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Linux/kernel/events/uprobes.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * User-space Probes (UProbes)
  4  *
  5  * Copyright (C) IBM Corporation, 2008-2012
  6  * Authors:
  7  *      Srikar Dronamraju
  8  *      Jim Keniston
  9  * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
 10  */
 11 
 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>         /* try_to_free_swap */
 23 #include <linux/ptrace.h>       /* user_enable_single_step */
 24 #include <linux/kdebug.h>       /* notifier mechanism */
 25 #include "../../mm/internal.h"  /* munlock_vma_page */
 26 #include <linux/percpu-rwsem.h>
 27 #include <linux/task_work.h>
 28 #include <linux/shmem_fs.h>
 29 
 30 #include <linux/uprobes.h>
 31 
 32 #define UINSNS_PER_PAGE                 (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
 33 #define MAX_UPROBE_XOL_SLOTS            UINSNS_PER_PAGE
 34 
 35 static struct rb_root uprobes_tree = RB_ROOT;
 36 /*
 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?
 39  */
 40 #define no_uprobe_events()      RB_EMPTY_ROOT(&uprobes_tree)
 41 
 42 static DEFINE_SPINLOCK(uprobes_treelock);       /* serialize rbtree access */
 43 
 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])
 48 
 49 DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem);
 50 
 51 /* Have a copy of original instruction */
 52 #define UPROBE_COPY_INSN        0
 53 
 54 struct uprobe {
 55         struct rb_node          rb_node;        /* node in the rb tree */
 56         refcount_t              ref;
 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 */
 62         loff_t                  offset;
 63         loff_t                  ref_ctr_offset;
 64         unsigned long           flags;
 65 
 66         /*
 67          * The generic code assumes that it has two members of unknown type
 68          * owned by the arch-specific code:
 69          *
 70          *      insn -  copy_insn() saves the original instruction here for
 71          *              arch_uprobe_analyze_insn().
 72          *
 73          *      ixol -  potentially modified instruction to execute out of
 74          *              line, copied to xol_area by xol_get_insn_slot().
 75          */
 76         struct arch_uprobe      arch;
 77 };
 78 
 79 struct delayed_uprobe {
 80         struct list_head list;
 81         struct uprobe *uprobe;
 82         struct mm_struct *mm;
 83 };
 84 
 85 static DEFINE_MUTEX(delayed_uprobe_lock);
 86 static LIST_HEAD(delayed_uprobe_list);
 87 
 88 /*
 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().
 92  *
 93  * On a breakpoint hit, thread contests for a slot.  It frees the
 94  * slot after singlestep. Currently a fixed number of slots are
 95  * allocated.
 96  */
 97 struct xol_area {
 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 */
101 
102         struct vm_special_mapping       xol_mapping;
103         struct page                     *pages[2];
104         /*
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.
108          */
109         unsigned long                   vaddr;          /* Page(s) of instruction slots */
110 };
111 
112 /*
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
118  *        executable vma.
119  */
120 static bool valid_vma(struct vm_area_struct *vma, bool is_register)
121 {
122         vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE;
123 
124         if (is_register)
125                 flags |= VM_WRITE;
126 
127         return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
128 }
129 
130 static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
131 {
132         return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
133 }
134 
135 static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
136 {
137         return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start);
138 }
139 
140 /**
141  * __replace_page - replace page in vma by new page.
142  * based on replace_page in mm/ksm.c
143  *
144  * @vma:      vma that holds the pte pointing to page
145  * @addr:     address the old @page is mapped at
146  * @page:     the cowed page we are replacing by kpage
147  * @kpage:    the modified page we replace page by
148  *
149  * Returns 0 on success, -EFAULT on failure.
150  */
151 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
152                                 struct page *old_page, struct page *new_page)
153 {
154         struct mm_struct *mm = vma->vm_mm;
155         struct page_vma_mapped_walk pvmw = {
156                 .page = old_page,
157                 .vma = vma,
158                 .address = addr,
159         };
160         int err;
161         struct mmu_notifier_range range;
162         struct mem_cgroup *memcg;
163 
164         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr,
165                                 addr + PAGE_SIZE);
166 
167         VM_BUG_ON_PAGE(PageTransHuge(old_page), old_page);
168 
169         err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
170                         false);
171         if (err)
172                 return err;
173 
174         /* For try_to_free_swap() and munlock_vma_page() below */
175         lock_page(old_page);
176 
177         mmu_notifier_invalidate_range_start(&range);
178         err = -EAGAIN;
179         if (!page_vma_mapped_walk(&pvmw)) {
180                 mem_cgroup_cancel_charge(new_page, memcg, false);
181                 goto unlock;
182         }
183         VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
184 
185         get_page(new_page);
186         page_add_new_anon_rmap(new_page, vma, addr, false);
187         mem_cgroup_commit_charge(new_page, memcg, false, false);
188         lru_cache_add_active_or_unevictable(new_page, vma);
189 
190         if (!PageAnon(old_page)) {
191                 dec_mm_counter(mm, mm_counter_file(old_page));
192                 inc_mm_counter(mm, MM_ANONPAGES);
193         }
194 
195         flush_cache_page(vma, addr, pte_pfn(*pvmw.pte));
196         ptep_clear_flush_notify(vma, addr, pvmw.pte);
197         set_pte_at_notify(mm, addr, pvmw.pte,
198                         mk_pte(new_page, vma->vm_page_prot));
199 
200         page_remove_rmap(old_page, false);
201         if (!page_mapped(old_page))
202                 try_to_free_swap(old_page);
203         page_vma_mapped_walk_done(&pvmw);
204 
205         if (vma->vm_flags & VM_LOCKED)
206                 munlock_vma_page(old_page);
207         put_page(old_page);
208 
209         err = 0;
210  unlock:
211         mmu_notifier_invalidate_range_end(&range);
212         unlock_page(old_page);
213         return err;
214 }
215 
216 /**
217  * is_swbp_insn - check if instruction is breakpoint instruction.
218  * @insn: instruction to be checked.
219  * Default implementation of is_swbp_insn
220  * Returns true if @insn is a breakpoint instruction.
221  */
222 bool __weak is_swbp_insn(uprobe_opcode_t *insn)
223 {
224         return *insn == UPROBE_SWBP_INSN;
225 }
226 
227 /**
228  * is_trap_insn - check if instruction is breakpoint instruction.
229  * @insn: instruction to be checked.
230  * Default implementation of is_trap_insn
231  * Returns true if @insn is a breakpoint instruction.
232  *
233  * This function is needed for the case where an architecture has multiple
234  * trap instructions (like powerpc).
235  */
236 bool __weak is_trap_insn(uprobe_opcode_t *insn)
237 {
238         return is_swbp_insn(insn);
239 }
240 
241 static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len)
242 {
243         void *kaddr = kmap_atomic(page);
244         memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
245         kunmap_atomic(kaddr);
246 }
247 
248 static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
249 {
250         void *kaddr = kmap_atomic(page);
251         memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
252         kunmap_atomic(kaddr);
253 }
254 
255 static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
256 {
257         uprobe_opcode_t old_opcode;
258         bool is_swbp;
259 
260         /*
261          * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here.
262          * We do not check if it is any other 'trap variant' which could
263          * be conditional trap instruction such as the one powerpc supports.
264          *
265          * The logic is that we do not care if the underlying instruction
266          * is a trap variant; uprobes always wins over any other (gdb)
267          * breakpoint.
