x86/xen: resume timer irqs early
[linux/fpc-iii.git] / kernel / events / uprobes.c
blobad8e1bdca70e4c702ff5c6e86255dc74a8b98259
1 /*
2 * User-space Probes (UProbes)
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.
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.
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.
18 * Copyright (C) IBM Corporation, 2008-2012
19 * Authors:
20 * Srikar Dronamraju
21 * Jim Keniston
22 * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
25 #include <linux/kernel.h>
26 #include <linux/highmem.h>
27 #include <linux/pagemap.h> /* read_mapping_page */
28 #include <linux/slab.h>
29 #include <linux/sched.h>
30 #include <linux/export.h>
31 #include <linux/rmap.h> /* anon_vma_prepare */
32 #include <linux/mmu_notifier.h> /* set_pte_at_notify */
33 #include <linux/swap.h> /* try_to_free_swap */
34 #include <linux/ptrace.h> /* user_enable_single_step */
35 #include <linux/kdebug.h> /* notifier mechanism */
36 #include "../../mm/internal.h" /* munlock_vma_page */
37 #include <linux/percpu-rwsem.h>
39 #include <linux/uprobes.h>
41 #define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
42 #define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
44 static struct rb_root uprobes_tree = RB_ROOT;
46 * allows us to skip the uprobe_mmap if there are no uprobe events active
47 * at this time. Probably a fine grained per inode count is better?
49 #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree)
51 static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
53 #define UPROBES_HASH_SZ 13
54 /* serialize uprobe->pending_list */
55 static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
56 #define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
58 static struct percpu_rw_semaphore dup_mmap_sem;
60 /* Have a copy of original instruction */
61 #define UPROBE_COPY_INSN 0
62 /* Can skip singlestep */
63 #define UPROBE_SKIP_SSTEP 1
65 struct uprobe {
66 struct rb_node rb_node; /* node in the rb tree */
67 atomic_t ref;
68 struct rw_semaphore register_rwsem;
69 struct rw_semaphore consumer_rwsem;
70 struct list_head pending_list;
71 struct uprobe_consumer *consumers;
72 struct inode *inode; /* Also hold a ref to inode */
73 loff_t offset;
74 unsigned long flags;
75 struct arch_uprobe arch;
78 struct return_instance {
79 struct uprobe *uprobe;
80 unsigned long func;
81 unsigned long orig_ret_vaddr; /* original return address */
82 bool chained; /* true, if instance is nested */
84 struct return_instance *next; /* keep as stack */
88 * valid_vma: Verify if the specified vma is an executable vma
89 * Relax restrictions while unregistering: vm_flags might have
90 * changed after breakpoint was inserted.
91 * - is_register: indicates if we are in register context.
92 * - Return 1 if the specified virtual address is in an
93 * executable vma.
95 static bool valid_vma(struct vm_area_struct *vma, bool is_register)
97 vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED;
99 if (is_register)
100 flags |= VM_WRITE;
102 return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
105 static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
107 return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
110 static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
112 return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start);
116 * __replace_page - replace page in vma by new page.
117 * based on replace_page in mm/ksm.c
119 * @vma: vma that holds the pte pointing to page
120 * @addr: address the old @page is mapped at
121 * @page: the cowed page we are replacing by kpage
122 * @kpage: the modified page we replace page by
124 * Returns 0 on success, -EFAULT on failure.
126 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
127 struct page *page, struct page *kpage)
129 struct mm_struct *mm = vma->vm_mm;
130 spinlock_t *ptl;
131 pte_t *ptep;
132 int err;
133 /* For mmu_notifiers */
134 const unsigned long mmun_start = addr;
135 const unsigned long mmun_end = addr + PAGE_SIZE;
137 /* For try_to_free_swap() and munlock_vma_page() below */
138 lock_page(page);
140 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
141 err = -EAGAIN;
142 ptep = page_check_address(page, mm, addr, &ptl, 0);
143 if (!ptep)
144 goto unlock;
146 get_page(kpage);
147 page_add_new_anon_rmap(kpage, vma, addr);
149 if (!PageAnon(page)) {
150 dec_mm_counter(mm, MM_FILEPAGES);
151 inc_mm_counter(mm, MM_ANONPAGES);
154 flush_cache_page(vma, addr, pte_pfn(*ptep));
155 ptep_clear_flush(vma, addr, ptep);
156 set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
158 page_remove_rmap(page);
159 if (!page_mapped(page))
160 try_to_free_swap(page);
161 pte_unmap_unlock(ptep, ptl);
163 if (vma->vm_flags & VM_LOCKED)
164 munlock_vma_page(page);
165 put_page(page);
167 err = 0;
168 unlock:
169 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
170 unlock_page(page);
171 return err;
175 * is_swbp_insn - check if instruction is breakpoint instruction.
176 * @insn: instruction to be checked.
177 * Default implementation of is_swbp_insn
178 * Returns true if @insn is a breakpoint instruction.
180 bool __weak is_swbp_insn(uprobe_opcode_t *insn)
182 return *insn == UPROBE_SWBP_INSN;
186 * is_trap_insn - check if instruction is breakpoint instruction.
187 * @insn: instruction to be checked.
188 * Default implementation of is_trap_insn
189 * Returns true if @insn is a breakpoint instruction.
191 * This function is needed for the case where an architecture has multiple
192 * trap instructions (like powerpc).
194 bool __weak is_trap_insn(uprobe_opcode_t *insn)
196 return is_swbp_insn(insn);
199 static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len)
201 void *kaddr = kmap_atomic(page);
202 memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
203 kunmap_atomic(kaddr);
206 static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
208 void *kaddr = kmap_atomic(page);
209 memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
210 kunmap_atomic(kaddr);
213 static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
215 uprobe_opcode_t old_opcode;
216 bool is_swbp;
219 * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here.
220 * We do not check if it is any other 'trap variant' which could
221 * be conditional trap instruction such as the one powerpc supports.
223 * The logic is that we do not care if the underlying instruction
224 * is a trap variant; uprobes always wins over any other (gdb)
225 * breakpoint.
