1 // SPDX-License-Identifier: GPL-2.0+
3 * User-space Probes (UProbes)
5 * Copyright (C) IBM Corporation, 2008-2012
9 * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
12 #include <linux/kernel.h>
13 #include <linux/highmem.h>
14 #include <linux/pagemap.h> /* read_mapping_page */
15 #include <linux/slab.h>
16 #include <linux/sched.h>
17 #include <linux/sched/mm.h>
18 #include <linux/sched/coredump.h>
19 #include <linux/export.h>
20 #include <linux/rmap.h> /* anon_vma_prepare */
21 #include <linux/mmu_notifier.h> /* set_pte_at_notify */
22 #include <linux/swap.h> /* folio_free_swap */
23 #include <linux/ptrace.h> /* user_enable_single_step */
24 #include <linux/kdebug.h> /* notifier mechanism */
25 #include <linux/percpu-rwsem.h>
26 #include <linux/task_work.h>
27 #include <linux/shmem_fs.h>
28 #include <linux/khugepaged.h>
30 #include <linux/uprobes.h>
32 #define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
33 #define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
35 static struct rb_root uprobes_tree = RB_ROOT;
37 * allows us to skip the uprobe_mmap if there are no uprobe events active
38 * at this time. Probably a fine grained per inode count is better?
40 #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree)
42 static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
44 #define UPROBES_HASH_SZ 13
45 /* serialize uprobe->pending_list */
46 static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
47 #define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
49 DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem);
51 /* Have a copy of original instruction */
52 #define UPROBE_COPY_INSN 0
55 struct rb_node rb_node; /* node in the rb tree */
57 struct rw_semaphore register_rwsem;
58 struct rw_semaphore consumer_rwsem;
59 struct list_head pending_list;
60 struct uprobe_consumer *consumers;
61 struct inode *inode; /* Also hold a ref to inode */
63 loff_t ref_ctr_offset;
67 * The generic code assumes that it has two members of unknown type
68 * owned by the arch-specific code:
70 * insn - copy_insn() saves the original instruction here for
71 * arch_uprobe_analyze_insn().
73 * ixol - potentially modified instruction to execute out of
74 * line, copied to xol_area by xol_get_insn_slot().
76 struct arch_uprobe arch;
79 struct delayed_uprobe {
80 struct list_head list;
81 struct uprobe *uprobe;
85 static DEFINE_MUTEX(delayed_uprobe_lock);
86 static LIST_HEAD(delayed_uprobe_list);
89 * Execute out of line area: anonymous executable mapping installed
90 * by the probed task to execute the copy of the original instruction
91 * mangled by set_swbp().
93 * On a breakpoint hit, thread contests for a slot. It frees the
94 * slot after singlestep. Currently a fixed number of slots are
98 wait_queue_head_t wq; /* if all slots are busy */
99 atomic_t slot_count; /* number of in-use slots */
100 unsigned long *bitmap; /* 0 = free slot */
102 struct vm_special_mapping xol_mapping;
103 struct page *pages[2];
105 * We keep the vma's vm_start rather than a pointer to the vma
106 * itself. The probed process or a naughty kernel module could make
107 * the vma go away, and we must handle that reasonably gracefully.
109 unsigned long vaddr; /* Page(s) of instruction slots */
113 * valid_vma: Verify if the specified vma is an executable vma
114 * Relax restrictions while unregistering: vm_flags might have
115 * changed after breakpoint was inserted.
116 * - is_register: indicates if we are in register context.
117 * - Return 1 if the specified virtual address is in an
120 static bool valid_vma(struct vm_area_struct *vma, bool is_register)
122 vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE;
127 return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
130 static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
132 return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
135 static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
137 return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start);
141 * __replace_page - replace page in vma by new page.
142 * based on replace_page in mm/ksm.c
144 * @vma: vma that holds the pte pointing to page
145 * @addr: address the old @page is mapped at
146 * @old_page: the page we are replacing by new_page
147 * @new_page: the modified page we replace page by
149 * If @new_page is NULL, only unmap @old_page.
151 * Returns 0 on success, negative error code otherwise.
153 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
154 struct page *old_page, struct page *new_page)
156 struct folio *old_folio = page_folio(old_page);
157 struct folio *new_folio;
158 struct mm_struct *mm = vma->vm_mm;
159 DEFINE_FOLIO_VMA_WALK(pvmw, old_folio, vma, addr, 0);
161 struct mmu_notifier_range range;
163 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, addr,
167 new_folio = page_folio(new_page);
168 err = mem_cgroup_charge(new_folio, vma->vm_mm, GFP_KERNEL);
173 /* For folio_free_swap() below */
174 folio_lock(old_folio);
176 mmu_notifier_invalidate_range_start(&range);
178 if (!page_vma_mapped_walk(&pvmw))
180 VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
183 folio_get(new_folio);
184 page_add_new_anon_rmap(new_page, vma, addr);
185 folio_add_lru_vma(new_folio, vma);
187 /* no new page, just dec_mm_counter for old_page */
188 dec_mm_counter(mm, MM_ANONPAGES);
190 if (!folio_test_anon(old_folio)) {
191 dec_mm_counter(mm, mm_counter_file(old_page));
192 inc_mm_counter(mm, MM_ANONPAGES);
195 flush_cache_page(vma, addr, pte_pfn(ptep_get(pvmw.pte)));
196 ptep_clear_flush(vma, addr, pvmw.pte);
198 set_pte_at_notify(mm, addr, pvmw.pte,
199 mk_pte(new_page, vma->vm_page_prot));
201 page_remove_rmap(old_page, vma, false);
202 if (!folio_mapped(old_folio))
203 folio_free_swap(old_folio);
204 page_vma_mapped_walk_done(&pvmw);
205 folio_put(old_folio);
209 mmu_notifier_invalidate_range_end(&range);
210 folio_unlock(old_folio);
215 * is_swbp_insn - check if instruction is breakpoint instruction.
216 * @insn: instruction to be checked.
217 * Default implementation of is_swbp_insn
218 * Returns true if @insn is a breakpoint instruction.
220 bool __weak is_swbp_insn(uprobe_opcode_t *insn)
222 return *insn == UPROBE_SWBP_INSN;
226 * is_trap_insn - check if instruction is breakpoint instruction.
227 * @insn: instruction to be checked.
228 * Default implementation of is_trap_insn
229 * Returns true if @insn is a breakpoint instruction.
231 * This function is needed for the case where an architecture has multiple
232 * trap instructions (like powerpc).
234 bool __weak is_trap_insn(uprobe_opcode_t *insn)
236 return is_swbp_insn(insn);
239 static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len)
241 void *kaddr = kmap_atomic(page);
242 memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
243 kunmap_atomic(kaddr);
246 static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
248 void *kaddr = kmap_atomic(page);
249 memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
250 kunmap_atomic(kaddr);
253 static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
255 uprobe_opcode_t old_opcode;
259 * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here.
