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
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/rmap.h> /* anon_vma_prepare */
31 #include <linux/mmu_notifier.h> /* set_pte_at_notify */
32 #include <linux/swap.h> /* try_to_free_swap */
33 #include <linux/ptrace.h> /* user_enable_single_step */
34 #include <linux/kdebug.h> /* notifier mechanism */
36 #include <linux/uprobes.h>
38 #define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
39 #define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
41 static struct rb_root uprobes_tree
= RB_ROOT
;
43 static DEFINE_SPINLOCK(uprobes_treelock
); /* serialize rbtree access */
45 #define UPROBES_HASH_SZ 13
48 * We need separate register/unregister and mmap/munmap lock hashes because
49 * of mmap_sem nesting.
51 * uprobe_register() needs to install probes on (potentially) all processes
52 * and thus needs to acquire multiple mmap_sems (consequtively, not
53 * concurrently), whereas uprobe_mmap() is called while holding mmap_sem
54 * for the particular process doing the mmap.
56 * uprobe_register()->register_for_each_vma() needs to drop/acquire mmap_sem
57 * because of lock order against i_mmap_mutex. This means there's a hole in
58 * the register vma iteration where a mmap() can happen.
60 * Thus uprobe_register() can race with uprobe_mmap() and we can try and
61 * install a probe where one is already installed.
64 /* serialize (un)register */
65 static struct mutex uprobes_mutex
[UPROBES_HASH_SZ
];
67 #define uprobes_hash(v) (&uprobes_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
69 /* serialize uprobe->pending_list */
70 static struct mutex uprobes_mmap_mutex
[UPROBES_HASH_SZ
];
71 #define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
74 * uprobe_events allows us to skip the uprobe_mmap if there are no uprobe
75 * events active at this time. Probably a fine grained per inode count is
78 static atomic_t uprobe_events
= ATOMIC_INIT(0);
81 struct rb_node rb_node
; /* node in the rb tree */
83 struct rw_semaphore consumer_rwsem
;
84 struct list_head pending_list
;
85 struct uprobe_consumer
*consumers
;
86 struct inode
*inode
; /* Also hold a ref to inode */
89 struct arch_uprobe arch
;
93 * valid_vma: Verify if the specified vma is an executable vma
94 * Relax restrictions while unregistering: vm_flags might have
95 * changed after breakpoint was inserted.
96 * - is_register: indicates if we are in register context.
97 * - Return 1 if the specified virtual address is in an
100 static bool valid_vma(struct vm_area_struct
*vma
, bool is_register
)
108 if ((vma
->vm_flags
& (VM_HUGETLB
|VM_READ
|VM_WRITE
|VM_EXEC
|VM_SHARED
))
109 == (VM_READ
|VM_EXEC
))
115 static loff_t
vma_address(struct vm_area_struct
*vma
, loff_t offset
)
119 vaddr
= vma
->vm_start
+ offset
;
120 vaddr
-= vma
->vm_pgoff
<< PAGE_SHIFT
;
126 * __replace_page - replace page in vma by new page.
127 * based on replace_page in mm/ksm.c
129 * @vma: vma that holds the pte pointing to page
130 * @page: the cowed page we are replacing by kpage
131 * @kpage: the modified page we replace page by
133 * Returns 0 on success, -EFAULT on failure.
135 static int __replace_page(struct vm_area_struct
*vma
, struct page
*page
, struct page
*kpage
)
137 struct mm_struct
*mm
= vma
->vm_mm
;
142 addr
= page_address_in_vma(page
, vma
);
146 ptep
= page_check_address(page
, mm
, addr
, &ptl
, 0);
151 page_add_new_anon_rmap(kpage
, vma
, addr
);
153 if (!PageAnon(page
)) {
154 dec_mm_counter(mm
, MM_FILEPAGES
);
155 inc_mm_counter(mm
, MM_ANONPAGES
);
158 flush_cache_page(vma
, addr
, pte_pfn(*ptep
));
159 ptep_clear_flush(vma
, addr
, ptep
);
160 set_pte_at_notify(mm
, addr
, ptep
, mk_pte(kpage
, vma
->vm_page_prot
));
162 page_remove_rmap(page
);
163 if (!page_mapped(page
))
164 try_to_free_swap(page
);
166 pte_unmap_unlock(ptep
, ptl
);
172 * is_swbp_insn - check if instruction is breakpoint instruction.
173 * @insn: instruction to be checked.
174 * Default implementation of is_swbp_insn
175 * Returns true if @insn is a breakpoint instruction.
177 bool __weak
is_swbp_insn(uprobe_opcode_t
*insn
)
179 return *insn
== UPROBE_SWBP_INSN
;
184 * Expect the breakpoint instruction to be the smallest size instruction for
185 * the architecture. If an arch has variable length instruction and the
186 * breakpoint instruction is not of the smallest length instruction
187 * supported by that architecture then we need to modify read_opcode /
188 * write_opcode accordingly. This would never be a problem for archs that
189 * have fixed length instructions.
193 * write_opcode - write the opcode at a given virtual address.
194 * @auprobe: arch breakpointing information.
195 * @mm: the probed process address space.
196 * @vaddr: the virtual address to store the opcode.
197 * @opcode: opcode to be written at @vaddr.
199 * Called with mm->mmap_sem held (for read and with a reference to
202 * For mm @mm, write the opcode at @vaddr.
203 * Return 0 (success) or a negative errno.
