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 */
35 #include "../../mm/internal.h" /* munlock_vma_page */
36 #include <linux/percpu-rwsem.h>
38 #include <linux/uprobes.h>
40 #define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
41 #define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
43 static struct rb_root uprobes_tree = RB_ROOT;
45 * allows us to skip the uprobe_mmap if there are no uprobe events active
46 * at this time. Probably a fine grained per inode count is better?
48 #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree)
50 static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
52 #define UPROBES_HASH_SZ 13
53 /* serialize uprobe->pending_list */
54 static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
55 #define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
57 static struct percpu_rw_semaphore dup_mmap_sem;
59 /* Have a copy of original instruction */
60 #define UPROBE_COPY_INSN 0
61 /* Can skip singlestep */
62 #define UPROBE_SKIP_SSTEP 1
65 struct rb_node rb_node; /* node in the rb tree */
67 struct rw_semaphore register_rwsem;
68 struct rw_semaphore consumer_rwsem;
69 struct list_head pending_list;
70 struct uprobe_consumer *consumers;
71 struct inode *inode; /* Also hold a ref to inode */
74 struct arch_uprobe arch;
78 * valid_vma: Verify if the specified vma is an executable vma
79 * Relax restrictions while unregistering: vm_flags might have
80 * changed after breakpoint was inserted.
81 * - is_register: indicates if we are in register context.
82 * - Return 1 if the specified virtual address is in an
85 static bool valid_vma(struct vm_area_struct *vma, bool is_register)
87 vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED;
92 return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
95 static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
97 return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
100 static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
102 return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start);
106 * __replace_page - replace page in vma by new page.
107 * based on replace_page in mm/ksm.c
109 * @vma: vma that holds the pte pointing to page
110 * @addr: address the old @page is mapped at
111 * @page: the cowed page we are replacing by kpage
112 * @kpage: the modified page we replace page by
114 * Returns 0 on success, -EFAULT on failure.
116 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
117 struct page *page, struct page *kpage)
119 struct mm_struct *mm = vma->vm_mm;
123 /* For mmu_notifiers */
124 const unsigned long mmun_start = addr;
125 const unsigned long mmun_end = addr + PAGE_SIZE;
127 /* For try_to_free_swap() and munlock_vma_page() below */
130 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
132 ptep = page_check_address(page, mm, addr, &ptl, 0);
137 page_add_new_anon_rmap(kpage, vma, addr);
139 if (!PageAnon(page)) {
140 dec_mm_counter(mm, MM_FILEPAGES);
141 inc_mm_counter(mm, MM_ANONPAGES);
144 flush_cache_page(vma, addr, pte_pfn(*ptep));
145 ptep_clear_flush(vma, addr, ptep);
146 set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
148 page_remove_rmap(page);
149 if (!page_mapped(page))
150 try_to_free_swap(page);
151 pte_unmap_unlock(ptep, ptl);
153 if (vma->vm_flags & VM_LOCKED)
154 munlock_vma_page(page);
159 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
165 * is_swbp_insn - check if instruction is breakpoint instruction.
166 * @insn: instruction to be checked.
167 * Default implementation of is_swbp_insn
168 * Returns true if @insn is a breakpoint instruction.
170 bool __weak is_swbp_insn(uprobe_opcode_t *insn)
172 return *insn == UPROBE_SWBP_INSN;
175 static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *opcode)
177 void *kaddr = kmap_atomic(page);
178 memcpy(opcode, kaddr + (vaddr & ~PAGE_MASK), UPROBE_SWBP_INSN_SIZE);
179 kunmap_atomic(kaddr);
182 static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
184 uprobe_opcode_t old_opcode;
187 copy_opcode(page, vaddr, &old_opcode);
188 is_swbp = is_swbp_insn(&old_opcode);
190 if (is_swbp_insn(new_opcode)) {
191 if (is_swbp) /* register: already installed? */
194 if (!is_swbp) /* unregister: was it changed by us? */
203 * Expect the breakpoint instruction to be the smallest size instruction for
204 * the architecture. If an arch has variable length instruction and the
205 * breakpoint instruction is not of the smallest length instruction
206 * supported by that architecture then we need to modify is_swbp_at_addr and
207 * write_opcode accordingly. This would never be a problem for archs that
208 * have fixed length instructions.
