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2b144498 SD |
1 | /* |
2 | * Userspace Probes (UProbes) | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | * | |
18 | * Copyright (C) IBM Corporation, 2008-2011 | |
19 | * Authors: | |
20 | * Srikar Dronamraju | |
21 | * Jim Keniston | |
22 | */ | |
23 | ||
24 | #include <linux/kernel.h> | |
25 | #include <linux/highmem.h> | |
26 | #include <linux/pagemap.h> /* read_mapping_page */ | |
27 | #include <linux/slab.h> | |
28 | #include <linux/sched.h> | |
29 | #include <linux/rmap.h> /* anon_vma_prepare */ | |
30 | #include <linux/mmu_notifier.h> /* set_pte_at_notify */ | |
31 | #include <linux/swap.h> /* try_to_free_swap */ | |
32 | #include <linux/uprobes.h> | |
33 | ||
34 | static struct rb_root uprobes_tree = RB_ROOT; | |
35 | static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */ | |
36 | ||
37 | #define UPROBES_HASH_SZ 13 | |
38 | /* serialize (un)register */ | |
39 | static struct mutex uprobes_mutex[UPROBES_HASH_SZ]; | |
40 | #define uprobes_hash(v) (&uprobes_mutex[((unsigned long)(v)) %\ | |
41 | UPROBES_HASH_SZ]) | |
42 | ||
43 | /* serialize uprobe->pending_list */ | |
44 | static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ]; | |
45 | #define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) %\ | |
46 | UPROBES_HASH_SZ]) | |
47 | ||
48 | /* | |
49 | * uprobe_events allows us to skip the mmap_uprobe if there are no uprobe | |
50 | * events active at this time. Probably a fine grained per inode count is | |
51 | * better? | |
52 | */ | |
53 | static atomic_t uprobe_events = ATOMIC_INIT(0); | |
54 | ||
55 | /* | |
56 | * Maintain a temporary per vma info that can be used to search if a vma | |
57 | * has already been handled. This structure is introduced since extending | |
58 | * vm_area_struct wasnt recommended. | |
59 | */ | |
60 | struct vma_info { | |
61 | struct list_head probe_list; | |
62 | struct mm_struct *mm; | |
63 | loff_t vaddr; | |
64 | }; | |
65 | ||
66 | /* | |
67 | * valid_vma: Verify if the specified vma is an executable vma | |
68 | * Relax restrictions while unregistering: vm_flags might have | |
69 | * changed after breakpoint was inserted. | |
70 | * - is_register: indicates if we are in register context. | |
71 | * - Return 1 if the specified virtual address is in an | |
72 | * executable vma. | |
73 | */ | |
74 | static bool valid_vma(struct vm_area_struct *vma, bool is_register) | |
75 | { | |
76 | if (!vma->vm_file) | |
77 | return false; | |
78 | ||
79 | if (!is_register) | |
80 | return true; | |
81 | ||
82 | if ((vma->vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)) == | |
83 | (VM_READ|VM_EXEC)) | |
84 | return true; | |
85 | ||
86 | return false; | |
87 | } | |
88 | ||
89 | static loff_t vma_address(struct vm_area_struct *vma, loff_t offset) | |
90 | { | |
91 | loff_t vaddr; | |
92 | ||
93 | vaddr = vma->vm_start + offset; | |
94 | vaddr -= vma->vm_pgoff << PAGE_SHIFT; | |
95 | return vaddr; | |
96 | } | |
97 | ||
98 | /** | |
99 | * __replace_page - replace page in vma by new page. | |
100 | * based on replace_page in mm/ksm.c | |
101 | * | |
102 | * @vma: vma that holds the pte pointing to page | |
103 | * @page: the cowed page we are replacing by kpage | |
104 | * @kpage: the modified page we replace page by | |
105 | * | |
106 | * Returns 0 on success, -EFAULT on failure. | |
107 | */ | |
108 | static int __replace_page(struct vm_area_struct *vma, struct page *page, | |
109 | struct page *kpage) | |
110 | { | |
111 | struct mm_struct *mm = vma->vm_mm; | |
112 | pgd_t *pgd; | |
113 | pud_t *pud; | |
114 | pmd_t *pmd; | |
115 | pte_t *ptep; | |
116 | spinlock_t *ptl; | |
117 | unsigned long addr; | |
118 | int err = -EFAULT; | |
119 | ||
120 | addr = page_address_in_vma(page, vma); | |
121 | if (addr == -EFAULT) | |
122 | goto out; | |
123 | ||
124 | pgd = pgd_offset(mm, addr); | |
125 | if (!pgd_present(*pgd)) | |
126 | goto out; | |
127 | ||