205 static int write_opcode(struct arch_uprobe
*auprobe
, struct mm_struct
*mm
,
206 unsigned long vaddr
, uprobe_opcode_t opcode
)
208 struct page
*old_page
, *new_page
;
209 struct address_space
*mapping
;
210 void *vaddr_old
, *vaddr_new
;
211 struct vm_area_struct
*vma
;
212 struct uprobe
*uprobe
;
215 /* Read the page with vaddr into memory */
216 ret
= get_user_pages(NULL
, mm
, vaddr
, 1, 0, 0, &old_page
, &vma
);
223 * We are interested in text pages only. Our pages of interest
224 * should be mapped for read and execute only. We desist from
225 * adding probes in write mapped pages since the breakpoints
226 * might end up in the file copy.
228 if (!valid_vma(vma
, is_swbp_insn(&opcode
)))
231 uprobe
= container_of(auprobe
, struct uprobe
, arch
);
232 mapping
= uprobe
->inode
->i_mapping
;
233 if (mapping
!= vma
->vm_file
->f_mapping
)
237 new_page
= alloc_page_vma(GFP_HIGHUSER_MOVABLE
, vma
, vaddr
);
241 __SetPageUptodate(new_page
);
244 * lock page will serialize against do_wp_page()'s
245 * PageAnon() handling
248 /* copy the page now that we've got it stable */
249 vaddr_old
= kmap_atomic(old_page
);
250 vaddr_new
= kmap_atomic(new_page
);
252 memcpy(vaddr_new
, vaddr_old
, PAGE_SIZE
);
253 memcpy(vaddr_new
+ (vaddr
& ~PAGE_MASK
), &opcode
, UPROBE_SWBP_INSN_SIZE
);
255 kunmap_atomic(vaddr_new
);
256 kunmap_atomic(vaddr_old
);
258 ret
= anon_vma_prepare(vma
);
263 ret
= __replace_page(vma
, old_page
, new_page
);
264 unlock_page(new_page
);
267 unlock_page(old_page
);
268 page_cache_release(new_page
);
273 if (unlikely(ret
== -EAGAIN
))
279 * read_opcode - read the opcode at a given virtual address.
280 * @mm: the probed process address space.
281 * @vaddr: the virtual address to read the opcode.
282 * @opcode: location to store the read opcode.
284 * Called with mm->mmap_sem held (for read and with a reference to
287 * For mm @mm, read the opcode at @vaddr and store it in @opcode.
288 * Return 0 (success) or a negative errno.
290 static int read_opcode(struct mm_struct
*mm
, unsigned long vaddr
, uprobe_opcode_t
*opcode
)
296 ret
= get_user_pages(NULL
, mm
, vaddr
, 1, 0, 1, &page
, NULL
);
301 vaddr_new
= kmap_atomic(page
);
303 memcpy(opcode
, vaddr_new
+ vaddr
, UPROBE_SWBP_INSN_SIZE
);
304 kunmap_atomic(vaddr_new
);
312 static int is_swbp_at_addr(struct mm_struct
*mm
, unsigned long vaddr
)
314 uprobe_opcode_t opcode
;
317 if (current
->mm
== mm
) {
319 result
= __copy_from_user_inatomic(&opcode
, (void __user
*)vaddr
,
323 if (likely(result
== 0))
327 result
= read_opcode(mm
, vaddr
, &opcode
);
331 if (is_swbp_insn(&opcode
))
338 * set_swbp - store breakpoint at a given address.
339 * @auprobe: arch specific probepoint information.
340 * @mm: the probed process address space.
341 * @vaddr: the virtual address to insert the opcode.
343 * For mm @mm, store the breakpoint instruction at @vaddr.
344 * Return 0 (success) or a negative errno.
346 int __weak
set_swbp(struct arch_uprobe
*auprobe
, struct mm_struct
*mm
, unsigned long vaddr
)
350 * See the comment near uprobes_hash().
352 result
= is_swbp_at_addr(mm
, vaddr
);
359 return write_opcode(auprobe
, mm
, vaddr
, UPROBE_SWBP_INSN
);
363 * set_orig_insn - Restore the original instruction.
364 * @mm: the probed process address space.
365 * @auprobe: arch specific probepoint information.
366 * @vaddr: the virtual address to insert the opcode.
367 * @verify: if true, verify existance of breakpoint instruction.
369 * For mm @mm, restore the original opcode (opcode) at @vaddr.
370 * Return 0 (success) or a negative errno.
373 set_orig_insn(struct arch_uprobe
*auprobe
, struct mm_struct
*mm
, unsigned long vaddr
, bool verify
)
378 result
= is_swbp_at_addr(mm
, vaddr
);
385 return write_opcode(auprobe
, mm
, vaddr
, *(uprobe_opcode_t
*)auprobe
->insn
);
388 static int match_uprobe(struct uprobe
*l
, struct uprobe
*r
)
390 if (l
->inode
< r
->inode
)
393 if (l
->inode
> r
->inode
)
396 if (l
->offset
< r
->offset
)
399 if (l
->offset
> r
->offset
)
405 static struct uprobe
*__find_uprobe(struct inode
*inode
, loff_t offset
)
407 struct uprobe u
= { .inode
= inode
, .offset
= offset
};
408 struct rb_node
*n
= uprobes_tree
.rb_node
;
409 struct uprobe
*uprobe
;
413 uprobe
= rb_entry(n
, struct uprobe
, rb_node
);
414 match
= match_uprobe(&u
, uprobe
);
416 atomic_inc(&uprobe
->ref
);
429 * Find a uprobe corresponding to a given inode:offset
430 * Acquires uprobes_treelock
432 static struct uprobe
*find_uprobe(struct inode
*inode
, loff_t offset
)
434 struct uprobe
*uprobe
;
437 spin_lock_irqsave(&uprobes_treelock
, flags
);
438 uprobe
= __find_uprobe(inode
, offset
);
439 spin_unlock_irqrestore(&uprobes_treelock
, flags
);
444 static struct uprobe
*__insert_uprobe(struct uprobe
*uprobe
)
446 struct rb_node
**p
= &uprobes_tree
.rb_node
;
447 struct rb_node
*parent
= NULL
;
453 u
= rb_entry(parent
, struct uprobe
, rb_node
);
454 match
= match_uprobe(uprobe
, u
);
461 p
= &parent
->rb_left
;
463 p
= &parent
->rb_right
;
468 rb_link_node(&uprobe
->rb_node
, parent
, p
);
469 rb_insert_color(&uprobe
->rb_node
, &uprobes_tree
);
470 /* get access + creation ref */
471 atomic_set(&uprobe
->ref
, 2);
477 * Acquire uprobes_treelock.