268          */
269         copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE);
270         is_swbp = is_swbp_insn(&old_opcode);
271 
272         if (is_swbp_insn(new_opcode)) {
273                 if (is_swbp)            /* register: already installed? */
274                         return 0;
275         } else {
276                 if (!is_swbp)           /* unregister: was it changed by us? */
277                         return 0;
278         }
279 
280         return 1;
281 }
282 
283 static struct delayed_uprobe *
284 delayed_uprobe_check(struct uprobe *uprobe, struct mm_struct *mm)
285 {
286         struct delayed_uprobe *du;
287 
288         list_for_each_entry(du, &delayed_uprobe_list, list)
289                 if (du->uprobe == uprobe && du->mm == mm)
290                         return du;
291         return NULL;
292 }
293 
294 static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm)
295 {
296         struct delayed_uprobe *du;
297 
298         if (delayed_uprobe_check(uprobe, mm))
299                 return 0;
300 
301         du  = kzalloc(sizeof(*du), GFP_KERNEL);
302         if (!du)
303                 return -ENOMEM;
304 
305         du->uprobe = uprobe;
306         du->mm = mm;
307         list_add(&du->list, &delayed_uprobe_list);
308         return 0;
309 }
310 
311 static void delayed_uprobe_delete(struct delayed_uprobe *du)
312 {
313         if (WARN_ON(!du))
314                 return;
315         list_del(&du->list);
316         kfree(du);
317 }
318 
319 static void delayed_uprobe_remove(struct uprobe *uprobe, struct mm_struct *mm)
320 {
321         struct list_head *pos, *q;
322         struct delayed_uprobe *du;
323 
324         if (!uprobe && !mm)
325                 return;
326 
327         list_for_each_safe(pos, q, &delayed_uprobe_list) {
328                 du = list_entry(pos, struct delayed_uprobe, list);
329 
330                 if (uprobe && du->uprobe != uprobe)
331                         continue;
332                 if (mm && du->mm != mm)
333                         continue;
334 
335                 delayed_uprobe_delete(du);
336         }
337 }
338 
339 static bool valid_ref_ctr_vma(struct uprobe *uprobe,
340                               struct vm_area_struct *vma)
341 {
342         unsigned long vaddr = offset_to_vaddr(vma, uprobe->ref_ctr_offset);
343 
344         return uprobe->ref_ctr_offset &&
345                 vma->vm_file &&
346                 file_inode(vma->vm_file) == uprobe->inode &&
347                 (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
348                 vma->vm_start <= vaddr &&
349                 vma->vm_end > vaddr;
350 }
351 
352 static struct vm_area_struct *
353 find_ref_ctr_vma(struct uprobe *uprobe, struct mm_struct *mm)
354 {
355         struct vm_area_struct *tmp;
356 
357         for (tmp = mm->mmap; tmp; tmp = tmp->vm_next)
358                 if (valid_ref_ctr_vma(uprobe, tmp))
359                         return tmp;
360 
361         return NULL;
362 }
363 
364 static int
365 __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
366 {
367         void *kaddr;
368         struct page *page;
369         struct vm_area_struct *vma;
370         int ret;
371         short *ptr;
372 
373         if (!vaddr || !d)
374                 return -EINVAL;
375 
376         ret = get_user_pages_remote(NULL, mm, vaddr, 1,
377                         FOLL_WRITE, &page, &vma, NULL);
378         if (unlikely(ret <= 0)) {
379                 /*
380                  * We are asking for 1 page. If get_user_pages_remote() fails,
381                  * it may return 0, in that case we have to return error.
382                  */
383                 return ret == 0 ? -EBUSY : ret;
384         }
385 
386         kaddr = kmap_atomic(page);
387         ptr = kaddr + (vaddr & ~PAGE_MASK);
388 
389         if (unlikely(*ptr + d < 0)) {
390                 pr_warn("ref_ctr going negative. vaddr: 0x%lx, "
391                         "curr val: %d, delta: %d\n", vaddr, *ptr, d);
392                 ret = -EINVAL;
393                 goto out;
394         }
395 
396         *ptr += d;
397         ret = 0;
398 out:
399         kunmap_atomic(kaddr);
400         put_page(page);
401         return ret;
402 }
403 
404 static void update_ref_ctr_warn(struct uprobe *uprobe,
405                                 struct mm_struct *mm, short d)
406 {
407         pr_warn("ref_ctr %s failed for inode: 0x%lx offset: "
408                 "0x%llx ref_ctr_offset: 0x%llx of mm: 0x%pK\n",
409                 d > 0 ? "increment" : "decrement", uprobe->inode->i_ino,
410                 (unsigned long long) uprobe->offset,
411                 (unsigned long long) uprobe->ref_ctr_offset, mm);
412 }
413 
414 static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm,
415                           short d)
416 {
417         struct vm_area_struct *rc_vma;
418         unsigned long rc_vaddr;
419         int ret = 0;
420 
421         rc_vma = find_ref_ctr_vma(uprobe, mm);
422 
423         if (rc_vma) {
424                 rc_vaddr = offset_to_vaddr(rc_vma, uprobe->ref_ctr_offset);
425                 ret = __update_ref_ctr(mm, rc_vaddr, d);
426                 if (ret)
427                         update_ref_ctr_warn(uprobe, mm, d);
428 
429                 if (d > 0)
430                         return ret;
431         }
432 
433         mutex_lock(&delayed_uprobe_lock);
434         if (d > 0)
435                 ret = delayed_uprobe_add(uprobe, mm);
436         else
437                 delayed_uprobe_remove(uprobe, mm);
438         mutex_unlock(&delayed_uprobe_lock);
439 
440         return ret;
441 }
442 
443 /*
444  * NOTE:
445  * Expect the breakpoint instruction to be the smallest size instruction for
446  * the architecture. If an arch has variable length instruction and the
447  * breakpoint instruction is not of the smallest length instruction
448  * supported by that architecture then we need to modify is_trap_at_addr and
449  * uprobe_write_opcode accordingly. This would never be a problem for archs
450  * that have fixed length instructions.
451  *
452  * uprobe_write_opcode - write the opcode at a given virtual address.
453  * @mm: the probed process address space.
454  * @vaddr: the virtual address to store the opcode.
455  * @opcode: opcode to be written at @vaddr.
456  *
457  * Called with mm->mmap_sem held for write.
458  * Return 0 (success) or a negative errno.
459  */
460 int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
461                         unsigned long vaddr, uprobe_opcode_t opcode)
462 {
463         struct uprobe *uprobe;
464         struct page *old_page, *new_page;
465         struct vm_area_struct *vma;
466         int ret, is_register, ref_ctr_updated = 0;
467 
468         is_register = is_swbp_insn(&opcode);
469         uprobe = container_of(auprobe, struct uprobe, arch);
470 
471 retry:
472         /* Read the page with vaddr into memory */
473         ret = get_user_pages_remote(NULL, mm, vaddr, 1,
474                         FOLL_FORCE | FOLL_SPLIT, &old_page, &vma, NULL);
475         if (ret <= 0)
476                 return ret;
477 
478         ret = verify_opcode(old_page, vaddr, &opcode);
479         if (ret <= 0)
480                 goto put_old;
481 
482         /* We are going to replace instruction, update ref_ctr. */
483         if (!ref_ctr_updated && uprobe->ref_ctr_offset) {
484                 ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1);
485                 if (ret)
486                         goto put_old;
487 
488                 ref_ctr_updated = 1;
489         }
490 
491         ret = anon_vma_prepare(vma);
492         if (ret)
493                 goto put_old;
494 
495         ret = -ENOMEM;
496         new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
497         if (!new_page)
498                 goto put_old;
499 
500         __SetPageUptodate(new_page);
501         copy_highpage(new_page, old_page);
502         copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
503 
504         ret = __replace_page(vma, vaddr, old_page, new_page);
505         put_page(new_page);
506 put_old:
507         put_page(old_page);
508 
509         if (unlikely(ret == -EAGAIN))
510                 goto retry;
511 
512         /* Revert back reference counter if instruction update failed. */
513         if (ret && is_register && ref_ctr_updated)
514                 update_ref_ctr(uprobe, mm, -1);
515 
516         return ret;
517 }
518 
519 /**
520  * set_swbp - store breakpoint at a given address.
521  * @auprobe: arch specific probepoint information.
522  * @mm: the probed process address space.
523  * @vaddr: the virtual address to insert the opcode.
524  *
525  * For mm @mm, store the breakpoint instruction at @vaddr.
526  * Return 0 (success) or a negative errno.
527  */
528 int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
529 {
530         return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
531 }
532 
533 /**
534  * set_orig_insn - Restore the original instruction.
535  * @mm: the probed process address space.
536  * @auprobe: arch specific probepoint information.
537  * @vaddr: the virtual address to insert the opcode.
538  *
539  * For mm @mm, restore the original opcode (opcode) at @vaddr.
540  * Return 0 (success) or a negative errno.
541  */
542 int __weak
543 set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
544 {
545         return uprobe_write_opcode(auprobe, mm, vaddr,
546                         *(uprobe_opcode_t *)&auprobe->insn);
547 }
548 
549 static struct uprobe *get_uprobe(struct uprobe *uprobe)
550 {
551         refcount_inc(&uprobe->ref);
552         return uprobe;
553 }
554 
555 static void put_uprobe(struct uprobe *uprobe)
556 {
557         if (refcount_dec_and_test(&uprobe->ref)) {
558                 /*
559                  * If application munmap(exec_vma) before uprobe_unregister()
560                  * gets called, we don't get a chance to remove uprobe from
561                  * delayed_uprobe_list from remove_breakpoint(). Do it here.
