xref: /linux/mm/execmem.c (revision 989fe6771266bdb82a815d78802c5aa7c918fdfd) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2002 Richard Henderson
4  * Copyright (C) 2001 Rusty Russell, 2002, 2010 Rusty Russell IBM.
5  * Copyright (C) 2023 Luis Chamberlain <mcgrof@kernel.org>
6  * Copyright (C) 2024 Mike Rapoport IBM.
7  */
8 
9 #define pr_fmt(fmt) "execmem: " fmt
10 
11 #include <linux/mm.h>
12 #include <linux/mutex.h>
13 #include <linux/vmalloc.h>
14 #include <linux/execmem.h>
15 #include <linux/maple_tree.h>
16 #include <linux/set_memory.h>
17 #include <linux/moduleloader.h>
18 #include <linux/text-patching.h>
19 
20 #include <asm/tlbflush.h>
21 
22 #include "internal.h"
23 
24 static struct execmem_info *execmem_info __ro_after_init;
25 static struct execmem_info default_execmem_info __ro_after_init;
26 
27 #ifdef CONFIG_MMU
28 static void *execmem_vmalloc(struct execmem_range *range, size_t size,
29 			     pgprot_t pgprot, unsigned long vm_flags)
30 {
31 	bool kasan = range->flags & EXECMEM_KASAN_SHADOW;
32 	gfp_t gfp_flags = GFP_KERNEL | __GFP_NOWARN;
33 	unsigned int align = range->alignment;
34 	unsigned long start = range->start;
35 	unsigned long end = range->end;
36 	void *p;
37 
38 	if (kasan)
39 		vm_flags |= VM_DEFER_KMEMLEAK;
40 
41 	if (vm_flags & VM_ALLOW_HUGE_VMAP)
42 		align = PMD_SIZE;
43 
44 	p = __vmalloc_node_range(size, align, start, end, gfp_flags,
45 				 pgprot, vm_flags, NUMA_NO_NODE,
46 				 __builtin_return_address(0));
47 	if (!p && range->fallback_start) {
48 		start = range->fallback_start;
49 		end = range->fallback_end;
50 		p = __vmalloc_node_range(size, align, start, end, gfp_flags,
51 					 pgprot, vm_flags, NUMA_NO_NODE,
52 					 __builtin_return_address(0));
53 	}
54 
55 	if (!p) {
56 		pr_warn_ratelimited("unable to allocate memory\n");
57 		return NULL;
58 	}
59 
60 	if (kasan && (kasan_alloc_module_shadow(p, size, GFP_KERNEL) < 0)) {
61 		vfree(p);
62 		return NULL;
63 	}
64 
65 	return p;
66 }
67 
68 struct vm_struct *execmem_vmap(size_t size)
69 {
70 	struct execmem_range *range = &execmem_info->ranges[EXECMEM_MODULE_DATA];
71 	struct vm_struct *area;
72 
73 	area = __get_vm_area_node(size, range->alignment, PAGE_SHIFT, VM_ALLOC,
74 				  range->start, range->end, NUMA_NO_NODE,
75 				  GFP_KERNEL, __builtin_return_address(0));
76 	if (!area && range->fallback_start)
77 		area = __get_vm_area_node(size, range->alignment, PAGE_SHIFT, VM_ALLOC,
78 					  range->fallback_start, range->fallback_end,
79 					  NUMA_NO_NODE, GFP_KERNEL, __builtin_return_address(0));
80 
81 	return area;
82 }
83 #else
84 static void *execmem_vmalloc(struct execmem_range *range, size_t size,
85 			     pgprot_t pgprot, unsigned long vm_flags)
86 {
87 	return vmalloc(size);
88 }
89 #endif /* CONFIG_MMU */
90 
91 #ifdef CONFIG_ARCH_HAS_EXECMEM_ROX
92 struct execmem_cache {
93 	struct mutex mutex;
94 	struct maple_tree busy_areas;
95 	struct maple_tree free_areas;
96 	unsigned int pending_free_cnt;	/* protected by mutex */
97 };
98 
99 /* delay to schedule asynchronous free if fast path free fails */
100 #define FREE_DELAY	(msecs_to_jiffies(10))
101 
102 /* mark entries in busy_areas that should be freed asynchronously */
103 #define PENDING_FREE_MASK	(1 << (PAGE_SHIFT - 1))
104 
105 static struct execmem_cache execmem_cache = {
106 	.mutex = __MUTEX_INITIALIZER(execmem_cache.mutex),
107 	.busy_areas = MTREE_INIT_EXT(busy_areas, MT_FLAGS_LOCK_EXTERN,
108 				     execmem_cache.mutex),
109 	.free_areas = MTREE_INIT_EXT(free_areas, MT_FLAGS_LOCK_EXTERN,