227 copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE);
228 is_swbp = is_swbp_insn(&old_opcode);
230 if (is_swbp_insn(new_opcode)) {
231 if (is_swbp) /* register: already installed? */
232 return 0;
233 } else {
234 if (!is_swbp) /* unregister: was it changed by us? */
235 return 0;
238 return 1;
242 * NOTE:
243 * Expect the breakpoint instruction to be the smallest size instruction for
244 * the architecture. If an arch has variable length instruction and the
245 * breakpoint instruction is not of the smallest length instruction
246 * supported by that architecture then we need to modify is_trap_at_addr and
247 * write_opcode accordingly. This would never be a problem for archs that
248 * have fixed length instructions.
252 * write_opcode - write the opcode at a given virtual address.
253 * @mm: the probed process address space.
254 * @vaddr: the virtual address to store the opcode.
255 * @opcode: opcode to be written at @vaddr.
257 * Called with mm->mmap_sem held (for read and with a reference to
258 * mm).
260 * For mm @mm, write the opcode at @vaddr.
261 * Return 0 (success) or a negative errno.
263 static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
264 uprobe_opcode_t opcode)
266 struct page *old_page, *new_page;
267 struct vm_area_struct *vma;
268 int ret;
270 retry:
271 /* Read the page with vaddr into memory */
272 ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
273 if (ret <= 0)
274 return ret;
276 ret = verify_opcode(old_page, vaddr, &opcode);
277 if (ret <= 0)
278 goto put_old;
280 ret = -ENOMEM;
281 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
282 if (!new_page)
283 goto put_old;
285 __SetPageUptodate(new_page);
287 copy_highpage(new_page, old_page);
288 copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
290 ret = anon_vma_prepare(vma);
291 if (ret)
292 goto put_new;
294 ret = __replace_page(vma, vaddr, old_page, new_page);
296 put_new:
297 page_cache_release(new_page);
298 put_old:
299 put_page(old_page);
301 if (unlikely(ret == -EAGAIN))
302 goto retry;
303 return ret;
307 * set_swbp - store breakpoint at a given address.
308 * @auprobe: arch specific probepoint information.
309 * @mm: the probed process address space.
310 * @vaddr: the virtual address to insert the opcode.
312 * For mm @mm, store the breakpoint instruction at @vaddr.
313 * Return 0 (success) or a negative errno.
315 int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
317 return write_opcode(mm, vaddr, UPROBE_SWBP_INSN);
321 * set_orig_insn - Restore the original instruction.
322 * @mm: the probed process address space.
323 * @auprobe: arch specific probepoint information.
324 * @vaddr: the virtual address to insert the opcode.
326 * For mm @mm, restore the original opcode (opcode) at @vaddr.
327 * Return 0 (success) or a negative errno.
329 int __weak
330 set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
332 return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
335 static int match_uprobe(struct uprobe *l, struct uprobe *r)
337 if (l->inode < r->inode)
338 return -1;
340 if (l->inode > r->inode)
341 return 1;
343 if (l->offset < r->offset)
344 return -1;
346 if (l->offset > r->offset)
347 return 1;
349 return 0;
352 static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
354 struct uprobe u = { .inode = inode, .offset = offset };
355 struct rb_node *n = uprobes_tree.rb_node;
356 struct uprobe *uprobe;
357 int match;
359 while (n) {
360 uprobe = rb_entry(n, struct uprobe, rb_node);
361 match = match_uprobe(&u, uprobe);
362 if (!match) {
363 atomic_inc(&uprobe->ref);
364 return uprobe;
367 if (match < 0)
368 n = n->rb_left;
369 else
370 n = n->rb_right;
372 return NULL;
376 * Find a uprobe corresponding to a given inode:offset
377 * Acquires uprobes_treelock
379 static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
381 struct uprobe *uprobe;
383 spin_lock(&uprobes_treelock);
384 uprobe = __find_uprobe(inode, offset);
385 spin_unlock(&uprobes_treelock);
387 return uprobe;
390 static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
392 struct rb_node **p = &uprobes_tree.rb_node;
393 struct rb_node *parent = NULL;
394 struct uprobe *u;
395 int match;
397 while (*p) {
398 parent = *p;
399 u = rb_entry(parent, struct uprobe, rb_node);
400 match = match_uprobe(uprobe, u);
401 if (!match) {
402 atomic_inc(&u->ref);
403 return u;
406 if (match < 0)
407 p = &parent->rb_left;
408 else
409 p = &parent->rb_right;
413 u = NULL;
414 rb_link_node(&uprobe->rb_node, parent, p);
415 rb_insert_color(&uprobe->rb_node, &uprobes_tree);
416 /* get access + creation ref */
417 atomic_set(&uprobe->ref, 2);
419 return u;
423 * Acquire uprobes_treelock.
424 * Matching uprobe already exists in rbtree;
425 * increment (access refcount) and return the matching uprobe.
427 * No matching uprobe; insert the uprobe in rb_tree;
428 * get a double refcount (access + creation) and return NULL.
430 static struct uprobe *insert_uprobe(struct uprobe *uprobe)
432 struct uprobe *u;
434 spin_lock(&uprobes_treelock);
435 u = __insert_uprobe(uprobe);
436 spin_unlock(&uprobes_treelock);
438 return u;
441 static void put_uprobe(struct uprobe *uprobe)
443 if (atomic_dec_and_test(&uprobe->ref))
444 kfree(uprobe);
447 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
449 struct uprobe *uprobe, *cur_uprobe;
451 uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
452 if (!uprobe)
453 return NULL;
455 uprobe->inode = igrab(inode);
456 uprobe->offset = offset;
457 init_rwsem(&uprobe->register_rwsem);
458 init_rwsem(&uprobe->consumer_rwsem);
459 /* For now assume that the instruction need not be single-stepped */
460 __set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
462 /* add to uprobes_tree, sorted on inode:offset */
463 cur_uprobe = insert_uprobe(uprobe);
465 /* a uprobe exists for this inode:offset combination */
466 if (cur_uprobe) {
467 kfree(uprobe);
468 uprobe = cur_uprobe;
469 iput(inode);
472 return uprobe;
475 static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
477 down_write(&uprobe->consumer_rwsem);
478 uc->next = uprobe->consumers;
479 uprobe->consumers = uc;
480 up_write(&uprobe->consumer_rwsem);
484 * For uprobe @uprobe, delete the consumer @uc.