212 * write_opcode - write the opcode at a given virtual address.
213 * @mm: the probed process address space.
214 * @vaddr: the virtual address to store the opcode.
215 * @opcode: opcode to be written at @vaddr.
217 * Called with mm->mmap_sem held (for read and with a reference to
220 * For mm @mm, write the opcode at @vaddr.
221 * Return 0 (success) or a negative errno.
223 static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
224 uprobe_opcode_t opcode)
226 struct page *old_page, *new_page;
227 void *vaddr_old, *vaddr_new;
228 struct vm_area_struct *vma;
232 /* Read the page with vaddr into memory */
233 ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
237 ret = verify_opcode(old_page, vaddr, &opcode);
242 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
246 __SetPageUptodate(new_page);
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);
262 ret = __replace_page(vma, vaddr, old_page, new_page);
265 page_cache_release(new_page);
269 if (unlikely(ret == -EAGAIN))
275 * set_swbp - store breakpoint at a given address.
276 * @auprobe: arch specific probepoint information.
277 * @mm: the probed process address space.
278 * @vaddr: the virtual address to insert the opcode.
280 * For mm @mm, store the breakpoint instruction at @vaddr.
281 * Return 0 (success) or a negative errno.
283 int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
285 return write_opcode(mm, vaddr, UPROBE_SWBP_INSN);
289 * set_orig_insn - Restore the original instruction.
290 * @mm: the probed process address space.
291 * @auprobe: arch specific probepoint information.
292 * @vaddr: the virtual address to insert the opcode.
294 * For mm @mm, restore the original opcode (opcode) at @vaddr.
295 * Return 0 (success) or a negative errno.
298 set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
300 return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
303 static int match_uprobe(struct uprobe *l, struct uprobe *r)
305 if (l->inode < r->inode)
308 if (l->inode > r->inode)
311 if (l->offset < r->offset)
314 if (l->offset > r->offset)
320 static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
322 struct uprobe u = { .inode = inode, .offset = offset };
323 struct rb_node *n = uprobes_tree.rb_node;
324 struct uprobe *uprobe;
328 uprobe = rb_entry(n, struct uprobe, rb_node);
329 match = match_uprobe(&u, uprobe);
331 atomic_inc(&uprobe->ref);
344 * Find a uprobe corresponding to a given inode:offset
345 * Acquires uprobes_treelock
347 static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
349 struct uprobe *uprobe;
351 spin_lock(&uprobes_treelock);
352 uprobe = __find_uprobe(inode, offset);
353 spin_unlock(&uprobes_treelock);
358 static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
360 struct rb_node **p = &uprobes_tree.rb_node;
361 struct rb_node *parent = NULL;
367 u = rb_entry(parent, struct uprobe, rb_node);
368 match = match_uprobe(uprobe, u);
375 p = &parent->rb_left;
377 p = &parent->rb_right;
382 rb_link_node(&uprobe->rb_node, parent, p);
383 rb_insert_color(&uprobe->rb_node, &uprobes_tree);
384 /* get access + creation ref */
385 atomic_set(&uprobe->ref, 2);
391 * Acquire uprobes_treelock.
392 * Matching uprobe already exists in rbtree;
393 * increment (access refcount) and return the matching uprobe.
395 * No matching uprobe; insert the uprobe in rb_tree;
396 * get a double refcount (access + creation) and return NULL.
