1 /*
2 * Stack-less Just-In-Time compiler
3 *
4 * Copyright Zoltan Herczeg (hzmester@freemail.hu). All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without modification, are
7 * permitted provided that the following conditions are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright notice, this list of
10 * conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
13 * of conditions and the following disclaimer in the documentation and/or other materials
14 * provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) AND CONTRIBUTORS ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
19 * SHALL THE COPYRIGHT HOLDER(S) OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
21 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
22 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
24 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 /*
28 This file contains a simple executable memory allocator
29
30 It is assumed, that executable code blocks are usually medium (or sometimes
31 large) memory blocks, and the allocator is not too frequently called (less
32 optimized than other allocators). Thus, using it as a generic allocator is
33 not suggested.
34
35 How does it work:
36 Memory is allocated in continuous memory areas called chunks by alloc_chunk()
37 Chunk format:
38 [ block ][ block ] ... [ block ][ block terminator ]
39
40 All blocks and the block terminator is started with block_header. The block
41 header contains the size of the previous and the next block. These sizes
42 can also contain special values.
43 Block size:
44 0 - The block is a free_block, with a different size member.
45 1 - The block is a block terminator.
46 n - The block is used at the moment, and the value contains its size.
47 Previous block size:
48 0 - This is the first block of the memory chunk.
49 n - The size of the previous block.
50
51 Using these size values we can go forward or backward on the block chain.
52 The unused blocks are stored in a chain list pointed by free_blocks. This
53 list is useful if we need to find a suitable memory area when the allocator
54 is called.
55
56 When a block is freed, the new free block is connected to its adjacent free
57 blocks if possible.
58
59 [ free block ][ used block ][ free block ]
60 and "used block" is freed, the three blocks are connected together:
61 [ one big free block ]
62 */
63
64 /* --------------------------------------------------------------------- */
65 /* System (OS) functions */
66 /* --------------------------------------------------------------------- */
67
68 /* 64 KByte. */
69 #define CHUNK_SIZE 0x10000
70
71 struct chunk_header {
72 void *executable;
73 int fd;
74 };
75
76 /*
77 alloc_chunk / free_chunk :
78 * allocate executable system memory chunks
79 * the size is always divisible by CHUNK_SIZE
80 allocator_grab_lock / allocator_release_lock :
81 * make the allocator thread safe
82 * can be empty if the OS (or the application) does not support threading
83 * only the allocator requires this lock, sljit is fully thread safe
84 as it only uses local variables
85 */
86
87 #include <fcntl.h>
88
89 #ifndef O_NOATIME
90 #define O_NOATIME 0
91 #endif
92
93 #ifdef __O_TMPFILE
94 #ifndef O_TMPFILE
95 #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
96 #endif
97 #endif
98
99 int mkostemp(char *template, int flags);
100 char *secure_getenv(const char *name);
101
create_tempfile(void)102 static SLJIT_INLINE int create_tempfile(void)
103 {
104 int fd;
105
106 char tmp_name[256];
107 size_t tmp_name_len;
108 char *dir;
109 size_t len;
110
111 #ifdef P_tmpdir
112 len = (P_tmpdir != NULL) ? strlen(P_tmpdir) : 0;
113
114 if (len > 0 && len < sizeof(tmp_name)) {
115 strcpy(tmp_name, P_tmpdir);
116 tmp_name_len = len;
117 }
118 else {
119 strcpy(tmp_name, "/tmp");
120 tmp_name_len = 4;
121 }
122 #else
123 strcpy(tmp_name, "/tmp");
124 tmp_name_len = 4;
125 #endif
126
127 dir = secure_getenv("TMPDIR");
128 if (dir) {
129 len = strlen(dir);
130 if (len > 0 && len < sizeof(tmp_name)) {
131 strcpy(tmp_name, dir);
132 tmp_name_len = len;
133 }
134 }
135
136 SLJIT_ASSERT(tmp_name_len > 0 && tmp_name_len < sizeof(tmp_name));
137
138 while (tmp_name_len > 0 && tmp_name[tmp_name_len - 1] == '/') {
139 tmp_name_len--;
140 tmp_name[tmp_name_len] = '\0';
141 }
142
143 #ifdef O_TMPFILE