110 				     execmem_cache.mutex),
111 };
112 
113 static inline unsigned long mas_range_len(struct ma_state *mas)
114 {
115 	return mas->last - mas->index + 1;
116 }
117 
118 static int execmem_set_direct_map_valid(struct vm_struct *vm, bool valid)
119 {
120 	unsigned int nr = (1 << get_vm_area_page_order(vm));
121 	unsigned int updated = 0;
122 	int err = 0;
123 
124 	for (int i = 0; i < vm->nr_pages; i += nr) {
125 		err = set_direct_map_valid_noflush(vm->pages[i], nr, valid);
126 		if (err)
127 			goto err_restore;
128 		updated += nr;
129 	}
130 
131 	return 0;
132 
133 err_restore:
134 	for (int i = 0; i < updated; i += nr)
135 		set_direct_map_valid_noflush(vm->pages[i], nr, !valid);
136 
137 	return err;
138 }
139 
140 static int execmem_force_rw(void *ptr, size_t size)
141 {
142 	unsigned int nr = PAGE_ALIGN(size) >> PAGE_SHIFT;
143 	unsigned long addr = (unsigned long)ptr;
144 	int ret;
145 
146 	ret = set_memory_nx(addr, nr);
147 	if (ret)
148 		return ret;
149 
150 	return set_memory_rw(addr, nr);
151 }
152 
153 int execmem_restore_rox(void *ptr, size_t size)
154 {
155 	unsigned int nr = PAGE_ALIGN(size) >> PAGE_SHIFT;
156 	unsigned long addr = (unsigned long)ptr;
157 
158 	return set_memory_rox(addr, nr);
159 }
160 
161 static void execmem_cache_clean(struct work_struct *work)
162 {
163 	struct maple_tree *free_areas = &execmem_cache.free_areas;
164 	struct mutex *mutex = &execmem_cache.mutex;
165 	MA_STATE(mas, free_areas, 0, ULONG_MAX);
166 	void *area;
167 
168 	mutex_lock(mutex);
169 	mas_for_each(&mas, area, ULONG_MAX) {
170 		size_t size = mas_range_len(&mas);
171 
172 		if (IS_ALIGNED(size, PMD_SIZE) &&
173 		    IS_ALIGNED(mas.index, PMD_SIZE)) {
174 			struct vm_struct *vm = find_vm_area(area);
175 
176 			execmem_set_direct_map_valid(vm, true);
177 			mas_store_gfp(&mas, NULL, GFP_KERNEL);
178 			vfree(area);
179 		}
180 	}
181 	mutex_unlock(mutex);
182 }
183 
184 static DECLARE_WORK(execmem_cache_clean_work, execmem_cache_clean);
185 
186 static int execmem_cache_add_locked(void *ptr, size_t size, gfp_t gfp_mask)
187 {
188 	struct maple_tree *free_areas = &execmem_cache.free_areas;
189 	unsigned long addr = (unsigned long)ptr;
190 	MA_STATE(mas, free_areas, addr - 1, addr + 1);
191 	unsigned long lower, upper;
192 	void *area = NULL;
193 
194 	lower = addr;
195 	upper = addr + size - 1;
196 
197 	area = mas_walk(&mas);
198 	if (area && mas.last == addr - 1)
199 		lower = mas.index;
200 
201 	area = mas_next(&mas, ULONG_MAX);
202 	if (area && mas.index == addr + size)
203 		upper = mas.last;
204 
205 	mas_set_range(&mas, lower, upper);
206 	return mas_store_gfp(&mas, (void *)lower, gfp_mask);
207 }
208 
209 static int execmem_cache_add(void *ptr, size_t size, gfp_t gfp_mask)
210 {
211 	guard(mutex)(&execmem_cache.mutex);
212 
213 	return execmem_cache_add_locked(ptr, size, gfp_mask);
214 }
215 
216 static bool within_range(struct execmem_range *range, struct ma_state *mas,
217 			 size_t size)
218 {
219 	unsigned long addr = mas->index;
220 
221 	if (addr >= range->start && addr + size < range->end)
222 		return true;
223 
224 	if (range->fallback_start &&
225 	    addr >= range->fallback_start && addr + size < range->fallback_end)
226 		return true;
227 
228 	return false;
229 }
230 
231 static void *__execmem_cache_alloc(struct execmem_range *range, size_t size)
232 {
233 	struct maple_tree *free_areas = &execmem_cache.free_areas;
234 	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
