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TOMOYO Linux Cross Reference
Linux/kernel/events/uprobes.c

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  1 /*
  2  * User-space Probes (UProbes)
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License as published by
  6  * the Free Software Foundation; either version 2 of the License, or
  7  * (at your option) any later version.
  8  *
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write to the Free Software
 16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 17  *
 18  * Copyright (C) IBM Corporation, 2008-2012
 19  * Authors:
 20  *      Srikar Dronamraju
 21  *      Jim Keniston
 22  * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
 23  */
 24 
 25 #include <linux/kernel.h>
 26 #include <linux/highmem.h>
 27 #include <linux/pagemap.h>      /* read_mapping_page */
 28 #include <linux/slab.h>
 29 #include <linux/sched.h>
 30 #include <linux/sched/mm.h>
 31 #include <linux/sched/coredump.h>
 32 #include <linux/export.h>
 33 #include <linux/rmap.h>         /* anon_vma_prepare */
 34 #include <linux/mmu_notifier.h> /* set_pte_at_notify */
 35 #include <linux/swap.h>         /* try_to_free_swap */
 36 #include <linux/ptrace.h>       /* user_enable_single_step */
 37 #include <linux/kdebug.h>       /* notifier mechanism */
 38 #include "../../mm/internal.h"  /* munlock_vma_page */
 39 #include <linux/percpu-rwsem.h>
 40 #include <linux/task_work.h>
 41 #include <linux/shmem_fs.h>
 42 
 43 #include <linux/uprobes.h>
 44 
 45 #define UINSNS_PER_PAGE                 (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
 46 #define MAX_UPROBE_XOL_SLOTS            UINSNS_PER_PAGE
 47 
 48 static struct rb_root uprobes_tree = RB_ROOT;
 49 /*
 50  * allows us to skip the uprobe_mmap if there are no uprobe events active
 51  * at this time.  Probably a fine grained per inode count is better?
 52  */
 53 #define no_uprobe_events()      RB_EMPTY_ROOT(&uprobes_tree)
 54 
 55 static DEFINE_SPINLOCK(uprobes_treelock);       /* serialize rbtree access */
 56 
 57 #define UPROBES_HASH_SZ 13
 58 /* serialize uprobe->pending_list */
 59 static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
 60 #define uprobes_mmap_hash(v)    (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
 61 
 62 static struct percpu_rw_semaphore dup_mmap_sem;
 63 
 64 /* Have a copy of original instruction */
 65 #define UPROBE_COPY_INSN        0
 66 
 67 struct uprobe {
 68         struct rb_node          rb_node;        /* node in the rb tree */
 69         atomic_t                ref;
 70         struct rw_semaphore     register_rwsem;
 71         struct rw_semaphore     consumer_rwsem;
 72         struct list_head        pending_list;
 73         struct uprobe_consumer  *consumers;
 74         struct inode            *inode;         /* Also hold a ref to inode */
 75         loff_t                  offset;
 76         unsigned long           flags;
 77 
 78         /*
 79          * The generic code assumes that it has two members of unknown type
 80          * owned by the arch-specific code:
 81          *
 82          *      insn -  copy_insn() saves the original instruction here for
 83          *              arch_uprobe_analyze_insn().
 84          *
 85          *      ixol -  potentially modified instruction to execute out of
 86          *              line, copied to xol_area by xol_get_insn_slot().
 87          */
 88         struct arch_uprobe      arch;
 89 };
 90 
 91 /*
 92  * Execute out of line area: anonymous executable mapping installed
 93  * by the probed task to execute the copy of the original instruction
 94  * mangled by set_swbp().
 95  *
 96  * On a breakpoint hit, thread contests for a slot.  It frees the
 97  * slot after singlestep. Currently a fixed number of slots are
 98  * allocated.
 99  */
100 struct xol_area {
101         wait_queue_head_t               wq;             /* if all slots are busy */
102         atomic_t                        slot_count;     /* number of in-use slots */
103         unsigned long                   *bitmap;        /* 0 = free slot */
104 
105         struct vm_special_mapping       xol_mapping;
106         struct page                     *pages[2];
107         /*
108          * We keep the vma's vm_start rather than a pointer to the vma
109          * itself.  The probed process or a naughty kernel module could make
110          * the vma go away, and we must handle that reasonably gracefully.
111          */
112         unsigned long                   vaddr;          /* Page(s) of instruction slots */
113 };
114 
115 /*
116  * valid_vma: Verify if the specified vma is an executable vma
117  * Relax restrictions while unregistering: vm_flags might have
118  * changed after breakpoint was inserted.
119  *      - is_register: indicates if we are in register context.
120  *      - Return 1 if the specified virtual address is in an
121  *        executable vma.
122  */
123 static bool valid_vma(struct vm_area_struct *vma, bool is_register)
124 {
125         vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE;
126 
127         if (is_register)
128                 flags |= VM_WRITE;
129 
130         return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC;
131 }
132 
133 static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset)
134 {
135         return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
136 }
137 
138 static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr)
139 {
140         return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start);
141 }
142 
143 /**
144  * __replace_page - replace page in vma by new page.
145  * based on replace_page in mm/ksm.c
146  *
147  * @vma:      vma that holds the pte pointing to page
148  * @addr:     address the old @page is mapped at
149  * @page:     the cowed page we are replacing by kpage
150  * @kpage:    the modified page we replace page by
151  *
152  * Returns 0 on success, -EFAULT on failure.
153  */
154 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
155                                 struct page *old_page, struct page *new_page)
156 {
157         struct mm_struct *mm = vma->vm_mm;
158         struct page_vma_mapped_walk pvmw = {
159                 .page = old_page,
160                 .vma = vma,
161                 .address = addr,
162         };
163         int err;
164         /* For mmu_notifiers */
165         const unsigned long mmun_start = addr;
166         const unsigned long mmun_end   = addr + PAGE_SIZE;
167         struct mem_cgroup *memcg;
168 
169         VM_BUG_ON_PAGE(PageTransHuge(old_page), old_page);
170 
171         err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
172                         false);
173         if (err)
174                 return err;
175 
176         /* For try_to_free_swap() and munlock_vma_page() below */
177         lock_page(old_page);
178 
179         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
180         err = -EAGAIN;
181         if (!page_vma_mapped_walk(&pvmw)) {
182                 mem_cgroup_cancel_charge(new_page, memcg, false);
183                 goto unlock;
184         }
185         VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
186 
187         get_page(new_page);
188         page_add_new_anon_rmap(new_page, vma, addr, false);
189         mem_cgroup_commit_charge(new_page, memcg, false, false);
190         lru_cache_add_active_or_unevictable(new_page, vma);
191 
192         if (!PageAnon(old_page)) {
193                 dec_mm_counter(mm, mm_counter_file(old_page));
194                 inc_mm_counter(mm, MM_ANONPAGES);
195         }
196 
197         flush_cache_page(vma, addr, pte_pfn(*pvmw.pte));
198         ptep_clear_flush_notify(vma, addr, pvmw.pte);
199         set_pte_at_notify(mm, addr, pvmw.pte,
200                         mk_pte(new_page, vma->vm_page_prot));
201 
202         page_remove_rmap(old_page, false);
203         if (!page_mapped(old_page))
204                 try_to_free_swap(old_page);
205         page_vma_mapped_walk_done(&pvmw);
206 
207         if (vma->vm_flags & VM_LOCKED)
208                 munlock_vma_page(old_page);
209         put_page(old_page);
210 
211         err = 0;
212  unlock:
213         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
214         unlock_page(old_page);
215         return err;
216 }
217 
218 /**
219  * is_swbp_insn - check if instruction is breakpoint instruction.
220  * @insn: instruction to be checked.
221  * Default implementation of is_swbp_insn
222  * Returns true if @insn is a breakpoint instruction.
223  */
224 bool __weak is_swbp_insn(uprobe_opcode_t *insn)
225 {
226         return *insn == UPROBE_SWBP_INSN;
227 }
228 
229 /**
230  * is_trap_insn - check if instruction is breakpoint instruction.
