void minefield_admin_hide(int hide) {
47 int access = hide ? PAGE_NOACCESS : PAGE_READWRITE;
48 VirtualProtect(minefield_admin, minefield_npages*2, access, NULL);
51 static void minefield_init(void) {
56 for (size = 0x40000000; size > 0; size = ((size >> 3) * 7) &~ 0xFFF) {
57 printf("trying size=%d\n", size);
58 minefield_region = VirtualAlloc(NULL, size,
59 MEM_RESERVE, PAGE_NOACCESS);
63 minefield_size = size;
64 printf("got region %p size %d\n", minefield_region, minefield_size);
67 * Firstly, allocate a section of that to be the admin block.
68 * We'll need a two-byte field for each page.
70 minefield_admin = minefield_region;
71 minefield_npages = minefield_size / PAGESIZE;
72 admin_size = (minefield_npages * 2 + PAGESIZE-1) &~ (PAGESIZE-1);
73 minefield_npages = (minefield_size - admin_size) / PAGESIZE;
74 minefield_pages = (char *)minefield_region + admin_size;
75 printf("admin at %p, pages at %p, npages %x, admin_size %x\n",
76 minefield_admin, minefield_pages, minefield_npages,
80 * Commit the admin region.
82 VirtualAlloc(minefield_admin, minefield_npages * 2,
83 MEM_COMMIT, PAGE_READWRITE);
86 * Mark all pages as unused (0xFFFF).
88 for (i = 0; i < minefield_npages; i++)
89 minefield_admin[i] = 0xFFFF;
92 * Hide the admin region.
94 minefield_admin_hide(1);
96 minefield_initialised = 1;
99 static void minefield_bomb(void) {
100 div(1, *(int*)minefield_pages);
103 static void *minefield_alloc(int size) {
105 int pos, lim, region_end, region_start;
109 npages = (size + PAGESIZE-1) / PAGESIZE;
111 minefield_admin_hide(0);
114 * Search from current position until we find a contiguous
115 * bunch of npages+2 unused pages.
117 pos = minefield_curpos;
118 lim = minefield_npages;
120 /* Skip over used pages. */
121 while (pos < lim && minefield_admin[pos] != 0xFFFF)
123 /* Count unused pages. */
125 while (pos < lim && pos - start < npages+2 &&
126 minefield_admin[pos] == 0xFFFF)
128 if (pos - start == npages+2)
130 /* If we've reached the limit, reset the limit or stop. */
132 if (lim == minefield_npages) {
133 /* go round and start again at zero */
134 lim = minefield_curpos;
137 minefield_admin_hide(1);
143 minefield_curpos = pos-1;
146 * We have npages+2 unused pages starting at start. We leave
147 * the first and last of these alone and use the rest.
149 region_end = (start + npages+1) * PAGESIZE;
150 region_start = region_end - size;
151 /* FIXME: could align here if we wanted */
154 * Update the admin region.
156 for (i = start + 2; i < start + npages-1; i++)
157 minefield_admin[i] = 0xFFFE; /* used but no region starts here */
158 minefield_admin[start+1] = region_start % PAGESIZE;
160 minefield_admin_hide(1);
162 VirtualAlloc((char *)minefield_pages + region_start, size,
163 MEM_COMMIT, PAGE_READWRITE);
164 return (char *)minefield_pages + region_start;
167 static void minefield_free(void *ptr) {
168 int region_start, i, j;
170 minefield_admin_hide(0);
172 region_start = (char *)ptr - (char *)minefield_pages;
173 i = region_start / PAGESIZE;
174 if (i < 0 || i >= minefield_npages ||
175 minefield_admin[i] != region_start % PAGESIZE)
177 for (j = i; j < minefield_npages && minefield_admin[j] != 0xFFFF; j++) {
178 minefield_admin[j] = 0xFFFF;
181 VirtualFree(ptr, j*PAGESIZE - region_start, MEM_DECOMMIT);
183 minefield_admin_hide(1);
186 static int minefield_get_size(void *ptr) {
187 int region_start, i, j;
189 minefield_admin_hide(0);
191 region_start = (char *)ptr - (char *)minefield_pages;
192 i = region_start / PAGESIZE;
193 if (i < 0 || i >= minefield_npages ||
194 minefield_admin[i] != region_start % PAGESIZE)
196 for (j = i; j < minefield_npages && minefield_admin[j] != 0xFFFF; j++);
198 minefield_admin_hide(1);
200 return j*PAGESIZE - region_start;
203 static void *minefield_c_malloc(size_t size) {
204 if (!minefield_initialised) minefield_init();
205 return minefield_alloc(size);
208 static void minefield_c_free(void *p) {
209 if (!minefield_initialised) minefield_init();
214 * realloc _always_ moves the chunk, for rapid detection of code
215 * that assumes it won't.
217 static void *minefield_c_realloc(void *p, size_t size) {
220 if (!minefield_initialised) minefield_init();
221 q = minefield_alloc(size);
222 oldsize = minefield_get_size(p);
223 memcpy(q, p, (oldsize < size ? oldsize : size));
228 #endif /* MINEFIELD */
231 static FILE *fp = NULL;
233 void mlog(char *file, int line) {
235 fp = fopen("putty_mem.log", "w");
236 setvbuf(fp, NULL, _IONBF, BUFSIZ);
239 fprintf (fp, "%s:%d: ", file, line);
243 void *safemalloc(size_t size) {
246 p = minefield_c_malloc (size);
251 MessageBox(NULL, "Out of memory!", "PuTTY Fatal Error",
252 MB_SYSTEMMODAL | MB_ICONERROR | MB_OK);
257 fprintf(fp, "malloc(%d) returns %p\n", size, p);
262 void *saferealloc(void *ptr, size_t size) {
266 p = minefield_c_malloc (size);
272 p = minefield_c_realloc (ptr, size);
274 p = realloc (ptr, size);
278 MessageBox(NULL, "Out of memory!", "PuTTY Fatal Error",
279 MB_SYSTEMMODAL | MB_ICONERROR | MB_OK);
284 fprintf(fp, "realloc(%p,%d) returns %p\n", ptr, size, p);
289 void safefree(void *ptr) {
293 fprintf(fp, "free(%p)\n", ptr);
296 minefield_c_free (ptr);
303 fprintf(fp, "freeing null pointer - no action taken\n");
308 static FILE *debug_fp = NULL;
309 static int debug_got_console = 0;
311 void dprintf(char *fmt, ...) {
316 if (!debug_got_console) {
318 debug_got_console = 1;
321 debug_fp = fopen("debug.log", "w");
325 vsprintf(buf, fmt, ap);
326 WriteFile(GetStdHandle(STD_OUTPUT_HANDLE), buf, strlen(buf), &dw, NULL);
327 fputs(buf, debug_fp);