235 	MA_STATE(mas_free, free_areas, 0, ULONG_MAX);
236 	MA_STATE(mas_busy, busy_areas, 0, ULONG_MAX);
237 	struct mutex *mutex = &execmem_cache.mutex;
238 	unsigned long addr, last, area_size = 0;
239 	void *area, *ptr = NULL;
240 	int err;
241 
242 	mutex_lock(mutex);
243 	mas_for_each(&mas_free, area, ULONG_MAX) {
244 		area_size = mas_range_len(&mas_free);
245 
246 		if (area_size >= size && within_range(range, &mas_free, size))
247 			break;
248 	}
249 
250 	if (area_size < size)
251 		goto out_unlock;
252 
253 	addr = mas_free.index;
254 	last = mas_free.last;
255 
256 	/* insert allocated size to busy_areas at range [addr, addr + size) */
257 	mas_set_range(&mas_busy, addr, addr + size - 1);
258 	err = mas_store_gfp(&mas_busy, (void *)addr, GFP_KERNEL);
259 	if (err)
260 		goto out_unlock;
261 
262 	mas_store_gfp(&mas_free, NULL, GFP_KERNEL);
263 	if (area_size > size) {
264 		void *ptr = (void *)(addr + size);
265 
266 		/*
267 		 * re-insert remaining free size to free_areas at range
268 		 * [addr + size, last]
269 		 */
270 		mas_set_range(&mas_free, addr + size, last);
271 		err = mas_store_gfp(&mas_free, ptr, GFP_KERNEL);
272 		if (err) {
273 			mas_store_gfp(&mas_busy, NULL, GFP_KERNEL);
274 			goto out_unlock;
275 		}
276 	}
277 	ptr = (void *)addr;
278 
279 out_unlock:
280 	mutex_unlock(mutex);
281 	return ptr;
282 }
283 
284 static int execmem_cache_populate(struct execmem_range *range, size_t size)
285 {
286 	unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
287 	struct vm_struct *vm;
288 	size_t alloc_size;
289 	int err = -ENOMEM;
290 	void *p;
291 
292 	alloc_size = round_up(size, PMD_SIZE);
293 	p = execmem_vmalloc(range, alloc_size, PAGE_KERNEL, vm_flags);
294 	if (!p) {
295 		alloc_size = size;
296 		p = execmem_vmalloc(range, alloc_size, PAGE_KERNEL, vm_flags);
297 	}
298 
299 	if (!p)
300 		return err;
301 
302 	vm = find_vm_area(p);
303 	if (!vm)
304 		goto err_free_mem;
305 
306 	/* fill memory with instructions that will trap */
307 	execmem_fill_trapping_insns(p, alloc_size);
308 
309 	err = set_memory_rox((unsigned long)p, vm->nr_pages);
310 	if (err)
311 		goto err_free_mem;
312 
313 	err = execmem_cache_add(p, alloc_size, GFP_KERNEL);
314 	if (err)
315 		goto err_reset_direct_map;
316 
317 	return 0;
318 
319 err_reset_direct_map:
320 	execmem_set_direct_map_valid(vm, true);
321 err_free_mem:
322 	vfree(p);
323 	return err;
324 }
325 
326 static void *execmem_cache_alloc(struct execmem_range *range, size_t size)
327 {
328 	void *p;
329 	int err;
330 
331 	p = __execmem_cache_alloc(range, size);
332 	if (p)
333 		return p;
334 
335 	err = execmem_cache_populate(range, size);
336 	if (err)
337 		return NULL;
338 
339 	return __execmem_cache_alloc(range, size);
340 }
341 
342 static inline bool is_pending_free(void *ptr)
343 {
344 	return ((unsigned long)ptr & PENDING_FREE_MASK);
345 }
346 
347 static inline void *pending_free_set(void *ptr)
348 {
349 	return (void *)((unsigned long)ptr | PENDING_FREE_MASK);
350 }
351 
352 static inline void *pending_free_clear(void *ptr)
353 {
354 	return (void *)((unsigned long)ptr & ~PENDING_FREE_MASK);
355 }
356 
357 static int __execmem_cache_free(struct ma_state *mas, void *ptr, gfp_t gfp_mask)
358 {
359 	size_t size = mas_range_len(mas);
360 	int err;
361 
362 	err = execmem_force_rw(ptr, size);
363 	if (err)
364 		return err;
365 
366 	execmem_fill_trapping_insns(ptr, size);
367 	execmem_restore_rox(ptr, size);
368 
369 	err = execmem_cache_add_locked(ptr, size, gfp_mask);
370 	if (err)
371 		return err;