231  * @insn: instruction to be checked.
232  * Default implementation of is_trap_insn
233  * Returns true if @insn is a breakpoint instruction.
234  *
235  * This function is needed for the case where an architecture has multiple
236  * trap instructions (like powerpc).
237  */
238 bool __weak is_trap_insn(uprobe_opcode_t *insn)
239 {
240         return is_swbp_insn(insn);
241 }
242 
243 static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len)
244 {
245         void *kaddr = kmap_atomic(page);
246         memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
247         kunmap_atomic(kaddr);
248 }
249 
250 static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
251 {
252         void *kaddr = kmap_atomic(page);
253         memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
254         kunmap_atomic(kaddr);
255 }
256 
257 static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
258 {
259         uprobe_opcode_t old_opcode;
260         bool is_swbp;
261 
262         /*
263          * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here.
264          * We do not check if it is any other 'trap variant' which could
265          * be conditional trap instruction such as the one powerpc supports.
266          *
267          * The logic is that we do not care if the underlying instruction
268          * is a trap variant; uprobes always wins over any other (gdb)
269          * breakpoint.
270          */
271         copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE);
272         is_swbp = is_swbp_insn(&old_opcode);
273 
274         if (is_swbp_insn(new_opcode)) {
275                 if (is_swbp)            /* register: already installed? */
276                         return 0;
277         } else {
278                 if (!is_swbp)           /* unregister: was it changed by us? */
279                         return 0;
280         }
281 
282         return 1;
283 }
284 
285 /*
286  * NOTE:
287  * Expect the breakpoint instruction to be the smallest size instruction for
288  * the architecture. If an arch has variable length instruction and the
289  * breakpoint instruction is not of the smallest length instruction
290  * supported by that architecture then we need to modify is_trap_at_addr and
291  * uprobe_write_opcode accordingly. This would never be a problem for archs
292  * that have fixed length instructions.
293  *
294  * uprobe_write_opcode - write the opcode at a given virtual address.
295  * @mm: the probed process address space.
296  * @vaddr: the virtual address to store the opcode.
297  * @opcode: opcode to be written at @vaddr.
298  *
299  * Called with mm->mmap_sem held for write.
300  * Return 0 (success) or a negative errno.
301  */
302 int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr,
303                         uprobe_opcode_t opcode)
304 {
305         struct page *old_page, *new_page;
306         struct vm_area_struct *vma;
307         int ret;
308 
309 retry:
310         /* Read the page with vaddr into memory */
311         ret = get_user_pages_remote(NULL, mm, vaddr, 1,
312                         FOLL_FORCE | FOLL_SPLIT, &old_page, &vma, NULL);
313         if (ret <= 0)
314                 return ret;
315 
316         ret = verify_opcode(old_page, vaddr, &opcode);
317         if (ret <= 0)
318                 goto put_old;
319 
320         ret = anon_vma_prepare(vma);
321         if (ret)
322                 goto put_old;
323 
324         ret = -ENOMEM;
325         new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
326         if (!new_page)
327                 goto put_old;
328 
329         __SetPageUptodate(new_page);
330         copy_highpage(new_page, old_page);
331         copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
332 
333         ret = __replace_page(vma, vaddr, old_page, new_page);
334         put_page(new_page);
335 put_old:
336         put_page(old_page);
337 
338         if (unlikely(ret == -EAGAIN))
339                 goto retry;
340         return ret;
341 }
342 
343 /**
344  * set_swbp - store breakpoint at a given address.
345  * @auprobe: arch specific probepoint information.
346  * @mm: the probed process address space.
347  * @vaddr: the virtual address to insert the opcode.
348  *
349  * For mm @mm, store the breakpoint instruction at @vaddr.
350  * Return 0 (success) or a negative errno.
351  */
352 int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
353 {
354         return uprobe_write_opcode(mm, vaddr, UPROBE_SWBP_INSN);
355 }
356 
357 /**
358  * set_orig_insn - Restore the original instruction.
359  * @mm: the probed process address space.
360  * @auprobe: arch specific probepoint information.
361  * @vaddr: the virtual address to insert the opcode.
362  *
363  * For mm @mm, restore the original opcode (opcode) at @vaddr.
364  * Return 0 (success) or a negative errno.
365  */
366 int __weak
367 set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
368 {
369         return uprobe_write_opcode(mm, vaddr, *(uprobe_opcode_t *)&auprobe->insn);
370 }
371 
372 static struct uprobe *get_uprobe(struct uprobe *uprobe)
373 {
374         atomic_inc(&uprobe->ref);
375         return uprobe;
376 }
377 
378 static void put_uprobe(struct uprobe *uprobe)
379 {
380         if (atomic_dec_and_test(&uprobe->ref))
381                 kfree(uprobe);
382 }
383 
384 static int match_uprobe(struct uprobe *l, struct uprobe *r)
385 {
386         if (l->inode < r->inode)
387                 return -1;
388 
389         if (l->inode > r->inode)
390                 return 1;
391 
392         if (l->offset < r->offset)
393                 return -1;
394 
395         if (l->offset > r->offset)
396                 return 1;
397 
398         return 0;
399 }
400 
401 static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
402 {
403         struct uprobe u = { .inode = inode, .offset = offset };
404         struct rb_node *n = uprobes_tree.rb_node;
405         struct uprobe *uprobe;
406         int match;
407 
408         while (n) {
409                 uprobe = rb_entry(n, struct uprobe, rb_node);
410                 match = match_uprobe(&u, uprobe);
411                 if (!match)
412                         return get_uprobe(uprobe);
413 
414                 if (match < 0)
415                         n = n->rb_left;
416                 else
417                         n = n->rb_right;
418         }
419         return NULL;
420 }
421 
422 /*
423  * Find a uprobe corresponding to a given inode:offset
424  * Acquires uprobes_treelock
425  */
426 static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
427 {
428         struct uprobe *uprobe;
429 
430         spin_lock(&uprobes_treelock);
431         uprobe = __find_uprobe(inode, offset);
432         spin_unlock(&uprobes_treelock);
433 
434         return uprobe;
435 }
436 
437 static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
438 {
439         struct rb_node **p = &uprobes_tree.rb_node;
440         struct rb_node *parent = NULL;
441         struct uprobe *u;
442         int match;
443 
444         while (*p) {
445                 parent = *p;
446                 u = rb_entry(parent, struct uprobe, rb_node);
447                 match = match_uprobe(uprobe, u);
448                 if (!match)
449                         return get_uprobe(u);
450 
451                 if (match < 0)
452                         p = &parent->rb_left;
453                 else
454                         p = &parent->rb_right;
455 
456         }
457 
458         u = NULL;
459         rb_link_node(&uprobe->rb_node, parent, p);
460         rb_insert_color(&uprobe->rb_node, &uprobes_tree);
461         /* get access + creation ref */
462         atomic_set(&uprobe->ref, 2);
463 
464         return u;
465 }
466 
467 /*
468  * Acquire uprobes_treelock.
469  * Matching uprobe already exists in rbtree;
470  *      increment (access refcount) and return the matching uprobe.
471  *
472  * No matching uprobe; insert the uprobe in rb_tree;
473  *      get a double refcount (access + creation) and return NULL.
474  */
475 static struct uprobe *insert_uprobe(struct uprobe *uprobe)
476 {
477         struct uprobe *u;
478 
479         spin_lock(&uprobes_treelock);
480         u = __insert_uprobe(uprobe);
481         spin_unlock(&uprobes_treelock);
482 
483         return u;
484 }
485 
486 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
487 {
488         struct uprobe *uprobe, *cur_uprobe;
489 
490         uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
491         if (!uprobe)
492                 return NULL;
493 
494         uprobe->inode = igrab(inode);
495         uprobe->offset = offset;
496         init_rwsem(&uprobe->register_rwsem);
497         init_rwsem(&uprobe->consumer_rwsem);
498 
499         /* add to uprobes_tree, sorted on inode:offset */
500         cur_uprobe = insert_uprobe(uprobe);
501         /* a uprobe exists for this inode:offset combination */
502         if (cur_uprobe) {
503                 kfree(uprobe);
504                 uprobe = cur_uprobe;
505                 iput(inode);
506         }
507 
508         return uprobe;
509 }
510 
511 static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
512 {
513         down_write(&uprobe->consumer_rwsem);
514         uc->next = uprobe->consumers;
515         uprobe->consumers = uc;
516         up_write(&uprobe->consumer_rwsem);
517 }
518 
519 /*
520  * For uprobe @uprobe, delete the consumer @uc.