260 * We do not check if it is any other 'trap variant' which could
261 * be conditional trap instruction such as the one powerpc supports.
263 * The logic is that we do not care if the underlying instruction
264 * is a trap variant; uprobes always wins over any other (gdb)
267 copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE);
268 is_swbp = is_swbp_insn(&old_opcode);
270 if (is_swbp_insn(new_opcode)) {
271 if (is_swbp) /* register: already installed? */
274 if (!is_swbp) /* unregister: was it changed by us? */
281 static struct delayed_uprobe *
282 delayed_uprobe_check(struct uprobe *uprobe, struct mm_struct *mm)
284 struct delayed_uprobe *du;
286 list_for_each_entry(du, &delayed_uprobe_list, list)
287 if (du->uprobe == uprobe && du->mm == mm)
292 static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm)
294 struct delayed_uprobe *du;
296 if (delayed_uprobe_check(uprobe, mm))
299 du = kzalloc(sizeof(*du), GFP_KERNEL);
305 list_add(&du->list, &delayed_uprobe_list);
309 static void delayed_uprobe_delete(struct delayed_uprobe *du)
317 static void delayed_uprobe_remove(struct uprobe *uprobe, struct mm_struct *mm)
319 struct list_head *pos, *q;
320 struct delayed_uprobe *du;
325 list_for_each_safe(pos, q, &delayed_uprobe_list) {
326 du = list_entry(pos, struct delayed_uprobe, list);
328 if (uprobe && du->uprobe != uprobe)
330 if (mm && du->mm != mm)
333 delayed_uprobe_delete(du);
337 static bool valid_ref_ctr_vma(struct uprobe *uprobe,
338 struct vm_area_struct *vma)
340 unsigned long vaddr = offset_to_vaddr(vma, uprobe->ref_ctr_offset);
342 return uprobe->ref_ctr_offset &&
344 file_inode(vma->vm_file) == uprobe->inode &&
345 (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
346 vma->vm_start <= vaddr &&
350 static struct vm_area_struct *
351 find_ref_ctr_vma(struct uprobe *uprobe, struct mm_struct *mm)
353 VMA_ITERATOR(vmi, mm, 0);
354 struct vm_area_struct *tmp;
356 for_each_vma(vmi, tmp)
357 if (valid_ref_ctr_vma(uprobe, tmp))
364 __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
374 ret = get_user_pages_remote(mm, vaddr, 1,
375 FOLL_WRITE, &page, NULL);
376 if (unlikely(ret <= 0)) {
378 * We are asking for 1 page. If get_user_pages_remote() fails,
379 * it may return 0, in that case we have to return error.
381 return ret == 0 ? -EBUSY : ret;
384 kaddr = kmap_atomic(page);
385 ptr = kaddr + (vaddr & ~PAGE_MASK);
387 if (unlikely(*ptr + d < 0)) {
388 pr_warn("ref_ctr going negative. vaddr: 0x%lx, "
389 "curr val: %d, delta: %d\n", vaddr, *ptr, d);
397 kunmap_atomic(kaddr);
402 static void update_ref_ctr_warn(struct uprobe *uprobe,
403 struct mm_struct *mm, short d)
405 pr_warn("ref_ctr %s failed for inode: 0x%lx offset: "
406 "0x%llx ref_ctr_offset: 0x%llx of mm: 0x%pK\n",
407 d > 0 ? "increment" : "decrement", uprobe->inode->i_ino,
408 (unsigned long long) uprobe->offset,
409 (unsigned long long) uprobe->ref_ctr_offset, mm);
412 static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm,
415 struct vm_area_struct *rc_vma;
416 unsigned long rc_vaddr;
419 rc_vma = find_ref_ctr_vma(uprobe, mm);
422 rc_vaddr = offset_to_vaddr(rc_vma, uprobe->ref_ctr_offset);
423 ret = __update_ref_ctr(mm, rc_vaddr, d);
425 update_ref_ctr_warn(uprobe, mm, d);
431 mutex_lock(&delayed_uprobe_lock);
433 ret = delayed_uprobe_add(uprobe, mm);
435 delayed_uprobe_remove(uprobe, mm);
436 mutex_unlock(&delayed_uprobe_lock);
443 * Expect the breakpoint instruction to be the smallest size instruction for
444 * the architecture. If an arch has variable length instruction and the
445 * breakpoint instruction is not of the smallest length instruction
446 * supported by that architecture then we need to modify is_trap_at_addr and
447 * uprobe_write_opcode accordingly. This would never be a problem for archs
448 * that have fixed length instructions.
450 * uprobe_write_opcode - write the opcode at a given virtual address.
451 * @auprobe: arch specific probepoint information.
452 * @mm: the probed process address space.
453 * @vaddr: the virtual address to store the opcode.
454 * @opcode: opcode to be written at @vaddr.
456 * Called with mm->mmap_lock held for write.
457 * Return 0 (success) or a negative errno.
459 int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
460 unsigned long vaddr, uprobe_opcode_t opcode)
462 struct uprobe *uprobe;
463 struct page *old_page, *new_page;
464 struct vm_area_struct *vma;
465 int ret, is_register, ref_ctr_updated = 0;
466 bool orig_page_huge = false;
467 unsigned int gup_flags = FOLL_FORCE;
469 is_register = is_swbp_insn(&opcode);
470 uprobe = container_of(auprobe, struct uprobe, arch);
474 gup_flags |= FOLL_SPLIT_PMD;
475 /* Read the page with vaddr into memory */
476 old_page = get_user_page_vma_remote(mm, vaddr, gup_flags, &vma);
477 if (IS_ERR(old_page))
478 return PTR_ERR(old_page);
480 ret = verify_opcode(old_page, vaddr, &opcode);
484 if (WARN(!is_register && PageCompound(old_page),
485 "uprobe unregister should never work on compound page\n")) {
490 /* We are going to replace instruction, update ref_ctr. */
491 if (!ref_ctr_updated && uprobe->ref_ctr_offset) {
492 ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1);
500 if (!is_register && !PageAnon(old_page))
503 ret = anon_vma_prepare(vma);
508 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
512 __SetPageUptodate(new_page);
513 copy_highpage(new_page, old_page);
514 copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
517 struct page *orig_page;
520 VM_BUG_ON_PAGE(!PageAnon(old_page), old_page);
522 index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT;
523 orig_page = find_get_page(vma->vm_file->f_inode->i_mapping,
527 if (PageUptodate(orig_page) &&
528 pages_identical(new_page, orig_page)) {
529 /* let go new_page */
533 if (PageCompound(orig_page))
534 orig_page_huge = true;
540 ret = __replace_page(vma, vaddr, old_page, new_page);
546 if (unlikely(ret == -EAGAIN))
549 /* Revert back reference counter if instruction update failed. */
550 if (ret && is_register && ref_ctr_updated)
551 update_ref_ctr(uprobe, mm, -1);
553 /* try collapse pmd for compound page */
554 if (!ret && orig_page_huge)
555 collapse_pte_mapped_thp(mm, vaddr, false);
561 * set_swbp - store breakpoint at a given address.