562                  */
563                 mutex_lock(&delayed_uprobe_lock);
564                 delayed_uprobe_remove(uprobe, NULL);
565                 mutex_unlock(&delayed_uprobe_lock);
566                 kfree(uprobe);
567         }
568 }
569 
570 static int match_uprobe(struct uprobe *l, struct uprobe *r)
571 {
572         if (l->inode < r->inode)
573                 return -1;
574 
575         if (l->inode > r->inode)
576                 return 1;
577 
578         if (l->offset < r->offset)
579                 return -1;
580 
581         if (l->offset > r->offset)
582                 return 1;
583 
584         return 0;
585 }
586 
587 static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
588 {
589         struct uprobe u = { .inode = inode, .offset = offset };
590         struct rb_node *n = uprobes_tree.rb_node;
591         struct uprobe *uprobe;
592         int match;
593 
594         while (n) {
595                 uprobe = rb_entry(n, struct uprobe, rb_node);
596                 match = match_uprobe(&u, uprobe);
597                 if (!match)
598                         return get_uprobe(uprobe);
599 
600                 if (match < 0)
601                         n = n->rb_left;
602                 else
603                         n = n->rb_right;
604         }
605         return NULL;
606 }
607 
608 /*
609  * Find a uprobe corresponding to a given inode:offset
610  * Acquires uprobes_treelock
611  */
612 static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
613 {
614         struct uprobe *uprobe;
615 
616         spin_lock(&uprobes_treelock);
617         uprobe = __find_uprobe(inode, offset);
618         spin_unlock(&uprobes_treelock);
619 
620         return uprobe;
621 }
622 
623 static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
624 {
625         struct rb_node **p = &uprobes_tree.rb_node;
626         struct rb_node *parent = NULL;
627         struct uprobe *u;
628         int match;
629 
630         while (*p) {
631                 parent = *p;
632                 u = rb_entry(parent, struct uprobe, rb_node);
633                 match = match_uprobe(uprobe, u);
634                 if (!match)
635                         return get_uprobe(u);
636 
637                 if (match < 0)
638                         p = &parent->rb_left;
639                 else
640                         p = &parent->rb_right;
641 
642         }
643 
644         u = NULL;
645         rb_link_node(&uprobe->rb_node, parent, p);
646         rb_insert_color(&uprobe->rb_node, &uprobes_tree);
647         /* get access + creation ref */
648         refcount_set(&uprobe->ref, 2);
649 
650         return u;
651 }
652 
653 /*
654  * Acquire uprobes_treelock.
655  * Matching uprobe already exists in rbtree;
656  *      increment (access refcount) and return the matching uprobe.
657  *
658  * No matching uprobe; insert the uprobe in rb_tree;
659  *      get a double refcount (access + creation) and return NULL.
660  */
661 static struct uprobe *insert_uprobe(struct uprobe *uprobe)
662 {
663         struct uprobe *u;
664 
665         spin_lock(&uprobes_treelock);
666         u = __insert_uprobe(uprobe);
667         spin_unlock(&uprobes_treelock);
668 
669         return u;
670 }
671 
672 static void
673 ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe)
674 {
675         pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx "
676                 "ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n",
677                 uprobe->inode->i_ino, (unsigned long long) uprobe->offset,
678                 (unsigned long long) cur_uprobe->ref_ctr_offset,
679                 (unsigned long long) uprobe->ref_ctr_offset);
680 }
681 
682 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
683                                    loff_t ref_ctr_offset)
684 {
685         struct uprobe *uprobe, *cur_uprobe;
686 
687         uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
688         if (!uprobe)
689                 return NULL;
690 
691         uprobe->inode = inode;
692         uprobe->offset = offset;
693         uprobe->ref_ctr_offset = ref_ctr_offset;
694         init_rwsem(&uprobe->register_rwsem);
695         init_rwsem(&uprobe->consumer_rwsem);
696 
697         /* add to uprobes_tree, sorted on inode:offset */
698         cur_uprobe = insert_uprobe(uprobe);
699         /* a uprobe exists for this inode:offset combination */
700         if (cur_uprobe) {
701                 if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
702                         ref_ctr_mismatch_warn(cur_uprobe, uprobe);
703                         put_uprobe(cur_uprobe);
704                         kfree(uprobe);
705                         return ERR_PTR(-EINVAL);
706                 }
707                 kfree(uprobe);
708                 uprobe = cur_uprobe;
709         }
710 
711         return uprobe;
712 }
713 
714 static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
715 {
716         down_write(&uprobe->consumer_rwsem);
717         uc->next = uprobe->consumers;
718         uprobe->consumers = uc;
719         up_write(&uprobe->consumer_rwsem);
720 }
721 
722 /*
723  * For uprobe @uprobe, delete the consumer @uc.
724  * Return true if the @uc is deleted successfully
725  * or return false.
726  */
727 static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
728 {
729         struct uprobe_consumer **con;
730         bool ret = false;
731 
732         down_write(&uprobe->consumer_rwsem);
733         for (con = &uprobe->consumers; *con; con = &(*con)->next) {
734                 if (*con == uc) {
735                         *con = uc->next;
736                         ret = true;
737                         break;
738                 }
739         }
740         up_write(&uprobe->consumer_rwsem);
741 
742         return ret;
743 }
744 
745 static int __copy_insn(struct address_space *mapping, struct file *filp,
746                         void *insn, int nbytes, loff_t offset)
747 {
748         struct page *page;
749         /*
750          * Ensure that the page that has the original instruction is populated
751          * and in page-cache. If ->readpage == NULL it must be shmem_mapping(),
752          * see uprobe_register().
753          */
754         if (mapping->a_ops->readpage)
755                 page = read_mapping_page(mapping, offset >> PAGE_SHIFT, filp);
756         else
757                 page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
758         if (IS_ERR(page))
759                 return PTR_ERR(page);
760 
761         copy_from_page(page, offset, insn, nbytes);
762         put_page(page);
763 
764         return 0;
765 }
766 
767 static int copy_insn(struct uprobe *uprobe, struct file *filp)
768 {
769         struct address_space *mapping = uprobe->inode->i_mapping;
770         loff_t offs = uprobe->offset;
771         void *insn = &uprobe->arch.insn;
772         int size = sizeof(uprobe->arch.insn);
773         int len, err = -EIO;
774 
775         /* Copy only available bytes, -EIO if nothing was read */
776         do {
777                 if (offs >= i_size_read(uprobe->inode))
778                         break;
779 
780                 len = min_t(int, size, PAGE_SIZE - (offs & ~PAGE_MASK));
781                 err = __copy_insn(mapping, filp, insn, len, offs);
782                 if (err)
783                         break;
784 
785                 insn += len;
786                 offs += len;
787                 size -= len;
788         } while (size);
789 
790         return err;
791 }
792 
793 static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
794                                 struct mm_struct *mm, unsigned long vaddr)
795 {
796         int ret = 0;
797 
798         if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
799                 return ret;
800 
801         /* TODO: move this into _register, until then we abuse this sem. */
802         down_write(&uprobe->consumer_rwsem);
803         if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
804                 goto out;
805 
806         ret = copy_insn(uprobe, file);
807         if (ret)
808                 goto out;
809 
810         ret = -ENOTSUPP;
811         if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn))
812                 goto out;
813 
814         ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
815         if (ret)
816                 goto out;
817 
818         /* uprobe_write_opcode() assumes we don't cross page boundary */
819         BUG_ON((uprobe->offset & ~PAGE_MASK) +
820                         UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
821 
822         smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
823         set_bit(UPROBE_COPY_INSN, &uprobe->flags);
824 
825  out:
826         up_write(&uprobe->consumer_rwsem);
827 
828         return ret;
829 }
830 
831 static inline bool consumer_filter(struct uprobe_consumer *uc,
832                                    enum uprobe_filter_ctx ctx, struct mm_struct *mm)
833 {
834         return !uc->filter || uc->filter(uc, ctx, mm);
835 }
836 
837 static bool filter_chain(struct uprobe *uprobe,
838                          enum uprobe_filter_ctx ctx, struct mm_struct *mm)
839 {
840         struct uprobe_consumer *uc;
841         bool ret = false;
842 
843         down_read(&uprobe->consumer_rwsem);
844         for (uc = uprobe->consumers; uc; uc = uc->next) {
845                 ret = consumer_filter(uc, ctx, mm);
846                 if (ret)
847                         break;
848         }
849         up_read(&uprobe->consumer_rwsem);
850 
851         return ret;
852 }
853 
854 static int
855 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
856                         struct vm_area_struct *vma, unsigned long vaddr)
857 {
858         bool first_uprobe;
859         int ret;
860 
861         ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
862         if (ret)
863                 return ret;
864 
865         /*
866          * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
867          * the task can hit this breakpoint right after __replace_page().
868          */
869         first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
870         if (first_uprobe)
871                 set_bit(MMF_HAS_UPROBES, &mm->flags);
872 
873         ret = set_swbp(&uprobe->arch, mm, vaddr);
874         if (!ret)
875                 clear_bit(MMF_RECALC_UPROBES, &mm->flags);
876         else if (first_uprobe)
877                 clear_bit(MMF_HAS_UPROBES, &mm->flags);
878 
879         return ret;
880 }
881 
882 static int
883 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
884 {
885         set_bit(MMF_RECALC_UPROBES, &mm->flags);
886         return set_orig_insn(&uprobe->arch, mm, vaddr);
887 }
888 
889 static inline bool uprobe_is_active(struct uprobe *uprobe)
890 {
891         return !RB_EMPTY_NODE(&uprobe->rb_node);
892 }
893 /*
894  * There could be threads that have already hit the breakpoint. They
895  * will recheck the current insn and restart if find_uprobe() fails.
896  * See find_active_uprobe().