478 * Matching uprobe already exists in rbtree;
479 * increment (access refcount) and return the matching uprobe.
481 * No matching uprobe; insert the uprobe in rb_tree;
482 * get a double refcount (access + creation) and return NULL.
484 static struct uprobe
*insert_uprobe(struct uprobe
*uprobe
)
489 spin_lock_irqsave(&uprobes_treelock
, flags
);
490 u
= __insert_uprobe(uprobe
);
491 spin_unlock_irqrestore(&uprobes_treelock
, flags
);
493 /* For now assume that the instruction need not be single-stepped */
494 uprobe
->flags
|= UPROBE_SKIP_SSTEP
;
499 static void put_uprobe(struct uprobe
*uprobe
)
501 if (atomic_dec_and_test(&uprobe
->ref
))
505 static struct uprobe
*alloc_uprobe(struct inode
*inode
, loff_t offset
)
507 struct uprobe
*uprobe
, *cur_uprobe
;
509 uprobe
= kzalloc(sizeof(struct uprobe
), GFP_KERNEL
);
513 uprobe
->inode
= igrab(inode
);
514 uprobe
->offset
= offset
;
515 init_rwsem(&uprobe
->consumer_rwsem
);
517 /* add to uprobes_tree, sorted on inode:offset */
518 cur_uprobe
= insert_uprobe(uprobe
);
520 /* a uprobe exists for this inode:offset combination */
526 atomic_inc(&uprobe_events
);
532 static void handler_chain(struct uprobe
*uprobe
, struct pt_regs
*regs
)
534 struct uprobe_consumer
*uc
;
536 if (!(uprobe
->flags
& UPROBE_RUN_HANDLER
))
539 down_read(&uprobe
->consumer_rwsem
);
540 for (uc
= uprobe
->consumers
; uc
; uc
= uc
->next
) {
541 if (!uc
->filter
|| uc
->filter(uc
, current
))
542 uc
->handler(uc
, regs
);
544 up_read(&uprobe
->consumer_rwsem
);
547 /* Returns the previous consumer */
548 static struct uprobe_consumer
*
549 consumer_add(struct uprobe
*uprobe
, struct uprobe_consumer
*uc
)
551 down_write(&uprobe
->consumer_rwsem
);
552 uc
->next
= uprobe
->consumers
;
553 uprobe
->consumers
= uc
;
554 up_write(&uprobe
->consumer_rwsem
);
560 * For uprobe @uprobe, delete the consumer @uc.
561 * Return true if the @uc is deleted successfully
564 static bool consumer_del(struct uprobe
*uprobe
, struct uprobe_consumer
*uc
)
566 struct uprobe_consumer
**con
;
569 down_write(&uprobe
->consumer_rwsem
);
570 for (con
= &uprobe
->consumers
; *con
; con
= &(*con
)->next
) {
577 up_write(&uprobe
->consumer_rwsem
);
583 __copy_insn(struct address_space
*mapping
, struct file
*filp
, char *insn
,
584 unsigned long nbytes
, loff_t offset
)
594 if (!mapping
->a_ops
->readpage
)
597 idx
= offset
>> PAGE_CACHE_SHIFT
;
598 off
= offset
& ~PAGE_MASK
;
601 * Ensure that the page that has the original instruction is
602 * populated and in page-cache.
604 page
= read_mapping_page(mapping
, idx
, filp
);
606 return PTR_ERR(page
);
608 vaddr
= kmap_atomic(page
);
609 memcpy(insn
, vaddr
+ off
, nbytes
);
610 kunmap_atomic(vaddr
);
611 page_cache_release(page
);
616 static int copy_insn(struct uprobe
*uprobe
, struct file
*filp
)
618 struct address_space
*mapping
;
619 unsigned long nbytes
;
622 nbytes
= PAGE_SIZE
- (uprobe
->offset
& ~PAGE_MASK
);
623 mapping
= uprobe
->inode
->i_mapping
;
625 /* Instruction at end of binary; copy only available bytes */
626 if (uprobe
->offset
+ MAX_UINSN_BYTES
> uprobe
->inode
->i_size
)
627 bytes
= uprobe
->inode
->i_size
- uprobe
->offset
;
629 bytes
= MAX_UINSN_BYTES
;
631 /* Instruction at the page-boundary; copy bytes in second page */
632 if (nbytes
< bytes
) {
633 int err
= __copy_insn(mapping
, filp
, uprobe
->arch
.insn
+ nbytes
,
634 bytes
- nbytes
, uprobe
->offset
+ nbytes
);
639 return __copy_insn(mapping
, filp
, uprobe
->arch
.insn
, bytes
, uprobe
->offset
);
643 * How mm->uprobes_state.count gets updated
644 * uprobe_mmap() increments the count if
645 * - it successfully adds a breakpoint.