562 * @auprobe: arch specific probepoint information.
563 * @mm: the probed process address space.
564 * @vaddr: the virtual address to insert the opcode.
566 * For mm @mm, store the breakpoint instruction at @vaddr.
567 * Return 0 (success) or a negative errno.
569 int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
571 return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
575 * set_orig_insn - Restore the original instruction.
576 * @mm: the probed process address space.
577 * @auprobe: arch specific probepoint information.
578 * @vaddr: the virtual address to insert the opcode.
580 * For mm @mm, restore the original opcode (opcode) at @vaddr.
581 * Return 0 (success) or a negative errno.
584 set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
586 return uprobe_write_opcode(auprobe, mm, vaddr,
587 *(uprobe_opcode_t *)&auprobe->insn);
590 static struct uprobe *get_uprobe(struct uprobe *uprobe)
592 refcount_inc(&uprobe->ref);
596 static void put_uprobe(struct uprobe *uprobe)
598 if (refcount_dec_and_test(&uprobe->ref)) {
600 * If application munmap(exec_vma) before uprobe_unregister()
601 * gets called, we don't get a chance to remove uprobe from
602 * delayed_uprobe_list from remove_breakpoint(). Do it here.
604 mutex_lock(&delayed_uprobe_lock);
605 delayed_uprobe_remove(uprobe, NULL);
606 mutex_unlock(&delayed_uprobe_lock);
611 static __always_inline
612 int uprobe_cmp(const struct inode *l_inode, const loff_t l_offset,
613 const struct uprobe *r)
615 if (l_inode < r->inode)
618 if (l_inode > r->inode)
621 if (l_offset < r->offset)
624 if (l_offset > r->offset)
630 #define __node_2_uprobe(node) \
631 rb_entry((node), struct uprobe, rb_node)
633 struct __uprobe_key {
638 static inline int __uprobe_cmp_key(const void *key, const struct rb_node *b)
640 const struct __uprobe_key *a = key;
641 return uprobe_cmp(a->inode, a->offset, __node_2_uprobe(b));
644 static inline int __uprobe_cmp(struct rb_node *a, const struct rb_node *b)
646 struct uprobe *u = __node_2_uprobe(a);
647 return uprobe_cmp(u->inode, u->offset, __node_2_uprobe(b));
650 static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
652 struct __uprobe_key key = {
656 struct rb_node *node = rb_find(&key, &uprobes_tree, __uprobe_cmp_key);
659 return get_uprobe(__node_2_uprobe(node));
665 * Find a uprobe corresponding to a given inode:offset
666 * Acquires uprobes_treelock
668 static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
670 struct uprobe *uprobe;
672 spin_lock(&uprobes_treelock);
673 uprobe = __find_uprobe(inode, offset);
674 spin_unlock(&uprobes_treelock);
679 static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
681 struct rb_node *node;
683 node = rb_find_add(&uprobe->rb_node, &uprobes_tree, __uprobe_cmp);
685 return get_uprobe(__node_2_uprobe(node));
687 /* get access + creation ref */
688 refcount_set(&uprobe->ref, 2);
693 * Acquire uprobes_treelock.
694 * Matching uprobe already exists in rbtree;
695 * increment (access refcount) and return the matching uprobe.
697 * No matching uprobe; insert the uprobe in rb_tree;
698 * get a double refcount (access + creation) and return NULL.
700 static struct uprobe *insert_uprobe(struct uprobe *uprobe)
704 spin_lock(&uprobes_treelock);
705 u = __insert_uprobe(uprobe);
706 spin_unlock(&uprobes_treelock);
712 ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe)
714 pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx "
715 "ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n",
716 uprobe->inode->i_ino, (unsigned long long) uprobe->offset,
717 (unsigned long long) cur_uprobe->ref_ctr_offset,
718 (unsigned long long) uprobe->ref_ctr_offset);
721 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
722 loff_t ref_ctr_offset)
724 struct uprobe *uprobe, *cur_uprobe;
726 uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
730 uprobe->inode = inode;
731 uprobe->offset = offset;
732 uprobe->ref_ctr_offset = ref_ctr_offset;
733 init_rwsem(&uprobe->register_rwsem);
734 init_rwsem(&uprobe->consumer_rwsem);
736 /* add to uprobes_tree, sorted on inode:offset */
737 cur_uprobe = insert_uprobe(uprobe);
738 /* a uprobe exists for this inode:offset combination */
740 if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
741 ref_ctr_mismatch_warn(cur_uprobe, uprobe);
742 put_uprobe(cur_uprobe);
744 return ERR_PTR(-EINVAL);
753 static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
755 down_write(&uprobe->consumer_rwsem);
756 uc->next = uprobe->consumers;
757 uprobe->consumers = uc;
758 up_write(&uprobe->consumer_rwsem);
762 * For uprobe @uprobe, delete the consumer @uc.
763 * Return true if the @uc is deleted successfully
766 static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
768 struct uprobe_consumer **con;
771 down_write(&uprobe->consumer_rwsem);
772 for (con = &uprobe->consumers; *con; con = &(*con)->next) {
779 up_write(&uprobe->consumer_rwsem);
784 static int __copy_insn(struct address_space *mapping, struct file *filp,
785 void *insn, int nbytes, loff_t offset)
789 * Ensure that the page that has the original instruction is populated
790 * and in page-cache. If ->read_folio == NULL it must be shmem_mapping(),
791 * see uprobe_register().
793 if (mapping->a_ops->read_folio)
794 page = read_mapping_page(mapping, offset >> PAGE_SHIFT, filp);
796 page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
798 return PTR_ERR(page);
800 copy_from_page(page, offset, insn, nbytes);
806 static int copy_insn(struct uprobe *uprobe, struct file *filp)
808 struct address_space *mapping = uprobe->inode->i_mapping;
809 loff_t offs = uprobe->offset;
810 void *insn = &uprobe->arch.insn;
811 int size = sizeof(uprobe->arch.insn);
814 /* Copy only available bytes, -EIO if nothing was read */
816 if (offs >= i_size_read(uprobe->inode))
819 len = min_t(int, size, PAGE_SIZE - (offs & ~PAGE_MASK));
820 err = __copy_insn(mapping, filp, insn, len, offs);
832 static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
833 struct mm_struct *mm, unsigned long vaddr)
837 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
840 /* TODO: move this into _register, until then we abuse this sem. */
841 down_write(&uprobe->consumer_rwsem);
842 if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
845 ret = copy_insn(uprobe, file);
850 if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn))
853 ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
857 smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
858 set_bit(UPROBE_COPY_INSN, &uprobe->flags);
861 up_write(&uprobe->consumer_rwsem);
866 static inline bool consumer_filter(struct uprobe_consumer *uc,
867 enum uprobe_filter_ctx ctx, struct mm_struct *mm)
869 return !uc->filter || uc->filter(uc, ctx, mm);
872 static bool filter_chain(struct uprobe *uprobe,
873 enum uprobe_filter_ctx ctx, struct mm_struct *mm)
875 struct uprobe_consumer *uc;
878 down_read(&uprobe->consumer_rwsem);
879 for (uc = uprobe->consumers; uc; uc = uc->next) {
880 ret = consumer_filter(uc, ctx, mm);
884 up_read(&uprobe->consumer_rwsem);
890 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
891 struct vm_area_struct *vma, unsigned long vaddr)
896 ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
901 * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
902 * the task can hit this breakpoint right after __replace_page().