897  */
898 static void delete_uprobe(struct uprobe *uprobe)
899 {
900         if (WARN_ON(!uprobe_is_active(uprobe)))
901                 return;
902 
903         spin_lock(&uprobes_treelock);
904         rb_erase(&uprobe->rb_node, &uprobes_tree);
905         spin_unlock(&uprobes_treelock);
906         RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
907         put_uprobe(uprobe);
908 }
909 
910 struct map_info {
911         struct map_info *next;
912         struct mm_struct *mm;
913         unsigned long vaddr;
914 };
915 
916 static inline struct map_info *free_map_info(struct map_info *info)
917 {
918         struct map_info *next = info->next;
919         kfree(info);
920         return next;
921 }
922 
923 static struct map_info *
924 build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
925 {
926         unsigned long pgoff = offset >> PAGE_SHIFT;
927         struct vm_area_struct *vma;
928         struct map_info *curr = NULL;
929         struct map_info *prev = NULL;
930         struct map_info *info;
931         int more = 0;
932 
933  again:
934         i_mmap_lock_read(mapping);
935         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
936                 if (!valid_vma(vma, is_register))
937                         continue;
938 
939                 if (!prev && !more) {
940                         /*
941                          * Needs GFP_NOWAIT to avoid i_mmap_rwsem recursion through
942                          * reclaim. This is optimistic, no harm done if it fails.
943                          */
944                         prev = kmalloc(sizeof(struct map_info),
945                                         GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
946                         if (prev)
947                                 prev->next = NULL;
948                 }
949                 if (!prev) {
950                         more++;
951                         continue;
952                 }
953 
954                 if (!mmget_not_zero(vma->vm_mm))
955                         continue;
956 
957                 info = prev;
958                 prev = prev->next;
959                 info->next = curr;
960                 curr = info;
961 
962                 info->mm = vma->vm_mm;
963                 info->vaddr = offset_to_vaddr(vma, offset);
964         }
965         i_mmap_unlock_read(mapping);
966 
967         if (!more)
968                 goto out;
969 
970         prev = curr;
971         while (curr) {
972                 mmput(curr->mm);
973                 curr = curr->next;
974         }
975 
976         do {
977                 info = kmalloc(sizeof(struct map_info), GFP_KERNEL);
978                 if (!info) {
979                         curr = ERR_PTR(-ENOMEM);
980                         goto out;
981                 }
982                 info->next = prev;
983                 prev = info;
984         } while (--more);
985 
986         goto again;
987  out:
988         while (prev)
989                 prev = free_map_info(prev);
990         return curr;
991 }
992 
993 static int
994 register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
995 {
996         bool is_register = !!new;
997         struct map_info *info;
998         int err = 0;
999 
1000         percpu_down_write(&dup_mmap_sem);
1001         info = build_map_info(uprobe->inode->i_mapping,
1002                                         uprobe->offset, is_register);
1003         if (IS_ERR(info)) {
1004                 err = PTR_ERR(info);
1005                 goto out;
1006         }
1007 
1008         while (info) {
1009                 struct mm_struct *mm = info->mm;
1010                 struct vm_area_struct *vma;
1011 
1012                 if (err && is_register)
1013                         goto free;
1014 
1015                 down_write(&mm->mmap_sem);
1016                 vma = find_vma(mm, info->vaddr);
1017                 if (!vma || !valid_vma(vma, is_register) ||
1018                     file_inode(vma->vm_file) != uprobe->inode)
1019                         goto unlock;
1020 
1021                 if (vma->vm_start > info->vaddr ||
1022                     vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
1023                         goto unlock;
1024 
1025                 if (is_register) {
1026                         /* consult only the "caller", new consumer. */
1027                         if (consumer_filter(new,
1028                                         UPROBE_FILTER_REGISTER, mm))
1029                                 err = install_breakpoint(uprobe, mm, vma, info->vaddr);
1030                 } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
1031                         if (!filter_chain(uprobe,
1032                                         UPROBE_FILTER_UNREGISTER, mm))
1033                                 err |= remove_breakpoint(uprobe, mm, info->vaddr);
1034                 }
1035 
1036  unlock:
1037                 up_write(&mm->mmap_sem);
1038  free:
1039                 mmput(mm);
1040                 info = free_map_info(info);
1041         }
1042  out:
1043         percpu_up_write(&dup_mmap_sem);
1044         return err;
1045 }
1046 
1047 static void
1048 __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
1049 {
1050         int err;
1051 
1052         if (WARN_ON(!consumer_del(uprobe, uc)))
1053                 return;
1054 
1055         err = register_for_each_vma(uprobe, NULL);
1056         /* TODO : cant unregister? schedule a worker thread */
1057         if (!uprobe->consumers && !err)
1058                 delete_uprobe(uprobe);
1059 }
1060 
1061 /*
1062  * uprobe_unregister - unregister an already registered probe.
1063  * @inode: the file in which the probe has to be removed.
1064  * @offset: offset from the start of the file.
1065  * @uc: identify which probe if multiple probes are colocated.
1066  */
1067 void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
1068 {
1069         struct uprobe *uprobe;
1070 
1071         uprobe = find_uprobe(inode, offset);
1072         if (WARN_ON(!uprobe))
1073                 return;
1074 
1075         down_write(&uprobe->register_rwsem);
1076         __uprobe_unregister(uprobe, uc);
1077         up_write(&uprobe->register_rwsem);
1078         put_uprobe(uprobe);
1079 }
1080 EXPORT_SYMBOL_GPL(uprobe_unregister);
1081 
1082 /*
1083  * __uprobe_register - register a probe
1084  * @inode: the file in which the probe has to be placed.
1085  * @offset: offset from the start of the file.
1086  * @uc: information on howto handle the probe..
1087  *
1088  * Apart from the access refcount, __uprobe_register() takes a creation
1089  * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
1090  * inserted into the rbtree (i.e first consumer for a @inode:@offset
1091  * tuple).  Creation refcount stops uprobe_unregister from freeing the
1092  * @uprobe even before the register operation is complete. Creation
1093  * refcount is released when the last @uc for the @uprobe
1094  * unregisters. Caller of __uprobe_register() is required to keep @inode
1095  * (and the containing mount) referenced.
1096  *
1097  * Return errno if it cannot successully install probes
1098  * else return 0 (success)
1099  */
1100 static int __uprobe_register(struct inode *inode, loff_t offset,
1101                              loff_t ref_ctr_offset, struct uprobe_consumer *uc)
1102 {
1103         struct uprobe *uprobe;
1104         int ret;
1105 
1106         /* Uprobe must have at least one set consumer */
1107         if (!uc->handler && !uc->ret_handler)
1108                 return -EINVAL;
1109 
1110         /* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
1111         if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping))
1112                 return -EIO;
1113         /* Racy, just to catch the obvious mistakes */
1114         if (offset > i_size_read(inode))
1115                 return -EINVAL;
1116 
1117  retry:
1118         uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
1119         if (!uprobe)
1120                 return -ENOMEM;
1121         if (IS_ERR(uprobe))
1122                 return PTR_ERR(uprobe);
1123 
1124         /*
1125          * We can race with uprobe_unregister()->delete_uprobe().
1126          * Check uprobe_is_active() and retry if it is false.
1127          */
1128         down_write(&uprobe->register_rwsem);
1129         ret = -EAGAIN;
1130         if (likely(uprobe_is_active(uprobe))) {
1131                 consumer_add(uprobe, uc);
1132                 ret = register_for_each_vma(uprobe, uc);
1133                 if (ret)
1134                         __uprobe_unregister(uprobe, uc);
1135         }
1136         up_write(&uprobe->register_rwsem);
1137         put_uprobe(uprobe);
1138 
1139         if (unlikely(ret == -EAGAIN))
1140                 goto retry;
1141         return ret;
1142 }
1143 
1144 int uprobe_register(struct inode *inode, loff_t offset,
1145                     struct uprobe_consumer *uc)
1146 {
1147         return __uprobe_register(inode, offset, 0, uc);
1148 }
1149 EXPORT_SYMBOL_GPL(uprobe_register);
1150 
1151 int uprobe_register_refctr(struct inode *inode, loff_t offset,
1152                            loff_t ref_ctr_offset, struct uprobe_consumer *uc)
1153 {
1154         return __uprobe_register(inode, offset, ref_ctr_offset, uc);
1155 }
1156 EXPORT_SYMBOL_GPL(uprobe_register_refctr);
1157 
1158 /*
1159  * uprobe_apply - unregister an already registered probe.
1160  * @inode: the file in which the probe has to be removed.
1161  * @offset: offset from the start of the file.