398 static struct uprobe *insert_uprobe(struct uprobe *uprobe)
402 spin_lock(&uprobes_treelock);
403 u = __insert_uprobe(uprobe);
404 spin_unlock(&uprobes_treelock);
409 static void put_uprobe(struct uprobe *uprobe)
411 if (atomic_dec_and_test(&uprobe->ref))
415 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
417 struct uprobe *uprobe, *cur_uprobe;
419 uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
423 uprobe->inode = igrab(inode);
424 uprobe->offset = offset;
425 init_rwsem(&uprobe->register_rwsem);
426 init_rwsem(&uprobe->consumer_rwsem);
427 /* For now assume that the instruction need not be single-stepped */
428 __set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
430 /* add to uprobes_tree, sorted on inode:offset */
431 cur_uprobe = insert_uprobe(uprobe);
433 /* a uprobe exists for this inode:offset combination */
443 static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
445 struct uprobe_consumer *uc;
447 down_read(&uprobe->register_rwsem);
448 for (uc = uprobe->consumers; uc; uc = uc->next)
449 uc->handler(uc, regs);
450 up_read(&uprobe->register_rwsem);
453 static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
455 down_write(&uprobe->consumer_rwsem);
456 uc->next = uprobe->consumers;
457 uprobe->consumers = uc;
458 up_write(&uprobe->consumer_rwsem);
462 * For uprobe @uprobe, delete the consumer @uc.
463 * Return true if the @uc is deleted successfully
466 static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
468 struct uprobe_consumer **con;
471 down_write(&uprobe->consumer_rwsem);
472 for (con = &uprobe->consumers; *con; con = &(*con)->next) {
479 up_write(&uprobe->consumer_rwsem);
485 __copy_insn(struct address_space *mapping, struct file *filp, char *insn,
486 unsigned long nbytes, loff_t offset)
496 if (!mapping->a_ops->readpage)
499 idx = offset >> PAGE_CACHE_SHIFT;
500 off = offset & ~PAGE_MASK;
503 * Ensure that the page that has the original instruction is
504 * populated and in page-cache.
506 page = read_mapping_page(mapping, idx, filp);
508 return PTR_ERR(page);
510 vaddr = kmap_atomic(page);
511 memcpy(insn, vaddr + off, nbytes);
512 kunmap_atomic(vaddr);
513 page_cache_release(page);
518 static int copy_insn(struct uprobe *uprobe, struct file *filp)
520 struct address_space *mapping;
521 unsigned long nbytes;
524 nbytes = PAGE_SIZE - (uprobe->offset & ~PAGE_MASK);
525 mapping = uprobe->inode->i_mapping;
527 /* Instruction at end of binary; copy only available bytes */
528 if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
529 bytes = uprobe->inode->i_size - uprobe->offset;
531 bytes = MAX_UINSN_BYTES;
533 /* Instruction at the page-boundary; copy bytes in second page */
534 if (nbytes < bytes) {
535 int err = __copy_insn(mapping, filp, uprobe->arch.insn + nbytes,
536 bytes - nbytes, uprobe->offset + nbytes);
541 return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
544 static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
545 struct mm_struct *mm, unsigned long vaddr)
549 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
552 /* TODO: move this into _register, until then we abuse this sem. */
553 down_write(&uprobe->consumer_rwsem);
554 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
557 ret = copy_insn(uprobe, file);
562 if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
565 ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
569 /* write_opcode() assumes we don't cross page boundary */
570 BUG_ON((uprobe->offset & ~PAGE_MASK) +
571 UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
573 smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
574 set_bit(UPROBE_COPY_INSN, &uprobe->flags);
577 up_write(&uprobe->consumer_rwsem);
582 static inline bool consumer_filter(struct uprobe_consumer *uc)
584 return true; /* TODO: !uc->filter || uc->filter(...) */
587 static bool filter_chain(struct uprobe *uprobe)
589 struct uprobe_consumer *uc;
592 down_read(&uprobe->consumer_rwsem);
593 for (uc = uprobe->consumers; uc; uc = uc->next) {
594 ret = consumer_filter(uc);
598 up_read(&uprobe->consumer_rwsem);
604 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
605 struct vm_area_struct *vma, unsigned long vaddr)
610 ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
615 * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
616 * the task can hit this breakpoint right after __replace_page().
618 first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
620 set_bit(MMF_HAS_UPROBES, &mm->flags);
622 ret = set_swbp(&uprobe->arch, mm, vaddr);
624 clear_bit(MMF_RECALC_UPROBES, &mm->flags);
625 else if (first_uprobe)
626 clear_bit(MMF_HAS_UPROBES, &mm->flags);
632 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
634 set_bit(MMF_RECALC_UPROBES, &mm->flags);
635 return set_orig_insn(&uprobe->arch, mm, vaddr);
638 static inline bool uprobe_is_active(struct uprobe *uprobe)
640 return !RB_EMPTY_NODE(&uprobe->rb_node);
643 * There could be threads that have already hit the breakpoint. They
644 * will recheck the current insn and restart if find_uprobe() fails.