904 first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
906 set_bit(MMF_HAS_UPROBES, &mm->flags);
908 ret = set_swbp(&uprobe->arch, mm, vaddr);
910 clear_bit(MMF_RECALC_UPROBES, &mm->flags);
911 else if (first_uprobe)
912 clear_bit(MMF_HAS_UPROBES, &mm->flags);
918 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
920 set_bit(MMF_RECALC_UPROBES, &mm->flags);
921 return set_orig_insn(&uprobe->arch, mm, vaddr);
924 static inline bool uprobe_is_active(struct uprobe *uprobe)
926 return !RB_EMPTY_NODE(&uprobe->rb_node);
929 * There could be threads that have already hit the breakpoint. They
930 * will recheck the current insn and restart if find_uprobe() fails.
931 * See find_active_uprobe().
933 static void delete_uprobe(struct uprobe *uprobe)
935 if (WARN_ON(!uprobe_is_active(uprobe)))
938 spin_lock(&uprobes_treelock);
939 rb_erase(&uprobe->rb_node, &uprobes_tree);
940 spin_unlock(&uprobes_treelock);
941 RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
946 struct map_info *next;
947 struct mm_struct *mm;
951 static inline struct map_info *free_map_info(struct map_info *info)
953 struct map_info *next = info->next;
958 static struct map_info *
959 build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
961 unsigned long pgoff = offset >> PAGE_SHIFT;
962 struct vm_area_struct *vma;
963 struct map_info *curr = NULL;
964 struct map_info *prev = NULL;
965 struct map_info *info;
969 i_mmap_lock_read(mapping);
970 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
971 if (!valid_vma(vma, is_register))
974 if (!prev && !more) {
976 * Needs GFP_NOWAIT to avoid i_mmap_rwsem recursion through
977 * reclaim. This is optimistic, no harm done if it fails.
979 prev = kmalloc(sizeof(struct map_info),
980 GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
989 if (!mmget_not_zero(vma->vm_mm))
997 info->mm = vma->vm_mm;
998 info->vaddr = offset_to_vaddr(vma, offset);
1000 i_mmap_unlock_read(mapping);
1012 info = kmalloc(sizeof(struct map_info), GFP_KERNEL);
1014 curr = ERR_PTR(-ENOMEM);
1024 prev = free_map_info(prev);
1029 register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
1031 bool is_register = !!new;
1032 struct map_info *info;
1035 percpu_down_write(&dup_mmap_sem);
1036 info = build_map_info(uprobe->inode->i_mapping,
1037 uprobe->offset, is_register);
1039 err = PTR_ERR(info);
1044 struct mm_struct *mm = info->mm;
1045 struct vm_area_struct *vma;
1047 if (err && is_register)
1050 mmap_write_lock(mm);
1051 vma = find_vma(mm, info->vaddr);
1052 if (!vma || !valid_vma(vma, is_register) ||
1053 file_inode(vma->vm_file) != uprobe->inode)
1056 if (vma->vm_start > info->vaddr ||
1057 vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
1061 /* consult only the "caller", new consumer. */
1062 if (consumer_filter(new,
1063 UPROBE_FILTER_REGISTER, mm))
1064 err = install_breakpoint(uprobe, mm, vma, info->vaddr);
1065 } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
1066 if (!filter_chain(uprobe,
1067 UPROBE_FILTER_UNREGISTER, mm))
1068 err |= remove_breakpoint(uprobe, mm, info->vaddr);
1072 mmap_write_unlock(mm);
1075 info = free_map_info(info);
1078 percpu_up_write(&dup_mmap_sem);
1083 __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
1087 if (WARN_ON(!consumer_del(uprobe, uc)))
1090 err = register_for_each_vma(uprobe, NULL);
1091 /* TODO : cant unregister? schedule a worker thread */
1092 if (!uprobe->consumers && !err)
1093 delete_uprobe(uprobe);
1097 * uprobe_unregister - unregister an already registered probe.
1098 * @inode: the file in which the probe has to be removed.
1099 * @offset: offset from the start of the file.
1100 * @uc: identify which probe if multiple probes are colocated.
1102 void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
1104 struct uprobe *uprobe;
1106 uprobe = find_uprobe(inode, offset);
1107 if (WARN_ON(!uprobe))
1110 down_write(&uprobe->register_rwsem);
1111 __uprobe_unregister(uprobe, uc);
1112 up_write(&uprobe->register_rwsem);
1115 EXPORT_SYMBOL_GPL(uprobe_unregister);
1118 * __uprobe_register - register a probe
1119 * @inode: the file in which the probe has to be placed.
1120 * @offset: offset from the start of the file.
1121 * @uc: information on howto handle the probe..
1123 * Apart from the access refcount, __uprobe_register() takes a creation
1124 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
1125 * inserted into the rbtree (i.e first consumer for a @inode:@offset
1126 * tuple). Creation refcount stops uprobe_unregister from freeing the
1127 * @uprobe even before the register operation is complete. Creation
1128 * refcount is released when the last @uc for the @uprobe
1129 * unregisters. Caller of __uprobe_register() is required to keep @inode
1130 * (and the containing mount) referenced.
1132 * Return errno if it cannot successully install probes
1133 * else return 0 (success)
1135 static int __uprobe_register(struct inode *inode, loff_t offset,
1136 loff_t ref_ctr_offset, struct uprobe_consumer *uc)
1138 struct uprobe *uprobe;
1141 /* Uprobe must have at least one set consumer */
1142 if (!uc->handler && !uc->ret_handler)
1145 /* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
1146 if (!inode->i_mapping->a_ops->read_folio &&
1147 !shmem_mapping(inode->i_mapping))
1149 /* Racy, just to catch the obvious mistakes */
1150 if (offset > i_size_read(inode))
1154 * This ensures that copy_from_page(), copy_to_page() and
1155 * __update_ref_ctr() can't cross page boundary.
1157 if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE))
1159 if (!IS_ALIGNED(ref_ctr_offset, sizeof(short)))
1163 uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
1167 return PTR_ERR(uprobe);
1170 * We can race with uprobe_unregister()->delete_uprobe().