1162  * @uc: consumer which wants to add more or remove some breakpoints
1163  * @add: add or remove the breakpoints
1164  */
1165 int uprobe_apply(struct inode *inode, loff_t offset,
1166                         struct uprobe_consumer *uc, bool add)
1167 {
1168         struct uprobe *uprobe;
1169         struct uprobe_consumer *con;
1170         int ret = -ENOENT;
1171 
1172         uprobe = find_uprobe(inode, offset);
1173         if (WARN_ON(!uprobe))
1174                 return ret;
1175 
1176         down_write(&uprobe->register_rwsem);
1177         for (con = uprobe->consumers; con && con != uc ; con = con->next)
1178                 ;
1179         if (con)
1180                 ret = register_for_each_vma(uprobe, add ? uc : NULL);
1181         up_write(&uprobe->register_rwsem);
1182         put_uprobe(uprobe);
1183 
1184         return ret;
1185 }
1186 
1187 static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
1188 {
1189         struct vm_area_struct *vma;
1190         int err = 0;
1191 
1192         down_read(&mm->mmap_sem);
1193         for (vma = mm->mmap; vma; vma = vma->vm_next) {
1194                 unsigned long vaddr;
1195                 loff_t offset;
1196 
1197                 if (!valid_vma(vma, false) ||
1198                     file_inode(vma->vm_file) != uprobe->inode)
1199                         continue;
1200 
1201                 offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
1202                 if (uprobe->offset <  offset ||
1203                     uprobe->offset >= offset + vma->vm_end - vma->vm_start)
1204                         continue;
1205 
1206                 vaddr = offset_to_vaddr(vma, uprobe->offset);
1207                 err |= remove_breakpoint(uprobe, mm, vaddr);
1208         }
1209         up_read(&mm->mmap_sem);
1210 
1211         return err;
1212 }
1213 
1214 static struct rb_node *
1215 find_node_in_range(struct inode *inode, loff_t min, loff_t max)
1216 {
1217         struct rb_node *n = uprobes_tree.rb_node;
1218 
1219         while (n) {
1220                 struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
1221 
1222                 if (inode < u->inode) {
1223                         n = n->rb_left;
1224                 } else if (inode > u->inode) {
1225                         n = n->rb_right;
1226                 } else {
1227                         if (max < u->offset)
1228                                 n = n->rb_left;
1229                         else if (min > u->offset)
1230                                 n = n->rb_right;
1231                         else
1232                                 break;
1233                 }
1234         }
1235 
1236         return n;
1237 }
1238 
1239 /*
1240  * For a given range in vma, build a list of probes that need to be inserted.
1241  */
1242 static void build_probe_list(struct inode *inode,
1243                                 struct vm_area_struct *vma,
1244                                 unsigned long start, unsigned long end,
1245                                 struct list_head *head)
1246 {
1247         loff_t min, max;
1248         struct rb_node *n, *t;
1249         struct uprobe *u;
1250 
1251         INIT_LIST_HEAD(head);
1252         min = vaddr_to_offset(vma, start);
1253         max = min + (end - start) - 1;
1254 
1255         spin_lock(&uprobes_treelock);
1256         n = find_node_in_range(inode, min, max);
1257         if (n) {
1258                 for (t = n; t; t = rb_prev(t)) {
1259                         u = rb_entry(t, struct uprobe, rb_node);
1260                         if (u->inode != inode || u->offset < min)
1261                                 break;
1262                         list_add(&u->pending_list, head);
1263                         get_uprobe(u);
1264                 }
1265                 for (t = n; (t = rb_next(t)); ) {
1266                         u = rb_entry(t, struct uprobe, rb_node);
1267                         if (u->inode != inode || u->offset > max)
1268                                 break;
1269                         list_add(&u->pending_list, head);
1270                         get_uprobe(u);
1271                 }
1272         }
1273         spin_unlock(&uprobes_treelock);
1274 }
1275 
1276 /* @vma contains reference counter, not the probed instruction. */
1277 static int delayed_ref_ctr_inc(struct vm_area_struct *vma)
1278 {
1279         struct list_head *pos, *q;
1280         struct delayed_uprobe *du;
1281         unsigned long vaddr;
1282         int ret = 0, err = 0;
1283 
1284         mutex_lock(&delayed_uprobe_lock);
1285         list_for_each_safe(pos, q, &delayed_uprobe_list) {
1286                 du = list_entry(pos, struct delayed_uprobe, list);
1287 
1288                 if (du->mm != vma->vm_mm ||
1289                     !valid_ref_ctr_vma(du->uprobe, vma))
1290                         continue;
1291 
1292                 vaddr = offset_to_vaddr(vma, du->uprobe->ref_ctr_offset);
1293                 ret = __update_ref_ctr(vma->vm_mm, vaddr, 1);
1294                 if (ret) {
1295                         update_ref_ctr_warn(du->uprobe, vma->vm_mm, 1);
1296                         if (!err)
1297                                 err = ret;
1298                 }
1299                 delayed_uprobe_delete(du);
1300         }
1301         mutex_unlock(&delayed_uprobe_lock);
1302         return err;
1303 }
1304 
1305 /*
1306  * Called from mmap_region/vma_adjust with mm->mmap_sem acquired.
1307  *
1308  * Currently we ignore all errors and always return 0, the callers
1309  * can't handle the failure anyway.
1310  */
1311 int uprobe_mmap(struct vm_area_struct *vma)
1312 {
1313         struct list_head tmp_list;
1314         struct uprobe *uprobe, *u;
1315         struct inode *inode;
1316 
1317         if (no_uprobe_events())
1318                 return 0;
1319 
1320         if (vma->vm_file &&
1321             (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE &&
1322             test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags))
1323                 delayed_ref_ctr_inc(vma);
1324 
1325         if (!valid_vma(vma, true))
1326                 return 0;
1327 
1328         inode = file_inode(vma->vm_file);
1329         if (!inode)
1330                 return 0;
1331 
1332         mutex_lock(uprobes_mmap_hash(inode));
1333         build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
1334         /*
1335          * We can race with uprobe_unregister(), this uprobe can be already
1336          * removed. But in this case filter_chain() must return false, all
1337          * consumers have gone away.
1338          */
1339         list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1340                 if (!fatal_signal_pending(current) &&
1341                     filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
1342                         unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
1343                         install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1344                 }
1345                 put_uprobe(uprobe);
1346         }
1347         mutex_unlock(uprobes_mmap_hash(inode));
1348 
1349         return 0;
1350 }
1351 
1352 static bool
1353 vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1354 {
1355         loff_t min, max;
1356         struct inode *inode;
1357         struct rb_node *n;
1358 
1359         inode = file_inode(vma->vm_file);
1360 
1361         min = vaddr_to_offset(vma, start);
1362         max = min + (end - start) - 1;
1363 
1364         spin_lock(&uprobes_treelock);
1365         n = find_node_in_range(inode, min, max);
1366         spin_unlock(&uprobes_treelock);
1367 
1368         return !!n;
1369 }
1370 
1371 /*
1372  * Called in context of a munmap of a vma.
1373  */
1374 void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1375 {
1376         if (no_uprobe_events() || !valid_vma(vma, false))
1377                 return;
1378 
1379         if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
1380                 return;
1381 
1382         if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||
1383              test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))
1384                 return;
1385 
1386         if (vma_has_uprobes(vma, start, end))
1387                 set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
1388 }
1389 
1390 /* Slot allocation for XOL */
1391 static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
1392 {
1393         struct vm_area_struct *vma;
1394         int ret;
1395 
1396         if (down_write_killable(&mm->mmap_sem))
1397                 return -EINTR;
1398 
1399         if (mm->uprobes_state.xol_area) {
1400                 ret = -EALREADY;
1401                 goto fail;
1402         }
1403 
1404         if (!area->vaddr) {
1405                 /* Try to map as high as possible, this is only a hint. */
1406                 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE,
1407                                                 PAGE_SIZE, 0, 0);
1408                 if (area->vaddr & ~PAGE_MASK) {
1409                         ret = area->vaddr;
1410                         goto fail;
1411                 }
1412         }
1413 
1414         vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1415                                 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
1416                                 &area->xol_mapping);
1417         if (IS_ERR(vma)) {
1418                 ret = PTR_ERR(vma);
1419                 goto fail;
1420         }
1421 
1422         ret = 0;
1423         /* pairs with get_xol_area() */
1424         smp_store_release(&mm->uprobes_state.xol_area, area); /* ^^^ */
1425  fail:
1426         up_write(&mm->mmap_sem);
1427 
1428         return ret;
1429 }
1430 
1431 static struct xol_area *__create_xol_area(unsigned long vaddr)
1432 {
1433         struct mm_struct *mm = current->mm;
1434         uprobe_opcode_t insn = UPROBE_SWBP_INSN;
1435         struct xol_area *area;
1436 
1437         area = kmalloc(sizeof(*area), GFP_KERNEL);
1438         if (unlikely(!area))
1439                 goto out;
1440 
1441         area->bitmap = kcalloc(BITS_TO_LONGS(UINSNS_PER_PAGE), sizeof(long),
1442                                GFP_KERNEL);
1443         if (!area->bitmap)
1444                 goto free_area;
1445 
1446         area->xol_mapping.name = "[uprobes]";
1447         area->xol_mapping.fault = NULL;
1448         area->xol_mapping.pages = area->pages;
1449         area->pages[0] = alloc_page(GFP_HIGHUSER);
1450         if (!area->pages[0])
1451                 goto free_bitmap;
1452         area->pages[1] = NULL;
1453 
1454         area->vaddr = vaddr;
1455         init_waitqueue_head(&area->wq);
1456         /* Reserve the 1st slot for get_trampoline_vaddr() */
1457         set_bit(0, area->bitmap);
1458         atomic_set(&area->slot_count, 1);
1459         arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE);
1460 
1461         if (!xol_add_vma(mm, area))
1462                 return area;
1463 
1464         __free_page(area->pages[0]);
1465  free_bitmap:
1466         kfree(area->bitmap);
1467  free_area:
1468         kfree(area);
1469  out:
1470         return NULL;
1471 }
1472 
1473 /*
1474  * get_xol_area - Allocate process's xol_area if necessary.