645 * See find_active_uprobe().
647 static void delete_uprobe(struct uprobe *uprobe)
649 if (WARN_ON(!uprobe_is_active(uprobe)))
652 spin_lock(&uprobes_treelock);
653 rb_erase(&uprobe->rb_node, &uprobes_tree);
654 spin_unlock(&uprobes_treelock);
655 RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
661 struct map_info *next;
662 struct mm_struct *mm;
666 static inline struct map_info *free_map_info(struct map_info *info)
668 struct map_info *next = info->next;
673 static struct map_info *
674 build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
676 unsigned long pgoff = offset >> PAGE_SHIFT;
677 struct vm_area_struct *vma;
678 struct map_info *curr = NULL;
679 struct map_info *prev = NULL;
680 struct map_info *info;
684 mutex_lock(&mapping->i_mmap_mutex);
685 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
686 if (!valid_vma(vma, is_register))
689 if (!prev && !more) {
691 * Needs GFP_NOWAIT to avoid i_mmap_mutex recursion through
692 * reclaim. This is optimistic, no harm done if it fails.
694 prev = kmalloc(sizeof(struct map_info),
695 GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
704 if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
712 info->mm = vma->vm_mm;
713 info->vaddr = offset_to_vaddr(vma, offset);
715 mutex_unlock(&mapping->i_mmap_mutex);
727 info = kmalloc(sizeof(struct map_info), GFP_KERNEL);
729 curr = ERR_PTR(-ENOMEM);
739 prev = free_map_info(prev);
743 static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
745 struct map_info *info;
748 percpu_down_write(&dup_mmap_sem);
749 info = build_map_info(uprobe->inode->i_mapping,
750 uprobe->offset, is_register);
757 struct mm_struct *mm = info->mm;
758 struct vm_area_struct *vma;
760 if (err && is_register)
763 down_write(&mm->mmap_sem);
764 vma = find_vma(mm, info->vaddr);
765 if (!vma || !valid_vma(vma, is_register) ||
766 vma->vm_file->f_mapping->host != uprobe->inode)
769 if (vma->vm_start > info->vaddr ||
770 vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
774 /* consult only the "caller", new consumer. */
775 if (consumer_filter(uprobe->consumers))
776 err = install_breakpoint(uprobe, mm, vma, info->vaddr);
777 } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
778 if (!filter_chain(uprobe))
779 err |= remove_breakpoint(uprobe, mm, info->vaddr);
783 up_write(&mm->mmap_sem);
786 info = free_map_info(info);
789 percpu_up_write(&dup_mmap_sem);
793 static int __uprobe_register(struct uprobe *uprobe, struct uprobe_consumer *uc)
795 consumer_add(uprobe, uc);
796 return register_for_each_vma(uprobe, true);
799 static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
803 if (!consumer_del(uprobe, uc)) /* WARN? */
806 err = register_for_each_vma(uprobe, false);
807 /* TODO : cant unregister? schedule a worker thread */
808 if (!uprobe->consumers && !err)
809 delete_uprobe(uprobe);
813 * uprobe_register - register a probe
814 * @inode: the file in which the probe has to be placed.
815 * @offset: offset from the start of the file.
816 * @uc: information on howto handle the probe..
818 * Apart from the access refcount, uprobe_register() takes a creation
819 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
820 * inserted into the rbtree (i.e first consumer for a @inode:@offset
821 * tuple). Creation refcount stops uprobe_unregister from freeing the
822 * @uprobe even before the register operation is complete. Creation
823 * refcount is released when the last @uc for the @uprobe
826 * Return errno if it cannot successully install probes
827 * else return 0 (success)
829 int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
831 struct uprobe *uprobe;
834 /* Racy, just to catch the obvious mistakes */
835 if (offset > i_size_read(inode))
839 uprobe = alloc_uprobe(inode, offset);
843 * We can race with uprobe_unregister()->delete_uprobe().