1171 * Check uprobe_is_active() and retry if it is false.
1173 down_write(&uprobe->register_rwsem);
1175 if (likely(uprobe_is_active(uprobe))) {
1176 consumer_add(uprobe, uc);
1177 ret = register_for_each_vma(uprobe, uc);
1179 __uprobe_unregister(uprobe, uc);
1181 up_write(&uprobe->register_rwsem);
1184 if (unlikely(ret == -EAGAIN))
1189 int uprobe_register(struct inode *inode, loff_t offset,
1190 struct uprobe_consumer *uc)
1192 return __uprobe_register(inode, offset, 0, uc);
1194 EXPORT_SYMBOL_GPL(uprobe_register);
1196 int uprobe_register_refctr(struct inode *inode, loff_t offset,
1197 loff_t ref_ctr_offset, struct uprobe_consumer *uc)
1199 return __uprobe_register(inode, offset, ref_ctr_offset, uc);
1201 EXPORT_SYMBOL_GPL(uprobe_register_refctr);
1204 * uprobe_apply - unregister an already registered probe.
1205 * @inode: the file in which the probe has to be removed.
1206 * @offset: offset from the start of the file.
1207 * @uc: consumer which wants to add more or remove some breakpoints
1208 * @add: add or remove the breakpoints
1210 int uprobe_apply(struct inode *inode, loff_t offset,
1211 struct uprobe_consumer *uc, bool add)
1213 struct uprobe *uprobe;
1214 struct uprobe_consumer *con;
1217 uprobe = find_uprobe(inode, offset);
1218 if (WARN_ON(!uprobe))
1221 down_write(&uprobe->register_rwsem);
1222 for (con = uprobe->consumers; con && con != uc ; con = con->next)
1225 ret = register_for_each_vma(uprobe, add ? uc : NULL);
1226 up_write(&uprobe->register_rwsem);
1232 static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
1234 VMA_ITERATOR(vmi, mm, 0);
1235 struct vm_area_struct *vma;
1239 for_each_vma(vmi, vma) {
1240 unsigned long vaddr;
1243 if (!valid_vma(vma, false) ||
1244 file_inode(vma->vm_file) != uprobe->inode)
1247 offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
1248 if (uprobe->offset < offset ||
1249 uprobe->offset >= offset + vma->vm_end - vma->vm_start)
1252 vaddr = offset_to_vaddr(vma, uprobe->offset);
1253 err |= remove_breakpoint(uprobe, mm, vaddr);
1255 mmap_read_unlock(mm);
1260 static struct rb_node *
1261 find_node_in_range(struct inode *inode, loff_t min, loff_t max)
1263 struct rb_node *n = uprobes_tree.rb_node;
1266 struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
1268 if (inode < u->inode) {
1270 } else if (inode > u->inode) {
1273 if (max < u->offset)
1275 else if (min > u->offset)
1286 * For a given range in vma, build a list of probes that need to be inserted.
1288 static void build_probe_list(struct inode *inode,
1289 struct vm_area_struct *vma,
1290 unsigned long start, unsigned long end,
1291 struct list_head *head)
1294 struct rb_node *n, *t;
1297 INIT_LIST_HEAD(head);
1298 min = vaddr_to_offset(vma, start);
1299 max = min + (end - start) - 1;
1301 spin_lock(&uprobes_treelock);
1302 n = find_node_in_range(inode, min, max);
1304 for (t = n; t; t = rb_prev(t)) {
1305 u = rb_entry(t, struct uprobe, rb_node);
1306 if (u->inode != inode || u->offset < min)
1308 list_add(&u->pending_list, head);
1311 for (t = n; (t = rb_next(t)); ) {
1312 u = rb_entry(t, struct uprobe, rb_node);
1313 if (u->inode != inode || u->offset > max)
1315 list_add(&u->pending_list, head);
1319 spin_unlock(&uprobes_treelock);
1322 /* @vma contains reference counter, not the probed instruction. */
1323 static int delayed_ref_ctr_inc(struct vm_area_struct *vma)
1325 struct list_head *pos, *q;
1326 struct delayed_uprobe *du;
1327 unsigned long vaddr;
1328 int ret = 0, err = 0;
1330 mutex_lock(&delayed_uprobe_lock);
1331 list_for_each_safe(pos, q, &delayed_uprobe_list) {
1332 du = list_entry(pos, struct delayed_uprobe, list);
1334 if (du->mm != vma->vm_mm ||
1335 !valid_ref_ctr_vma(du->uprobe, vma))
1338 vaddr = offset_to_vaddr(vma, du->uprobe->ref_ctr_offset);
1339 ret = __update_ref_ctr(vma->vm_mm, vaddr, 1);
1341 update_ref_ctr_warn(du->uprobe, vma->vm_mm, 1);
1345 delayed_uprobe_delete(du);
1347 mutex_unlock(&delayed_uprobe_lock);
1352 * Called from mmap_region/vma_merge with mm->mmap_lock acquired.
1354 * Currently we ignore all errors and always return 0, the callers
1355 * can't handle the failure anyway.
1357 int uprobe_mmap(struct vm_area_struct *vma)
1359 struct list_head tmp_list;
1360 struct uprobe *uprobe, *u;
1361 struct inode *inode;
1363 if (no_uprobe_events())
1367 (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
1368 test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags))
1369 delayed_ref_ctr_inc(vma);
1371 if (!valid_vma(vma, true))
1374 inode = file_inode(vma->vm_file);
1378 mutex_lock(uprobes_mmap_hash(inode));
1379 build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
1381 * We can race with uprobe_unregister(), this uprobe can be already
1382 * removed. But in this case filter_chain() must return false, all
1383 * consumers have gone away.
1385 list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1386 if (!fatal_signal_pending(current) &&
1387 filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
1388 unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
1389 install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1393 mutex_unlock(uprobes_mmap_hash(inode));
1399 vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1402 struct inode *inode;
1405 inode = file_inode(vma->vm_file);
1407 min = vaddr_to_offset(vma, start);
1408 max = min + (end - start) - 1;
1410 spin_lock(&uprobes_treelock);
1411 n = find_node_in_range(inode, min, max);
1412 spin_unlock(&uprobes_treelock);
1418 * Called in context of a munmap of a vma.