1475  * This area will be used for storing instructions for execution out of line.
1476  *
1477  * Returns the allocated area or NULL.
1478  */
1479 static struct xol_area *get_xol_area(void)
1480 {
1481         struct mm_struct *mm = current->mm;
1482         struct xol_area *area;
1483 
1484         if (!mm->uprobes_state.xol_area)
1485                 __create_xol_area(0);
1486 
1487         /* Pairs with xol_add_vma() smp_store_release() */
1488         area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */
1489         return area;
1490 }
1491 
1492 /*
1493  * uprobe_clear_state - Free the area allocated for slots.
1494  */
1495 void uprobe_clear_state(struct mm_struct *mm)
1496 {
1497         struct xol_area *area = mm->uprobes_state.xol_area;
1498 
1499         mutex_lock(&delayed_uprobe_lock);
1500         delayed_uprobe_remove(NULL, mm);
1501         mutex_unlock(&delayed_uprobe_lock);
1502 
1503         if (!area)
1504                 return;
1505 
1506         put_page(area->pages[0]);
1507         kfree(area->bitmap);
1508         kfree(area);
1509 }
1510 
1511 void uprobe_start_dup_mmap(void)
1512 {
1513         percpu_down_read(&dup_mmap_sem);
1514 }
1515 
1516 void uprobe_end_dup_mmap(void)
1517 {
1518         percpu_up_read(&dup_mmap_sem);
1519 }
1520 
1521 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
1522 {
1523         if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {
1524                 set_bit(MMF_HAS_UPROBES, &newmm->flags);
1525                 /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */
1526                 set_bit(MMF_RECALC_UPROBES, &newmm->flags);
1527         }
1528 }
1529 
1530 /*
1531  *  - search for a free slot.
1532  */
1533 static unsigned long xol_take_insn_slot(struct xol_area *area)
1534 {
1535         unsigned long slot_addr;
1536         int slot_nr;
1537 
1538         do {
1539                 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1540                 if (slot_nr < UINSNS_PER_PAGE) {
1541                         if (!test_and_set_bit(slot_nr, area->bitmap))
1542                                 break;
1543 
1544                         slot_nr = UINSNS_PER_PAGE;
1545                         continue;
1546                 }
1547                 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1548         } while (slot_nr >= UINSNS_PER_PAGE);
1549 
1550         slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1551         atomic_inc(&area->slot_count);
1552 
1553         return slot_addr;
1554 }
1555 
1556 /*
1557  * xol_get_insn_slot - allocate a slot for xol.
1558  * Returns the allocated slot address or 0.
1559  */
1560 static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
1561 {
1562         struct xol_area *area;
1563         unsigned long xol_vaddr;
1564 
1565         area = get_xol_area();
1566         if (!area)
1567                 return 0;
1568 
1569         xol_vaddr = xol_take_insn_slot(area);
1570         if (unlikely(!xol_vaddr))
1571                 return 0;
1572 
1573         arch_uprobe_copy_ixol(area->pages[0], xol_vaddr,
1574                               &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
1575 
1576         return xol_vaddr;
1577 }
1578 
1579 /*
1580  * xol_free_insn_slot - If slot was earlier allocated by
1581  * @xol_get_insn_slot(), make the slot available for
1582  * subsequent requests.
1583  */
1584 static void xol_free_insn_slot(struct task_struct *tsk)
1585 {
1586         struct xol_area *area;
1587         unsigned long vma_end;
1588         unsigned long slot_addr;
1589 
1590         if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1591                 return;
1592 
1593         slot_addr = tsk->utask->xol_vaddr;
1594         if (unlikely(!slot_addr))
1595                 return;
1596 
1597         area = tsk->mm->uprobes_state.xol_area;
1598         vma_end = area->vaddr + PAGE_SIZE;
1599         if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1600                 unsigned long offset;
1601                 int slot_nr;
1602 
1603                 offset = slot_addr - area->vaddr;
1604                 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1605                 if (slot_nr >= UINSNS_PER_PAGE)
1606                         return;
1607 
1608                 clear_bit(slot_nr, area->bitmap);
1609                 atomic_dec(&area->slot_count);
1610                 smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
1611                 if (waitqueue_active(&area->wq))
1612                         wake_up(&area->wq);
1613 
1614                 tsk->utask->xol_vaddr = 0;
1615         }
1616 }
1617 
1618 void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
1619                                   void *src, unsigned long len)
1620 {
1621         /* Initialize the slot */
1622         copy_to_page(page, vaddr, src, len);
1623 
1624         /*
1625          * We probably need flush_icache_user_range() but it needs vma.
1626          * This should work on most of architectures by default. If
1627          * architecture needs to do something different it can define
1628          * its own version of the function.
1629          */
1630         flush_dcache_page(page);
1631 }
1632 
1633 /**
1634  * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1635  * @regs: Reflects the saved state of the task after it has hit a breakpoint
1636  * instruction.
1637  * Return the address of the breakpoint instruction.
1638  */
1639 unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1640 {
1641         return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1642 }
1643 
1644 unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
1645 {
1646         struct uprobe_task *utask = current->utask;
1647 
1648         if (unlikely(utask && utask->active_uprobe))
1649                 return utask->vaddr;
1650 
1651         return instruction_pointer(regs);
1652 }
1653 
1654 static struct return_instance *free_ret_instance(struct return_instance *ri)
1655 {
1656         struct return_instance *next = ri->next;
1657         put_uprobe(ri->uprobe);
1658         kfree(ri);
1659         return next;
1660 }
1661 
1662 /*
1663  * Called with no locks held.
1664  * Called in context of an exiting or an exec-ing thread.
1665  */
1666 void uprobe_free_utask(struct task_struct *t)
1667 {
1668         struct uprobe_task *utask = t->utask;
1669         struct return_instance *ri;
1670 
1671         if (!utask)
1672                 return;
1673 
1674         if (utask->active_uprobe)
1675                 put_uprobe(utask->active_uprobe);
1676 
1677         ri = utask->return_instances;
1678         while (ri)
1679                 ri = free_ret_instance(ri);
1680 
1681         xol_free_insn_slot(t);
1682         kfree(utask);
1683         t->utask = NULL;
1684 }
1685 
1686 /*
1687  * Allocate a uprobe_task object for the task if if necessary.
1688  * Called when the thread hits a breakpoint.
1689  *
1690  * Returns:
1691  * - pointer to new uprobe_task on success
1692  * - NULL otherwise
1693  */
1694 static struct uprobe_task *get_utask(void)
1695 {
1696         if (!current->utask)
1697                 current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1698         return current->utask;
1699 }
1700 
1701 static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask)
1702 {
1703         struct uprobe_task *n_utask;
1704         struct return_instance **p, *o, *n;
1705 
1706         n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1707         if (!n_utask)
1708                 return -ENOMEM;
1709         t->utask = n_utask;
1710 
1711         p = &n_utask->return_instances;
1712         for (o = o_utask->return_instances; o; o = o->next) {
1713                 n = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1714                 if (!n)
1715                         return -ENOMEM;
1716 
1717                 *n = *o;
1718                 get_uprobe(n->uprobe);
1719                 n->next = NULL;
1720 
1721                 *p = n;
1722                 p = &n->next;
1723                 n_utask->depth++;
1724         }
1725 
1726         return 0;
1727 }
1728 
1729 static void uprobe_warn(struct task_struct *t, const char *msg)
1730 {
1731         pr_warn("uprobe: %s:%d failed to %s\n",
1732                         current->comm, current->pid, msg);
1733 }
1734 
1735 static void dup_xol_work(struct callback_head *work)
1736 {
1737         if (current->flags & PF_EXITING)
1738                 return;
1739 
1740         if (!__create_xol_area(current->utask->dup_xol_addr) &&
1741                         !fatal_signal_pending(current))
1742                 uprobe_warn(current, "dup xol area");
1743 }
1744 
1745 /*
1746  * Called in context of a new clone/fork from copy_process.