521  * Return true if the @uc is deleted successfully
522  * or return false.
523  */
524 static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
525 {
526         struct uprobe_consumer **con;
527         bool ret = false;
528 
529         down_write(&uprobe->consumer_rwsem);
530         for (con = &uprobe->consumers; *con; con = &(*con)->next) {
531                 if (*con == uc) {
532                         *con = uc->next;
533                         ret = true;
534                         break;
535                 }
536         }
537         up_write(&uprobe->consumer_rwsem);
538 
539         return ret;
540 }
541 
542 static int __copy_insn(struct address_space *mapping, struct file *filp,
543                         void *insn, int nbytes, loff_t offset)
544 {
545         struct page *page;
546         /*
547          * Ensure that the page that has the original instruction is populated
548          * and in page-cache. If ->readpage == NULL it must be shmem_mapping(),
549          * see uprobe_register().
550          */
551         if (mapping->a_ops->readpage)
552                 page = read_mapping_page(mapping, offset >> PAGE_SHIFT, filp);
553         else
554                 page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
555         if (IS_ERR(page))
556                 return PTR_ERR(page);
557 
558         copy_from_page(page, offset, insn, nbytes);
559         put_page(page);
560 
561         return 0;
562 }
563 
564 static int copy_insn(struct uprobe *uprobe, struct file *filp)
565 {
566         struct address_space *mapping = uprobe->inode->i_mapping;
567         loff_t offs = uprobe->offset;
568         void *insn = &uprobe->arch.insn;
569         int size = sizeof(uprobe->arch.insn);
570         int len, err = -EIO;
571 
572         /* Copy only available bytes, -EIO if nothing was read */
573         do {
574                 if (offs >= i_size_read(uprobe->inode))
575                         break;
576 
577                 len = min_t(int, size, PAGE_SIZE - (offs & ~PAGE_MASK));
578                 err = __copy_insn(mapping, filp, insn, len, offs);
579                 if (err)
580                         break;
581 
582                 insn += len;
583                 offs += len;
584                 size -= len;
585         } while (size);
586 
587         return err;
588 }
589 
590 static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
591                                 struct mm_struct *mm, unsigned long vaddr)
592 {
593         int ret = 0;
594 
595         if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
596                 return ret;
597 
598         /* TODO: move this into _register, until then we abuse this sem. */
599         down_write(&uprobe->consumer_rwsem);
600         if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
601                 goto out;
602 
603         ret = copy_insn(uprobe, file);
604         if (ret)
605                 goto out;
606 
607         ret = -ENOTSUPP;
608         if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn))
609                 goto out;
610 
611         ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
612         if (ret)
613                 goto out;
614 
615         /* uprobe_write_opcode() assumes we don't cross page boundary */
616         BUG_ON((uprobe->offset & ~PAGE_MASK) +
617                         UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
618 
619         smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
620         set_bit(UPROBE_COPY_INSN, &uprobe->flags);
621 
622  out:
623         up_write(&uprobe->consumer_rwsem);
624 
625         return ret;
626 }
627 
628 static inline bool consumer_filter(struct uprobe_consumer *uc,
629                                    enum uprobe_filter_ctx ctx, struct mm_struct *mm)
630 {
631         return !uc->filter || uc->filter(uc, ctx, mm);
632 }
633 
634 static bool filter_chain(struct uprobe *uprobe,
635                          enum uprobe_filter_ctx ctx, struct mm_struct *mm)
636 {
637         struct uprobe_consumer *uc;
638         bool ret = false;
639 
640         down_read(&uprobe->consumer_rwsem);
641         for (uc = uprobe->consumers; uc; uc = uc->next) {
642                 ret = consumer_filter(uc, ctx, mm);
643                 if (ret)
644                         break;
645         }
646         up_read(&uprobe->consumer_rwsem);
647 
648         return ret;
649 }
650 
651 static int
652 install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
653                         struct vm_area_struct *vma, unsigned long vaddr)
654 {
655         bool first_uprobe;
656         int ret;
657 
658         ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
659         if (ret)
660                 return ret;
661 
662         /*
663          * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(),
664          * the task can hit this breakpoint right after __replace_page().
665          */
666         first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags);
667         if (first_uprobe)
668                 set_bit(MMF_HAS_UPROBES, &mm->flags);
669 
670         ret = set_swbp(&uprobe->arch, mm, vaddr);
671         if (!ret)
672                 clear_bit(MMF_RECALC_UPROBES, &mm->flags);
673         else if (first_uprobe)
674                 clear_bit(MMF_HAS_UPROBES, &mm->flags);
675 
676         return ret;
677 }
678 
679 static int
680 remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
681 {
682         set_bit(MMF_RECALC_UPROBES, &mm->flags);
683         return set_orig_insn(&uprobe->arch, mm, vaddr);
684 }
685 
686 static inline bool uprobe_is_active(struct uprobe *uprobe)
687 {
688         return !RB_EMPTY_NODE(&uprobe->rb_node);
689 }
690 /*
691  * There could be threads that have already hit the breakpoint. They
692  * will recheck the current insn and restart if find_uprobe() fails.
693  * See find_active_uprobe().
694  */
695 static void delete_uprobe(struct uprobe *uprobe)
696 {
697         if (WARN_ON(!uprobe_is_active(uprobe)))
698                 return;
699 
700         spin_lock(&uprobes_treelock);
701         rb_erase(&uprobe->rb_node, &uprobes_tree);
702         spin_unlock(&uprobes_treelock);
703         RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
704         iput(uprobe->inode);
705         put_uprobe(uprobe);
706 }
707 
708 struct map_info {
709         struct map_info *next;
710         struct mm_struct *mm;
711         unsigned long vaddr;
712 };
713 
714 static inline struct map_info *free_map_info(struct map_info *info)
715 {
716         struct map_info *next = info->next;
717         kfree(info);
718         return next;
719 }
720 
721 static struct map_info *
722 build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
723 {
724         unsigned long pgoff = offset >> PAGE_SHIFT;
725         struct vm_area_struct *vma;
726         struct map_info *curr = NULL;
727         struct map_info *prev = NULL;
728         struct map_info *info;
729         int more = 0;
730 
731  again:
732         i_mmap_lock_read(mapping);
733         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
734                 if (!valid_vma(vma, is_register))
735                         continue;
736 
737                 if (!prev && !more) {
738                         /*
739                          * Needs GFP_NOWAIT to avoid i_mmap_rwsem recursion through
740                          * reclaim. This is optimistic, no harm done if it fails.
