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 /*
72 alloc_chunk / free_chunk :
73 * allocate executable system memory chunks
74 * the size is always divisible by CHUNK_SIZE
75 SLJIT_ALLOCATOR_LOCK / SLJIT_ALLOCATOR_UNLOCK :
76 * provided as part of sljitUtils
77 * only the allocator requires this lock, sljit is fully thread safe
78 as it only uses local variables
79 */
80
81 #ifdef _WIN32
82 #define SLJIT_UPDATE_WX_FLAGS(from, to, enable_exec)
83
alloc_chunk(sljit_uw size)84 static SLJIT_INLINE void* alloc_chunk(sljit_uw size)
85 {
86 return VirtualAlloc(NULL, size, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
87 }
88
free_chunk(void * chunk,sljit_uw size)89 static SLJIT_INLINE void free_chunk(void *chunk, sljit_uw size)
90 {
91 SLJIT_UNUSED_ARG(size);
92 VirtualFree(chunk, 0, MEM_RELEASE);
93 }
94
95 #else /* POSIX */
96
97 #if defined(__APPLE__) && defined(MAP_JIT)
98 /*
99 On macOS systems, returns MAP_JIT if it is defined _and_ we're running on a
100 version where it's OK to have more than one JIT block or where MAP_JIT is
101 required.
102 On non-macOS systems, returns MAP_JIT if it is defined.
103 */
104 #include <TargetConditionals.h>
105 #if TARGET_OS_OSX
106 #if defined SLJIT_CONFIG_X86 && SLJIT_CONFIG_X86
107 #ifdef MAP_ANON
108 #include <sys/utsname.h>
109 #include <stdlib.h>
110
111 #define SLJIT_MAP_JIT (get_map_jit_flag())
112
get_map_jit_flag()113 static SLJIT_INLINE int get_map_jit_flag()
114 {
115 sljit_sw page_size;
116 void *ptr;
117 struct utsname name;
118 static int map_jit_flag = -1;
119
120 if (map_jit_flag < 0) {
121 map_jit_flag = 0;
122 uname(&name);
123
124 /* Kernel version for 10.14.0 (Mojave) or later */
125 if (atoi(name.release) >= 18) {
126 page_size = get_page_alignment() + 1;
127 /* Only use MAP_JIT if a hardened runtime is used */
128 ptr = mmap(NULL, page_size, PROT_WRITE | PROT_EXEC,
129 MAP_PRIVATE | MAP_ANON, -1, 0);
130
131 if (ptr != MAP_FAILED)
132 munmap(ptr, page_size);
133 else
134 map_jit_flag = MAP_JIT;
135 }
136 }
137 return map_jit_flag;
138 }
139 #endif /* MAP_ANON */
140 #else /* !SLJIT_CONFIG_X86 */
141 #if !(defined SLJIT_CONFIG_ARM && SLJIT_CONFIG_ARM)
142 #error Unsupported architecture
143 #endif /* SLJIT_CONFIG_ARM */
144 #include <pthread.h>
145
146 #define SLJIT_MAP_JIT (MAP_JIT)
147 #define SLJIT_UPDATE_WX_FLAGS(from, to, enable_exec) \
148 apple_update_wx_flags(enable_exec)
149
apple_update_wx_flags(sljit_s32 enable_exec)150 static SLJIT_INLINE void apple_update_wx_flags(sljit_s32 enable_exec)
151 {
152 pthread_jit_write_protect_np(enable_exec);
153 }
154 #endif /* SLJIT_CONFIG_X86 */
155 #else /* !TARGET_OS_OSX */
156 #define SLJIT_MAP_JIT (MAP_JIT)
157 #endif /* TARGET_OS_OSX */
158 #endif /* __APPLE__ && MAP_JIT */
159 #ifndef SLJIT_UPDATE_WX_FLAGS
160 #define SLJIT_UPDATE_WX_FLAGS(from, to, enable_exec)
161 #endif /* !SLJIT_UPDATE_WX_FLAGS */
162 #ifndef SLJIT_MAP_JIT
163 #define SLJIT_MAP_JIT (0)
164 #endif /* !SLJIT_MAP_JIT */
165
alloc_chunk(sljit_uw size)166 static SLJIT_INLINE void* alloc_chunk(sljit_uw size)
167 {
168 void *retval;
169 int prot = PROT_READ | PROT_WRITE | PROT_EXEC;
170 int flags = MAP_PRIVATE;
171 int fd = -1;
172
173 #ifdef PROT_MAX
174 prot |= PROT_MAX(prot);
175 #endif
176
177 #ifdef MAP_ANON
178 flags |= MAP_ANON | SLJIT_MAP_JIT;
179 #else /* !MAP_ANON */
180 if (SLJIT_UNLIKELY((dev_zero < 0) && open_dev_zero()))
181 return NULL;
182
183 fd = dev_zero;
184 #endif /* MAP_ANON */
185
186 retval = mmap(NULL, size, prot, flags, fd, 0);