844 * Check uprobe_is_active() and retry if it is false.
846 down_write(&uprobe->register_rwsem);
848 if (likely(uprobe_is_active(uprobe))) {
849 ret = __uprobe_register(uprobe, uc);
851 __uprobe_unregister(uprobe, uc);
853 up_write(&uprobe->register_rwsem);
856 if (unlikely(ret == -EAGAIN))
862 * uprobe_unregister - unregister a already registered probe.
863 * @inode: the file in which the probe has to be removed.
864 * @offset: offset from the start of the file.
865 * @uc: identify which probe if multiple probes are colocated.
867 void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
869 struct uprobe *uprobe;
871 uprobe = find_uprobe(inode, offset);
875 down_write(&uprobe->register_rwsem);
876 __uprobe_unregister(uprobe, uc);
877 up_write(&uprobe->register_rwsem);
881 static struct rb_node *
882 find_node_in_range(struct inode *inode, loff_t min, loff_t max)
884 struct rb_node *n = uprobes_tree.rb_node;
887 struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
889 if (inode < u->inode) {
891 } else if (inode > u->inode) {
896 else if (min > u->offset)
907 * For a given range in vma, build a list of probes that need to be inserted.
909 static void build_probe_list(struct inode *inode,
910 struct vm_area_struct *vma,
911 unsigned long start, unsigned long end,
912 struct list_head *head)
915 struct rb_node *n, *t;
918 INIT_LIST_HEAD(head);
919 min = vaddr_to_offset(vma, start);
920 max = min + (end - start) - 1;
922 spin_lock(&uprobes_treelock);
923 n = find_node_in_range(inode, min, max);
925 for (t = n; t; t = rb_prev(t)) {
926 u = rb_entry(t, struct uprobe, rb_node);
927 if (u->inode != inode || u->offset < min)
929 list_add(&u->pending_list, head);
932 for (t = n; (t = rb_next(t)); ) {
933 u = rb_entry(t, struct uprobe, rb_node);
934 if (u->inode != inode || u->offset > max)
936 list_add(&u->pending_list, head);
940 spin_unlock(&uprobes_treelock);
944 * Called from mmap_region/vma_adjust with mm->mmap_sem acquired.
946 * Currently we ignore all errors and always return 0, the callers
947 * can't handle the failure anyway.
949 int uprobe_mmap(struct vm_area_struct *vma)
951 struct list_head tmp_list;
952 struct uprobe *uprobe, *u;
955 if (no_uprobe_events() || !valid_vma(vma, true))
958 inode = vma->vm_file->f_mapping->host;
962 mutex_lock(uprobes_mmap_hash(inode));
963 build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
965 * We can race with uprobe_unregister(), this uprobe can be already
966 * removed. But in this case filter_chain() must return false, all
967 * consumers have gone away.
969 list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
970 if (!fatal_signal_pending(current) &&
971 filter_chain(uprobe)) {
972 unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
973 install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
977 mutex_unlock(uprobes_mmap_hash(inode));
983 vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)
989 inode = vma->vm_file->f_mapping->host;
991 min = vaddr_to_offset(vma, start);
992 max = min + (end - start) - 1;
994 spin_lock(&uprobes_treelock);
995 n = find_node_in_range(inode, min, max);
996 spin_unlock(&uprobes_treelock);
1002 * Called in context of a munmap of a vma.
1004 void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1006 if (no_uprobe_events() || !valid_vma(vma, false))
1009 if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
1012 if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||
1013 test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))
1016 if (vma_has_uprobes(vma, start, end))
1017 set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
1020 /* Slot allocation for XOL */
1021 static int xol_add_vma(struct xol_area *area)
1023 struct mm_struct *mm;
1026 area->page = alloc_page(GFP_HIGHUSER);
1033 down_write(&mm->mmap_sem);
1034 if (mm->uprobes_state.xol_area)
1039 /* Try to map as high as possible, this is only a hint. */
1040 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0);
1041 if (area->vaddr & ~PAGE_MASK) {
1046 ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1047 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page);
1051 smp_wmb(); /* pairs with get_xol_area() */
1052 mm->uprobes_state.xol_area = area;
1056 up_write(&mm->mmap_sem);
1058 __free_page(area->page);
1063 static struct xol_area *get_xol_area(struct mm_struct *mm)
1065 struct xol_area *area;
1067 area = mm->uprobes_state.xol_area;
1068 smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
1074 * xol_alloc_area - Allocate process's xol_area.