646 * - it cannot add a breakpoint, but sees that there is a underlying
647 * breakpoint (via a is_swbp_at_addr()).
649 * uprobe_munmap() decrements the count if
650 * - it sees a underlying breakpoint, (via is_swbp_at_addr)
651 * (Subsequent uprobe_unregister wouldnt find the breakpoint
652 * unless a uprobe_mmap kicks in, since the old vma would be
653 * dropped just after uprobe_munmap.)
655 * uprobe_register increments the count if:
656 * - it successfully adds a breakpoint.
658 * uprobe_unregister decrements the count if:
659 * - it sees a underlying breakpoint and removes successfully.
660 * (via is_swbp_at_addr)
661 * (Subsequent uprobe_munmap wouldnt find the breakpoint
662 * since there is no underlying breakpoint after the
663 * breakpoint removal.)
666 install_breakpoint(struct uprobe
*uprobe
, struct mm_struct
*mm
,
667 struct vm_area_struct
*vma
, unsigned long vaddr
)
672 * If probe is being deleted, unregister thread could be done with
673 * the vma-rmap-walk through. Adding a probe now can be fatal since
674 * nobody will be able to cleanup. Also we could be from fork or
675 * mremap path, where the probe might have already been inserted.
676 * Hence behave as if probe already existed.
678 if (!uprobe
->consumers
)
681 if (!(uprobe
->flags
& UPROBE_COPY_INSN
)) {
682 ret
= copy_insn(uprobe
, vma
->vm_file
);
686 if (is_swbp_insn((uprobe_opcode_t
*)uprobe
->arch
.insn
))
689 ret
= arch_uprobe_analyze_insn(&uprobe
->arch
, mm
, vaddr
);
693 /* write_opcode() assumes we don't cross page boundary */
694 BUG_ON((uprobe
->offset
& ~PAGE_MASK
) +
695 UPROBE_SWBP_INSN_SIZE
> PAGE_SIZE
);
697 uprobe
->flags
|= UPROBE_COPY_INSN
;
701 * Ideally, should be updating the probe count after the breakpoint
702 * has been successfully inserted. However a thread could hit the
703 * breakpoint we just inserted even before the probe count is
704 * incremented. If this is the first breakpoint placed, breakpoint
705 * notifier might ignore uprobes and pass the trap to the thread.
706 * Hence increment before and decrement on failure.
708 atomic_inc(&mm
->uprobes_state
.count
);
709 ret
= set_swbp(&uprobe
->arch
, mm
, vaddr
);
711 atomic_dec(&mm
->uprobes_state
.count
);
717 remove_breakpoint(struct uprobe
*uprobe
, struct mm_struct
*mm
, unsigned long vaddr
)
719 if (!set_orig_insn(&uprobe
->arch
, mm
, vaddr
, true))
720 atomic_dec(&mm
->uprobes_state
.count
);
724 * There could be threads that have already hit the breakpoint. They
725 * will recheck the current insn and restart if find_uprobe() fails.
726 * See find_active_uprobe().
728 static void delete_uprobe(struct uprobe
*uprobe
)
732 spin_lock_irqsave(&uprobes_treelock
, flags
);
733 rb_erase(&uprobe
->rb_node
, &uprobes_tree
);
734 spin_unlock_irqrestore(&uprobes_treelock
, flags
);
737 atomic_dec(&uprobe_events
);
741 struct map_info
*next
;
742 struct mm_struct
*mm
;
746 static inline struct map_info
*free_map_info(struct map_info
*info
)
748 struct map_info
*next
= info
->next
;
753 static struct map_info
*
754 build_map_info(struct address_space
*mapping
, loff_t offset
, bool is_register
)
756 unsigned long pgoff
= offset
>> PAGE_SHIFT
;
757 struct prio_tree_iter iter
;
758 struct vm_area_struct
*vma
;
759 struct map_info
*curr
= NULL
;
760 struct map_info
*prev
= NULL
;
761 struct map_info
*info
;
765 mutex_lock(&mapping
->i_mmap_mutex
);
766 vma_prio_tree_foreach(vma
, &iter
, &mapping
->i_mmap
, pgoff
, pgoff
) {
767 if (!valid_vma(vma
, is_register
))
770 if (!prev
&& !more
) {
772 * Needs GFP_NOWAIT to avoid i_mmap_mutex recursion through
773 * reclaim. This is optimistic, no harm done if it fails.
775 prev
= kmalloc(sizeof(struct map_info
),
776 GFP_NOWAIT
| __GFP_NOMEMALLOC
| __GFP_NOWARN
);
785 if (!atomic_inc_not_zero(&vma
->vm_mm
->mm_users
))
793 info
->mm
= vma
->vm_mm
;
794 info
->vaddr
= vma_address(vma
, offset
);
796 mutex_unlock(&mapping
->i_mmap_mutex
);
808 info
= kmalloc(sizeof(struct map_info
), GFP_KERNEL
);
810 curr
= ERR_PTR(-ENOMEM
);
820 prev
= free_map_info(prev
);
824 static int register_for_each_vma(struct uprobe
*uprobe
, bool is_register
)
826 struct map_info
*info
;
829 info
= build_map_info(uprobe
->inode
->i_mapping
,
830 uprobe
->offset
, is_register
);
832 return PTR_ERR(info
);
835 struct mm_struct
*mm
= info
->mm
;
836 struct vm_area_struct
*vma
;
841 down_write(&mm
->mmap_sem
);
842 vma
= find_vma(mm
, (unsigned long)info
->vaddr
);
843 if (!vma
|| !valid_vma(vma
, is_register
))
846 if (vma
->vm_file
->f_mapping
->host
!= uprobe
->inode
||
847 vma_address(vma
, uprobe
->offset
) != info
->vaddr
)
851 err
= install_breakpoint(uprobe
, mm
, vma
, info
->vaddr
);
853 * We can race against uprobe_mmap(), see the
854 * comment near uprobe_hash().