187 if (retval == MAP_FAILED)
188 return NULL;
189
190 if (mprotect(retval, size, PROT_READ | PROT_WRITE | PROT_EXEC) < 0) {
191 munmap(retval, size);
192 return NULL;
193 }
194
195 SLJIT_UPDATE_WX_FLAGS(retval, (uint8_t *)retval + size, 0);
196
197 return retval;
198 }
199
free_chunk(void * chunk,sljit_uw size)200 static SLJIT_INLINE void free_chunk(void *chunk, sljit_uw size)
201 {
202 munmap(chunk, size);
203 }
204
205 #endif /* windows */
206
207 /* --------------------------------------------------------------------- */
208 /* Common functions */
209 /* --------------------------------------------------------------------- */
210
211 #define CHUNK_MASK (~(CHUNK_SIZE - 1))
212
213 struct block_header {
214 sljit_uw size;
215 sljit_uw prev_size;
216 };
217
218 struct free_block {
219 struct block_header header;
220 struct free_block *next;
221 struct free_block *prev;
222 sljit_uw size;
223 };
224
225 #define AS_BLOCK_HEADER(base, offset) \
226 ((struct block_header*)(((sljit_u8*)base) + offset))
227 #define AS_FREE_BLOCK(base, offset) \
228 ((struct free_block*)(((sljit_u8*)base) + offset))
229 #define MEM_START(base) ((void*)(((sljit_u8*)base) + sizeof(struct block_header)))
230 #define ALIGN_SIZE(size) (((size) + sizeof(struct block_header) + 7) & ~7)
231
232 static struct free_block* free_blocks;
233 static sljit_uw allocated_size;
234 static sljit_uw total_size;
235
sljit_insert_free_block(struct free_block * free_block,sljit_uw size)236 static SLJIT_INLINE void sljit_insert_free_block(struct free_block *free_block, sljit_uw size)
237 {
238 free_block->header.size = 0;
239 free_block->size = size;
240
241 free_block->next = free_blocks;
242 free_block->prev = NULL;
243 if (free_blocks)
244 free_blocks->prev = free_block;
245 free_blocks = free_block;
246 }
247
sljit_remove_free_block(struct free_block * free_block)248 static SLJIT_INLINE void sljit_remove_free_block(struct free_block *free_block)
249 {
250 if (free_block->next)
251 free_block->next->prev = free_block->prev;
252
253 if (free_block->prev)
254 free_block->prev->next = free_block->next;
255 else {
256 SLJIT_ASSERT(free_blocks == free_block);
257 free_blocks = free_block->next;
258 }
259 }
260
sljit_malloc_exec(sljit_uw size)261 SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size)
262 {
263 struct block_header *header;
264 struct block_header *next_header;
265 struct free_block *free_block;
266 sljit_uw chunk_size;
267
268 SLJIT_ALLOCATOR_LOCK();
269 if (size < (64 - sizeof(struct block_header)))
270 size = (64 - sizeof(struct block_header));
271 size = ALIGN_SIZE(size);
272
273 free_block = free_blocks;
274 while (free_block) {
275 if (free_block->size >= size) {
276 chunk_size = free_block->size;
277 SLJIT_UPDATE_WX_FLAGS(NULL, NULL, 0);
278 if (chunk_size > size + 64) {
279 /* We just cut a block from the end of the free block. */
280 chunk_size -= size;
281 free_block->size = chunk_size;
282 header = AS_BLOCK_HEADER(free_block, chunk_size);
283 header->prev_size = chunk_size;
284 AS_BLOCK_HEADER(header, size)->prev_size = size;
285 }
286 else {
287 sljit_remove_free_block(free_block);
288 header = (struct block_header*)free_block;
289 size = chunk_size;
290 }
291 allocated_size += size;
292 header->size = size;
293 SLJIT_ALLOCATOR_UNLOCK();
294 return MEM_START(header);
295 }
296 free_block = free_block->next;
297 }
298
299 chunk_size = (size + sizeof(struct block_header) + CHUNK_SIZE - 1) & CHUNK_MASK;
300 header = (struct block_header*)alloc_chunk(chunk_size);