1075 * This area will be used for storing instructions for execution out of
1078 * Returns the allocated area or NULL.
1080 static struct xol_area *xol_alloc_area(void)
1082 struct xol_area *area;
1084 area = kzalloc(sizeof(*area), GFP_KERNEL);
1085 if (unlikely(!area))
1088 area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL);
1093 init_waitqueue_head(&area->wq);
1094 if (!xol_add_vma(area))
1098 kfree(area->bitmap);
1101 return get_xol_area(current->mm);
1105 * uprobe_clear_state - Free the area allocated for slots.
1107 void uprobe_clear_state(struct mm_struct *mm)
1109 struct xol_area *area = mm->uprobes_state.xol_area;
1114 put_page(area->page);
1115 kfree(area->bitmap);
1119 void uprobe_start_dup_mmap(void)
1121 percpu_down_read(&dup_mmap_sem);
1124 void uprobe_end_dup_mmap(void)
1126 percpu_up_read(&dup_mmap_sem);
1129 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
1131 newmm->uprobes_state.xol_area = NULL;
1133 if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {
1134 set_bit(MMF_HAS_UPROBES, &newmm->flags);
1135 /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */
1136 set_bit(MMF_RECALC_UPROBES, &newmm->flags);
1141 * - search for a free slot.
1143 static unsigned long xol_take_insn_slot(struct xol_area *area)
1145 unsigned long slot_addr;
1149 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1150 if (slot_nr < UINSNS_PER_PAGE) {
1151 if (!test_and_set_bit(slot_nr, area->bitmap))
1154 slot_nr = UINSNS_PER_PAGE;
1157 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1158 } while (slot_nr >= UINSNS_PER_PAGE);
1160 slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1161 atomic_inc(&area->slot_count);
1167 * xol_get_insn_slot - If was not allocated a slot, then
1169 * Returns the allocated slot address or 0.
1171 static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot_addr)
1173 struct xol_area *area;
1174 unsigned long offset;
1177 area = get_xol_area(current->mm);
1179 area = xol_alloc_area();
1183 current->utask->xol_vaddr = xol_take_insn_slot(area);
1186 * Initialize the slot if xol_vaddr points to valid
1189 if (unlikely(!current->utask->xol_vaddr))
1192 current->utask->vaddr = slot_addr;
1193 offset = current->utask->xol_vaddr & ~PAGE_MASK;
1194 vaddr = kmap_atomic(area->page);
1195 memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
1196 kunmap_atomic(vaddr);
1198 * We probably need flush_icache_user_range() but it needs vma.
1199 * This should work on supported architectures too.
1201 flush_dcache_page(area->page);
1203 return current->utask->xol_vaddr;
1207 * xol_free_insn_slot - If slot was earlier allocated by
1208 * @xol_get_insn_slot(), make the slot available for
1209 * subsequent requests.
1211 static void xol_free_insn_slot(struct task_struct *tsk)
1213 struct xol_area *area;
1214 unsigned long vma_end;
1215 unsigned long slot_addr;
1217 if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1220 slot_addr = tsk->utask->xol_vaddr;
1222 if (unlikely(!slot_addr || IS_ERR_VALUE(slot_addr)))
1225 area = tsk->mm->uprobes_state.xol_area;
1226 vma_end = area->vaddr + PAGE_SIZE;
1227 if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1228 unsigned long offset;
1231 offset = slot_addr - area->vaddr;
1232 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1233 if (slot_nr >= UINSNS_PER_PAGE)
1236 clear_bit(slot_nr, area->bitmap);
1237 atomic_dec(&area->slot_count);
1238 if (waitqueue_active(&area->wq))
1241 tsk->utask->xol_vaddr = 0;
1246 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1247 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1249 * Return the address of the breakpoint instruction.
1251 unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1253 return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1257 * Called with no locks held.