859 remove_breakpoint(uprobe
, mm
, info
->vaddr
);
862 up_write(&mm
->mmap_sem
);
865 info
= free_map_info(info
);
871 static int __uprobe_register(struct uprobe
*uprobe
)
873 return register_for_each_vma(uprobe
, true);
876 static void __uprobe_unregister(struct uprobe
*uprobe
)
878 if (!register_for_each_vma(uprobe
, false))
879 delete_uprobe(uprobe
);
881 /* TODO : cant unregister? schedule a worker thread */
885 * uprobe_register - register a probe
886 * @inode: the file in which the probe has to be placed.
887 * @offset: offset from the start of the file.
888 * @uc: information on howto handle the probe..
890 * Apart from the access refcount, uprobe_register() takes a creation
891 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
892 * inserted into the rbtree (i.e first consumer for a @inode:@offset
893 * tuple). Creation refcount stops uprobe_unregister from freeing the
894 * @uprobe even before the register operation is complete. Creation
895 * refcount is released when the last @uc for the @uprobe
898 * Return errno if it cannot successully install probes
899 * else return 0 (success)
901 int uprobe_register(struct inode
*inode
, loff_t offset
, struct uprobe_consumer
*uc
)
903 struct uprobe
*uprobe
;
906 if (!inode
|| !uc
|| uc
->next
)
909 if (offset
> i_size_read(inode
))
913 mutex_lock(uprobes_hash(inode
));
914 uprobe
= alloc_uprobe(inode
, offset
);
916 if (uprobe
&& !consumer_add(uprobe
, uc
)) {
917 ret
= __uprobe_register(uprobe
);
919 uprobe
->consumers
= NULL
;
920 __uprobe_unregister(uprobe
);
922 uprobe
->flags
|= UPROBE_RUN_HANDLER
;
926 mutex_unlock(uprobes_hash(inode
));
933 * uprobe_unregister - unregister a already registered probe.
934 * @inode: the file in which the probe has to be removed.
935 * @offset: offset from the start of the file.
936 * @uc: identify which probe if multiple probes are colocated.
938 void uprobe_unregister(struct inode
*inode
, loff_t offset
, struct uprobe_consumer
*uc
)
940 struct uprobe
*uprobe
;
945 uprobe
= find_uprobe(inode
, offset
);
949 mutex_lock(uprobes_hash(inode
));
951 if (consumer_del(uprobe
, uc
)) {
952 if (!uprobe
->consumers
) {
953 __uprobe_unregister(uprobe
);
954 uprobe
->flags
&= ~UPROBE_RUN_HANDLER
;
958 mutex_unlock(uprobes_hash(inode
));
964 * Of all the nodes that correspond to the given inode, return the node
965 * with the least offset.
967 static struct rb_node
*find_least_offset_node(struct inode
*inode
)
969 struct uprobe u
= { .inode
= inode
, .offset
= 0};
970 struct rb_node
*n
= uprobes_tree
.rb_node
;
971 struct rb_node
*close_node
= NULL
;
972 struct uprobe
*uprobe
;
976 uprobe
= rb_entry(n
, struct uprobe
, rb_node
);
977 match
= match_uprobe(&u
, uprobe
);
979 if (uprobe
->inode
== inode
)
995 * For a given inode, build a list of probes that need to be inserted.
997 static void build_probe_list(struct inode
*inode
, struct list_head
*head
)
999 struct uprobe
*uprobe
;
1000 unsigned long flags
;
1003 spin_lock_irqsave(&uprobes_treelock
, flags
);
1005 n
= find_least_offset_node(inode
);
1007 for (; n
; n
= rb_next(n
)) {
1008 uprobe
= rb_entry(n
, struct uprobe
, rb_node
);
1009 if (uprobe
->inode
!= inode
)
1012 list_add(&uprobe
->pending_list
, head
);
1013 atomic_inc(&uprobe
->ref
);
1016 spin_unlock_irqrestore(&uprobes_treelock
, flags
);
1020 * Called from mmap_region.
1021 * called with mm->mmap_sem acquired.
1023 * Return -ve no if we fail to insert probes and we cannot
1025 * Return 0 otherwise. i.e:
1027 * - successful insertion of probes
1028 * - (or) no possible probes to be inserted.
1029 * - (or) insertion of probes failed but we can bail-out.
1031 int uprobe_mmap(struct vm_area_struct
*vma
)
1033 struct list_head tmp_list
;
1034 struct uprobe
*uprobe
;
1035 struct inode
*inode
;
1038 if (!atomic_read(&uprobe_events
) || !valid_vma(vma
, true))
1041 inode
= vma
->vm_file
->f_mapping
->host
;
1045 INIT_LIST_HEAD(&tmp_list
);
1046 mutex_lock(uprobes_mmap_hash(inode
));
1047 build_probe_list(inode
, &tmp_list
);
1052 list_for_each_entry(uprobe
, &tmp_list
, pending_list
) {
1054 loff_t vaddr
= vma_address(vma
, uprobe
->offset
);
1056 if (vaddr
< vma
->vm_start
|| vaddr
>= vma
->vm_end
) {
1061 ret
= install_breakpoint(uprobe
, vma
->vm_mm
, vma
, vaddr
);
1063 * We can race against uprobe_register(), see the
1064 * comment near uprobe_hash().