128 | pud = pud_offset(pgd, addr); | |
129 | if (!pud_present(*pud)) | |
130 | goto out; | |
131 | ||
132 | pmd = pmd_offset(pud, addr); | |
133 | if (!pmd_present(*pmd)) | |
134 | goto out; | |
135 | ||
136 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); | |
137 | if (!ptep) | |
138 | goto out; | |
139 | ||
140 | get_page(kpage); | |
141 | page_add_new_anon_rmap(kpage, vma, addr); | |
142 | ||
143 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
144 | ptep_clear_flush(vma, addr, ptep); | |
145 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); | |
146 | ||
147 | page_remove_rmap(page); | |
148 | if (!page_mapped(page)) | |
149 | try_to_free_swap(page); | |
150 | put_page(page); | |
151 | pte_unmap_unlock(ptep, ptl); | |
152 | err = 0; | |
153 | ||
154 | out: | |
155 | return err; | |
156 | } | |
157 | ||
158 | /** | |
159 | * is_bkpt_insn - check if instruction is breakpoint instruction. | |
160 | * @insn: instruction to be checked. | |
161 | * Default implementation of is_bkpt_insn | |
162 | * Returns true if @insn is a breakpoint instruction. | |
163 | */ | |
164 | bool __weak is_bkpt_insn(uprobe_opcode_t *insn) | |
165 | { | |
166 | return (*insn == UPROBES_BKPT_INSN); | |
167 | } | |
168 | ||
169 | /* | |
170 | * NOTE: | |
171 | * Expect the breakpoint instruction to be the smallest size instruction for | |
172 | * the architecture. If an arch has variable length instruction and the | |
173 | * breakpoint instruction is not of the smallest length instruction | |
174 | * supported by that architecture then we need to modify read_opcode / | |
175 | * write_opcode accordingly. This would never be a problem for archs that | |
176 | * have fixed length instructions. | |
177 | */ | |
178 | ||
179 | /* | |
180 | * write_opcode - write the opcode at a given virtual address. | |
181 | * @mm: the probed process address space. | |
182 | * @uprobe: the breakpointing information. | |
183 | * @vaddr: the virtual address to store the opcode. | |
184 | * @opcode: opcode to be written at @vaddr. | |
185 | * | |
186 | * Called with mm->mmap_sem held (for read and with a reference to | |
187 | * mm). | |
188 | * | |
189 | * For mm @mm, write the opcode at @vaddr. | |
190 | * Return 0 (success) or a negative errno. | |
191 | */ | |
192 | static int write_opcode(struct mm_struct *mm, struct uprobe *uprobe, | |
193 | unsigned long vaddr, uprobe_opcode_t opcode) | |
194 | { | |
195 | struct page *old_page, *new_page; | |
196 | struct address_space *mapping; | |
197 | void *vaddr_old, *vaddr_new; | |
198 | struct vm_area_struct *vma; | |
199 | loff_t addr; | |
200 | int ret; | |
201 | ||
202 | /* Read the page with vaddr into memory */ | |
203 | ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma); | |
204 | if (ret <= 0) | |
205 | return ret; | |
206 | ret = -EINVAL; | |
207 | ||
208 | /* | |
209 | * We are interested in text pages only. Our pages of interest | |
210 | * should be mapped for read and execute only. We desist from | |
211 | * adding probes in write mapped pages since the breakpoints | |
212 | * might end up in the file copy. | |
213 | */ | |
214 | if (!valid_vma(vma, is_bkpt_insn(&opcode))) | |
215 | goto put_out; | |
216 | ||
217 | mapping = uprobe->inode->i_mapping; | |
218 | if (mapping != vma->vm_file->f_mapping) | |
219 | goto put_out; | |
220 | ||
221 | addr = vma_address(vma, uprobe->offset); | |
222 | if (vaddr != (unsigned long)addr) | |
223 | goto put_out; | |
224 | ||
225 | ret = -ENOMEM; | |
226 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr); | |
227 | if (!new_page) | |
228 | goto put_out; | |
229 | ||
230 | __SetPageUptodate(new_page); | |
231 | ||
232 | /* | |
233 | * lock page will serialize against do_wp_page()'s | |
234 | * PageAnon() handling | |
235 | */ | |
236 | lock_page(old_page); | |
237 | /* copy the page now that we've got it stable */ | |
238 | vaddr_old = kmap_atomic(old_page); | |
239 | vaddr_new = kmap_atomic(new_page); | |