144 fd = open(tmp_name, O_TMPFILE | O_EXCL | O_RDWR | O_NOATIME | O_CLOEXEC, S_IRUSR | S_IWUSR);
145 if (fd != -1)
146 return fd;
147 #endif
148
149 if (tmp_name_len + 7 >= sizeof(tmp_name))
150 {
151 return -1;
152 }
153
154 strcpy(tmp_name + tmp_name_len, "/XXXXXX");
155 fd = mkostemp(tmp_name, O_CLOEXEC | O_NOATIME);
156
157 if (fd == -1)
158 return fd;
159
160 if (unlink(tmp_name)) {
161 close(fd);
162 return -1;
163 }
164
165 return fd;
166 }
167
alloc_chunk(sljit_uw size)168 static SLJIT_INLINE struct chunk_header* alloc_chunk(sljit_uw size)
169 {
170 struct chunk_header *retval;
171 int fd;
172
173 fd = create_tempfile();
174 if (fd == -1)
175 return NULL;
176
177 if (ftruncate(fd, size)) {
178 close(fd);
179 return NULL;
180 }
181
182 retval = (struct chunk_header *)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
183
184 if (retval == MAP_FAILED) {
185 close(fd);
186 return NULL;
187 }
188
189 retval->executable = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_SHARED, fd, 0);
190
191 if (retval->executable == MAP_FAILED) {
192 munmap(retval, size);
193 close(fd);
194 return NULL;
195 }
196
197 retval->fd = fd;
198 return retval;
199 }
200
free_chunk(void * chunk,sljit_uw size)201 static SLJIT_INLINE void free_chunk(void *chunk, sljit_uw size)
202 {
203 struct chunk_header *header = ((struct chunk_header *)chunk) - 1;
204
205 int fd = header->fd;
206 munmap(header->executable, size);
207 munmap(header, size);
208 close(fd);
209 }
210
211 /* --------------------------------------------------------------------- */
212 /* Common functions */
213 /* --------------------------------------------------------------------- */
214
215 #define CHUNK_MASK (~(CHUNK_SIZE - 1))
216
217 struct block_header {
218 sljit_uw size;
219 sljit_uw prev_size;
220 sljit_sw executable_offset;
221 };
222
223 struct free_block {
224 struct block_header header;
225 struct free_block *next;
226 struct free_block *prev;
227 sljit_uw size;
228 };
229
230 #define AS_BLOCK_HEADER(base, offset) \
231 ((struct block_header*)(((sljit_u8*)base) + offset))
232 #define AS_FREE_BLOCK(base, offset) \
233 ((struct free_block*)(((sljit_u8*)base) + offset))
234 #define MEM_START(base) ((void*)((base) + 1))
235 #define ALIGN_SIZE(size) (((size) + sizeof(struct block_header) + 7) & ~7)
236
237 static struct free_block* free_blocks;
238 static sljit_uw allocated_size;
239 static sljit_uw total_size;
240
sljit_insert_free_block(struct free_block * free_block,sljit_uw size)241 static SLJIT_INLINE void sljit_insert_free_block(struct free_block *free_block, sljit_uw size)
242 {
243 free_block->header.size = 0;
244 free_block->size = size;
245
246 free_block->next = free_blocks;
247 free_block->prev = NULL;
248 if (free_blocks)
249 free_blocks->prev = free_block;
250 free_blocks = free_block;
251 }
252
sljit_remove_free_block(struct free_block * free_block)253 static SLJIT_INLINE void sljit_remove_free_block(struct free_block *free_block)
254 {
255 if (free_block->next)
256 free_block->next->prev = free_block->prev;
257
258 if (free_block->prev)
259 free_block->prev->next = free_block->next;
260 else {
261 SLJIT_ASSERT(free_blocks == free_block);
262 free_blocks = free_block->next;
263 }
264 }
265
sljit_malloc_exec(sljit_uw size)266 SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size)
267 {
268 struct chunk_header *chunk_header;
269 struct block_header *header;
270 struct block_header *next_header;
271 struct free_block *free_block;
272 sljit_uw chunk_size;
273 sljit_sw executable_offset;
274
275 allocator_grab_lock();
276 if (size < (64 - sizeof(struct block_header)))
277 size = (64 - sizeof(struct block_header));
278 size = ALIGN_SIZE(size);
279
280 free_block = free_blocks;
281 while (free_block) {
282 if (free_block->size >= size) {
283 chunk_size = free_block->size;
284 if (chunk_size > size + 64) {
285 /* We just cut a block from the end of the free block. */
286 chunk_size -= size;
287 free_block->size = chunk_size;
288 header = AS_BLOCK_HEADER(free_block, chunk_size);
289 header->prev_size = chunk_size;
290 header->executable_offset = free_block->header.executable_offset;
291 AS_BLOCK_HEADER(header, size)->prev_size = size;
292 }
293 else {
294 sljit_remove_free_block(free_block);
295 header = (struct block_header*)free_block;
296 size = chunk_size;