1066 if (ret
== -EEXIST
) {
1069 if (!is_swbp_at_addr(vma
->vm_mm
, vaddr
))
1073 * Unable to insert a breakpoint, but
1074 * breakpoint lies underneath. Increment the
1077 atomic_inc(&vma
->vm_mm
->uprobes_state
.count
);
1086 mutex_unlock(uprobes_mmap_hash(inode
));
1089 atomic_sub(count
, &vma
->vm_mm
->uprobes_state
.count
);
1095 * Called in context of a munmap of a vma.
1097 void uprobe_munmap(struct vm_area_struct
*vma
, unsigned long start
, unsigned long end
)
1099 struct list_head tmp_list
;
1100 struct uprobe
*uprobe
;
1101 struct inode
*inode
;
1103 if (!atomic_read(&uprobe_events
) || !valid_vma(vma
, false))
1106 if (!atomic_read(&vma
->vm_mm
->uprobes_state
.count
))
1109 inode
= vma
->vm_file
->f_mapping
->host
;
1113 INIT_LIST_HEAD(&tmp_list
);
1114 mutex_lock(uprobes_mmap_hash(inode
));
1115 build_probe_list(inode
, &tmp_list
);
1117 list_for_each_entry(uprobe
, &tmp_list
, pending_list
) {
1118 loff_t vaddr
= vma_address(vma
, uprobe
->offset
);
1120 if (vaddr
>= start
&& vaddr
< end
) {
1122 * An unregister could have removed the probe before
1123 * unmap. So check before we decrement the count.
1125 if (is_swbp_at_addr(vma
->vm_mm
, vaddr
) == 1)
1126 atomic_dec(&vma
->vm_mm
->uprobes_state
.count
);
1130 mutex_unlock(uprobes_mmap_hash(inode
));
1133 /* Slot allocation for XOL */
1134 static int xol_add_vma(struct xol_area
*area
)
1136 struct mm_struct
*mm
;
1139 area
->page
= alloc_page(GFP_HIGHUSER
);
1146 down_write(&mm
->mmap_sem
);
1147 if (mm
->uprobes_state
.xol_area
)
1152 /* Try to map as high as possible, this is only a hint. */
1153 area
->vaddr
= get_unmapped_area(NULL
, TASK_SIZE
- PAGE_SIZE
, PAGE_SIZE
, 0, 0);
1154 if (area
->vaddr
& ~PAGE_MASK
) {
1159 ret
= install_special_mapping(mm
, area
->vaddr
, PAGE_SIZE
,
1160 VM_EXEC
|VM_MAYEXEC
|VM_DONTCOPY
|VM_IO
, &area
->page
);
1164 smp_wmb(); /* pairs with get_xol_area() */
1165 mm
->uprobes_state
.xol_area
= area
;
1169 up_write(&mm
->mmap_sem
);
1171 __free_page(area
->page
);
1176 static struct xol_area
*get_xol_area(struct mm_struct
*mm
)
1178 struct xol_area
*area
;
1180 area
= mm
->uprobes_state
.xol_area
;
1181 smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
1187 * xol_alloc_area - Allocate process's xol_area.
1188 * This area will be used for storing instructions for execution out of
1191 * Returns the allocated area or NULL.
1193 static struct xol_area
*xol_alloc_area(void)
1195 struct xol_area
*area
;
1197 area
= kzalloc(sizeof(*area
), GFP_KERNEL
);
1198 if (unlikely(!area
))
1201 area
->bitmap
= kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE
) * sizeof(long), GFP_KERNEL
);
1206 init_waitqueue_head(&area
->wq
);
1207 if (!xol_add_vma(area
))
1211 kfree(area
->bitmap
);
1214 return get_xol_area(current
->mm
);
1218 * uprobe_clear_state - Free the area allocated for slots.
1220 void uprobe_clear_state(struct mm_struct
*mm
)
1222 struct xol_area
*area
= mm
->uprobes_state
.xol_area
;
1227 put_page(area
->page
);
1228 kfree(area
->bitmap
);
1233 * uprobe_reset_state - Free the area allocated for slots.
1235 void uprobe_reset_state(struct mm_struct
*mm
)
1237 mm
->uprobes_state
.xol_area
= NULL
;
1238 atomic_set(&mm
->uprobes_state
.count
, 0);
1242 * - search for a free slot.
1244 static unsigned long xol_take_insn_slot(struct xol_area
*area
)
1246 unsigned long slot_addr
;
1250 slot_nr
= find_first_zero_bit(area
->bitmap
, UINSNS_PER_PAGE
);
1251 if (slot_nr
< UINSNS_PER_PAGE
) {
1252 if (!test_and_set_bit(slot_nr
, area
->bitmap
))
1255 slot_nr
= UINSNS_PER_PAGE
;
1258 wait_event(area
->wq
, (atomic_read(&area
->slot_count
) < UINSNS_PER_PAGE
));
1259 } while (slot_nr
>= UINSNS_PER_PAGE
);
1261 slot_addr
= area
->vaddr
+ (slot_nr
* UPROBE_XOL_SLOT_BYTES
);
1262 atomic_inc(&area
->slot_count
);
1268 * xol_get_insn_slot - If was not allocated a slot, then
1270 * Returns the allocated slot address or 0.