240 | ||
241 | memcpy(vaddr_new, vaddr_old, PAGE_SIZE); | |
242 | /* poke the new insn in, ASSUMES we don't cross page boundary */ | |
243 | vaddr &= ~PAGE_MASK; | |
244 | BUG_ON(vaddr + uprobe_opcode_sz > PAGE_SIZE); | |
245 | memcpy(vaddr_new + vaddr, &opcode, uprobe_opcode_sz); | |
246 | ||
247 | kunmap_atomic(vaddr_new); | |
248 | kunmap_atomic(vaddr_old); | |
249 | ||
250 | ret = anon_vma_prepare(vma); | |
251 | if (ret) | |
252 | goto unlock_out; | |
253 | ||
254 | lock_page(new_page); | |
255 | ret = __replace_page(vma, old_page, new_page); | |
256 | unlock_page(new_page); | |
257 | ||
258 | unlock_out: | |
259 | unlock_page(old_page); | |
260 | page_cache_release(new_page); | |
261 | ||
262 | put_out: | |
263 | put_page(old_page); /* we did a get_page in the beginning */ | |
264 | return ret; | |
265 | } | |
266 | ||
267 | /** | |
268 | * read_opcode - read the opcode at a given virtual address. | |
269 | * @mm: the probed process address space. | |
270 | * @vaddr: the virtual address to read the opcode. | |
271 | * @opcode: location to store the read opcode. | |
272 | * | |
273 | * Called with mm->mmap_sem held (for read and with a reference to | |
274 | * mm. | |
275 | * | |
276 | * For mm @mm, read the opcode at @vaddr and store it in @opcode. | |
277 | * Return 0 (success) or a negative errno. | |
278 | */ | |
279 | static int read_opcode(struct mm_struct *mm, unsigned long vaddr, | |
280 | uprobe_opcode_t *opcode) | |
281 | { | |
282 | struct page *page; | |
283 | void *vaddr_new; | |
284 | int ret; | |
285 | ||
286 | ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL); | |
287 | if (ret <= 0) | |
288 | return ret; | |
289 | ||
290 | lock_page(page); | |
291 | vaddr_new = kmap_atomic(page); | |
292 | vaddr &= ~PAGE_MASK; | |
293 | memcpy(opcode, vaddr_new + vaddr, uprobe_opcode_sz); | |
294 | kunmap_atomic(vaddr_new); | |
295 | unlock_page(page); | |
296 | put_page(page); /* we did a get_user_pages in the beginning */ | |
297 | return 0; | |
298 | } | |
299 | ||
300 | static int is_bkpt_at_addr(struct mm_struct *mm, unsigned long vaddr) | |
301 | { | |
302 | uprobe_opcode_t opcode; | |
303 | int result = read_opcode(mm, vaddr, &opcode); | |
304 | ||
305 | if (result) | |
306 | return result; | |
307 | ||
308 | if (is_bkpt_insn(&opcode)) | |
309 | return 1; | |
310 | ||
311 | return 0; | |
312 | } | |
313 | ||
314 | /** | |
315 | * set_bkpt - store breakpoint at a given address. | |
316 | * @mm: the probed process address space. | |
317 | * @uprobe: the probepoint information. | |
318 | * @vaddr: the virtual address to insert the opcode. | |
319 | * | |
320 | * For mm @mm, store the breakpoint instruction at @vaddr. | |
321 | * Return 0 (success) or a negative errno. | |
322 | */ | |
323 | int __weak set_bkpt(struct mm_struct *mm, struct uprobe *uprobe, | |
324 | unsigned long vaddr) | |
325 | { | |
326 | int result = is_bkpt_at_addr(mm, vaddr); | |
327 | ||
328 | if (result == 1) | |
329 | return -EEXIST; | |
330 | ||
331 | if (result) | |
332 | return result; | |
333 | ||
334 | return write_opcode(mm, uprobe, vaddr, UPROBES_BKPT_INSN); | |
335 | } | |
336 | ||
337 | /** | |
338 | * set_orig_insn - Restore the original instruction. | |
339 | * @mm: the probed process address space. | |
340 | * @uprobe: the probepoint information. | |
341 | * @vaddr: the virtual address to insert the opcode. | |
342 | * @verify: if true, verify existance of breakpoint instruction. | |
343 | * | |
344 | * For mm @mm, restore the original opcode (opcode) at @vaddr. | |
345 | * Return 0 (success) or a negative errno. | |
346 | */ | |
347 | int __weak set_orig_insn(struct mm_struct *mm, struct uprobe *uprobe, | |
348 | unsigned long vaddr, bool verify) | |
349 | { | |
350 | if (verify) { | |
351 | int result = is_bkpt_at_addr(mm, vaddr); | |
352 | ||
353 | if (!result) | |
354 | return -EINVAL; | |
355 | ||
356 | if (result != 1) | |
357 | return result; | |