1420 void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1422 if (no_uprobe_events() || !valid_vma(vma, false))
1425 if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
1428 if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||
1429 test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))
1432 if (vma_has_uprobes(vma, start, end))
1433 set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
1436 /* Slot allocation for XOL */
1437 static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
1439 struct vm_area_struct *vma;
1442 if (mmap_write_lock_killable(mm))
1445 if (mm->uprobes_state.xol_area) {
1451 /* Try to map as high as possible, this is only a hint. */
1452 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE,
1454 if (IS_ERR_VALUE(area->vaddr)) {
1460 vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1461 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
1462 &area->xol_mapping);
1469 /* pairs with get_xol_area() */
1470 smp_store_release(&mm->uprobes_state.xol_area, area); /* ^^^ */
1472 mmap_write_unlock(mm);
1477 static struct xol_area *__create_xol_area(unsigned long vaddr)
1479 struct mm_struct *mm = current->mm;
1480 uprobe_opcode_t insn = UPROBE_SWBP_INSN;
1481 struct xol_area *area;
1483 area = kmalloc(sizeof(*area), GFP_KERNEL);
1484 if (unlikely(!area))
1487 area->bitmap = kcalloc(BITS_TO_LONGS(UINSNS_PER_PAGE), sizeof(long),
1492 area->xol_mapping.name = "[uprobes]";
1493 area->xol_mapping.fault = NULL;
1494 area->xol_mapping.pages = area->pages;
1495 area->pages[0] = alloc_page(GFP_HIGHUSER);
1496 if (!area->pages[0])
1498 area->pages[1] = NULL;
1500 area->vaddr = vaddr;
1501 init_waitqueue_head(&area->wq);
1502 /* Reserve the 1st slot for get_trampoline_vaddr() */
1503 set_bit(0, area->bitmap);
1504 atomic_set(&area->slot_count, 1);
1505 arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE);
1507 if (!xol_add_vma(mm, area))
1510 __free_page(area->pages[0]);
1512 kfree(area->bitmap);
1520 * get_xol_area - Allocate process's xol_area if necessary.
1521 * This area will be used for storing instructions for execution out of line.
1523 * Returns the allocated area or NULL.
1525 static struct xol_area *get_xol_area(void)
1527 struct mm_struct *mm = current->mm;
1528 struct xol_area *area;
1530 if (!mm->uprobes_state.xol_area)
1531 __create_xol_area(0);
1533 /* Pairs with xol_add_vma() smp_store_release() */
1534 area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */
1539 * uprobe_clear_state - Free the area allocated for slots.
1541 void uprobe_clear_state(struct mm_struct *mm)
1543 struct xol_area *area = mm->uprobes_state.xol_area;
1545 mutex_lock(&delayed_uprobe_lock);
1546 delayed_uprobe_remove(NULL, mm);
1547 mutex_unlock(&delayed_uprobe_lock);
1552 put_page(area->pages[0]);
1553 kfree(area->bitmap);
1557 void uprobe_start_dup_mmap(void)
1559 percpu_down_read(&dup_mmap_sem);
1562 void uprobe_end_dup_mmap(void)
1564 percpu_up_read(&dup_mmap_sem);
1567 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
1569 if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {
1570 set_bit(MMF_HAS_UPROBES, &newmm->flags);
1571 /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */
1572 set_bit(MMF_RECALC_UPROBES, &newmm->flags);
1577 * - search for a free slot.
1579 static unsigned long xol_take_insn_slot(struct xol_area *area)
1581 unsigned long slot_addr;
1585 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1586 if (slot_nr < UINSNS_PER_PAGE) {
1587 if (!test_and_set_bit(slot_nr, area->bitmap))
1590 slot_nr = UINSNS_PER_PAGE;
1593 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1594 } while (slot_nr >= UINSNS_PER_PAGE);
1596 slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1597 atomic_inc(&area->slot_count);
1603 * xol_get_insn_slot - allocate a slot for xol.
1604 * Returns the allocated slot address or 0.
1606 static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
1608 struct xol_area *area;
1609 unsigned long xol_vaddr;
1611 area = get_xol_area();
1615 xol_vaddr = xol_take_insn_slot(area);
1616 if (unlikely(!xol_vaddr))
1619 arch_uprobe_copy_ixol(area->pages[0], xol_vaddr,
1620 &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
1626 * xol_free_insn_slot - If slot was earlier allocated by
1627 * @xol_get_insn_slot(), make the slot available for
1628 * subsequent requests.
1630 static void xol_free_insn_slot(struct task_struct *tsk)
1632 struct xol_area *area;
1633 unsigned long vma_end;
1634 unsigned long slot_addr;
1636 if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1639 slot_addr = tsk->utask->xol_vaddr;
1640 if (unlikely(!slot_addr))
1643 area = tsk->mm->uprobes_state.xol_area;
1644 vma_end = area->vaddr + PAGE_SIZE;
1645 if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1646 unsigned long offset;
1649 offset = slot_addr - area->vaddr;
1650 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1651 if (slot_nr >= UINSNS_PER_PAGE)
1654 clear_bit(slot_nr, area->bitmap);
1655 atomic_dec(&area->slot_count);
1656 smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
1657 if (waitqueue_active(&area->wq))
1660 tsk->utask->xol_vaddr = 0;
1664 void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
1665 void *src, unsigned long len)
1667 /* Initialize the slot */
1668 copy_to_page(page, vaddr, src, len);
1671 * We probably need flush_icache_user_page() but it needs vma.
1672 * This should work on most of architectures by default. If
1673 * architecture needs to do something different it can define
1674 * its own version of the function.
1676 flush_dcache_page(page);
1680 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1681 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1683 * Return the address of the breakpoint instruction.
1685 unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1687 return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1690 unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
1692 struct uprobe_task *utask = current->utask;
1694 if (unlikely(utask && utask->active_uprobe))
1695 return utask->vaddr;
1697 return instruction_pointer(regs);
1700 static struct return_instance *free_ret_instance(struct return_instance *ri)
1702 struct return_instance *next = ri->next;
1703 put_uprobe(ri->uprobe);
1709 * Called with no locks held.
1710 * Called in context of an exiting or an exec-ing thread.
1712 void uprobe_free_utask(struct task_struct *t)
1714 struct uprobe_task *utask = t->utask;
1715 struct return_instance *ri;
1720 if (utask->active_uprobe)
1721 put_uprobe(utask->active_uprobe);
1723 ri = utask->return_instances;
1725 ri = free_ret_instance(ri);
1727 xol_free_insn_slot(t);
1733 * Allocate a uprobe_task object for the task if necessary.
1734 * Called when the thread hits a breakpoint.
1737 * - pointer to new uprobe_task on success
1740 static struct uprobe_task *get_utask(void)
1742 if (!current->utask)
1743 current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1744 return current->utask;
1747 static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask)
1749 struct uprobe_task *n_utask;
1750 struct return_instance **p, *o, *n;
1752 n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1757 p = &n_utask->return_instances;
1758 for (o = o_utask->return_instances; o; o = o->next) {
1759 n = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1764 get_uprobe(n->uprobe);
1775 static void uprobe_warn(struct task_struct *t, const char *msg)
1777 pr_warn("uprobe: %s:%d failed to %s\n",
1778 current->comm, current->pid, msg);
1781 static void dup_xol_work(struct callback_head *work)
1783 if (current->flags & PF_EXITING)
1786 if (!__create_xol_area(current->utask->dup_xol_addr) &&
1787 !fatal_signal_pending(current))
1788 uprobe_warn(current, "dup xol area");
1792 * Called in context of a new clone/fork from copy_process.