1258 * Called in context of a exiting or a exec-ing thread.
1260 void uprobe_free_utask(struct task_struct *t)
1262 struct uprobe_task *utask = t->utask;
1267 if (utask->active_uprobe)
1268 put_uprobe(utask->active_uprobe);
1270 xol_free_insn_slot(t);
1276 * Called in context of a new clone/fork from copy_process.
1278 void uprobe_copy_process(struct task_struct *t)
1284 * Allocate a uprobe_task object for the task.
1285 * Called when the thread hits a breakpoint for the first time.
1288 * - pointer to new uprobe_task on success
1291 static struct uprobe_task *add_utask(void)
1293 struct uprobe_task *utask;
1295 utask = kzalloc(sizeof *utask, GFP_KERNEL);
1296 if (unlikely(!utask))
1299 current->utask = utask;
1303 /* Prepare to single-step probed instruction out of line. */
1305 pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr)
1307 if (xol_get_insn_slot(uprobe, vaddr) && !arch_uprobe_pre_xol(&uprobe->arch, regs))
1314 * If we are singlestepping, then ensure this thread is not connected to
1315 * non-fatal signals until completion of singlestep. When xol insn itself
1316 * triggers the signal, restart the original insn even if the task is
1317 * already SIGKILL'ed (since coredump should report the correct ip). This
1318 * is even more important if the task has a handler for SIGSEGV/etc, The
1319 * _same_ instruction should be repeated again after return from the signal
1320 * handler, and SSTEP can never finish in this case.
1322 bool uprobe_deny_signal(void)
1324 struct task_struct *t = current;
1325 struct uprobe_task *utask = t->utask;
1327 if (likely(!utask || !utask->active_uprobe))
1330 WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1332 if (signal_pending(t)) {
1333 spin_lock_irq(&t->sighand->siglock);
1334 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1335 spin_unlock_irq(&t->sighand->siglock);
1337 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1338 utask->state = UTASK_SSTEP_TRAPPED;
1339 set_tsk_thread_flag(t, TIF_UPROBE);
1340 set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
1348 * Avoid singlestepping the original instruction if the original instruction
1349 * is a NOP or can be emulated.
1351 static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
1353 if (test_bit(UPROBE_SKIP_SSTEP, &uprobe->flags)) {
1354 if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
1356 clear_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
1361 static void mmf_recalc_uprobes(struct mm_struct *mm)
1363 struct vm_area_struct *vma;
1365 for (vma = mm->mmap; vma; vma = vma->vm_next) {
1366 if (!valid_vma(vma, false))
1369 * This is not strictly accurate, we can race with
1370 * uprobe_unregister() and see the already removed
1371 * uprobe if delete_uprobe() was not yet called.
1372 * Or this uprobe can be filtered out.
1374 if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
1378 clear_bit(MMF_HAS_UPROBES, &mm->flags);
1381 static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
1384 uprobe_opcode_t opcode;
1387 pagefault_disable();
1388 result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
1392 if (likely(result == 0))
1395 result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
1399 copy_opcode(page, vaddr, &opcode);
1402 return is_swbp_insn(&opcode);
1405 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
1407 struct mm_struct *mm = current->mm;
1408 struct uprobe *uprobe = NULL;
1409 struct vm_area_struct *vma;
1411 down_read(&mm->mmap_sem);
1412 vma = find_vma(mm, bp_vaddr);
1413 if (vma && vma->vm_start <= bp_vaddr) {
1414 if (valid_vma(vma, false)) {
1415 struct inode *inode = vma->vm_file->f_mapping->host;
1416 loff_t offset = vaddr_to_offset(vma, bp_vaddr);
1418 uprobe = find_uprobe(inode, offset);
1422 *is_swbp = is_swbp_at_addr(mm, bp_vaddr);
1427 if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
1428 mmf_recalc_uprobes(mm);
1429 up_read(&mm->mmap_sem);
1435 * Run handler and ask thread to singlestep.