358 | } | |
359 | return write_opcode(mm, uprobe, vaddr, | |
360 | *(uprobe_opcode_t *)uprobe->insn); | |
361 | } | |
362 | ||
363 | static int match_uprobe(struct uprobe *l, struct uprobe *r) | |
364 | { | |
365 | if (l->inode < r->inode) | |
366 | return -1; | |
367 | if (l->inode > r->inode) | |
368 | return 1; | |
369 | else { | |
370 | if (l->offset < r->offset) | |
371 | return -1; | |
372 | ||
373 | if (l->offset > r->offset) | |
374 | return 1; | |
375 | } | |
376 | ||
377 | return 0; | |
378 | } | |
379 | ||
380 | static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset) | |
381 | { | |
382 | struct uprobe u = { .inode = inode, .offset = offset }; | |
383 | struct rb_node *n = uprobes_tree.rb_node; | |
384 | struct uprobe *uprobe; | |
385 | int match; | |
386 | ||
387 | while (n) { | |
388 | uprobe = rb_entry(n, struct uprobe, rb_node); | |
389 | match = match_uprobe(&u, uprobe); | |
390 | if (!match) { | |
391 | atomic_inc(&uprobe->ref); | |
392 | return uprobe; | |
393 | } | |
394 | if (match < 0) | |
395 | n = n->rb_left; | |
396 | else | |
397 | n = n->rb_right; | |
398 | } | |
399 | return NULL; | |
400 | } | |
401 | ||
402 | /* | |
403 | * Find a uprobe corresponding to a given inode:offset | |
404 | * Acquires uprobes_treelock | |
405 | */ | |
406 | static struct uprobe *find_uprobe(struct inode *inode, loff_t offset) | |
407 | { | |
408 | struct uprobe *uprobe; | |
409 | unsigned long flags; | |
410 | ||
411 | spin_lock_irqsave(&uprobes_treelock, flags); | |
412 | uprobe = __find_uprobe(inode, offset); | |
413 | spin_unlock_irqrestore(&uprobes_treelock, flags); | |
414 | return uprobe; | |
415 | } | |
416 | ||
417 | static struct uprobe *__insert_uprobe(struct uprobe *uprobe) | |
418 | { | |
419 | struct rb_node **p = &uprobes_tree.rb_node; | |
420 | struct rb_node *parent = NULL; | |
421 | struct uprobe *u; | |
422 | int match; | |
423 | ||
424 | while (*p) { | |
425 | parent = *p; | |
426 | u = rb_entry(parent, struct uprobe, rb_node); | |
427 | match = match_uprobe(uprobe, u); | |
428 | if (!match) { | |
429 | atomic_inc(&u->ref); | |
430 | return u; | |
431 | } | |
432 | ||
433 | if (match < 0) | |
434 | p = &parent->rb_left; | |
435 | else | |
436 | p = &parent->rb_right; | |
437 | ||
438 | } | |
439 | u = NULL; | |
440 | rb_link_node(&uprobe->rb_node, parent, p); | |
441 | rb_insert_color(&uprobe->rb_node, &uprobes_tree); | |
442 | /* get access + creation ref */ | |
443 | atomic_set(&uprobe->ref, 2); | |
444 | return u; | |
445 | } | |
446 | ||
447 | /* | |
448 | * Acquires uprobes_treelock. | |
449 | * Matching uprobe already exists in rbtree; | |
450 | * increment (access refcount) and return the matching uprobe. | |
451 | * | |
452 | * No matching uprobe; insert the uprobe in rb_tree; | |
453 | * get a double refcount (access + creation) and return NULL. | |
454 | */ | |
455 | static struct uprobe *insert_uprobe(struct uprobe *uprobe) | |
456 | { | |
457 | unsigned long flags; | |
458 | struct uprobe *u; | |
459 | ||
460 | spin_lock_irqsave(&uprobes_treelock, flags); | |
461 | u = __insert_uprobe(uprobe); | |
462 | spin_unlock_irqrestore(&uprobes_treelock, flags); | |
463 | return u; | |
464 | } | |
465 | ||
466 | static void put_uprobe(struct uprobe *uprobe) | |
467 | { | |
468 | if (atomic_dec_and_test(&uprobe->ref)) | |
469 | kfree(uprobe); | |
470 | } | |
471 | ||
472 | static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset) | |
473 | { | |
474 | struct uprobe *uprobe, *cur_uprobe; | |
475 | ||
476 | uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL); | |
477 | if (!uprobe) | |
478 | return NULL; | |
479 | ||
480 | uprobe->inode = igrab(inode); | |
481 | uprobe->offset = offset; | |
482 | init_rwsem(&uprobe->consumer_rwsem); | |
483 | INIT_LIST_HEAD(&uprobe->pending_list); | |
484 | ||
485 | /* add to uprobes_tree, sorted on inode:offset */ | |
486 | cur_uprobe = insert_uprobe(uprobe); | |
487 | ||
