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
);