485 * Return true if the @uc is deleted successfully
486 * or return false.
488 static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
490 struct uprobe_consumer **con;
491 bool ret = false;
493 down_write(&uprobe->consumer_rwsem);
494 for (con = &uprobe->consumers; *con; con = &(*con)->next) {
495 if (*con == uc) {
496 *con = uc->next;
497 ret = true;
498 break;
501 up_write(&uprobe->consumer_rwsem);
503 return ret;
506 static int
507 __copy_insn(struct address_space *mapping, struct file *filp, char *insn,
508 unsigned long nbytes, loff_t offset)
510 struct page *page;
512 if (!mapping->a_ops->readpage)
513 return -EIO;
515 * Ensure that the page that has the original instruction is
516 * populated and in page-cache.
518 page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);
519 if (IS_ERR(page))
520 return PTR_ERR(page);
522 copy_from_page(page, offset, insn, nbytes);
523 page_cache_release(page);
525 return 0;
528 static int copy_insn(struct uprobe *uprobe, struct file *filp)
530 struct address_space *mapping;
531 unsigned long nbytes;
532 int bytes;
534 nbytes = PAGE_SIZE - (uprobe->offset & ~PAGE_MASK);
535 mapping = uprobe->inode->i_mapping;
537 /* Instruction at end of binary; copy only available bytes */
538 if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
539 bytes = uprobe->inode->i_size - uprobe->offset;
540 else
541 bytes = MAX_UINSN_BYTES;
543 /* Instruction at the page-boundary; copy bytes in second page */
544 if (nbytes < bytes) {
545 int err = __copy_insn(mapping, filp, uprobe->arch.insn + nbytes,
546 bytes - nbytes, uprobe->offset + nbytes);
547 if (err)
548 return err;
549 bytes = nbytes;
551 return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
554 static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
555 struct mm_struct *mm, unsigned long vaddr)
557 int ret = 0;
559 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
560 return ret;
562 /* TODO: move this into _register, until then we abuse this sem. */
563 down_write(&uprobe->consumer_rwsem);
564 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
565 goto out;
567 ret = copy_insn(uprobe, file);
568 if (ret)
569 goto out;
571 ret = -ENOTSUPP;
572 if (is_trap_insn((uprobe_opcode_t *)uprobe->arch.insn))
573 goto out;
575 ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
576 if (ret)
577 goto out;
579 /* write_opcode() assumes we don't cross page boundary */
580 BUG_ON((uprobe->offset & ~PAGE_MASK) +
581 UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
583 smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
584 set_bit(UPROBE_COPY_INSN, &uprobe->flags);
586 out:
587 up_write(&uprobe->consumer_rwsem);
589 return ret;
592 static inline bool consumer_filter(struct uprobe_consumer *uc,
593 enum uprobe_filter_ctx ctx, struct mm_struct *mm)
595 return !uc->filter || uc->filter(uc, ctx, mm);
598 static bool filter_chain(struct uprobe *uprobe,
599 enum uprobe_filter_ctx ctx, struct mm_struct *mm)
601 struct uprobe_consumer *uc;
602 bool ret = false;
604 down_read(&uprobe->consumer_rwsem);
605 for (uc = uprobe->consumers; uc; uc = uc->next) {
606 ret = consumer_filter(uc, ctx, mm);
607 if (ret)
608 break;
610 up_read(&uprobe->consumer_rwsem);
612 return ret;
615 static int
616 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
617 struct vm_area_struct *vma, unsigned long vaddr)
619 bool first_uprobe;
620 int ret;
622 ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
623 if (ret)
624 return ret;
627 * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
628 * the task can hit this breakpoint right after __replace_page().
630 first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
631 if (first_uprobe)
632 set_bit(MMF_HAS_UPROBES, &mm->flags);
634 ret = set_swbp(&uprobe->arch, mm, vaddr);
635 if (!ret)
636 clear_bit(MMF_RECALC_UPROBES, &mm->flags);
637 else if (first_uprobe)
638 clear_bit(MMF_HAS_UPROBES, &mm->flags);
640 return ret;
643 static int
644 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
646 set_bit(MMF_RECALC_UPROBES, &mm->flags);
647 return set_orig_insn(&uprobe->arch, mm, vaddr);
650 static inline bool uprobe_is_active(struct uprobe *uprobe)
652 return !RB_EMPTY_NODE(&uprobe->rb_node);
655 * There could be threads that have already hit the breakpoint. They
656 * will recheck the current insn and restart if find_uprobe() fails.
657 * See find_active_uprobe().
659 static void delete_uprobe(struct uprobe *uprobe)
661 if (WARN_ON(!uprobe_is_active(uprobe)))
662 return;
664 spin_lock(&uprobes_treelock);
665 rb_erase(&uprobe->rb_node, &uprobes_tree);
666 spin_unlock(&uprobes_treelock);
667 RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
668 iput(uprobe->inode);
669 put_uprobe(uprobe);
672 struct map_info {
673 struct map_info *next;
674 struct mm_struct *mm;
675 unsigned long vaddr;
678 static inline struct map_info *free_map_info(struct map_info *info)
680 struct map_info *next = info->next;
681 kfree(info);
682 return next;
685 static struct map_info *
686 build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
688 unsigned long pgoff = offset >> PAGE_SHIFT;
689 struct vm_area_struct *vma;
690 struct map_info *curr = NULL;
691 struct map_info *prev = NULL;
692 struct map_info *info;
693 int more = 0;
695 again:
696 mutex_lock(&mapping->i_mmap_mutex);
697 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
698 if (!valid_vma(vma, is_register))
699 continue;
701 if (!prev && !more) {
703 * Needs GFP_NOWAIT to avoid i_mmap_mutex recursion through
704 * reclaim. This is optimistic, no harm done if it fails.