741                          */
742                         prev = kmalloc(sizeof(struct map_info),
743                                         GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
744                         if (prev)
745                                 prev->next = NULL;
746                 }
747                 if (!prev) {
748                         more++;
749                         continue;
750                 }
751 
752                 if (!mmget_not_zero(vma->vm_mm))
753                         continue;
754 
755                 info = prev;
756                 prev = prev->next;
757                 info->next = curr;
758                 curr = info;
759 
760                 info->mm = vma->vm_mm;
761                 info->vaddr = offset_to_vaddr(vma, offset);
762         }
763         i_mmap_unlock_read(mapping);
764 
765         if (!more)
766                 goto out;
767 
768         prev = curr;
769         while (curr) {
770                 mmput(curr->mm);
771                 curr = curr->next;
772         }
773 
774         do {
775                 info = kmalloc(sizeof(struct map_info), GFP_KERNEL);
776                 if (!info) {
777                         curr = ERR_PTR(-ENOMEM);
778                         goto out;
779                 }
780                 info->next = prev;
781                 prev = info;
782         } while (--more);
783 
784         goto again;
785  out:
786         while (prev)
787                 prev = free_map_info(prev);
788         return curr;
789 }
790 
791 static int
792 register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
793 {
794         bool is_register = !!new;
795         struct map_info *info;
796         int err = 0;
797 
798         percpu_down_write(&dup_mmap_sem);
799         info = build_map_info(uprobe->inode->i_mapping,
800                                         uprobe->offset, is_register);
801         if (IS_ERR(info)) {
802                 err = PTR_ERR(info);
803                 goto out;
804         }
805 
806         while (info) {
807                 struct mm_struct *mm = info->mm;
808                 struct vm_area_struct *vma;
809 
810                 if (err && is_register)
811                         goto free;
812 
813                 down_write(&mm->mmap_sem);
814                 vma = find_vma(mm, info->vaddr);
815                 if (!vma || !valid_vma(vma, is_register) ||
816                     file_inode(vma->vm_file) != uprobe->inode)
817                         goto unlock;
818 
819                 if (vma->vm_start > info->vaddr ||
820                     vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
821                         goto unlock;
822 
823                 if (is_register) {
824                         /* consult only the "caller", new consumer. */
825                         if (consumer_filter(new,
826                                         UPROBE_FILTER_REGISTER, mm))
827                                 err = install_breakpoint(uprobe, mm, vma, info->vaddr);
828                 } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
829                         if (!filter_chain(uprobe,
830                                         UPROBE_FILTER_UNREGISTER, mm))
831                                 err |= remove_breakpoint(uprobe, mm, info->vaddr);
832                 }
833 
834  unlock:
835                 up_write(&mm->mmap_sem);
836  free:
837                 mmput(mm);
838                 info = free_map_info(info);
839         }
840  out:
841         percpu_up_write(&dup_mmap_sem);
842         return err;
843 }
844 
845 static int __uprobe_register(struct uprobe *uprobe, struct uprobe_consumer *uc)
846 {
847         consumer_add(uprobe, uc);
848         return register_for_each_vma(uprobe, uc);
849 }
850 
851 static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
852 {
853         int err;
854 
855         if (WARN_ON(!consumer_del(uprobe, uc)))
856                 return;
857 
858         err = register_for_each_vma(uprobe, NULL);
859         /* TODO : cant unregister? schedule a worker thread */
860         if (!uprobe->consumers && !err)
861                 delete_uprobe(uprobe);
862 }
863 
864 /*
865  * uprobe_register - register a probe
866  * @inode: the file in which the probe has to be placed.
867  * @offset: offset from the start of the file.
868  * @uc: information on howto handle the probe..
869  *
870  * Apart from the access refcount, uprobe_register() takes a creation
871  * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
872  * inserted into the rbtree (i.e first consumer for a @inode:@offset
873  * tuple).  Creation refcount stops uprobe_unregister from freeing the
874  * @uprobe even before the register operation is complete. Creation
875  * refcount is released when the last @uc for the @uprobe
876  * unregisters.
877  *
878  * Return errno if it cannot successully install probes
879  * else return 0 (success)
880  */
881 int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
882 {
883         struct uprobe *uprobe;
884         int ret;
885 
886         /* Uprobe must have at least one set consumer */
887         if (!uc->handler && !uc->ret_handler)
888                 return -EINVAL;
889 
890         /* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
891         if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping))
892                 return -EIO;
893         /* Racy, just to catch the obvious mistakes */
894         if (offset > i_size_read(inode))
895                 return -EINVAL;
896 
897  retry:
898         uprobe = alloc_uprobe(inode, offset);
899         if (!uprobe)
900                 return -ENOMEM;
901         /*
902          * We can race with uprobe_unregister()->delete_uprobe().
903          * Check uprobe_is_active() and retry if it is false.
904          */
905         down_write(&uprobe->register_rwsem);
906         ret = -EAGAIN;
907         if (likely(uprobe_is_active(uprobe))) {
908                 ret = __uprobe_register(uprobe, uc);
909                 if (ret)
910                         __uprobe_unregister(uprobe, uc);
911         }
912         up_write(&uprobe->register_rwsem);
913         put_uprobe(uprobe);
914 
915         if (unlikely(ret == -EAGAIN))
916                 goto retry;
917         return ret;
918 }
919 EXPORT_SYMBOL_GPL(uprobe_register);
920 
921 /*
922  * uprobe_apply - unregister a already registered probe.
923  * @inode: the file in which the probe has to be removed.
924  * @offset: offset from the start of the file.
925  * @uc: consumer which wants to add more or remove some breakpoints
926  * @add: add or remove the breakpoints
927  */
928 int uprobe_apply(struct inode *inode, loff_t offset,
929                         struct uprobe_consumer *uc, bool add)
930 {
931         struct uprobe *uprobe;
932         struct uprobe_consumer *con;
933         int ret = -ENOENT;
934 
935         uprobe = find_uprobe(inode, offset);
936         if (WARN_ON(!uprobe))
937                 return ret;
938 
939         down_write(&uprobe->register_rwsem);
940         for (con = uprobe->consumers; con && con != uc ; con = con->next)
941                 ;
942         if (con)
943                 ret = register_for_each_vma(uprobe, add ? uc : NULL);
944         up_write(&uprobe->register_rwsem);
945         put_uprobe(uprobe);
946 
947         return ret;
948 }
949 
950 /*
951  * uprobe_unregister - unregister a already registered probe.
952  * @inode: the file in which the probe has to be removed.
953  * @offset: offset from the start of the file.
954  * @uc: identify which probe if multiple probes are colocated.
955  */
956 void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
957 {
958         struct uprobe *uprobe;
959 
960         uprobe = find_uprobe(inode, offset);
961         if (WARN_ON(!uprobe))
962                 return;
963 
964         down_write(&uprobe->register_rwsem);
965         __uprobe_unregister(uprobe, uc);
966         up_write(&uprobe->register_rwsem);
967         put_uprobe(uprobe);
968 }
969 EXPORT_SYMBOL_GPL(uprobe_unregister);
970 
971 static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
972 {
973         struct vm_area_struct *vma;
974         int err = 0;
975 
976         down_read(&mm->mmap_sem);
977         for (vma = mm->mmap; vma; vma = vma->vm_next) {
978                 unsigned long vaddr;
979                 loff_t offset;
980 
981                 if (!valid_vma(vma, false) ||
982                     file_inode(vma->vm_file) != uprobe->inode)
983                         continue;
984 
985                 offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
986                 if (uprobe->offset <  offset ||
987                     uprobe->offset >= offset + vma->vm_end - vma->vm_start)
988                         continue;
989 
990                 vaddr = offset_to_vaddr(vma, uprobe->offset);
991                 err |= remove_breakpoint(uprobe, mm, vaddr);
992         }
993         up_read(&mm->mmap_sem);
994 
995         return err;
996 }
997 
998 static struct rb_node *
999 find_node_in_range(struct inode *inode, loff_t min, loff_t max)
1000 {
1001         struct rb_node *n = uprobes_tree.rb_node;
1002 
1003         while (n) {
1004                 struct uprobe *u = rb_entry(n, struct uprobe, rb_node);
1005 
1006                 if (inode < u->inode) {
1007                         n = n->rb_left;
1008                 } else if (inode > u->inode) {
1009                         n = n->rb_right;
1010                 } else {
1011                         if (max < u->offset)
1012                                 n = n->rb_left;
1013                         else if (min > u->offset)
1014                                 n = n->rb_right;
1015                         else
1016                                 break;
1017                 }
1018         }
1019 
1020         return n;
1021 }
1022 
1023 /*
1024  * For a given range in vma, build a list of probes that need to be inserted.