301 if (!header) {
302 SLJIT_ALLOCATOR_UNLOCK();
303 return NULL;
304 }
305
306 chunk_size -= sizeof(struct block_header);
307 total_size += chunk_size;
308
309 header->prev_size = 0;
310 if (chunk_size > size + 64) {
311 /* Cut the allocated space into a free and a used block. */
312 allocated_size += size;
313 header->size = size;
314 chunk_size -= size;
315
316 free_block = AS_FREE_BLOCK(header, size);
317 free_block->header.prev_size = size;
318 sljit_insert_free_block(free_block, chunk_size);
319 next_header = AS_BLOCK_HEADER(free_block, chunk_size);
320 }
321 else {
322 /* All space belongs to this allocation. */
323 allocated_size += chunk_size;
324 header->size = chunk_size;
325 next_header = AS_BLOCK_HEADER(header, chunk_size);
326 }
327 next_header->size = 1;
328 next_header->prev_size = chunk_size;
329 SLJIT_ALLOCATOR_UNLOCK();
330 return MEM_START(header);
331 }
332
sljit_free_exec(void * ptr)333 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr)
334 {
335 struct block_header *header;
336 struct free_block* free_block;
337
338 SLJIT_ALLOCATOR_LOCK();
339 header = AS_BLOCK_HEADER(ptr, -(sljit_sw)sizeof(struct block_header));
340 allocated_size -= header->size;
341
342 /* Connecting free blocks together if possible. */
343 SLJIT_UPDATE_WX_FLAGS(NULL, NULL, 0);
344
345 /* If header->prev_size == 0, free_block will equal to header.
346 In this case, free_block->header.size will be > 0. */
347 free_block = AS_FREE_BLOCK(header, -(sljit_sw)header->prev_size);
348 if (SLJIT_UNLIKELY(!free_block->header.size)) {
349 free_block->size += header->size;
350 header = AS_BLOCK_HEADER(free_block, free_block->size);
351 header->prev_size = free_block->size;
352 }
353 else {
354 free_block = (struct free_block*)header;
355 sljit_insert_free_block(free_block, header->size);
356 }
357
358 header = AS_BLOCK_HEADER(free_block, free_block->size);
359 if (SLJIT_UNLIKELY(!header->size)) {
360 free_block->size += ((struct free_block*)header)->size;
361 sljit_remove_free_block((struct free_block*)header);
362 header = AS_BLOCK_HEADER(free_block, free_block->size);
363 header->prev_size = free_block->size;
364 }
365
366 /* The whole chunk is free. */
367 if (SLJIT_UNLIKELY(!free_block->header.prev_size && header->size == 1)) {
368 /* If this block is freed, we still have (allocated_size / 2) free space. */
369 if (total_size - free_block->size > (allocated_size * 3 / 2)) {
370 total_size -= free_block->size;
371 sljit_remove_free_block(free_block);
372 free_chunk(free_block, free_block->size + sizeof(struct block_header));
373 }
374 }
375
376 SLJIT_UPDATE_WX_FLAGS(NULL, NULL, 1);
377 SLJIT_ALLOCATOR_UNLOCK();
378 }
379
sljit_free_unused_memory_exec(void)380 SLJIT_API_FUNC_ATTRIBUTE void sljit_free_unused_memory_exec(void)
381 {
382 struct free_block* free_block;
383 struct free_block* next_free_block;
384
385 SLJIT_ALLOCATOR_LOCK();
386 SLJIT_UPDATE_WX_FLAGS(NULL, NULL, 0);
387
388 free_block = free_blocks;
389 while (free_block) {
390 next_free_block = free_block->next;
391 if (!free_block->header.prev_size &&
392 AS_BLOCK_HEADER(free_block, free_block->size)->size == 1) {
393 total_size -= free_block->size;
394 sljit_remove_free_block(free_block);
395 free_chunk(free_block, free_block->size + sizeof(struct block_header));
396 }
397 free_block = next_free_block;
398 }
399
400 SLJIT_ASSERT((total_size && free_blocks) || (!total_size && !free_blocks));
401 SLJIT_UPDATE_WX_FLAGS(NULL, NULL, 1);
402 SLJIT_ALLOCATOR_UNLOCK();
403 }
404