706 prev = kmalloc(sizeof(struct map_info),
707 GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
708 if (prev)
709 prev->next = NULL;
711 if (!prev) {
712 more++;
713 continue;
716 if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
717 continue;
719 info = prev;
720 prev = prev->next;
721 info->next = curr;
722 curr = info;
724 info->mm = vma->vm_mm;
725 info->vaddr = offset_to_vaddr(vma, offset);
727 mutex_unlock(&mapping->i_mmap_mutex);
729 if (!more)
730 goto out;
732 prev = curr;
733 while (curr) {
734 mmput(curr->mm);
735 curr = curr->next;
738 do {
739 info = kmalloc(sizeof(struct map_info), GFP_KERNEL);
740 if (!info) {
741 curr = ERR_PTR(-ENOMEM);
742 goto out;
744 info->next = prev;
745 prev = info;
746 } while (--more);
748 goto again;
749 out:
750 while (prev)
751 prev = free_map_info(prev);
752 return curr;
755 static int
756 register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
758 bool is_register = !!new;
759 struct map_info *info;
760 int err = 0;
762 percpu_down_write(&dup_mmap_sem);
763 info = build_map_info(uprobe->inode->i_mapping,
764 uprobe->offset, is_register);
765 if (IS_ERR(info)) {
766 err = PTR_ERR(info);
767 goto out;
770 while (info) {
771 struct mm_struct *mm = info->mm;
772 struct vm_area_struct *vma;
774 if (err && is_register)
775 goto free;
777 down_write(&mm->mmap_sem);
778 vma = find_vma(mm, info->vaddr);
779 if (!vma || !valid_vma(vma, is_register) ||
780 file_inode(vma->vm_file) != uprobe->inode)
781 goto unlock;
783 if (vma->vm_start > info->vaddr ||
784 vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
785 goto unlock;
787 if (is_register) {
788 /* consult only the "caller", new consumer. */
789 if (consumer_filter(new,
790 UPROBE_FILTER_REGISTER, mm))
791 err = install_breakpoint(uprobe, mm, vma, info->vaddr);
792 } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
793 if (!filter_chain(uprobe,
794 UPROBE_FILTER_UNREGISTER, mm))
795 err |= remove_breakpoint(uprobe, mm, info->vaddr);
798 unlock:
799 up_write(&mm->mmap_sem);
800 free:
801 mmput(mm);
802 info = free_map_info(info);
804 out:
805 percpu_up_write(&dup_mmap_sem);
806 return err;
809 static int __uprobe_register(struct uprobe *uprobe, struct uprobe_consumer *uc)
811 consumer_add(uprobe, uc);
812 return register_for_each_vma(uprobe, uc);
815 static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
817 int err;
819 if (!consumer_del(uprobe, uc)) /* WARN? */
820 return;
822 err = register_for_each_vma(uprobe, NULL);
823 /* TODO : cant unregister? schedule a worker thread */
824 if (!uprobe->consumers && !err)
825 delete_uprobe(uprobe);
829 * uprobe_register - register a probe
830 * @inode: the file in which the probe has to be placed.
831 * @offset: offset from the start of the file.
832 * @uc: information on howto handle the probe..
834 * Apart from the access refcount, uprobe_register() takes a creation
835 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
836 * inserted into the rbtree (i.e first consumer for a @inode:@offset
837 * tuple). Creation refcount stops uprobe_unregister from freeing the
838 * @uprobe even before the register operation is complete. Creation
839 * refcount is released when the last @uc for the @uprobe
840 * unregisters.
842 * Return errno if it cannot successully install probes
843 * else return 0 (success)
845 int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
847 struct uprobe *uprobe;
848 int ret;
850 /* Uprobe must have at least one set consumer */
851 if (!uc->handler && !uc->ret_handler)
852 return -EINVAL;
854 /* Racy, just to catch the obvious mistakes */
855 if (offset > i_size_read(inode))
856 return -EINVAL;
858 retry:
859 uprobe = alloc_uprobe(inode, offset);
860 if (!uprobe)
861 return -ENOMEM;
863 * We can race with uprobe_unregister()->delete_uprobe().
864 * Check uprobe_is_active() and retry if it is false.
866 down_write(&uprobe->register_rwsem);
867 ret = -EAGAIN;
868 if (likely(uprobe_is_active(uprobe))) {
869 ret = __uprobe_register(uprobe, uc);
870 if (ret)
871 __uprobe_unregister(uprobe, uc);
873 up_write(&uprobe->register_rwsem);
874 put_uprobe(uprobe);
876 if (unlikely(ret == -EAGAIN))
877 goto retry;
878 return ret;
880 EXPORT_SYMBOL_GPL(uprobe_register);
883 * uprobe_apply - unregister a already registered probe.
884 * @inode: the file in which the probe has to be removed.
885 * @offset: offset from the start of the file.
886 * @uc: consumer which wants to add more or remove some breakpoints
887 * @add: add or remove the breakpoints
889 int uprobe_apply(struct inode *inode, loff_t offset,
890 struct uprobe_consumer *uc, bool add)
892 struct uprobe *uprobe;
893 struct uprobe_consumer *con;
894 int ret = -ENOENT;
896 uprobe = find_uprobe(inode, offset);
897 if (!uprobe)
898 return ret;
900 down_write(&uprobe->register_rwsem);
901 for (con = uprobe->consumers; con && con != uc ; con = con->next)
903 if (con)
904 ret = register_for_each_vma(uprobe, add ? uc : NULL);
905 up_write(&uprobe->register_rwsem);
906 put_uprobe(uprobe);
908 return ret;
912 * uprobe_unregister - unregister a already registered probe.
913 * @inode: the file in which the probe has to be removed.
914 * @offset: offset from the start of the file.
915 * @uc: identify which probe if multiple probes are colocated.