1025  */
1026 static void build_probe_list(struct inode *inode,
1027                                 struct vm_area_struct *vma,
1028                                 unsigned long start, unsigned long end,
1029                                 struct list_head *head)
1030 {
1031         loff_t min, max;
1032         struct rb_node *n, *t;
1033         struct uprobe *u;
1034 
1035         INIT_LIST_HEAD(head);
1036         min = vaddr_to_offset(vma, start);
1037         max = min + (end - start) - 1;
1038 
1039         spin_lock(&uprobes_treelock);
1040         n = find_node_in_range(inode, min, max);
1041         if (n) {
1042                 for (t = n; t; t = rb_prev(t)) {
1043                         u = rb_entry(t, struct uprobe, rb_node);
1044                         if (u->inode != inode || u->offset < min)
1045                                 break;
1046                         list_add(&u->pending_list, head);
1047                         get_uprobe(u);
1048                 }
1049                 for (t = n; (t = rb_next(t)); ) {
1050                         u = rb_entry(t, struct uprobe, rb_node);
1051                         if (u->inode != inode || u->offset > max)
1052                                 break;
1053                         list_add(&u->pending_list, head);
1054                         get_uprobe(u);
1055                 }
1056         }
1057         spin_unlock(&uprobes_treelock);
1058 }
1059 
1060 /*
1061  * Called from mmap_region/vma_adjust with mm->mmap_sem acquired.
1062  *
1063  * Currently we ignore all errors and always return 0, the callers
1064  * can't handle the failure anyway.
1065  */
1066 int uprobe_mmap(struct vm_area_struct *vma)
1067 {
1068         struct list_head tmp_list;
1069         struct uprobe *uprobe, *u;
1070         struct inode *inode;
1071 
1072         if (no_uprobe_events() || !valid_vma(vma, true))
1073                 return 0;
1074 
1075         inode = file_inode(vma->vm_file);
1076         if (!inode)
1077                 return 0;
1078 
1079         mutex_lock(uprobes_mmap_hash(inode));
1080         build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
1081         /*
1082          * We can race with uprobe_unregister(), this uprobe can be already
1083          * removed. But in this case filter_chain() must return false, all
1084          * consumers have gone away.
1085          */
1086         list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1087                 if (!fatal_signal_pending(current) &&
1088                     filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
1089                         unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
1090                         install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1091                 }
1092                 put_uprobe(uprobe);
1093         }
1094         mutex_unlock(uprobes_mmap_hash(inode));
1095 
1096         return 0;
1097 }
1098 
1099 static bool
1100 vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1101 {
1102         loff_t min, max;
1103         struct inode *inode;
1104         struct rb_node *n;
1105 
1106         inode = file_inode(vma->vm_file);
1107 
1108         min = vaddr_to_offset(vma, start);
1109         max = min + (end - start) - 1;
1110 
1111         spin_lock(&uprobes_treelock);
1112         n = find_node_in_range(inode, min, max);
1113         spin_unlock(&uprobes_treelock);
1114 
1115         return !!n;
1116 }
1117 
1118 /*
1119  * Called in context of a munmap of a vma.
1120  */
1121 void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1122 {
1123         if (no_uprobe_events() || !valid_vma(vma, false))
1124                 return;
1125 
1126         if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
1127                 return;
1128 
1129         if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) ||
1130              test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags))
1131                 return;
1132 
1133         if (vma_has_uprobes(vma, start, end))
1134                 set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags);
1135 }
1136 
1137 /* Slot allocation for XOL */
1138 static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
1139 {
1140         struct vm_area_struct *vma;
1141         int ret;
1142 
1143         if (down_write_killable(&mm->mmap_sem))
1144                 return -EINTR;
1145 
1146         if (mm->uprobes_state.xol_area) {
1147                 ret = -EALREADY;
1148                 goto fail;
1149         }
1150 
1151         if (!area->vaddr) {
1152                 /* Try to map as high as possible, this is only a hint. */
1153                 area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE,
1154                                                 PAGE_SIZE, 0, 0);
1155                 if (area->vaddr & ~PAGE_MASK) {
1156                         ret = area->vaddr;
1157                         goto fail;
1158                 }
1159         }
1160 
1161         vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1162                                 VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
1163                                 &area->xol_mapping);
1164         if (IS_ERR(vma)) {
1165                 ret = PTR_ERR(vma);
1166                 goto fail;
1167         }
1168 
1169         ret = 0;
1170         smp_wmb();      /* pairs with get_xol_area() */
1171         mm->uprobes_state.xol_area = area;
1172  fail:
1173         up_write(&mm->mmap_sem);
1174 
1175         return ret;
1176 }
1177 
1178 static struct xol_area *__create_xol_area(unsigned long vaddr)
1179 {
1180         struct mm_struct *mm = current->mm;
1181         uprobe_opcode_t insn = UPROBE_SWBP_INSN;
1182         struct xol_area *area;
1183 
1184         area = kmalloc(sizeof(*area), GFP_KERNEL);
1185         if (unlikely(!area))
1186                 goto out;
1187 
1188         area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL);
1189         if (!area->bitmap)
1190                 goto free_area;
1191 
1192         area->xol_mapping.name = "[uprobes]";
1193         area->xol_mapping.fault = NULL;
1194         area->xol_mapping.pages = area->pages;
1195         area->pages[0] = alloc_page(GFP_HIGHUSER);
1196         if (!area->pages[0])
1197                 goto free_bitmap;
1198         area->pages[1] = NULL;
1199 
1200         area->vaddr = vaddr;
1201         init_waitqueue_head(&area->wq);
1202         /* Reserve the 1st slot for get_trampoline_vaddr() */
1203         set_bit(0, area->bitmap);
1204         atomic_set(&area->slot_count, 1);
1205         arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE);
1206 
1207         if (!xol_add_vma(mm, area))
1208                 return area;
1209 
1210         __free_page(area->pages[0]);
1211  free_bitmap:
1212         kfree(area->bitmap);
1213  free_area:
1214         kfree(area);
1215  out:
1216         return NULL;
1217 }
1218 
1219 /*
1220  * get_xol_area - Allocate process's xol_area if necessary.
1221  * This area will be used for storing instructions for execution out of line.
1222  *
1223  * Returns the allocated area or NULL.
1224  */
1225 static struct xol_area *get_xol_area(void)
1226 {
1227         struct mm_struct *mm = current->mm;
1228         struct xol_area *area;
1229 
1230         if (!mm->uprobes_state.xol_area)
1231                 __create_xol_area(0);
1232 
1233         area = mm->uprobes_state.xol_area;
1234         smp_read_barrier_depends();     /* pairs with wmb in xol_add_vma() */
1235         return area;
1236 }
1237 
1238 /*
1239  * uprobe_clear_state - Free the area allocated for slots.
1240  */
1241 void uprobe_clear_state(struct mm_struct *mm)
1242 {
1243         struct xol_area *area = mm->uprobes_state.xol_area;
1244 
1245         if (!area)
1246                 return;
1247 
1248         put_page(area->pages[0]);
1249         kfree(area->bitmap);
1250         kfree(area);
1251 }
1252 
1253 void uprobe_start_dup_mmap(void)
1254 {
1255         percpu_down_read(&dup_mmap_sem);
1256 }
1257 
1258 void uprobe_end_dup_mmap(void)
1259 {
1260         percpu_up_read(&dup_mmap_sem);
1261 }
1262 
1263 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
1264 {
1265         if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) {
1266                 set_bit(MMF_HAS_UPROBES, &newmm->flags);
1267                 /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */
1268                 set_bit(MMF_RECALC_UPROBES, &newmm->flags);
1269         }
1270 }
1271 
1272 /*
1273  *  - search for a free slot.
1274  */
1275 static unsigned long xol_take_insn_slot(struct xol_area *area)
1276 {
1277         unsigned long slot_addr;
1278         int slot_nr;
1279 
1280         do {
1281                 slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1282                 if (slot_nr < UINSNS_PER_PAGE) {
1283                         if (!test_and_set_bit(slot_nr, area->bitmap))
1284                                 break;
1285 
1286                         slot_nr = UINSNS_PER_PAGE;
1287                         continue;
1288                 }
1289                 wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1290         } while (slot_nr >= UINSNS_PER_PAGE);
1291 
1292         slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1293         atomic_inc(&area->slot_count);
1294 
1295         return slot_addr;
1296 }
1297 
1298 /*
1299  * xol_get_insn_slot - allocate a slot for xol.