1436 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
1438 static void handle_swbp(struct pt_regs *regs)
1440 struct uprobe_task *utask;
1441 struct uprobe *uprobe;
1442 unsigned long bp_vaddr;
1443 int uninitialized_var(is_swbp);
1445 bp_vaddr = uprobe_get_swbp_addr(regs);
1446 uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
1450 /* No matching uprobe; signal SIGTRAP. */
1451 send_sig(SIGTRAP, current, 0);
1454 * Either we raced with uprobe_unregister() or we can't
1455 * access this memory. The latter is only possible if
1456 * another thread plays with our ->mm. In both cases
1457 * we can simply restart. If this vma was unmapped we
1458 * can pretend this insn was not executed yet and get
1459 * the (correct) SIGSEGV after restart.
1461 instruction_pointer_set(regs, bp_vaddr);
1466 * TODO: move copy_insn/etc into _register and remove this hack.
1467 * After we hit the bp, _unregister + _register can install the
1468 * new and not-yet-analyzed uprobe at the same address, restart.
1470 smp_rmb(); /* pairs with wmb() in install_breakpoint() */
1471 if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
1474 utask = current->utask;
1476 utask = add_utask();
1477 /* Cannot allocate; re-execute the instruction. */
1482 handler_chain(uprobe, regs);
1483 if (can_skip_sstep(uprobe, regs))
1486 if (!pre_ssout(uprobe, regs, bp_vaddr)) {
1487 utask->active_uprobe = uprobe;
1488 utask->state = UTASK_SSTEP;
1494 * cannot singlestep; cannot skip instruction;
1495 * re-execute the instruction.
1497 instruction_pointer_set(regs, bp_vaddr);
1503 * Perform required fix-ups and disable singlestep.
1504 * Allow pending signals to take effect.
1506 static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
1508 struct uprobe *uprobe;
1510 uprobe = utask->active_uprobe;
1511 if (utask->state == UTASK_SSTEP_ACK)
1512 arch_uprobe_post_xol(&uprobe->arch, regs);
1513 else if (utask->state == UTASK_SSTEP_TRAPPED)
1514 arch_uprobe_abort_xol(&uprobe->arch, regs);
1519 utask->active_uprobe = NULL;
1520 utask->state = UTASK_RUNNING;
1521 xol_free_insn_slot(current);
1523 spin_lock_irq(¤t->sighand->siglock);
1524 recalc_sigpending(); /* see uprobe_deny_signal() */
1525 spin_unlock_irq(¤t->sighand->siglock);
1529 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
1530 * allows the thread to return from interrupt. After that handle_swbp()
1531 * sets utask->active_uprobe.
1533 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
1534 * and allows the thread to return from interrupt.
1536 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
1537 * uprobe_notify_resume().
1539 void uprobe_notify_resume(struct pt_regs *regs)
1541 struct uprobe_task *utask;
1543 clear_thread_flag(TIF_UPROBE);
1545 utask = current->utask;
1546 if (utask && utask->active_uprobe)
1547 handle_singlestep(utask, regs);
1553 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
1554 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
1556 int uprobe_pre_sstep_notifier(struct pt_regs *regs)
1558 if (!current->mm || !test_bit(MMF_HAS_UPROBES, ¤t->mm->flags))
1561 set_thread_flag(TIF_UPROBE);
1566 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
1567 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
1569 int uprobe_post_sstep_notifier(struct pt_regs *regs)
1571 struct uprobe_task *utask = current->utask;
1573 if (!current->mm || !utask || !utask->active_uprobe)
1574 /* task is currently not uprobed */
1577 utask->state = UTASK_SSTEP_ACK;
1578 set_thread_flag(TIF_UPROBE);
1582 static struct notifier_block uprobe_exception_nb = {
1583 .notifier_call = arch_uprobe_exception_notify,
1584 .priority = INT_MAX-1, /* notified after kprobes, kgdb */
1587 static int __init init_uprobes(void)
1591 for (i = 0; i < UPROBES_HASH_SZ; i++)
1592 mutex_init(&uprobes_mmap_mutex[i]);
1594 if (percpu_init_rwsem(&dup_mmap_sem))
1597 return register_die_notifier(&uprobe_exception_nb);
1599 module_init(init_uprobes);
1601 static void __exit exit_uprobes(void)
1604 module_exit(exit_uprobes);