372 
373 	mas_store_gfp(mas, NULL, gfp_mask);
374 	return 0;
375 }
376 
377 static void execmem_cache_free_slow(struct work_struct *work);
378 static DECLARE_DELAYED_WORK(execmem_cache_free_work, execmem_cache_free_slow);
379 
380 static void execmem_cache_free_slow(struct work_struct *work)
381 {
382 	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
383 	MA_STATE(mas, busy_areas, 0, ULONG_MAX);
384 	void *area;
385 
386 	guard(mutex)(&execmem_cache.mutex);
387 
388 	if (!execmem_cache.pending_free_cnt)
389 		return;
390 
391 	mas_for_each(&mas, area, ULONG_MAX) {
392 		if (!is_pending_free(area))
393 			continue;
394 
395 		area = pending_free_clear(area);
396 		if (__execmem_cache_free(&mas, area, GFP_KERNEL))
397 			continue;
398 
399 		execmem_cache.pending_free_cnt--;
400 	}
401 
402 	if (execmem_cache.pending_free_cnt)
403 		schedule_delayed_work(&execmem_cache_free_work, FREE_DELAY);
404 	else
405 		schedule_work(&execmem_cache_clean_work);
406 }
407 
408 static bool execmem_cache_free(void *ptr)
409 {
410 	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
411 	unsigned long addr = (unsigned long)ptr;
412 	MA_STATE(mas, busy_areas, addr, addr);
413 	void *area;
414 	int err;
415 
416 	guard(mutex)(&execmem_cache.mutex);
417 
418 	area = mas_walk(&mas);
419 	if (!area)
420 		return false;
421 
422 	err = __execmem_cache_free(&mas, area, GFP_KERNEL | __GFP_NORETRY);
423 	if (err) {
424 		/*
425 		 * mas points to exact slot we've got the area from, nothing
426 		 * else can modify the tree because of the mutex, so there
427 		 * won't be any allocations in mas_store_gfp() and it will just
428 		 * change the pointer.
429 		 */
430 		area = pending_free_set(area);
431 		mas_store_gfp(&mas, area, GFP_KERNEL);
432 		execmem_cache.pending_free_cnt++;
433 		schedule_delayed_work(&execmem_cache_free_work, FREE_DELAY);
434 		return true;
435 	}
436 
437 	schedule_work(&execmem_cache_clean_work);
438 
439 	return true;
440 }
441 
442 #else /* CONFIG_ARCH_HAS_EXECMEM_ROX */
443 /*
444  * when ROX cache is not used the permissions defined by architectures for
445  * execmem ranges that are updated before use (e.g. EXECMEM_MODULE_TEXT) must
446  * be writable anyway
447  */
448 static inline int execmem_force_rw(void *ptr, size_t size)
449 {
450 	return 0;
451 }
452 
453 static void *execmem_cache_alloc(struct execmem_range *range, size_t size)
454 {
455 	return NULL;
456 }
457 
458 static bool execmem_cache_free(void *ptr)
459 {
460 	return false;
461 }
462 #endif /* CONFIG_ARCH_HAS_EXECMEM_ROX */
463 
464 void *execmem_alloc(enum execmem_type type, size_t size)
465 {
466 	struct execmem_range *range = &execmem_info->ranges[type];
467 	bool use_cache = range->flags & EXECMEM_ROX_CACHE;
468 	unsigned long vm_flags = VM_FLUSH_RESET_PERMS;
469 	pgprot_t pgprot = range->pgprot;
470 	void *p = NULL;
471 
472 	size = PAGE_ALIGN(size);
473 
474 	if (use_cache)
475 		p = execmem_cache_alloc(range, size);
476 	else
477 		p = execmem_vmalloc(range, size, pgprot, vm_flags);
478 
479 	return kasan_reset_tag(p);
480 }
481 
482 void *execmem_alloc_rw(enum execmem_type type, size_t size)
483 {
484 	void *p __free(execmem) = execmem_alloc(type, size);
485 	int err;
486 
487 	if (!p)
488 		return NULL;
489 
490 	err = execmem_force_rw(p, size);
491 	if (err)
492 		return NULL;
493 
494 	return no_free_ptr(p);
495 }
496 
497 void execmem_free(void *ptr)
498 {
499 	/*
500 	 * This memory may be RO, and freeing RO memory in an interrupt is not
501 	 * supported by vmalloc.