1300  * Returns the allocated slot address or 0.
1301  */
1302 static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
1303 {
1304         struct xol_area *area;
1305         unsigned long xol_vaddr;
1306 
1307         area = get_xol_area();
1308         if (!area)
1309                 return 0;
1310 
1311         xol_vaddr = xol_take_insn_slot(area);
1312         if (unlikely(!xol_vaddr))
1313                 return 0;
1314 
1315         arch_uprobe_copy_ixol(area->pages[0], xol_vaddr,
1316                               &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
1317 
1318         return xol_vaddr;
1319 }
1320 
1321 /*
1322  * xol_free_insn_slot - If slot was earlier allocated by
1323  * @xol_get_insn_slot(), make the slot available for
1324  * subsequent requests.
1325  */
1326 static void xol_free_insn_slot(struct task_struct *tsk)
1327 {
1328         struct xol_area *area;
1329         unsigned long vma_end;
1330         unsigned long slot_addr;
1331 
1332         if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1333                 return;
1334 
1335         slot_addr = tsk->utask->xol_vaddr;
1336         if (unlikely(!slot_addr))
1337                 return;
1338 
1339         area = tsk->mm->uprobes_state.xol_area;
1340         vma_end = area->vaddr + PAGE_SIZE;
1341         if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1342                 unsigned long offset;
1343                 int slot_nr;
1344 
1345                 offset = slot_addr - area->vaddr;
1346                 slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1347                 if (slot_nr >= UINSNS_PER_PAGE)
1348                         return;
1349 
1350                 clear_bit(slot_nr, area->bitmap);
1351                 atomic_dec(&area->slot_count);
1352                 smp_mb__after_atomic(); /* pairs with prepare_to_wait() */
1353                 if (waitqueue_active(&area->wq))
1354                         wake_up(&area->wq);
1355 
1356                 tsk->utask->xol_vaddr = 0;
1357         }
1358 }
1359 
1360 void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
1361                                   void *src, unsigned long len)
1362 {
1363         /* Initialize the slot */
1364         copy_to_page(page, vaddr, src, len);
1365 
1366         /*
1367          * We probably need flush_icache_user_range() but it needs vma.
1368          * This should work on most of architectures by default. If
1369          * architecture needs to do something different it can define
1370          * its own version of the function.
1371          */
1372         flush_dcache_page(page);
1373 }
1374 
1375 /**
1376  * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1377  * @regs: Reflects the saved state of the task after it has hit a breakpoint
1378  * instruction.
1379  * Return the address of the breakpoint instruction.
1380  */
1381 unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1382 {
1383         return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1384 }
1385 
1386 unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
1387 {
1388         struct uprobe_task *utask = current->utask;
1389 
1390         if (unlikely(utask && utask->active_uprobe))
1391                 return utask->vaddr;
1392 
1393         return instruction_pointer(regs);
1394 }
1395 
1396 static struct return_instance *free_ret_instance(struct return_instance *ri)
1397 {
1398         struct return_instance *next = ri->next;
1399         put_uprobe(ri->uprobe);
1400         kfree(ri);
1401         return next;
1402 }
1403 
1404 /*
1405  * Called with no locks held.
1406  * Called in context of a exiting or a exec-ing thread.
1407  */
1408 void uprobe_free_utask(struct task_struct *t)
1409 {
1410         struct uprobe_task *utask = t->utask;
1411         struct return_instance *ri;
1412 
1413         if (!utask)
1414                 return;
1415 
1416         if (utask->active_uprobe)
1417                 put_uprobe(utask->active_uprobe);
1418 
1419         ri = utask->return_instances;
1420         while (ri)
1421                 ri = free_ret_instance(ri);
1422 
1423         xol_free_insn_slot(t);
1424         kfree(utask);
1425         t->utask = NULL;
1426 }
1427 
1428 /*
1429  * Allocate a uprobe_task object for the task if if necessary.
1430  * Called when the thread hits a breakpoint.
1431  *
1432  * Returns:
1433  * - pointer to new uprobe_task on success
1434  * - NULL otherwise
1435  */
1436 static struct uprobe_task *get_utask(void)
1437 {
1438         if (!current->utask)
1439                 current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1440         return current->utask;
1441 }
1442 
1443 static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask)
1444 {
1445         struct uprobe_task *n_utask;
1446         struct return_instance **p, *o, *n;
1447 
1448         n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
1449         if (!n_utask)
1450                 return -ENOMEM;
1451         t->utask = n_utask;
1452 
1453         p = &n_utask->return_instances;
1454         for (o = o_utask->return_instances; o; o = o->next) {
1455                 n = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1456                 if (!n)
1457                         return -ENOMEM;
1458 
1459                 *n = *o;
1460                 get_uprobe(n->uprobe);
1461                 n->next = NULL;
1462 
1463                 *p = n;
1464                 p = &n->next;
1465                 n_utask->depth++;
1466         }
1467 
1468         return 0;
1469 }
1470 
1471 static void uprobe_warn(struct task_struct *t, const char *msg)
1472 {
1473         pr_warn("uprobe: %s:%d failed to %s\n",
1474                         current->comm, current->pid, msg);
1475 }
1476 
1477 static void dup_xol_work(struct callback_head *work)
1478 {
1479         if (current->flags & PF_EXITING)
1480                 return;
1481 
1482         if (!__create_xol_area(current->utask->dup_xol_addr) &&
1483                         !fatal_signal_pending(current))
1484                 uprobe_warn(current, "dup xol area");
1485 }
1486 
1487 /*
1488  * Called in context of a new clone/fork from copy_process.
1489  */
1490 void uprobe_copy_process(struct task_struct *t, unsigned long flags)
1491 {
1492         struct uprobe_task *utask = current->utask;
1493         struct mm_struct *mm = current->mm;
1494         struct xol_area *area;
1495 
1496         t->utask = NULL;
1497 
1498         if (!utask || !utask->return_instances)
1499                 return;
1500 
1501         if (mm == t->mm && !(flags & CLONE_VFORK))
1502                 return;
1503 
1504         if (dup_utask(t, utask))
1505                 return uprobe_warn(t, "dup ret instances");
1506 
1507         /* The task can fork() after dup_xol_work() fails */
1508         area = mm->uprobes_state.xol_area;
1509         if (!area)
1510                 return uprobe_warn(t, "dup xol area");
1511 
1512         if (mm == t->mm)
1513                 return;
1514 
1515         t->utask->dup_xol_addr = area->vaddr;
1516         init_task_work(&t->utask->dup_xol_work, dup_xol_work);
1517         task_work_add(t, &t->utask->dup_xol_work, true);
1518 }
1519 
1520 /*
1521  * Current area->vaddr notion assume the trampoline address is always
1522  * equal area->vaddr.
1523  *
1524  * Returns -1 in case the xol_area is not allocated.