1747  */
1748 void uprobe_copy_process(struct task_struct *t, unsigned long flags)
1749 {
1750         struct uprobe_task *utask = current->utask;
1751         struct mm_struct *mm = current->mm;
1752         struct xol_area *area;
1753 
1754         t->utask = NULL;
1755 
1756         if (!utask || !utask->return_instances)
1757                 return;
1758 
1759         if (mm == t->mm && !(flags & CLONE_VFORK))
1760                 return;
1761 
1762         if (dup_utask(t, utask))
1763                 return uprobe_warn(t, "dup ret instances");
1764 
1765         /* The task can fork() after dup_xol_work() fails */
1766         area = mm->uprobes_state.xol_area;
1767         if (!area)
1768                 return uprobe_warn(t, "dup xol area");
1769 
1770         if (mm == t->mm)
1771                 return;
1772 
1773         t->utask->dup_xol_addr = area->vaddr;
1774         init_task_work(&t->utask->dup_xol_work, dup_xol_work);
1775         task_work_add(t, &t->utask->dup_xol_work, true);
1776 }
1777 
1778 /*
1779  * Current area->vaddr notion assume the trampoline address is always
1780  * equal area->vaddr.
1781  *
1782  * Returns -1 in case the xol_area is not allocated.
1783  */
1784 static unsigned long get_trampoline_vaddr(void)
1785 {
1786         struct xol_area *area;
1787         unsigned long trampoline_vaddr = -1;
1788 
1789         /* Pairs with xol_add_vma() smp_store_release() */
1790         area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */
1791         if (area)
1792                 trampoline_vaddr = area->vaddr;
1793 
1794         return trampoline_vaddr;
1795 }
1796 
1797 static void cleanup_return_instances(struct uprobe_task *utask, bool chained,
1798                                         struct pt_regs *regs)
1799 {
1800         struct return_instance *ri = utask->return_instances;
1801         enum rp_check ctx = chained ? RP_CHECK_CHAIN_CALL : RP_CHECK_CALL;
1802 
1803         while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
1804                 ri = free_ret_instance(ri);
1805                 utask->depth--;
1806         }
1807         utask->return_instances = ri;
1808 }
1809 
1810 static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
1811 {
1812         struct return_instance *ri;
1813         struct uprobe_task *utask;
1814         unsigned long orig_ret_vaddr, trampoline_vaddr;
1815         bool chained;
1816 
1817         if (!get_xol_area())
1818                 return;
1819 
1820         utask = get_utask();
1821         if (!utask)
1822                 return;
1823 
1824         if (utask->depth >= MAX_URETPROBE_DEPTH) {
1825                 printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to"
1826                                 " nestedness limit pid/tgid=%d/%d\n",
1827                                 current->pid, current->tgid);
1828                 return;
1829         }
1830 
1831         ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1832         if (!ri)
1833                 return;
1834 
1835         trampoline_vaddr = get_trampoline_vaddr();
1836         orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
1837         if (orig_ret_vaddr == -1)
1838                 goto fail;
1839 
1840         /* drop the entries invalidated by longjmp() */
1841         chained = (orig_ret_vaddr == trampoline_vaddr);
1842         cleanup_return_instances(utask, chained, regs);
1843 
1844         /*
1845          * We don't want to keep trampoline address in stack, rather keep the
1846          * original return address of first caller thru all the consequent
1847          * instances. This also makes breakpoint unwrapping easier.
1848          */
1849         if (chained) {
1850                 if (!utask->return_instances) {
1851                         /*
1852                          * This situation is not possible. Likely we have an
1853                          * attack from user-space.
1854                          */
1855                         uprobe_warn(current, "handle tail call");
1856                         goto fail;
1857                 }
1858                 orig_ret_vaddr = utask->return_instances->orig_ret_vaddr;
1859         }
1860 
1861         ri->uprobe = get_uprobe(uprobe);
1862         ri->func = instruction_pointer(regs);
1863         ri->stack = user_stack_pointer(regs);
1864         ri->orig_ret_vaddr = orig_ret_vaddr;
1865         ri->chained = chained;
1866 
1867         utask->depth++;
1868         ri->next = utask->return_instances;
1869         utask->return_instances = ri;
1870 
1871         return;
1872  fail:
1873         kfree(ri);
1874 }
1875 
1876 /* Prepare to single-step probed instruction out of line. */
1877 static int
1878 pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
1879 {
1880         struct uprobe_task *utask;
1881         unsigned long xol_vaddr;
1882         int err;
1883 
1884         utask = get_utask();
1885         if (!utask)
1886                 return -ENOMEM;
1887 
1888         xol_vaddr = xol_get_insn_slot(uprobe);
1889         if (!xol_vaddr)
1890                 return -ENOMEM;
1891 
1892         utask->xol_vaddr = xol_vaddr;
1893         utask->vaddr = bp_vaddr;
1894 
1895         err = arch_uprobe_pre_xol(&uprobe->arch, regs);
1896         if (unlikely(err)) {
1897                 xol_free_insn_slot(current);
1898                 return err;
1899         }
1900 
1901         utask->active_uprobe = uprobe;
1902         utask->state = UTASK_SSTEP;
1903         return 0;
1904 }
1905 
1906 /*
1907  * If we are singlestepping, then ensure this thread is not connected to
1908  * non-fatal signals until completion of singlestep.  When xol insn itself
1909  * triggers the signal,  restart the original insn even if the task is
1910  * already SIGKILL'ed (since coredump should report the correct ip).  This
1911  * is even more important if the task has a handler for SIGSEGV/etc, The
1912  * _same_ instruction should be repeated again after return from the signal
1913  * handler, and SSTEP can never finish in this case.
1914  */
1915 bool uprobe_deny_signal(void)
1916 {
1917         struct task_struct *t = current;
1918         struct uprobe_task *utask = t->utask;
1919 
1920         if (likely(!utask || !utask->active_uprobe))
1921                 return false;
1922 
1923         WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1924 
1925         if (signal_pending(t)) {
1926                 spin_lock_irq(&t->sighand->siglock);
1927                 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1928                 spin_unlock_irq(&t->sighand->siglock);
1929 
1930                 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1931                         utask->state = UTASK_SSTEP_TRAPPED;
1932                         set_tsk_thread_flag(t, TIF_UPROBE);
1933                 }
1934         }
1935 
1936         return true;
1937 }
1938 
1939 static void mmf_recalc_uprobes(struct mm_struct *mm)
1940 {
1941         struct vm_area_struct *vma;
1942 
1943         for (vma = mm->mmap; vma; vma = vma->vm_next) {
1944                 if (!valid_vma(vma, false))
1945                         continue;
1946                 /*
1947                  * This is not strictly accurate, we can race with
1948                  * uprobe_unregister() and see the already removed
1949                  * uprobe if delete_uprobe() was not yet called.
1950                  * Or this uprobe can be filtered out.
1951                  */
1952                 if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
1953                         return;
1954         }
1955 
1956         clear_bit(MMF_HAS_UPROBES, &mm->flags);
1957 }
1958 
1959 static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
1960 {
1961         struct page *page;
1962         uprobe_opcode_t opcode;
1963         int result;
1964 
1965         pagefault_disable();
1966         result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
1967         pagefault_enable();
1968 
1969         if (likely(result == 0))
1970                 goto out;
1971 
1972         /*
1973          * The NULL 'tsk' here ensures that any faults that occur here
1974          * will not be accounted to the task.  'mm' *is* current->mm,
1975          * but we treat this as a 'remote' access since it is
1976          * essentially a kernel access to the memory.
1977          */
1978         result = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &page,
1979                         NULL, NULL);
1980         if (result < 0)
1981                 return result;
1982 
1983         copy_from_page(page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
1984         put_page(page);
1985  out:
1986         /* This needs to return true for any variant of the trap insn */
1987         return is_trap_insn(&opcode);
1988 }
1989 
1990 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
1991 {
1992         struct mm_struct *mm = current->mm;
1993         struct uprobe *uprobe = NULL;
1994         struct vm_area_struct *vma;
1995 
1996         down_read(&mm->mmap_sem);
1997         vma = find_vma(mm, bp_vaddr);
1998         if (vma && vma->vm_start <= bp_vaddr) {
1999                 if (valid_vma(vma, false)) {
2000                         struct inode *inode = file_inode(vma->vm_file);
2001                         loff_t offset = vaddr_to_offset(vma, bp_vaddr);
2002 
2003                         uprobe = find_uprobe(inode, offset);
2004                 }
2005 
2006                 if (!uprobe)
2007                         *is_swbp = is_trap_at_addr(mm, bp_vaddr);
2008         } else {
2009                 *is_swbp = -EFAULT;
2010         }
2011 
2012         if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
2013                 mmf_recalc_uprobes(mm);
2014         up_read(&mm->mmap_sem);
2015 
2016         return uprobe;
2017 }
2018 
2019 static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
2020 {
2021         struct uprobe_consumer *uc;
2022         int remove = UPROBE_HANDLER_REMOVE;
2023         bool need_prep = false; /* prepare return uprobe, when needed */
2024 
2025         down_read(&uprobe->register_rwsem);
2026         for (uc = uprobe->consumers; uc; uc = uc->next) {
2027                 int rc = 0;
2028 
2029                 if (uc->handler) {
2030                         rc = uc->handler(uc, regs);
2031                         WARN(rc & ~UPROBE_HANDLER_MASK,
2032                                 "bad rc=0x%x from %ps()\n", rc, uc->handler);
2033                 }
2034 
2035                 if (uc->ret_handler)
2036                         need_prep = true;
2037 
2038                 remove &= rc;
2039         }
2040 
2041         if (need_prep && !remove)
2042                 prepare_uretprobe(uprobe, regs); /* put bp at return */
2043 
2044         if (remove && uprobe->consumers) {
2045                 WARN_ON(!uprobe_is_active(uprobe));
2046                 unapply_uprobe(uprobe, current->mm);
2047         }
2048         up_read(&uprobe->register_rwsem);
2049 }
2050 
2051 static void
2052 handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
2053 {
2054         struct uprobe *uprobe = ri->uprobe;
2055         struct uprobe_consumer *uc;
2056 
2057         down_read(&uprobe->register_rwsem);
2058         for (uc = uprobe->consumers; uc; uc = uc->next) {
2059                 if (uc->ret_handler)
2060                         uc->ret_handler(uc, ri->func, regs);
2061         }
2062         up_read(&uprobe->register_rwsem);
2063 }
2064 
2065 static struct return_instance *find_next_ret_chain(struct return_instance *ri)
2066 {
2067         bool chained;
2068 
2069         do {
2070                 chained = ri->chained;
2071                 ri = ri->next;  /* can't be NULL if chained */
2072         } while (chained);
2073 
2074         return ri;
2075 }
2076 
2077 static void handle_trampoline(struct pt_regs *regs)
2078 {
2079         struct uprobe_task *utask;
2080         struct return_instance *ri, *next;
2081         bool valid;
2082 
2083         utask = current->utask;
2084         if (!utask)
2085                 goto sigill;
2086 
2087         ri = utask->return_instances;
2088         if (!ri)
2089                 goto sigill;
2090 
2091         do {
2092                 /*
2093                  * We should throw out the frames invalidated by longjmp().