502 	 */
503 	WARN_ON(in_interrupt());
504 
505 	if (!execmem_cache_free(ptr))
506 		vfree(ptr);
507 }
508 
509 bool execmem_is_rox(enum execmem_type type)
510 {
511 	return !!(execmem_info->ranges[type].flags & EXECMEM_ROX_CACHE);
512 }
513 
514 static bool execmem_validate(struct execmem_info *info)
515 {
516 	struct execmem_range *r = &info->ranges[EXECMEM_DEFAULT];
517 
518 	if (!r->alignment || !r->start || !r->end || !pgprot_val(r->pgprot)) {
519 		pr_crit("Invalid parameters for execmem allocator, module loading will fail");
520 		return false;
521 	}
522 
523 	if (!IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX)) {
524 		for (int i = EXECMEM_DEFAULT; i < EXECMEM_TYPE_MAX; i++) {
525 			r = &info->ranges[i];
526 
527 			if (r->flags & EXECMEM_ROX_CACHE) {
528 				pr_warn_once("ROX cache is not supported\n");
529 				r->flags &= ~EXECMEM_ROX_CACHE;
530 			}
531 		}
532 	}
533 
534 	return true;
535 }
536 
537 static void execmem_init_missing(struct execmem_info *info)
538 {
539 	struct execmem_range *default_range = &info->ranges[EXECMEM_DEFAULT];
540 
541 	for (int i = EXECMEM_DEFAULT + 1; i < EXECMEM_TYPE_MAX; i++) {
542 		struct execmem_range *r = &info->ranges[i];
543 
544 		if (!r->start) {
545 			if (i == EXECMEM_MODULE_DATA)
546 				r->pgprot = PAGE_KERNEL;
547 			else
548 				r->pgprot = default_range->pgprot;
549 			r->alignment = default_range->alignment;
550 			r->start = default_range->start;
551 			r->end = default_range->end;
552 			r->flags = default_range->flags;
553 			r->fallback_start = default_range->fallback_start;
554 			r->fallback_end = default_range->fallback_end;
555 		}
556 	}
557 }
558 
559 struct execmem_info * __weak execmem_arch_setup(void)
560 {
561 	return NULL;
562 }
563 
564 static void __init __execmem_init(void)
565 {
566 	struct execmem_info *info = execmem_arch_setup();
567 
568 	if (!info) {
569 		info = execmem_info = &default_execmem_info;
570 		info->ranges[EXECMEM_DEFAULT].start = VMALLOC_START;
571 		info->ranges[EXECMEM_DEFAULT].end = VMALLOC_END;
572 		info->ranges[EXECMEM_DEFAULT].pgprot = PAGE_KERNEL_EXEC;
573 		info->ranges[EXECMEM_DEFAULT].alignment = 1;
574 	}
575 
576 	if (!execmem_validate(info))
577 		return;
578 
579 	execmem_init_missing(info);
580 
581 	execmem_info = info;
582 }
583 
584 #ifdef CONFIG_ARCH_WANTS_EXECMEM_LATE
585 static int __init execmem_late_init(void)
586 {
587 	__execmem_init();
588 	return 0;
589 }
590 core_initcall(execmem_late_init);
591 #else
592 void __init execmem_init(void)
593 {
594 	__execmem_init();
595 }
596 #endif
597