917 void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
919 struct uprobe *uprobe;
921 uprobe = find_uprobe(inode, offset);
922 if (!uprobe)
923 return;
925 down_write(&uprobe->register_rwsem);
926 __uprobe_unregister(uprobe, uc);
927 up_write(&uprobe->register_rwsem);
928 put_uprobe(uprobe);
930 EXPORT_SYMBOL_GPL(uprobe_unregister);
932 static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
934 struct vm_area_struct *vma;
935 int err = 0;
937 down_read(&mm->mmap_sem);
938 for (vma = mm->mmap; vma; vma = vma->vm_next) {
939 unsigned long vaddr;
940 loff_t offset;
942 if (!valid_vma(vma, false) ||
943 file_inode(vma->vm_file) != uprobe->inode)
944 continue;
946 offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
947 if (uprobe->offset < offset ||
948 uprobe->offset >= offset + vma->vm_end - vma->vm_start)
949 continue;
951 vaddr = offset_to_vaddr(vma, uprobe->offset);
952 err |= remove_breakpoint(uprobe, mm, vaddr);
954 up_read(&mm->mmap_sem);
956 return err;
959 static struct rb_node *
960 find_node_in_range(struct inode *inode, loff_t min, loff_t max)
962 struct rb_node *n = uprobes_tree.rb_node;
964 while (n) {
965 struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
967 if (inode < u->inode) {
968 n = n->rb_left;
969 } else if (inode > u->inode) {
970 n = n->rb_right;
971 } else {
972 if (max < u->offset)
973 n = n->rb_left;
974 else if (min > u->offset)
975 n = n->rb_right;
976 else
977 break;
981 return n;
985 * For a given range in vma, build a list of probes that need to be inserted.
987 static void build_probe_list(struct inode *inode,
988 struct vm_area_struct *vma,
989 unsigned long start, unsigned long end,
990 struct list_head *head)
992 loff_t min, max;
993 struct rb_node *n, *t;
994 struct uprobe *u;
996 INIT_LIST_HEAD(head);
997 min = vaddr_to_offset(vma, start);
998 max = min + (end - start) - 1;
1000 spin_lock(&uprobes_treelock);
1001 n = find_node_in_range(inode, min, max);
1002 if (n) {
1003 for (t = n; t; t = rb_prev(t)) {
1004 u = rb_entry(t, struct uprobe, rb_node);
1005 if (u->inode != inode || u->offset < min)
1006 break;
1007 list_add(&u->pending_list, head);
1008 atomic_inc(&u->ref);
1010 for (t = n; (t = rb_next(t)); ) {
1011 u = rb_entry(t, struct uprobe, rb_node);
1012 if (u->inode != inode || u->offset > max)
1013 break;
1014 list_add(&u->pending_list, head);
1015 atomic_inc(&u->ref);
1018 spin_unlock(&uprobes_treelock);
1022 * Called from mmap_region/vma_adjust with mm->mmap_sem acquired.
1024 * Currently we ignore all errors and always return 0, the callers
1025 * can't handle the failure anyway.
1027 int uprobe_mmap(struct vm_area_struct *vma)
1029 struct list_head tmp_list;
1030 struct uprobe *uprobe, *u;
1031 struct inode *inode;
1033 if (no_uprobe_events() || !valid_vma(vma, true))
1034 return 0;
1036 inode = file_inode(vma->vm_file);
1037 if (!inode)
1038 return 0;
1040 mutex_lock(uprobes_mmap_hash(inode));
1041 build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
1043 * We can race with uprobe_unregister(), this uprobe can be already
1044 * removed. But in this case filter_chain() must return false, all
1045 * consumers have gone away.
1047 list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1048 if (!fatal_signal_pending(current) &&
1049 filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
1050 unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
1051 install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1053 put_uprobe(uprobe);
1055 mutex_unlock(uprobes_mmap_hash(inode));
1057 return 0;
1060 static bool
1061 vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1063 loff_t min, max;
1064 struct inode *inode;
1065 struct rb_node *n;
1067 inode = file_inode(vma->vm_file);
1069 min = vaddr_to_offset(vma, start);
1070 max = min + (end - start) - 1;
1072 spin_lock(&uprobes_treelock);
1073 n = find_node_in_range(inode, min, max);
1074 spin_unlock(&uprobes_treelock);
1076 return !!n;
1080 * Called in context of a munmap of a vma.
1082 void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1084 if (no_uprobe_events() || !valid_vma(vma, false))
1085 return;
1087 if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
1088 return;
1090 if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||
1091 test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))
1092 return;
1094 if (vma_has_uprobes(vma, start, end))
1095 set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
1098 /* Slot allocation for XOL */
1099 static int xol_add_vma(struct xol_area *area)
1101 struct mm_struct *mm = current->mm;
1102 int ret = -EALREADY;
1104 down_write(&mm->mmap_sem);
1105 if (mm->uprobes_state.xol_area)
1106 goto fail;
1108 ret = -ENOMEM;
1109 /* Try to map as high as possible, this is only a hint. */
1110 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0);
1111 if (area->vaddr & ~PAGE_MASK) {
1112 ret = area->vaddr;
1113 goto fail;
1116 ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1117 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page);
1118 if (ret)
1119 goto fail;
1121 smp_wmb(); /* pairs with get_xol_area() */
1122 mm->uprobes_state.xol_area = area;
1123 ret = 0;
1124 fail:
1125 up_write(&mm->mmap_sem);
1127 return ret;
1131 * get_xol_area - Allocate process's xol_area if necessary.
1132 * This area will be used for storing instructions for execution out of line.
1134 * Returns the allocated area or NULL.
1136 static struct xol_area *get_xol_area(void)
1138 struct mm_struct *mm = current->mm;
1139 struct xol_area *area;
1140 uprobe_opcode_t insn = UPROBE_SWBP_INSN;
1142 area = mm->uprobes_state.xol_area;
1143 if (area)
1144 goto ret;
1146 area = kzalloc(sizeof(*area), GFP_KERNEL);
1147 if (unlikely(!area))
1148 goto out;
1150 area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL);
1151 if (!area->bitmap)
1152 goto free_area;
1154 area->page = alloc_page(GFP_HIGHUSER);
1155 if (!area->page)
1156 goto free_bitmap;
1158 /* allocate first slot of task's xol_area for the return probes */
1159 set_bit(0, area->bitmap);
1160 copy_to_page(area->page, 0, &insn, UPROBE_SWBP_INSN_SIZE);
1161 atomic_set(&area->slot_count, 1);
1162 init_waitqueue_head(&area->wq);
1164 if (!xol_add_vma(area))
1165 return area;
1167 __free_page(area->page);
1168 free_bitmap:
1169 kfree(area->bitmap);
1170 free_area:
1171 kfree(area);
1172 out:
1173 area = mm->uprobes_state.xol_area;
1174 ret:
1175 smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
1176 return area;
1180 * uprobe_clear_state - Free the area allocated for slots.