2094                  * If this chain is valid, then the next one should be alive
2095                  * or NULL; the latter case means that nobody but ri->func
2096                  * could hit this trampoline on return. TODO: sigaltstack().
2097                  */
2098                 next = find_next_ret_chain(ri);
2099                 valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
2100 
2101                 instruction_pointer_set(regs, ri->orig_ret_vaddr);
2102                 do {
2103                         if (valid)
2104                                 handle_uretprobe_chain(ri, regs);
2105                         ri = free_ret_instance(ri);
2106                         utask->depth--;
2107                 } while (ri != next);
2108         } while (!valid);
2109 
2110         utask->return_instances = ri;
2111         return;
2112 
2113  sigill:
2114         uprobe_warn(current, "handle uretprobe, sending SIGILL.");
2115         force_sig(SIGILL);
2116 
2117 }
2118 
2119 bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
2120 {
2121         return false;
2122 }
2123 
2124 bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
2125                                         struct pt_regs *regs)
2126 {
2127         return true;
2128 }
2129 
2130 /*
2131  * Run handler and ask thread to singlestep.
2132  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
2133  */
2134 static void handle_swbp(struct pt_regs *regs)
2135 {
2136         struct uprobe *uprobe;
2137         unsigned long bp_vaddr;
2138         int uninitialized_var(is_swbp);
2139 
2140         bp_vaddr = uprobe_get_swbp_addr(regs);
2141         if (bp_vaddr == get_trampoline_vaddr())
2142                 return handle_trampoline(regs);
2143 
2144         uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
2145         if (!uprobe) {
2146                 if (is_swbp > 0) {
2147                         /* No matching uprobe; signal SIGTRAP. */
2148                         send_sig(SIGTRAP, current, 0);
2149                 } else {
2150                         /*
2151                          * Either we raced with uprobe_unregister() or we can't
2152                          * access this memory. The latter is only possible if
2153                          * another thread plays with our ->mm. In both cases
2154                          * we can simply restart. If this vma was unmapped we
2155                          * can pretend this insn was not executed yet and get
2156                          * the (correct) SIGSEGV after restart.
2157                          */
2158                         instruction_pointer_set(regs, bp_vaddr);
2159                 }
2160                 return;
2161         }
2162 
2163         /* change it in advance for ->handler() and restart */
2164         instruction_pointer_set(regs, bp_vaddr);
2165 
2166         /*
2167          * TODO: move copy_insn/etc into _register and remove this hack.
2168          * After we hit the bp, _unregister + _register can install the
2169          * new and not-yet-analyzed uprobe at the same address, restart.
2170          */
2171         if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
2172                 goto out;
2173 
2174         /*
2175          * Pairs with the smp_wmb() in prepare_uprobe().
2176          *
2177          * Guarantees that if we see the UPROBE_COPY_INSN bit set, then
2178          * we must also see the stores to &uprobe->arch performed by the
2179          * prepare_uprobe() call.
2180          */
2181         smp_rmb();
2182 
2183         /* Tracing handlers use ->utask to communicate with fetch methods */
2184         if (!get_utask())
2185                 goto out;
2186 
2187         if (arch_uprobe_ignore(&uprobe->arch, regs))
2188                 goto out;
2189 
2190         handler_chain(uprobe, regs);
2191 
2192         if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
2193                 goto out;
2194 
2195         if (!pre_ssout(uprobe, regs, bp_vaddr))
2196                 return;
2197 
2198         /* arch_uprobe_skip_sstep() succeeded, or restart if can't singlestep */
2199 out:
2200         put_uprobe(uprobe);
2201 }
2202 
2203 /*
2204  * Perform required fix-ups and disable singlestep.
2205  * Allow pending signals to take effect.
2206  */
2207 static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
2208 {
2209         struct uprobe *uprobe;
2210         int err = 0;
2211 
2212         uprobe = utask->active_uprobe;
2213         if (utask->state == UTASK_SSTEP_ACK)
2214                 err = arch_uprobe_post_xol(&uprobe->arch, regs);
2215         else if (utask->state == UTASK_SSTEP_TRAPPED)
2216                 arch_uprobe_abort_xol(&uprobe->arch, regs);
2217         else
2218                 WARN_ON_ONCE(1);
2219 
2220         put_uprobe(uprobe);
2221         utask->active_uprobe = NULL;
2222         utask->state = UTASK_RUNNING;
2223         xol_free_insn_slot(current);
2224 
2225         spin_lock_irq(&current->sighand->siglock);
2226         recalc_sigpending(); /* see uprobe_deny_signal() */
2227         spin_unlock_irq(&current->sighand->siglock);
2228 
2229         if (unlikely(err)) {
2230                 uprobe_warn(current, "execute the probed insn, sending SIGILL.");
2231                 force_sig(SIGILL);
2232         }
2233 }
2234 
2235 /*
2236  * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
2237  * allows the thread to return from interrupt. After that handle_swbp()
2238  * sets utask->active_uprobe.
2239  *
2240  * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
2241  * and allows the thread to return from interrupt.
2242  *
2243  * While returning to userspace, thread notices the TIF_UPROBE flag and calls
2244  * uprobe_notify_resume().
2245  */
2246 void uprobe_notify_resume(struct pt_regs *regs)
2247 {
2248         struct uprobe_task *utask;
2249 
2250         clear_thread_flag(TIF_UPROBE);
2251 
2252         utask = current->utask;
2253         if (utask && utask->active_uprobe)
2254                 handle_singlestep(utask, regs);
2255         else
2256                 handle_swbp(regs);
2257 }
2258 
2259 /*
2260  * uprobe_pre_sstep_notifier gets called from interrupt context as part of
2261  * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
2262  */
2263 int uprobe_pre_sstep_notifier(struct pt_regs *regs)
2264 {
2265         if (!current->mm)
2266                 return 0;
2267 
2268         if (!test_bit(MMF_HAS_UPROBES, &current->mm->flags) &&
2269             (!current->utask || !current->utask->return_instances))
2270                 return 0;
2271 
2272         set_thread_flag(TIF_UPROBE);
2273         return 1;
2274 }
2275 
2276 /*
2277  * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
2278  * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
2279  */
2280 int uprobe_post_sstep_notifier(struct pt_regs *regs)
2281 {
2282         struct uprobe_task *utask = current->utask;
2283 
2284         if (!current->mm || !utask || !utask->active_uprobe)
2285                 /* task is currently not uprobed */
2286                 return 0;
2287 
2288         utask->state = UTASK_SSTEP_ACK;
2289         set_thread_flag(TIF_UPROBE);
2290         return 1;
2291 }
2292 
2293 static struct notifier_block uprobe_exception_nb = {
2294         .notifier_call          = arch_uprobe_exception_notify,
2295         .priority               = INT_MAX-1,    /* notified after kprobes, kgdb */
2296 };
2297 
2298 void __init uprobes_init(void)
2299 {
2300         int i;
2301 
2302         for (i = 0; i < UPROBES_HASH_SZ; i++)
2303                 mutex_init(&uprobes_mmap_mutex[i]);
2304 
2305         BUG_ON(register_die_notifier(&uprobe_exception_nb));
2306 }
2307 

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