1794 void uprobe_copy_process(struct task_struct *t, unsigned long flags)
1796 struct uprobe_task *utask = current->utask;
1797 struct mm_struct *mm = current->mm;
1798 struct xol_area *area;
1802 if (!utask || !utask->return_instances)
1805 if (mm == t->mm && !(flags & CLONE_VFORK))
1808 if (dup_utask(t, utask))
1809 return uprobe_warn(t, "dup ret instances");
1811 /* The task can fork() after dup_xol_work() fails */
1812 area = mm->uprobes_state.xol_area;
1814 return uprobe_warn(t, "dup xol area");
1819 t->utask->dup_xol_addr = area->vaddr;
1820 init_task_work(&t->utask->dup_xol_work, dup_xol_work);
1821 task_work_add(t, &t->utask->dup_xol_work, TWA_RESUME);
1825 * Current area->vaddr notion assume the trampoline address is always
1826 * equal area->vaddr.
1828 * Returns -1 in case the xol_area is not allocated.
1830 static unsigned long get_trampoline_vaddr(void)
1832 struct xol_area *area;
1833 unsigned long trampoline_vaddr = -1;
1835 /* Pairs with xol_add_vma() smp_store_release() */
1836 area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */
1838 trampoline_vaddr = area->vaddr;
1840 return trampoline_vaddr;
1843 static void cleanup_return_instances(struct uprobe_task *utask, bool chained,
1844 struct pt_regs *regs)
1846 struct return_instance *ri = utask->return_instances;
1847 enum rp_check ctx = chained ? RP_CHECK_CHAIN_CALL : RP_CHECK_CALL;
1849 while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
1850 ri = free_ret_instance(ri);
1853 utask->return_instances = ri;
1856 static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
1858 struct return_instance *ri;
1859 struct uprobe_task *utask;
1860 unsigned long orig_ret_vaddr, trampoline_vaddr;
1863 if (!get_xol_area())
1866 utask = get_utask();
1870 if (utask->depth >= MAX_URETPROBE_DEPTH) {
1871 printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to"
1872 " nestedness limit pid/tgid=%d/%d\n",
1873 current->pid, current->tgid);
1877 ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1881 trampoline_vaddr = get_trampoline_vaddr();
1882 orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
1883 if (orig_ret_vaddr == -1)
1886 /* drop the entries invalidated by longjmp() */
1887 chained = (orig_ret_vaddr == trampoline_vaddr);
1888 cleanup_return_instances(utask, chained, regs);
1891 * We don't want to keep trampoline address in stack, rather keep the
1892 * original return address of first caller thru all the consequent
1893 * instances. This also makes breakpoint unwrapping easier.
1896 if (!utask->return_instances) {
1898 * This situation is not possible. Likely we have an
1899 * attack from user-space.
1901 uprobe_warn(current, "handle tail call");
1904 orig_ret_vaddr = utask->return_instances->orig_ret_vaddr;
1907 ri->uprobe = get_uprobe(uprobe);
1908 ri->func = instruction_pointer(regs);
1909 ri->stack = user_stack_pointer(regs);
1910 ri->orig_ret_vaddr = orig_ret_vaddr;
1911 ri->chained = chained;
1914 ri->next = utask->return_instances;
1915 utask->return_instances = ri;
1922 /* Prepare to single-step probed instruction out of line. */
1924 pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
1926 struct uprobe_task *utask;
1927 unsigned long xol_vaddr;
1930 utask = get_utask();
1934 xol_vaddr = xol_get_insn_slot(uprobe);
1938 utask->xol_vaddr = xol_vaddr;
1939 utask->vaddr = bp_vaddr;
1941 err = arch_uprobe_pre_xol(&uprobe->arch, regs);
1942 if (unlikely(err)) {
1943 xol_free_insn_slot(current);
1947 utask->active_uprobe = uprobe;
1948 utask->state = UTASK_SSTEP;
1953 * If we are singlestepping, then ensure this thread is not connected to
1954 * non-fatal signals until completion of singlestep. When xol insn itself
1955 * triggers the signal, restart the original insn even if the task is
1956 * already SIGKILL'ed (since coredump should report the correct ip). This
1957 * is even more important if the task has a handler for SIGSEGV/etc, The
1958 * _same_ instruction should be repeated again after return from the signal
1959 * handler, and SSTEP can never finish in this case.
1961 bool uprobe_deny_signal(void)
1963 struct task_struct *t = current;
1964 struct uprobe_task *utask = t->utask;
1966 if (likely(!utask || !utask->active_uprobe))
1969 WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1971 if (task_sigpending(t)) {
1972 spin_lock_irq(&t->sighand->siglock);
1973 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1974 spin_unlock_irq(&t->sighand->siglock);
1976 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1977 utask->state = UTASK_SSTEP_TRAPPED;
1978 set_tsk_thread_flag(t, TIF_UPROBE);
1985 static void mmf_recalc_uprobes(struct mm_struct *mm)
1987 VMA_ITERATOR(vmi, mm, 0);
1988 struct vm_area_struct *vma;
1990 for_each_vma(vmi, vma) {
1991 if (!valid_vma(vma, false))
1994 * This is not strictly accurate, we can race with
1995 * uprobe_unregister() and see the already removed
1996 * uprobe if delete_uprobe() was not yet called.
1997 * Or this uprobe can be filtered out.
1999 if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
2003 clear_bit(MMF_HAS_UPROBES, &mm->flags);
2006 static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
2009 uprobe_opcode_t opcode;
2012 if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE)))
2015 pagefault_disable();
2016 result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
2019 if (likely(result == 0))
2023 * The NULL 'tsk' here ensures that any faults that occur here
2024 * will not be accounted to the task. 'mm' *is* current->mm,
2025 * but we treat this as a 'remote' access since it is
2026 * essentially a kernel access to the memory.