488 | /* a uprobe exists for this inode:offset combination */ | |
489 | if (cur_uprobe) { | |
490 | kfree(uprobe); | |
491 | uprobe = cur_uprobe; | |
492 | iput(inode); | |
493 | } else | |
494 | atomic_inc(&uprobe_events); | |
495 | return uprobe; | |
496 | } | |
497 | ||
498 | /* Returns the previous consumer */ | |
499 | static struct uprobe_consumer *add_consumer(struct uprobe *uprobe, | |
500 | struct uprobe_consumer *consumer) | |
501 | { | |
502 | down_write(&uprobe->consumer_rwsem); | |
503 | consumer->next = uprobe->consumers; | |
504 | uprobe->consumers = consumer; | |
505 | up_write(&uprobe->consumer_rwsem); | |
506 | return consumer->next; | |
507 | } | |
508 | ||
509 | /* | |
510 | * For uprobe @uprobe, delete the consumer @consumer. | |
511 | * Return true if the @consumer is deleted successfully | |
512 | * or return false. | |
513 | */ | |
514 | static bool del_consumer(struct uprobe *uprobe, | |
515 | struct uprobe_consumer *consumer) | |
516 | { | |
517 | struct uprobe_consumer **con; | |
518 | bool ret = false; | |
519 | ||
520 | down_write(&uprobe->consumer_rwsem); | |
521 | for (con = &uprobe->consumers; *con; con = &(*con)->next) { | |
522 | if (*con == consumer) { | |
523 | *con = consumer->next; | |
524 | ret = true; | |
525 | break; | |
526 | } | |
527 | } | |
528 | up_write(&uprobe->consumer_rwsem); | |
529 | return ret; | |
530 | } | |
531 | ||
532 | static int __copy_insn(struct address_space *mapping, | |
533 | struct vm_area_struct *vma, char *insn, | |
534 | unsigned long nbytes, unsigned long offset) | |
535 | { | |
536 | struct file *filp = vma->vm_file; | |
537 | struct page *page; | |
538 | void *vaddr; | |
539 | unsigned long off1; | |
540 | unsigned long idx; | |
541 | ||
542 | if (!filp) | |
543 | return -EINVAL; | |
544 | ||
545 | idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT); | |
546 | off1 = offset &= ~PAGE_MASK; | |
547 | ||
548 | /* | |
549 | * Ensure that the page that has the original instruction is | |
550 | * populated and in page-cache. | |
551 | */ | |
552 | page = read_mapping_page(mapping, idx, filp); | |
553 | if (IS_ERR(page)) | |
554 | return PTR_ERR(page); | |
555 | ||
556 | vaddr = kmap_atomic(page); | |
557 | memcpy(insn, vaddr + off1, nbytes); | |
558 | kunmap_atomic(vaddr); | |
559 | page_cache_release(page); | |
560 | return 0; | |
561 | } | |
562 | ||
563 | static int copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, | |
564 | unsigned long addr) | |
565 | { | |
566 | struct address_space *mapping; | |
567 | int bytes; | |
568 | unsigned long nbytes; | |
569 | ||
570 | addr &= ~PAGE_MASK; | |
571 | nbytes = PAGE_SIZE - addr; | |
572 | mapping = uprobe->inode->i_mapping; | |
573 | ||
574 | /* Instruction at end of binary; copy only available bytes */ | |
575 | if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size) | |
576 | bytes = uprobe->inode->i_size - uprobe->offset; | |
577 | else | |
578 | bytes = MAX_UINSN_BYTES; | |
579 | ||
580 | /* Instruction at the page-boundary; copy bytes in second page */ | |
581 | if (nbytes < bytes) { | |
582 | if (__copy_insn(mapping, vma, uprobe->insn + nbytes, | |
583 | bytes - nbytes, uprobe->offset + nbytes)) | |
584 | return -ENOMEM; | |
585 | ||
586 | bytes = nbytes; | |
587 | } | |
588 | return __copy_insn(mapping, vma, uprobe->insn, bytes, uprobe->offset); | |
589 | } | |
590 | ||
591 | static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe, | |
592 | struct vm_area_struct *vma, loff_t vaddr) | |
593 | { | |
594 | unsigned long addr; | |
595 | int ret; | |
596 | ||
597 | /* | |
598 | * If probe is being deleted, unregister thread could be done with | |
599 | * the vma-rmap-walk through. Adding a probe now can be fatal since | |
600 | * nobody will be able to cleanup. Also we could be from fork or | |
601 | * mremap path, where the probe might have already been inserted. | |
602 | * Hence behave as if probe already existed. | |
603 | */ | |