1272 static unsigned long xol_get_insn_slot(struct uprobe
*uprobe
, unsigned long slot_addr
)
1274 struct xol_area
*area
;
1275 unsigned long offset
;
1278 area
= get_xol_area(current
->mm
);
1280 area
= xol_alloc_area();
1284 current
->utask
->xol_vaddr
= xol_take_insn_slot(area
);
1287 * Initialize the slot if xol_vaddr points to valid
1290 if (unlikely(!current
->utask
->xol_vaddr
))
1293 current
->utask
->vaddr
= slot_addr
;
1294 offset
= current
->utask
->xol_vaddr
& ~PAGE_MASK
;
1295 vaddr
= kmap_atomic(area
->page
);
1296 memcpy(vaddr
+ offset
, uprobe
->arch
.insn
, MAX_UINSN_BYTES
);
1297 kunmap_atomic(vaddr
);
1299 return current
->utask
->xol_vaddr
;
1303 * xol_free_insn_slot - If slot was earlier allocated by
1304 * @xol_get_insn_slot(), make the slot available for
1305 * subsequent requests.
1307 static void xol_free_insn_slot(struct task_struct
*tsk
)
1309 struct xol_area
*area
;
1310 unsigned long vma_end
;
1311 unsigned long slot_addr
;
1313 if (!tsk
->mm
|| !tsk
->mm
->uprobes_state
.xol_area
|| !tsk
->utask
)
1316 slot_addr
= tsk
->utask
->xol_vaddr
;
1318 if (unlikely(!slot_addr
|| IS_ERR_VALUE(slot_addr
)))
1321 area
= tsk
->mm
->uprobes_state
.xol_area
;
1322 vma_end
= area
->vaddr
+ PAGE_SIZE
;
1323 if (area
->vaddr
<= slot_addr
&& slot_addr
< vma_end
) {
1324 unsigned long offset
;
1327 offset
= slot_addr
- area
->vaddr
;
1328 slot_nr
= offset
/ UPROBE_XOL_SLOT_BYTES
;
1329 if (slot_nr
>= UINSNS_PER_PAGE
)
1332 clear_bit(slot_nr
, area
->bitmap
);
1333 atomic_dec(&area
->slot_count
);
1334 if (waitqueue_active(&area
->wq
))
1337 tsk
->utask
->xol_vaddr
= 0;
1342 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1343 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1345 * Return the address of the breakpoint instruction.
1347 unsigned long __weak
uprobe_get_swbp_addr(struct pt_regs
*regs
)
1349 return instruction_pointer(regs
) - UPROBE_SWBP_INSN_SIZE
;
1353 * Called with no locks held.
1354 * Called in context of a exiting or a exec-ing thread.
1356 void uprobe_free_utask(struct task_struct
*t
)
1358 struct uprobe_task
*utask
= t
->utask
;
1363 if (utask
->active_uprobe
)
1364 put_uprobe(utask
->active_uprobe
);
1366 xol_free_insn_slot(t
);
1372 * Called in context of a new clone/fork from copy_process.
1374 void uprobe_copy_process(struct task_struct
*t
)
1380 * Allocate a uprobe_task object for the task.
1381 * Called when the thread hits a breakpoint for the first time.
1384 * - pointer to new uprobe_task on success
1387 static struct uprobe_task
*add_utask(void)
1389 struct uprobe_task
*utask
;
1391 utask
= kzalloc(sizeof *utask
, GFP_KERNEL
);
1392 if (unlikely(!utask
))
1395 current
->utask
= utask
;
1399 /* Prepare to single-step probed instruction out of line. */
1401 pre_ssout(struct uprobe
*uprobe
, struct pt_regs
*regs
, unsigned long vaddr
)
1403 if (xol_get_insn_slot(uprobe
, vaddr
) && !arch_uprobe_pre_xol(&uprobe
->arch
, regs
))
1410 * If we are singlestepping, then ensure this thread is not connected to
1411 * non-fatal signals until completion of singlestep. When xol insn itself
1412 * triggers the signal, restart the original insn even if the task is
1413 * already SIGKILL'ed (since coredump should report the correct ip). This
1414 * is even more important if the task has a handler for SIGSEGV/etc, The
1415 * _same_ instruction should be repeated again after return from the signal
1416 * handler, and SSTEP can never finish in this case.
1418 bool uprobe_deny_signal(void)
1420 struct task_struct
*t
= current
;
1421 struct uprobe_task
*utask
= t
->utask
;
1423 if (likely(!utask
|| !utask
->active_uprobe
))
1426 WARN_ON_ONCE(utask
->state
!= UTASK_SSTEP
);
1428 if (signal_pending(t
)) {
1429 spin_lock_irq(&t
->sighand
->siglock
);
1430 clear_tsk_thread_flag(t
, TIF_SIGPENDING
);
1431 spin_unlock_irq(&t
->sighand
->siglock
);
1433 if (__fatal_signal_pending(t
) || arch_uprobe_xol_was_trapped(t
)) {
1434 utask
->state
= UTASK_SSTEP_TRAPPED
;
1435 set_tsk_thread_flag(t
, TIF_UPROBE
);
1436 set_tsk_thread_flag(t
, TIF_NOTIFY_RESUME
);
1444 * Avoid singlestepping the original instruction if the original instruction
1445 * is a NOP or can be emulated.