1182 void uprobe_clear_state(struct mm_struct *mm)
1184 struct xol_area *area = mm->uprobes_state.xol_area;
1186 if (!area)
1187 return;
1189 put_page(area->page);
1190 kfree(area->bitmap);
1191 kfree(area);
1194 void uprobe_start_dup_mmap(void)
1196 percpu_down_read(&dup_mmap_sem);
1199 void uprobe_end_dup_mmap(void)
1201 percpu_up_read(&dup_mmap_sem);
1204 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
1206 newmm->uprobes_state.xol_area = NULL;
1208 if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {
1209 set_bit(MMF_HAS_UPROBES, &newmm->flags);
1210 /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */
1211 set_bit(MMF_RECALC_UPROBES, &newmm->flags);
1216 * - search for a free slot.
1218 static unsigned long xol_take_insn_slot(struct xol_area *area)
1220 unsigned long slot_addr;
1221 int slot_nr;
1223 do {
1224 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1225 if (slot_nr < UINSNS_PER_PAGE) {
1226 if (!test_and_set_bit(slot_nr, area->bitmap))
1227 break;
1229 slot_nr = UINSNS_PER_PAGE;
1230 continue;
1232 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1233 } while (slot_nr >= UINSNS_PER_PAGE);
1235 slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1236 atomic_inc(&area->slot_count);
1238 return slot_addr;
1242 * xol_get_insn_slot - allocate a slot for xol.
1243 * Returns the allocated slot address or 0.
1245 static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
1247 struct xol_area *area;
1248 unsigned long xol_vaddr;
1250 area = get_xol_area();
1251 if (!area)
1252 return 0;
1254 xol_vaddr = xol_take_insn_slot(area);
1255 if (unlikely(!xol_vaddr))
1256 return 0;
1258 /* Initialize the slot */
1259 copy_to_page(area->page, xol_vaddr, uprobe->arch.insn, MAX_UINSN_BYTES);
1261 * We probably need flush_icache_user_range() but it needs vma.
1262 * This should work on supported architectures too.
1264 flush_dcache_page(area->page);
1266 return xol_vaddr;
1270 * xol_free_insn_slot - If slot was earlier allocated by
1271 * @xol_get_insn_slot(), make the slot available for
1272 * subsequent requests.
1274 static void xol_free_insn_slot(struct task_struct *tsk)
1276 struct xol_area *area;
1277 unsigned long vma_end;
1278 unsigned long slot_addr;
1280 if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1281 return;
1283 slot_addr = tsk->utask->xol_vaddr;
1284 if (unlikely(!slot_addr))
1285 return;
1287 area = tsk->mm->uprobes_state.xol_area;
1288 vma_end = area->vaddr + PAGE_SIZE;
1289 if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1290 unsigned long offset;
1291 int slot_nr;
1293 offset = slot_addr - area->vaddr;
1294 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1295 if (slot_nr >= UINSNS_PER_PAGE)
1296 return;
1298 clear_bit(slot_nr, area->bitmap);
1299 atomic_dec(&area->slot_count);
1300 if (waitqueue_active(&area->wq))
1301 wake_up(&area->wq);
1303 tsk->utask->xol_vaddr = 0;
1308 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1309 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1310 * instruction.
1311 * Return the address of the breakpoint instruction.
1313 unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1315 return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1319 * Called with no locks held.
1320 * Called in context of a exiting or a exec-ing thread.
1322 void uprobe_free_utask(struct task_struct *t)
1324 struct uprobe_task *utask = t->utask;
1325 struct return_instance *ri, *tmp;
1327 if (!utask)
1328 return;
1330 if (utask->active_uprobe)
1331 put_uprobe(utask->active_uprobe);
1333 ri = utask->return_instances;
1334 while (ri) {
1335 tmp = ri;
1336 ri = ri->next;
1338 put_uprobe(tmp->uprobe);
1339 kfree(tmp);
1342 xol_free_insn_slot(t);
1343 kfree(utask);
1344 t->utask = NULL;
1348 * Called in context of a new clone/fork from copy_process.
1350 void uprobe_copy_process(struct task_struct *t)
1352 t->utask = NULL;
1356 * Allocate a uprobe_task object for the task if if necessary.
1357 * Called when the thread hits a breakpoint.
1359 * Returns:
1360 * - pointer to new uprobe_task on success
1361 * - NULL otherwise
1363 static struct uprobe_task *get_utask(void)
1365 if (!current->utask)
1366 current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1367 return current->utask;
1371 * Current area->vaddr notion assume the trampoline address is always
1372 * equal area->vaddr.
1374 * Returns -1 in case the xol_area is not allocated.
1376 static unsigned long get_trampoline_vaddr(void)
1378 struct xol_area *area;
1379 unsigned long trampoline_vaddr = -1;
1381 area = current->mm->uprobes_state.xol_area;
1382 smp_read_barrier_depends();
1383 if (area)
1384 trampoline_vaddr = area->vaddr;
1386 return trampoline_vaddr;
1389 static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
1391 struct return_instance *ri;
1392 struct uprobe_task *utask;
1393 unsigned long orig_ret_vaddr, trampoline_vaddr;
1394 bool chained = false;
1396 if (!get_xol_area())
1397 return;
1399 utask = get_utask();
1400 if (!utask)
1401 return;
1403 if (utask->depth >= MAX_URETPROBE_DEPTH) {
1404 printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to"
1405 " nestedness limit pid/tgid=%d/%d\n",
1406 current->pid, current->tgid);
1407 return;
1410 ri = kzalloc(sizeof(struct return_instance), GFP_KERNEL);
1411 if (!ri)
1412 goto fail;
1414 trampoline_vaddr = get_trampoline_vaddr();
1415 orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
1416 if (orig_ret_vaddr == -1)
1417 goto fail;
1420 * We don't want to keep trampoline address in stack, rather keep the
1421 * original return address of first caller thru all the consequent
1422 * instances. This also makes breakpoint unwrapping easier.