604 | if (!uprobe->consumers) | |
605 | return -EEXIST; | |
606 | ||
607 | addr = (unsigned long)vaddr; | |
608 | if (!(uprobe->flags & UPROBES_COPY_INSN)) { | |
609 | ret = copy_insn(uprobe, vma, addr); | |
610 | if (ret) | |
611 | return ret; | |
612 | ||
613 | if (is_bkpt_insn((uprobe_opcode_t *)uprobe->insn)) | |
614 | return -EEXIST; | |
615 | ||
616 | ret = analyze_insn(mm, uprobe); | |
617 | if (ret) | |
618 | return ret; | |
619 | ||
620 | uprobe->flags |= UPROBES_COPY_INSN; | |
621 | } | |
622 | ret = set_bkpt(mm, uprobe, addr); | |
623 | ||
624 | return ret; | |
625 | } | |
626 | ||
627 | static void remove_breakpoint(struct mm_struct *mm, struct uprobe *uprobe, | |
628 | loff_t vaddr) | |
629 | { | |
630 | set_orig_insn(mm, uprobe, (unsigned long)vaddr, true); | |
631 | } | |
632 | ||
633 | static void delete_uprobe(struct uprobe *uprobe) | |
634 | { | |
635 | unsigned long flags; | |
636 | ||
637 | spin_lock_irqsave(&uprobes_treelock, flags); | |
638 | rb_erase(&uprobe->rb_node, &uprobes_tree); | |
639 | spin_unlock_irqrestore(&uprobes_treelock, flags); | |
640 | iput(uprobe->inode); | |
641 | put_uprobe(uprobe); | |
642 | atomic_dec(&uprobe_events); | |
643 | } | |
644 | ||
645 | static struct vma_info *__find_next_vma_info(struct list_head *head, | |
646 | loff_t offset, struct address_space *mapping, | |
647 | struct vma_info *vi, bool is_register) | |
648 | { | |
649 | struct prio_tree_iter iter; | |
650 | struct vm_area_struct *vma; | |
651 | struct vma_info *tmpvi; | |
652 | loff_t vaddr; | |
653 | unsigned long pgoff = offset >> PAGE_SHIFT; | |
654 | int existing_vma; | |
655 | ||
656 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { | |
657 | if (!valid_vma(vma, is_register)) | |
658 | continue; | |
659 | ||
660 | existing_vma = 0; | |
661 | vaddr = vma_address(vma, offset); | |
662 | list_for_each_entry(tmpvi, head, probe_list) { | |
663 | if (tmpvi->mm == vma->vm_mm && tmpvi->vaddr == vaddr) { | |
664 | existing_vma = 1; | |
665 | break; | |
666 | } | |
667 | } | |
668 | ||
669 | /* | |
670 | * Another vma needs a probe to be installed. However skip | |
671 | * installing the probe if the vma is about to be unlinked. | |
672 | */ | |
673 | if (!existing_vma && | |
674 | atomic_inc_not_zero(&vma->vm_mm->mm_users)) { | |
675 | vi->mm = vma->vm_mm; | |
676 | vi->vaddr = vaddr; | |
677 | list_add(&vi->probe_list, head); | |
678 | return vi; | |
679 | } | |
680 | } | |
681 | return NULL; | |
682 | } | |
683 | ||
684 | /* | |
685 | * Iterate in the rmap prio tree and find a vma where a probe has not | |
686 | * yet been inserted. | |
687 | */ | |
688 | static struct vma_info *find_next_vma_info(struct list_head *head, | |
689 | loff_t offset, struct address_space *mapping, | |
690 | bool is_register) | |
691 | { | |
692 | struct vma_info *vi, *retvi; | |
693 | vi = kzalloc(sizeof(struct vma_info), GFP_KERNEL); | |
694 | if (!vi) | |
695 | return ERR_PTR(-ENOMEM); | |
696 | ||
697 | mutex_lock(&mapping->i_mmap_mutex); | |
698 | retvi = __find_next_vma_info(head, offset, mapping, vi, is_register); | |
699 | mutex_unlock(&mapping->i_mmap_mutex); | |
700 | ||
701 | if (!retvi) | |
702 | kfree(vi); | |
703 | return retvi; | |
704 | } | |
705 | ||
706 | static int register_for_each_vma(struct uprobe *uprobe, bool is_register) | |
707 | { | |
708 | struct list_head try_list; | |
709 | struct vm_area_struct *vma; | |
710 | struct address_space *mapping; | |
711 | struct vma_info *vi, *tmpvi; | |
712 | struct mm_struct *mm; | |
713 | loff_t vaddr; | |
714 | int ret = 0; | |
715 | ||
716 | mapping = uprobe->inode->i_mapping; | |
717 | INIT_LIST_HEAD(&try_list); | |
718 | while ((vi = find_next_vma_info(&try_list, uprobe->offset, | |
719 | mapping, is_register)) != NULL) { | |
720 | if (IS_ERR(vi)) { | |
721 | ret = PTR_ERR(vi); | |
722 | break; | |
723 | } | |
724 | mm = vi->mm; | |
725 | down_read(&mm->mmap_sem); | |
726 | vma = find_vma(mm, (unsigned long)vi->vaddr); | |