1447 static bool can_skip_sstep(struct uprobe
*uprobe
, struct pt_regs
*regs
)
1449 if (arch_uprobe_skip_sstep(&uprobe
->arch
, regs
))
1452 uprobe
->flags
&= ~UPROBE_SKIP_SSTEP
;
1456 static struct uprobe
*find_active_uprobe(unsigned long bp_vaddr
, int *is_swbp
)
1458 struct mm_struct
*mm
= current
->mm
;
1459 struct uprobe
*uprobe
= NULL
;
1460 struct vm_area_struct
*vma
;
1462 down_read(&mm
->mmap_sem
);
1463 vma
= find_vma(mm
, bp_vaddr
);
1464 if (vma
&& vma
->vm_start
<= bp_vaddr
) {
1465 if (valid_vma(vma
, false)) {
1466 struct inode
*inode
;
1469 inode
= vma
->vm_file
->f_mapping
->host
;
1470 offset
= bp_vaddr
- vma
->vm_start
;
1471 offset
+= (vma
->vm_pgoff
<< PAGE_SHIFT
);
1472 uprobe
= find_uprobe(inode
, offset
);
1476 *is_swbp
= is_swbp_at_addr(mm
, bp_vaddr
);
1480 up_read(&mm
->mmap_sem
);
1486 * Run handler and ask thread to singlestep.
1487 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
1489 static void handle_swbp(struct pt_regs
*regs
)
1491 struct uprobe_task
*utask
;
1492 struct uprobe
*uprobe
;
1493 unsigned long bp_vaddr
;
1494 int uninitialized_var(is_swbp
);
1496 bp_vaddr
= uprobe_get_swbp_addr(regs
);
1497 uprobe
= find_active_uprobe(bp_vaddr
, &is_swbp
);
1501 /* No matching uprobe; signal SIGTRAP. */
1502 send_sig(SIGTRAP
, current
, 0);
1505 * Either we raced with uprobe_unregister() or we can't
1506 * access this memory. The latter is only possible if
1507 * another thread plays with our ->mm. In both cases
1508 * we can simply restart. If this vma was unmapped we
1509 * can pretend this insn was not executed yet and get
1510 * the (correct) SIGSEGV after restart.
1512 instruction_pointer_set(regs
, bp_vaddr
);
1517 utask
= current
->utask
;
1519 utask
= add_utask();
1520 /* Cannot allocate; re-execute the instruction. */
1524 utask
->active_uprobe
= uprobe
;
1525 handler_chain(uprobe
, regs
);
1526 if (uprobe
->flags
& UPROBE_SKIP_SSTEP
&& can_skip_sstep(uprobe
, regs
))
1529 utask
->state
= UTASK_SSTEP
;
1530 if (!pre_ssout(uprobe
, regs
, bp_vaddr
)) {
1531 user_enable_single_step(current
);
1537 utask
->active_uprobe
= NULL
;
1538 utask
->state
= UTASK_RUNNING
;
1541 if (!(uprobe
->flags
& UPROBE_SKIP_SSTEP
))
1544 * cannot singlestep; cannot skip instruction;
1545 * re-execute the instruction.
1547 instruction_pointer_set(regs
, bp_vaddr
);
1554 * Perform required fix-ups and disable singlestep.
1555 * Allow pending signals to take effect.
1557 static void handle_singlestep(struct uprobe_task
*utask
, struct pt_regs
*regs
)
1559 struct uprobe
*uprobe
;
1561 uprobe
= utask
->active_uprobe
;
1562 if (utask
->state
== UTASK_SSTEP_ACK
)
1563 arch_uprobe_post_xol(&uprobe
->arch
, regs
);
1564 else if (utask
->state
== UTASK_SSTEP_TRAPPED
)
1565 arch_uprobe_abort_xol(&uprobe
->arch
, regs
);
1570 utask
->active_uprobe
= NULL
;
1571 utask
->state
= UTASK_RUNNING
;
1572 user_disable_single_step(current
);
1573 xol_free_insn_slot(current
);
1575 spin_lock_irq(¤t
->sighand
->siglock
);
1576 recalc_sigpending(); /* see uprobe_deny_signal() */
1577 spin_unlock_irq(¤t
->sighand
->siglock
);
1581 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on
1582 * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
1583 * allows the thread to return from interrupt.
1585 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
1586 * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from
1589 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
1590 * uprobe_notify_resume().
1592 void uprobe_notify_resume(struct pt_regs
*regs
)
1594 struct uprobe_task
*utask
;
1596 utask
= current
->utask
;
1597 if (!utask
|| utask
->state
== UTASK_BP_HIT
)
1600 handle_singlestep(utask
, regs
);
1604 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
1605 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
1607 int uprobe_pre_sstep_notifier(struct pt_regs
*regs
)
1609 struct uprobe_task
*utask
;
1611 if (!current
->mm
|| !atomic_read(¤t
->mm
->uprobes_state
.count
))
1612 /* task is currently not uprobed */
1615 utask
= current
->utask
;
1617 utask
->state
= UTASK_BP_HIT
;
1619 set_thread_flag(TIF_UPROBE
);
1625 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
1626 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
1628 int uprobe_post_sstep_notifier(struct pt_regs
*regs
)
1630 struct uprobe_task
*utask
= current
->utask
;
1632 if (!current
->mm
|| !utask
|| !utask
->active_uprobe
)
1633 /* task is currently not uprobed */
1636 utask
->state
= UTASK_SSTEP_ACK
;
1637 set_thread_flag(TIF_UPROBE
);
1641 static struct notifier_block uprobe_exception_nb
= {
1642 .notifier_call
= arch_uprobe_exception_notify
,
1643 .priority
= INT_MAX
-1, /* notified after kprobes, kgdb */
1646 static int __init
init_uprobes(void)
1650 for (i
= 0; i
< UPROBES_HASH_SZ
; i
++) {
1651 mutex_init(&uprobes_mutex
[i
]);
1652 mutex_init(&uprobes_mmap_mutex
[i
]);
1655 return register_die_notifier(&uprobe_exception_nb
);
1657 module_init(init_uprobes
);
1659 static void __exit
exit_uprobes(void)
1662 module_exit(exit_uprobes
);