1424 if (orig_ret_vaddr == trampoline_vaddr) {
1425 if (!utask->return_instances) {
1427 * This situation is not possible. Likely we have an
1428 * attack from user-space.
1430 pr_warn("uprobe: unable to set uretprobe pid/tgid=%d/%d\n",
1431 current->pid, current->tgid);
1432 goto fail;
1435 chained = true;
1436 orig_ret_vaddr = utask->return_instances->orig_ret_vaddr;
1439 atomic_inc(&uprobe->ref);
1440 ri->uprobe = uprobe;
1441 ri->func = instruction_pointer(regs);
1442 ri->orig_ret_vaddr = orig_ret_vaddr;
1443 ri->chained = chained;
1445 utask->depth++;
1447 /* add instance to the stack */
1448 ri->next = utask->return_instances;
1449 utask->return_instances = ri;
1451 return;
1453 fail:
1454 kfree(ri);
1457 /* Prepare to single-step probed instruction out of line. */
1458 static int
1459 pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
1461 struct uprobe_task *utask;
1462 unsigned long xol_vaddr;
1463 int err;
1465 utask = get_utask();
1466 if (!utask)
1467 return -ENOMEM;
1469 xol_vaddr = xol_get_insn_slot(uprobe);
1470 if (!xol_vaddr)
1471 return -ENOMEM;
1473 utask->xol_vaddr = xol_vaddr;
1474 utask->vaddr = bp_vaddr;
1476 err = arch_uprobe_pre_xol(&uprobe->arch, regs);
1477 if (unlikely(err)) {
1478 xol_free_insn_slot(current);
1479 return err;
1482 utask->active_uprobe = uprobe;
1483 utask->state = UTASK_SSTEP;
1484 return 0;
1488 * If we are singlestepping, then ensure this thread is not connected to
1489 * non-fatal signals until completion of singlestep. When xol insn itself
1490 * triggers the signal, restart the original insn even if the task is
1491 * already SIGKILL'ed (since coredump should report the correct ip). This
1492 * is even more important if the task has a handler for SIGSEGV/etc, The
1493 * _same_ instruction should be repeated again after return from the signal
1494 * handler, and SSTEP can never finish in this case.
1496 bool uprobe_deny_signal(void)
1498 struct task_struct *t = current;
1499 struct uprobe_task *utask = t->utask;
1501 if (likely(!utask || !utask->active_uprobe))
1502 return false;
1504 WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1506 if (signal_pending(t)) {
1507 spin_lock_irq(&t->sighand->siglock);
1508 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1509 spin_unlock_irq(&t->sighand->siglock);
1511 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1512 utask->state = UTASK_SSTEP_TRAPPED;
1513 set_tsk_thread_flag(t, TIF_UPROBE);
1514 set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
1518 return true;
1522 * Avoid singlestepping the original instruction if the original instruction
1523 * is a NOP or can be emulated.
1525 static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
1527 if (test_bit(UPROBE_SKIP_SSTEP, &uprobe->flags)) {
1528 if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
1529 return true;
1530 clear_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
1532 return false;
1535 static void mmf_recalc_uprobes(struct mm_struct *mm)
1537 struct vm_area_struct *vma;
1539 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1540 if (!valid_vma(vma, false))
1541 continue;
1543 * This is not strictly accurate, we can race with
1544 * uprobe_unregister() and see the already removed
1545 * uprobe if delete_uprobe() was not yet called.
1546 * Or this uprobe can be filtered out.
1548 if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
1549 return;
1552 clear_bit(MMF_HAS_UPROBES, &mm->flags);
1555 static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
1557 struct page *page;
1558 uprobe_opcode_t opcode;
1559 int result;
1561 pagefault_disable();
1562 result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
1563 sizeof(opcode));
1564 pagefault_enable();
1566 if (likely(result == 0))
1567 goto out;
1569 result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
1570 if (result < 0)
1571 return result;
1573 copy_from_page(page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
1574 put_page(page);
1575 out:
1576 /* This needs to return true for any variant of the trap insn */
1577 return is_trap_insn(&opcode);
1580 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
1582 struct mm_struct *mm = current->mm;
1583 struct uprobe *uprobe = NULL;
1584 struct vm_area_struct *vma;
1586 down_read(&mm->mmap_sem);
1587 vma = find_vma(mm, bp_vaddr);
1588 if (vma && vma->vm_start <= bp_vaddr) {
1589 if (valid_vma(vma, false)) {
1590 struct inode *inode = file_inode(vma->vm_file);
1591 loff_t offset = vaddr_to_offset(vma, bp_vaddr);
1593 uprobe = find_uprobe(inode, offset);
1596 if (!uprobe)
1597 *is_swbp = is_trap_at_addr(mm, bp_vaddr);
1598 } else {
1599 *is_swbp = -EFAULT;
1602 if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
1603 mmf_recalc_uprobes(mm);
1604 up_read(&mm->mmap_sem);
1606 return uprobe;
1609 static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
1611 struct uprobe_consumer *uc;
1612 int remove = UPROBE_HANDLER_REMOVE;
1613 bool need_prep = false; /* prepare return uprobe, when needed */
1615 down_read(&uprobe->register_rwsem);
1616 for (uc = uprobe->consumers; uc; uc = uc->next) {
1617 int rc = 0;
1619 if (uc->handler) {
1620 rc = uc->handler(uc, regs);
1621 WARN(rc & ~UPROBE_HANDLER_MASK,
1622 "bad rc=0x%x from %pf()\n", rc, uc->handler);
1625 if (uc->ret_handler)
1626 need_prep = true;
1628 remove &= rc;
1631 if (need_prep && !remove)
1632 prepare_uretprobe(uprobe, regs); /* put bp at return */
1634 if (remove && uprobe->consumers) {
1635 WARN_ON(!uprobe_is_active(uprobe));
1636 unapply_uprobe(uprobe, current->mm);
1638 up_read(&uprobe->register_rwsem);
1641 static void
1642 handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
1644 struct uprobe *uprobe = ri->uprobe;
1645 struct uprobe_consumer *uc;
1647 down_read(&uprobe->register_rwsem);
1648 for (uc = uprobe->consumers; uc; uc = uc->next) {
1649 if (uc->ret_handler)
1650 uc->ret_handler(uc, ri->func, regs);
1652 up_read(&uprobe->register_rwsem);
1655 static bool handle_trampoline(struct pt_regs *regs)
1657 struct uprobe_task *utask;
1658 struct return_instance *ri, *tmp;
1659 bool chained;
1661 utask = current->utask;
1662 if (!utask)
1663 return false;
1665 ri = utask->return_instances;
1666 if (!ri)
1667 return false;
1670 * TODO: we should throw out return_instance's invalidated by
1671 * longjmp(), currently we assume that the probed function always
1672 * returns.