727 | if (!vma || !valid_vma(vma, is_register)) { | |
728 | list_del(&vi->probe_list); | |
729 | kfree(vi); | |
730 | up_read(&mm->mmap_sem); | |
731 | mmput(mm); | |
732 | continue; | |
733 | } | |
734 | vaddr = vma_address(vma, uprobe->offset); | |
735 | if (vma->vm_file->f_mapping->host != uprobe->inode || | |
736 | vaddr != vi->vaddr) { | |
737 | list_del(&vi->probe_list); | |
738 | kfree(vi); | |
739 | up_read(&mm->mmap_sem); | |
740 | mmput(mm); | |
741 | continue; | |
742 | } | |
743 | ||
744 | if (is_register) | |
745 | ret = install_breakpoint(mm, uprobe, vma, vi->vaddr); | |
746 | else | |
747 | remove_breakpoint(mm, uprobe, vi->vaddr); | |
748 | ||
749 | up_read(&mm->mmap_sem); | |
750 | mmput(mm); | |
751 | if (is_register) { | |
752 | if (ret && ret == -EEXIST) | |
753 | ret = 0; | |
754 | if (ret) | |
755 | break; | |
756 | } | |
757 | } | |
758 | list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) { | |
759 | list_del(&vi->probe_list); | |
760 | kfree(vi); | |
761 | } | |
762 | return ret; | |
763 | } | |
764 | ||
765 | static int __register_uprobe(struct uprobe *uprobe) | |
766 | { | |
767 | return register_for_each_vma(uprobe, true); | |
768 | } | |
769 | ||
770 | static void __unregister_uprobe(struct uprobe *uprobe) | |
771 | { | |
772 | if (!register_for_each_vma(uprobe, false)) | |
773 | delete_uprobe(uprobe); | |
774 | ||
775 | /* TODO : cant unregister? schedule a worker thread */ | |
776 | } | |
777 | ||
778 | /* | |
779 | * register_uprobe - register a probe | |
780 | * @inode: the file in which the probe has to be placed. | |
781 | * @offset: offset from the start of the file. | |
782 | * @consumer: information on howto handle the probe.. | |
783 | * | |
784 | * Apart from the access refcount, register_uprobe() takes a creation | |
785 | * refcount (thro alloc_uprobe) if and only if this @uprobe is getting | |
786 | * inserted into the rbtree (i.e first consumer for a @inode:@offset | |
787 | * tuple). Creation refcount stops unregister_uprobe from freeing the | |
788 | * @uprobe even before the register operation is complete. Creation | |
789 | * refcount is released when the last @consumer for the @uprobe | |
790 | * unregisters. | |
791 | * | |
792 | * Return errno if it cannot successully install probes | |
793 | * else return 0 (success) | |
794 | */ | |
795 | int register_uprobe(struct inode *inode, loff_t offset, | |
796 | struct uprobe_consumer *consumer) | |
797 | { | |
798 | struct uprobe *uprobe; | |
799 | int ret = -EINVAL; | |
800 | ||
801 | if (!inode || !consumer || consumer->next) | |
802 | return ret; | |
803 | ||
804 | if (offset > i_size_read(inode)) | |
805 | return ret; | |
806 | ||
807 | ret = 0; | |
808 | mutex_lock(uprobes_hash(inode)); | |
809 | uprobe = alloc_uprobe(inode, offset); | |
810 | if (uprobe && !add_consumer(uprobe, consumer)) { | |
811 | ret = __register_uprobe(uprobe); | |
812 | if (ret) { | |
813 | uprobe->consumers = NULL; | |
814 | __unregister_uprobe(uprobe); | |
815 | } else | |
816 | uprobe->flags |= UPROBES_RUN_HANDLER; | |
817 | } | |
818 | ||
819 | mutex_unlock(uprobes_hash(inode)); | |
820 | put_uprobe(uprobe); | |
821 | ||
822 | return ret; | |
823 | } | |
824 | ||
825 | /* | |
826 | * unregister_uprobe - unregister a already registered probe. | |
827 | * @inode: the file in which the probe has to be removed. | |
828 | * @offset: offset from the start of the file. | |
829 | * @consumer: identify which probe if multiple probes are colocated. | |
830 | */ | |
831 | void unregister_uprobe(struct inode *inode, loff_t offset, | |
832 | struct uprobe_consumer *consumer) | |
833 | { | |
834 | struct uprobe *uprobe = NULL; | |
835 | ||
836 | if (!inode || !consumer) | |
837 | return; | |
838 | ||
839 | uprobe = find_uprobe(inode, offset); | |
840 | if (!uprobe) | |
841 | return; | |
842 | ||
843 | mutex_lock(uprobes_hash(inode)); | |
844 | if (!del_consumer(uprobe, consumer)) | |