1525  */
1526 static unsigned long get_trampoline_vaddr(void)
1527 {
1528         struct xol_area *area;
1529         unsigned long trampoline_vaddr = -1;
1530 
1531         area = current->mm->uprobes_state.xol_area;
1532         smp_read_barrier_depends();
1533         if (area)
1534                 trampoline_vaddr = area->vaddr;
1535 
1536         return trampoline_vaddr;
1537 }
1538 
1539 static void cleanup_return_instances(struct uprobe_task *utask, bool chained,
1540                                         struct pt_regs *regs)
1541 {
1542         struct return_instance *ri = utask->return_instances;
1543         enum rp_check ctx = chained ? RP_CHECK_CHAIN_CALL : RP_CHECK_CALL;
1544 
1545         while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
1546                 ri = free_ret_instance(ri);
1547                 utask->depth--;
1548         }
1549         utask->return_instances = ri;
1550 }
1551 
1552 static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
1553 {
1554         struct return_instance *ri;
1555         struct uprobe_task *utask;
1556         unsigned long orig_ret_vaddr, trampoline_vaddr;
1557         bool chained;
1558 
1559         if (!get_xol_area())
1560                 return;
1561 
1562         utask = get_utask();
1563         if (!utask)
1564                 return;
1565 
1566         if (utask->depth >= MAX_URETPROBE_DEPTH) {
1567                 printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to"
1568                                 " nestedness limit pid/tgid=%d/%d\n",
1569                                 current->pid, current->tgid);
1570                 return;
1571         }
1572 
1573         ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
1574         if (!ri)
1575                 return;
1576 
1577         trampoline_vaddr = get_trampoline_vaddr();
1578         orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
1579         if (orig_ret_vaddr == -1)
1580                 goto fail;
1581 
1582         /* drop the entries invalidated by longjmp() */
1583         chained = (orig_ret_vaddr == trampoline_vaddr);
1584         cleanup_return_instances(utask, chained, regs);
1585 
1586         /*
1587          * We don't want to keep trampoline address in stack, rather keep the
1588          * original return address of first caller thru all the consequent
1589          * instances. This also makes breakpoint unwrapping easier.
1590          */
1591         if (chained) {
1592                 if (!utask->return_instances) {
1593                         /*
1594                          * This situation is not possible. Likely we have an
1595                          * attack from user-space.
1596                          */
1597                         uprobe_warn(current, "handle tail call");
1598                         goto fail;
1599                 }
1600                 orig_ret_vaddr = utask->return_instances->orig_ret_vaddr;
1601         }
1602 
1603         ri->uprobe = get_uprobe(uprobe);
1604         ri->func = instruction_pointer(regs);
1605         ri->stack = user_stack_pointer(regs);
1606         ri->orig_ret_vaddr = orig_ret_vaddr;
1607         ri->chained = chained;
1608 
1609         utask->depth++;
1610         ri->next = utask->return_instances;
1611         utask->return_instances = ri;
1612 
1613         return;
1614  fail:
1615         kfree(ri);
1616 }
1617 
1618 /* Prepare to single-step probed instruction out of line. */
1619 static int
1620 pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
1621 {
1622         struct uprobe_task *utask;
1623         unsigned long xol_vaddr;
1624         int err;
1625 
1626         utask = get_utask();
1627         if (!utask)
1628                 return -ENOMEM;
1629 
1630         xol_vaddr = xol_get_insn_slot(uprobe);
1631         if (!xol_vaddr)
1632                 return -ENOMEM;
1633 
1634         utask->xol_vaddr = xol_vaddr;
1635         utask->vaddr = bp_vaddr;
1636 
1637         err = arch_uprobe_pre_xol(&uprobe->arch, regs);
1638         if (unlikely(err)) {
1639                 xol_free_insn_slot(current);
1640                 return err;
1641         }
1642 
1643         utask->active_uprobe = uprobe;
1644         utask->state = UTASK_SSTEP;
1645         return 0;
1646 }
1647 
1648 /*
1649  * If we are singlestepping, then ensure this thread is not connected to
1650  * non-fatal signals until completion of singlestep.  When xol insn itself
1651  * triggers the signal,  restart the original insn even if the task is
1652  * already SIGKILL'ed (since coredump should report the correct ip).  This
1653  * is even more important if the task has a handler for SIGSEGV/etc, The
1654  * _same_ instruction should be repeated again after return from the signal
1655  * handler, and SSTEP can never finish in this case.
1656  */
1657 bool uprobe_deny_signal(void)
1658 {
1659         struct task_struct *t = current;
1660         struct uprobe_task *utask = t->utask;
1661 
1662         if (likely(!utask || !utask->active_uprobe))
1663                 return false;
1664 
1665         WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1666 
1667         if (signal_pending(t)) {
1668                 spin_lock_irq(&t->sighand->siglock);
1669                 clear_tsk_thread_flag(t, TIF_SIGPENDING);
1670                 spin_unlock_irq(&t->sighand->siglock);
1671 
1672                 if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1673                         utask->state = UTASK_SSTEP_TRAPPED;
1674                         set_tsk_thread_flag(t, TIF_UPROBE);
1675                 }
1676         }
1677 
1678         return true;
1679 }
1680 
1681 static void mmf_recalc_uprobes(struct mm_struct *mm)
1682 {
1683         struct vm_area_struct *vma;
1684 
1685         for (vma = mm->mmap; vma; vma = vma->vm_next) {
1686                 if (!valid_vma(vma, false))
1687                         continue;
1688                 /*
1689                  * This is not strictly accurate, we can race with
1690                  * uprobe_unregister() and see the already removed
1691                  * uprobe if delete_uprobe() was not yet called.
1692                  * Or this uprobe can be filtered out.
1693                  */
1694                 if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
1695                         return;
1696         }
1697 
1698         clear_bit(MMF_HAS_UPROBES, &mm->flags);
1699 }
1700 
1701 static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
1702 {
1703         struct page *page;
1704         uprobe_opcode_t opcode;
1705         int result;
1706 
1707         pagefault_disable();
1708         result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
1709         pagefault_enable();
1710 
1711         if (likely(result == 0))
1712                 goto out;
1713 
1714         /*
1715          * The NULL 'tsk' here ensures that any faults that occur here
1716          * will not be accounted to the task.  'mm' *is* current->mm,
1717          * but we treat this as a 'remote' access since it is
1718          * essentially a kernel access to the memory.
1719          */
1720         result = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &page,
1721                         NULL, NULL);
1722         if (result < 0)
1723                 return result;
1724 
1725         copy_from_page(page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
1726         put_page(page);
1727  out:
1728         /* This needs to return true for any variant of the trap insn */
1729         return is_trap_insn(&opcode);
1730 }
1731 
1732 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
1733 {
1734         struct mm_struct *mm = current->mm;
1735         struct uprobe *uprobe = NULL;
1736         struct vm_area_struct *vma;
1737 
1738         down_read(&mm->mmap_sem);
1739         vma = find_vma(mm, bp_vaddr);
1740         if (vma && vma->vm_start <= bp_vaddr) {
1741                 if (valid_vma(vma, false)) {
1742                         struct inode *inode = file_inode(vma->vm_file);
1743                         loff_t offset = vaddr_to_offset(vma, bp_vaddr);
1744 
1745                         uprobe = find_uprobe(inode, offset);
1746                 }
1747 
1748                 if (!uprobe)
1749                         *is_swbp = is_trap_at_addr(mm, bp_vaddr);
1750         } else {
1751                 *is_swbp = -EFAULT;
1752         }
1753 
1754         if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
1755                 mmf_recalc_uprobes(mm);
1756         up_read(&mm->mmap_sem);
1757 
1758         return uprobe;
1759 }
1760 
1761 static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
1762 {
1763         struct uprobe_consumer *uc;
1764         int remove = UPROBE_HANDLER_REMOVE;
1765         bool need_prep = false; /* prepare return uprobe, when needed */
1766 
1767         down_read(&uprobe->register_rwsem);
1768         for (uc = uprobe->consumers; uc; uc = uc->next) {
1769                 int rc = 0;
1770 
1771                 if (uc->handler) {
1772                         rc = uc->handler(uc, regs);
1773                         WARN(rc & ~UPROBE_HANDLER_MASK,
1774                                 "bad rc=0x%x from %pf()\n", rc, uc->handler);
1775                 }
1776 
1777                 if (uc->ret_handler)
1778                         need_prep = true;
1779 
1780                 remove &= rc;
1781         }
1782 
1783         if (need_prep && !remove)
1784                 prepare_uretprobe(uprobe, regs); /* put bp at return */
1785 
1786         if (remove && uprobe->consumers) {
1787                 WARN_ON(!uprobe_is_active(uprobe));
1788                 unapply_uprobe(uprobe, current->mm);
1789         }
1790         up_read(&uprobe->register_rwsem);
1791 }
1792 
1793 static void
1794 handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
1795 {
1796         struct uprobe *uprobe = ri->uprobe;
1797         struct uprobe_consumer *uc;
1798 
1799         down_read(&uprobe->register_rwsem);
1800         for (uc = uprobe->consumers; uc; uc = uc->next) {
1801                 if (uc->ret_handler)
1802                         uc->ret_handler(uc, ri->func, regs);
1803         }
1804         up_read(&uprobe->register_rwsem);
1805 }
1806 
1807 static struct return_instance *find_next_ret_chain(struct return_instance *ri)
1808 {
1809         bool chained;
1810 
1811         do {
1812                 chained = ri->chained;
1813                 ri = ri->next;  /* can't be NULL if chained */
1814         } while (chained);
1815 
1816         return ri;
1817 }
1818 
1819 static void handle_trampoline(struct pt_regs *regs)
1820 {
1821         struct uprobe_task *utask;
1822         struct return_instance *ri, *next;
1823         bool valid;
1824 
1825         utask = current->utask;
1826         if (!utask)
1827                 goto sigill;
1828 
1829         ri = utask->return_instances;
1830         if (!ri)
1831                 goto sigill;
1832 
1833         do {
1834                 /*
1835                  * We should throw out the frames invalidated by longjmp().