1674 instruction_pointer_set(regs, ri->orig_ret_vaddr);
1676 for (;;) {
1677 handle_uretprobe_chain(ri, regs);
1679 chained = ri->chained;
1680 put_uprobe(ri->uprobe);
1682 tmp = ri;
1683 ri = ri->next;
1684 kfree(tmp);
1685 utask->depth--;
1687 if (!chained)
1688 break;
1689 BUG_ON(!ri);
1692 utask->return_instances = ri;
1694 return true;
1698 * Run handler and ask thread to singlestep.
1699 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
1701 static void handle_swbp(struct pt_regs *regs)
1703 struct uprobe *uprobe;
1704 unsigned long bp_vaddr;
1705 int uninitialized_var(is_swbp);
1707 bp_vaddr = uprobe_get_swbp_addr(regs);
1708 if (bp_vaddr == get_trampoline_vaddr()) {
1709 if (handle_trampoline(regs))
1710 return;
1712 pr_warn("uprobe: unable to handle uretprobe pid/tgid=%d/%d\n",
1713 current->pid, current->tgid);
1716 uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
1717 if (!uprobe) {
1718 if (is_swbp > 0) {
1719 /* No matching uprobe; signal SIGTRAP. */
1720 send_sig(SIGTRAP, current, 0);
1721 } else {
1723 * Either we raced with uprobe_unregister() or we can't
1724 * access this memory. The latter is only possible if
1725 * another thread plays with our ->mm. In both cases
1726 * we can simply restart. If this vma was unmapped we
1727 * can pretend this insn was not executed yet and get
1728 * the (correct) SIGSEGV after restart.
1730 instruction_pointer_set(regs, bp_vaddr);
1732 return;
1735 /* change it in advance for ->handler() and restart */
1736 instruction_pointer_set(regs, bp_vaddr);
1739 * TODO: move copy_insn/etc into _register and remove this hack.
1740 * After we hit the bp, _unregister + _register can install the
1741 * new and not-yet-analyzed uprobe at the same address, restart.
1743 smp_rmb(); /* pairs with wmb() in install_breakpoint() */
1744 if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
1745 goto out;
1747 handler_chain(uprobe, regs);
1748 if (can_skip_sstep(uprobe, regs))
1749 goto out;
1751 if (!pre_ssout(uprobe, regs, bp_vaddr))
1752 return;
1754 /* can_skip_sstep() succeeded, or restart if can't singlestep */
1755 out:
1756 put_uprobe(uprobe);
1760 * Perform required fix-ups and disable singlestep.
1761 * Allow pending signals to take effect.
1763 static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
1765 struct uprobe *uprobe;
1767 uprobe = utask->active_uprobe;
1768 if (utask->state == UTASK_SSTEP_ACK)
1769 arch_uprobe_post_xol(&uprobe->arch, regs);
1770 else if (utask->state == UTASK_SSTEP_TRAPPED)
1771 arch_uprobe_abort_xol(&uprobe->arch, regs);
1772 else
1773 WARN_ON_ONCE(1);
1775 put_uprobe(uprobe);
1776 utask->active_uprobe = NULL;
1777 utask->state = UTASK_RUNNING;
1778 xol_free_insn_slot(current);
1780 spin_lock_irq(&current->sighand->siglock);
1781 recalc_sigpending(); /* see uprobe_deny_signal() */
1782 spin_unlock_irq(&current->sighand->siglock);
1786 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
1787 * allows the thread to return from interrupt. After that handle_swbp()
1788 * sets utask->active_uprobe.
1790 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
1791 * and allows the thread to return from interrupt.
1793 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
1794 * uprobe_notify_resume().
1796 void uprobe_notify_resume(struct pt_regs *regs)
1798 struct uprobe_task *utask;
1800 clear_thread_flag(TIF_UPROBE);
1802 utask = current->utask;
1803 if (utask && utask->active_uprobe)
1804 handle_singlestep(utask, regs);
1805 else
1806 handle_swbp(regs);
1810 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
1811 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
1813 int uprobe_pre_sstep_notifier(struct pt_regs *regs)
1815 if (!current->mm)
1816 return 0;
1818 if (!test_bit(MMF_HAS_UPROBES, &current->mm->flags) &&
1819 (!current->utask || !current->utask->return_instances))
1820 return 0;
1822 set_thread_flag(TIF_UPROBE);
1823 return 1;
1827 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
1828 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
1830 int uprobe_post_sstep_notifier(struct pt_regs *regs)
1832 struct uprobe_task *utask = current->utask;
1834 if (!current->mm || !utask || !utask->active_uprobe)
1835 /* task is currently not uprobed */
1836 return 0;
1838 utask->state = UTASK_SSTEP_ACK;
1839 set_thread_flag(TIF_UPROBE);
1840 return 1;
1843 static struct notifier_block uprobe_exception_nb = {
1844 .notifier_call = arch_uprobe_exception_notify,
1845 .priority = INT_MAX-1, /* notified after kprobes, kgdb */
1848 static int __init init_uprobes(void)
1850 int i;
1852 for (i = 0; i < UPROBES_HASH_SZ; i++)
1853 mutex_init(&uprobes_mmap_mutex[i]);
1855 if (percpu_init_rwsem(&dup_mmap_sem))
1856 return -ENOMEM;
1858 return register_die_notifier(&uprobe_exception_nb);
1860 module_init(init_uprobes);
1862 static void __exit exit_uprobes(void)
1865 module_exit(exit_uprobes);