845 | goto unreg_out; | |
846 | ||
847 | if (!uprobe->consumers) { | |
848 | __unregister_uprobe(uprobe); | |
849 | uprobe->flags &= ~UPROBES_RUN_HANDLER; | |
850 | } | |
851 | ||
852 | unreg_out: | |
853 | mutex_unlock(uprobes_hash(inode)); | |
854 | if (uprobe) | |
855 | put_uprobe(uprobe); | |
856 | } | |
857 | ||
858 | /* | |
859 | * Of all the nodes that correspond to the given inode, return the node | |
860 | * with the least offset. | |
861 | */ | |
862 | static struct rb_node *find_least_offset_node(struct inode *inode) | |
863 | { | |
864 | struct uprobe u = { .inode = inode, .offset = 0}; | |
865 | struct rb_node *n = uprobes_tree.rb_node; | |
866 | struct rb_node *close_node = NULL; | |
867 | struct uprobe *uprobe; | |
868 | int match; | |
869 | ||
870 | while (n) { | |
871 | uprobe = rb_entry(n, struct uprobe, rb_node); | |
872 | match = match_uprobe(&u, uprobe); | |
873 | if (uprobe->inode == inode) | |
874 | close_node = n; | |
875 | ||
876 | if (!match) | |
877 | return close_node; | |
878 | ||
879 | if (match < 0) | |
880 | n = n->rb_left; | |
881 | else | |
882 | n = n->rb_right; | |
883 | } | |
884 | return close_node; | |
885 | } | |
886 | ||
887 | /* | |
888 | * For a given inode, build a list of probes that need to be inserted. | |
889 | */ | |
890 | static void build_probe_list(struct inode *inode, struct list_head *head) | |
891 | { | |
892 | struct uprobe *uprobe; | |
893 | struct rb_node *n; | |
894 | unsigned long flags; | |
895 | ||
896 | spin_lock_irqsave(&uprobes_treelock, flags); | |
897 | n = find_least_offset_node(inode); | |
898 | for (; n; n = rb_next(n)) { | |
899 | uprobe = rb_entry(n, struct uprobe, rb_node); | |
900 | if (uprobe->inode != inode) | |
901 | break; | |
902 | ||
903 | list_add(&uprobe->pending_list, head); | |
904 | atomic_inc(&uprobe->ref); | |
905 | } | |
906 | spin_unlock_irqrestore(&uprobes_treelock, flags); | |
907 | } | |
908 | ||
909 | /* | |
910 | * Called from mmap_region. | |
911 | * called with mm->mmap_sem acquired. | |
912 | * | |
913 | * Return -ve no if we fail to insert probes and we cannot | |
914 | * bail-out. | |
915 | * Return 0 otherwise. i.e : | |
916 | * - successful insertion of probes | |
917 | * - (or) no possible probes to be inserted. | |
918 | * - (or) insertion of probes failed but we can bail-out. | |
919 | */ | |
920 | int mmap_uprobe(struct vm_area_struct *vma) | |
921 | { | |
922 | struct list_head tmp_list; | |
923 | struct uprobe *uprobe, *u; | |
924 | struct inode *inode; | |
925 | int ret = 0; | |
926 | ||
927 | if (!atomic_read(&uprobe_events) || !valid_vma(vma, true)) | |
928 | return ret; /* Bail-out */ | |
929 | ||
930 | inode = vma->vm_file->f_mapping->host; | |
931 | if (!inode) | |
932 | return ret; | |
933 | ||
934 | INIT_LIST_HEAD(&tmp_list); | |
935 | mutex_lock(uprobes_mmap_hash(inode)); | |
936 | build_probe_list(inode, &tmp_list); | |
937 | list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) { | |
938 | loff_t vaddr; | |
939 | ||
940 | list_del(&uprobe->pending_list); | |
941 | if (!ret) { | |
942 | vaddr = vma_address(vma, uprobe->offset); | |
943 | if (vaddr < vma->vm_start || vaddr >= vma->vm_end) { | |
944 | put_uprobe(uprobe); | |
945 | continue; | |
946 | } | |
947 | ret = install_breakpoint(vma->vm_mm, uprobe, vma, | |
948 | vaddr); | |
949 | if (ret == -EEXIST) | |
950 | ret = 0; | |
951 | } | |
952 | put_uprobe(uprobe); | |
953 | } | |
954 | ||
955 | mutex_unlock(uprobes_mmap_hash(inode)); | |
956 | ||
957 | return ret; | |
958 | } | |
959 | ||
960 | static int __init init_uprobes(void) | |
961 | { | |
962 | int i; | |
963 | ||
964 | for (i = 0; i < UPROBES_HASH_SZ; i++) { | |
965 | mutex_init(&uprobes_mutex[i]); | |
966 | mutex_init(&uprobes_mmap_mutex[i]); | |
967 | } | |
968 | return 0; | |
969 | } | |
970 | ||
971 | static void __exit exit_uprobes(void) | |
972 | { | |
973 | } | |
974 | ||
975 | module_init(init_uprobes); | |
976 | module_exit(exit_uprobes); |