297 }
298 allocated_size += size;
299 header->size = size;
300 allocator_release_lock();
301 return MEM_START(header);
302 }
303 free_block = free_block->next;
304 }
305
306 chunk_size = sizeof(struct chunk_header) + sizeof(struct block_header);
307 chunk_size = (chunk_size + size + CHUNK_SIZE - 1) & CHUNK_MASK;
308
309 chunk_header = alloc_chunk(chunk_size);
310 if (!chunk_header) {
311 allocator_release_lock();
312 return NULL;
313 }
314
315 executable_offset = (sljit_sw)((sljit_u8*)chunk_header->executable - (sljit_u8*)chunk_header);
316
317 chunk_size -= sizeof(struct chunk_header) + sizeof(struct block_header);
318 total_size += chunk_size;
319
320 header = (struct block_header *)(chunk_header + 1);
321
322 header->prev_size = 0;
323 header->executable_offset = executable_offset;
324 if (chunk_size > size + 64) {
325 /* Cut the allocated space into a free and a used block. */
326 allocated_size += size;
327 header->size = size;
328 chunk_size -= size;
329
330 free_block = AS_FREE_BLOCK(header, size);
331 free_block->header.prev_size = size;
332 free_block->header.executable_offset = executable_offset;
333 sljit_insert_free_block(free_block, chunk_size);
334 next_header = AS_BLOCK_HEADER(free_block, chunk_size);
335 }
336 else {
337 /* All space belongs to this allocation. */
338 allocated_size += chunk_size;
339 header->size = chunk_size;
340 next_header = AS_BLOCK_HEADER(header, chunk_size);
341 }
342 next_header->size = 1;
343 next_header->prev_size = chunk_size;
344 next_header->executable_offset = executable_offset;
345 allocator_release_lock();
346 return MEM_START(header);
347 }
348
sljit_free_exec(void * ptr)349 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr)
350 {
351 struct block_header *header;
352 struct free_block* free_block;
353
354 allocator_grab_lock();
355 header = AS_BLOCK_HEADER(ptr, -(sljit_sw)sizeof(struct block_header));
356 header = AS_BLOCK_HEADER(header, -header->executable_offset);
357 allocated_size -= header->size;
358
359 /* Connecting free blocks together if possible. */
360
361 /* If header->prev_size == 0, free_block will equal to header.
362 In this case, free_block->header.size will be > 0. */
363 free_block = AS_FREE_BLOCK(header, -(sljit_sw)header->prev_size);
364 if (SLJIT_UNLIKELY(!free_block->header.size)) {
365 free_block->size += header->size;
366 header = AS_BLOCK_HEADER(free_block, free_block->size);
367 header->prev_size = free_block->size;
368 }
369 else {
370 free_block = (struct free_block*)header;
371 sljit_insert_free_block(free_block, header->size);
372 }
373
374 header = AS_BLOCK_HEADER(free_block, free_block->size);
375 if (SLJIT_UNLIKELY(!header->size)) {
376 free_block->size += ((struct free_block*)header)->size;
377 sljit_remove_free_block((struct free_block*)header);
378 header = AS_BLOCK_HEADER(free_block, free_block->size);
379 header->prev_size = free_block->size;
380 }
381
382 /* The whole chunk is free. */
383 if (SLJIT_UNLIKELY(!free_block->header.prev_size && header->size == 1)) {
384 /* If this block is freed, we still have (allocated_size / 2) free space. */
385 if (total_size - free_block->size > (allocated_size * 3 / 2)) {
386 total_size -= free_block->size;
387 sljit_remove_free_block(free_block);
388 free_chunk(free_block, free_block->size + sizeof(struct block_header));
389 }
390 }
391
392 allocator_release_lock();
393 }
394
sljit_free_unused_memory_exec(void)395 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_unused_memory_exec(void)
396 {
397 struct free_block* free_block;
398 struct free_block* next_free_block;
399
400 allocator_grab_lock();
401
402 free_block = free_blocks;
403 while (free_block) {
404 next_free_block = free_block->next;
405 if (!free_block->header.prev_size &&
406 AS_BLOCK_HEADER(free_block, free_block->size)->size == 1) {
407 total_size -= free_block->size;
408 sljit_remove_free_block(free_block);
409 free_chunk(free_block, free_block->size + sizeof(struct block_header));
410 }
411 free_block = next_free_block;
412 }
413
414 SLJIT_ASSERT((total_size && free_blocks) || (!total_size && !free_blocks));
415 allocator_release_lock();
416 }
417
sljit_exec_offset(void * ptr)418 SLJIT_API_FUNC_ATTRIBUTE sljit_sw sljit_exec_offset(void* ptr)
419 {
420 return ((struct block_header *)(ptr))[-1].executable_offset;
421 }
422