2028 result = get_user_pages_remote(mm, vaddr, 1, FOLL_FORCE, &page, NULL);
2032 copy_from_page(page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
2035 /* This needs to return true for any variant of the trap insn */
2036 return is_trap_insn(&opcode);
2039 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
2041 struct mm_struct *mm = current->mm;
2042 struct uprobe *uprobe = NULL;
2043 struct vm_area_struct *vma;
2046 vma = vma_lookup(mm, bp_vaddr);
2048 if (valid_vma(vma, false)) {
2049 struct inode *inode = file_inode(vma->vm_file);
2050 loff_t offset = vaddr_to_offset(vma, bp_vaddr);
2052 uprobe = find_uprobe(inode, offset);
2056 *is_swbp = is_trap_at_addr(mm, bp_vaddr);
2061 if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
2062 mmf_recalc_uprobes(mm);
2063 mmap_read_unlock(mm);
2068 static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
2070 struct uprobe_consumer *uc;
2071 int remove = UPROBE_HANDLER_REMOVE;
2072 bool need_prep = false; /* prepare return uprobe, when needed */
2074 down_read(&uprobe->register_rwsem);
2075 for (uc = uprobe->consumers; uc; uc = uc->next) {
2079 rc = uc->handler(uc, regs);
2080 WARN(rc & ~UPROBE_HANDLER_MASK,
2081 "bad rc=0x%x from %ps()\n", rc, uc->handler);
2084 if (uc->ret_handler)
2090 if (need_prep && !remove)
2091 prepare_uretprobe(uprobe, regs); /* put bp at return */
2093 if (remove && uprobe->consumers) {
2094 WARN_ON(!uprobe_is_active(uprobe));
2095 unapply_uprobe(uprobe, current->mm);
2097 up_read(&uprobe->register_rwsem);
2101 handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
2103 struct uprobe *uprobe = ri->uprobe;
2104 struct uprobe_consumer *uc;
2106 down_read(&uprobe->register_rwsem);
2107 for (uc = uprobe->consumers; uc; uc = uc->next) {
2108 if (uc->ret_handler)
2109 uc->ret_handler(uc, ri->func, regs);
2111 up_read(&uprobe->register_rwsem);
2114 static struct return_instance *find_next_ret_chain(struct return_instance *ri)
2119 chained = ri->chained;
2120 ri = ri->next; /* can't be NULL if chained */
2126 static void handle_trampoline(struct pt_regs *regs)
2128 struct uprobe_task *utask;
2129 struct return_instance *ri, *next;
2132 utask = current->utask;
2136 ri = utask->return_instances;
2142 * We should throw out the frames invalidated by longjmp().
2143 * If this chain is valid, then the next one should be alive
2144 * or NULL; the latter case means that nobody but ri->func
2145 * could hit this trampoline on return. TODO: sigaltstack().
2147 next = find_next_ret_chain(ri);
2148 valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
2150 instruction_pointer_set(regs, ri->orig_ret_vaddr);
2153 handle_uretprobe_chain(ri, regs);
2154 ri = free_ret_instance(ri);
2156 } while (ri != next);
2159 utask->return_instances = ri;
2163 uprobe_warn(current, "handle uretprobe, sending SIGILL.");
2168 bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
2173 bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
2174 struct pt_regs *regs)
2180 * Run handler and ask thread to singlestep.
2181 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
2183 static void handle_swbp(struct pt_regs *regs)
2185 struct uprobe *uprobe;
2186 unsigned long bp_vaddr;
2189 bp_vaddr = uprobe_get_swbp_addr(regs);
2190 if (bp_vaddr == get_trampoline_vaddr())
2191 return handle_trampoline(regs);
2193 uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
2196 /* No matching uprobe; signal SIGTRAP. */
2200 * Either we raced with uprobe_unregister() or we can't
2201 * access this memory. The latter is only possible if
2202 * another thread plays with our ->mm. In both cases
2203 * we can simply restart. If this vma was unmapped we
2204 * can pretend this insn was not executed yet and get
2205 * the (correct) SIGSEGV after restart.
2207 instruction_pointer_set(regs, bp_vaddr);
2212 /* change it in advance for ->handler() and restart */
2213 instruction_pointer_set(regs, bp_vaddr);
2216 * TODO: move copy_insn/etc into _register and remove this hack.
2217 * After we hit the bp, _unregister + _register can install the
2218 * new and not-yet-analyzed uprobe at the same address, restart.
2220 if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
2224 * Pairs with the smp_wmb() in prepare_uprobe().
2226 * Guarantees that if we see the UPROBE_COPY_INSN bit set, then
2227 * we must also see the stores to &uprobe->arch performed by the
2228 * prepare_uprobe() call.
2232 /* Tracing handlers use ->utask to communicate with fetch methods */
2236 if (arch_uprobe_ignore(&uprobe->arch, regs))
2239 handler_chain(uprobe, regs);
2241 if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
2244 if (!pre_ssout(uprobe, regs, bp_vaddr))
2247 /* arch_uprobe_skip_sstep() succeeded, or restart if can't singlestep */
2253 * Perform required fix-ups and disable singlestep.
2254 * Allow pending signals to take effect.
2256 static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
2258 struct uprobe *uprobe;
2261 uprobe = utask->active_uprobe;
2262 if (utask->state == UTASK_SSTEP_ACK)
2263 err = arch_uprobe_post_xol(&uprobe->arch, regs);
2264 else if (utask->state == UTASK_SSTEP_TRAPPED)
2265 arch_uprobe_abort_xol(&uprobe->arch, regs);
2270 utask->active_uprobe = NULL;
2271 utask->state = UTASK_RUNNING;
2272 xol_free_insn_slot(current);
2274 spin_lock_irq(¤t->sighand->siglock);
2275 recalc_sigpending(); /* see uprobe_deny_signal() */
2276 spin_unlock_irq(¤t->sighand->siglock);
2278 if (unlikely(err)) {
2279 uprobe_warn(current, "execute the probed insn, sending SIGILL.");
2285 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
2286 * allows the thread to return from interrupt. After that handle_swbp()
2287 * sets utask->active_uprobe.
2289 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
2290 * and allows the thread to return from interrupt.
2292 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
2293 * uprobe_notify_resume().
2295 void uprobe_notify_resume(struct pt_regs *regs)
2297 struct uprobe_task *utask;
2299 clear_thread_flag(TIF_UPROBE);
2301 utask = current->utask;
2302 if (utask && utask->active_uprobe)
2303 handle_singlestep(utask, regs);
2309 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
2310 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
2312 int uprobe_pre_sstep_notifier(struct pt_regs *regs)
2317 if (!test_bit(MMF_HAS_UPROBES, ¤t->mm->flags) &&
2318 (!current->utask || !current->utask->return_instances))
2321 set_thread_flag(TIF_UPROBE);
2326 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
2327 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
2329 int uprobe_post_sstep_notifier(struct pt_regs *regs)
2331 struct uprobe_task *utask = current->utask;
2333 if (!current->mm || !utask || !utask->active_uprobe)
2334 /* task is currently not uprobed */
2337 utask->state = UTASK_SSTEP_ACK;
2338 set_thread_flag(TIF_UPROBE);
2342 static struct notifier_block uprobe_exception_nb = {
2343 .notifier_call = arch_uprobe_exception_notify,
2344 .priority = INT_MAX-1, /* notified after kprobes, kgdb */
2347 void __init uprobes_init(void)
2351 for (i = 0; i < UPROBES_HASH_SZ; i++)
2352 mutex_init(&uprobes_mmap_mutex[i]);
2354 BUG_ON(register_die_notifier(&uprobe_exception_nb));