1836                  * If this chain is valid, then the next one should be alive
1837                  * or NULL; the latter case means that nobody but ri->func
1838                  * could hit this trampoline on return. TODO: sigaltstack().
1839                  */
1840                 next = find_next_ret_chain(ri);
1841                 valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
1842 
1843                 instruction_pointer_set(regs, ri->orig_ret_vaddr);
1844                 do {
1845                         if (valid)
1846                                 handle_uretprobe_chain(ri, regs);
1847                         ri = free_ret_instance(ri);
1848                         utask->depth--;
1849                 } while (ri != next);
1850         } while (!valid);
1851 
1852         utask->return_instances = ri;
1853         return;
1854 
1855  sigill:
1856         uprobe_warn(current, "handle uretprobe, sending SIGILL.");
1857         force_sig_info(SIGILL, SEND_SIG_FORCED, current);
1858 
1859 }
1860 
1861 bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
1862 {
1863         return false;
1864 }
1865 
1866 bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
1867                                         struct pt_regs *regs)
1868 {
1869         return true;
1870 }
1871 
1872 /*
1873  * Run handler and ask thread to singlestep.
1874  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
1875  */
1876 static void handle_swbp(struct pt_regs *regs)
1877 {
1878         struct uprobe *uprobe;
1879         unsigned long bp_vaddr;
1880         int uninitialized_var(is_swbp);
1881 
1882         bp_vaddr = uprobe_get_swbp_addr(regs);
1883         if (bp_vaddr == get_trampoline_vaddr())
1884                 return handle_trampoline(regs);
1885 
1886         uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
1887         if (!uprobe) {
1888                 if (is_swbp > 0) {
1889                         /* No matching uprobe; signal SIGTRAP. */
1890                         send_sig(SIGTRAP, current, 0);
1891                 } else {
1892                         /*
1893                          * Either we raced with uprobe_unregister() or we can't
1894                          * access this memory. The latter is only possible if
1895                          * another thread plays with our ->mm. In both cases
1896                          * we can simply restart. If this vma was unmapped we
1897                          * can pretend this insn was not executed yet and get
1898                          * the (correct) SIGSEGV after restart.
1899                          */
1900                         instruction_pointer_set(regs, bp_vaddr);
1901                 }
1902                 return;
1903         }
1904 
1905         /* change it in advance for ->handler() and restart */
1906         instruction_pointer_set(regs, bp_vaddr);
1907 
1908         /*
1909          * TODO: move copy_insn/etc into _register and remove this hack.
1910          * After we hit the bp, _unregister + _register can install the
1911          * new and not-yet-analyzed uprobe at the same address, restart.
1912          */
1913         smp_rmb(); /* pairs with wmb() in install_breakpoint() */
1914         if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
1915                 goto out;
1916 
1917         /* Tracing handlers use ->utask to communicate with fetch methods */
1918         if (!get_utask())
1919                 goto out;
1920 
1921         if (arch_uprobe_ignore(&uprobe->arch, regs))
1922                 goto out;
1923 
1924         handler_chain(uprobe, regs);
1925 
1926         if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
1927                 goto out;
1928 
1929         if (!pre_ssout(uprobe, regs, bp_vaddr))
1930                 return;
1931 
1932         /* arch_uprobe_skip_sstep() succeeded, or restart if can't singlestep */
1933 out:
1934         put_uprobe(uprobe);
1935 }
1936 
1937 /*
1938  * Perform required fix-ups and disable singlestep.
1939  * Allow pending signals to take effect.
1940  */
1941 static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
1942 {
1943         struct uprobe *uprobe;
1944         int err = 0;
1945 
1946         uprobe = utask->active_uprobe;
1947         if (utask->state == UTASK_SSTEP_ACK)
1948                 err = arch_uprobe_post_xol(&uprobe->arch, regs);
1949         else if (utask->state == UTASK_SSTEP_TRAPPED)
1950                 arch_uprobe_abort_xol(&uprobe->arch, regs);
1951         else
1952                 WARN_ON_ONCE(1);
1953 
1954         put_uprobe(uprobe);
1955         utask->active_uprobe = NULL;
1956         utask->state = UTASK_RUNNING;
1957         xol_free_insn_slot(current);
1958 
1959         spin_lock_irq(&current->sighand->siglock);
1960         recalc_sigpending(); /* see uprobe_deny_signal() */
1961         spin_unlock_irq(&current->sighand->siglock);
1962 
1963         if (unlikely(err)) {
1964                 uprobe_warn(current, "execute the probed insn, sending SIGILL.");
1965                 force_sig_info(SIGILL, SEND_SIG_FORCED, current);
1966         }
1967 }
1968 
1969 /*
1970  * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
1971  * allows the thread to return from interrupt. After that handle_swbp()
1972  * sets utask->active_uprobe.
1973  *
1974  * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
1975  * and allows the thread to return from interrupt.
1976  *
1977  * While returning to userspace, thread notices the TIF_UPROBE flag and calls
1978  * uprobe_notify_resume().
1979  */
1980 void uprobe_notify_resume(struct pt_regs *regs)
1981 {
1982         struct uprobe_task *utask;
1983 
1984         clear_thread_flag(TIF_UPROBE);
1985 
1986         utask = current->utask;
1987         if (utask && utask->active_uprobe)
1988                 handle_singlestep(utask, regs);
1989         else
1990                 handle_swbp(regs);
1991 }
1992 
1993 /*
1994  * uprobe_pre_sstep_notifier gets called from interrupt context as part of
1995  * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
1996  */
1997 int uprobe_pre_sstep_notifier(struct pt_regs *regs)
1998 {
1999         if (!current->mm)
2000                 return 0;
2001 
2002         if (!test_bit(MMF_HAS_UPROBES, &current->mm->flags) &&
2003             (!current->utask || !current->utask->return_instances))
2004                 return 0;
2005 
2006         set_thread_flag(TIF_UPROBE);
2007         return 1;
2008 }
2009 
2010 /*
2011  * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
2012  * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
2013  */
2014 int uprobe_post_sstep_notifier(struct pt_regs *regs)
2015 {
2016         struct uprobe_task *utask = current->utask;
2017 
2018         if (!current->mm || !utask || !utask->active_uprobe)
2019                 /* task is currently not uprobed */
2020                 return 0;
2021 
2022         utask->state = UTASK_SSTEP_ACK;
2023         set_thread_flag(TIF_UPROBE);
2024         return 1;
2025 }
2026 
2027 static struct notifier_block uprobe_exception_nb = {
2028         .notifier_call          = arch_uprobe_exception_notify,
2029         .priority               = INT_MAX-1,    /* notified after kprobes, kgdb */
2030 };
2031 
2032 static int __init init_uprobes(void)
2033 {
2034         int i;
2035 
2036         for (i = 0; i < UPROBES_HASH_SZ; i++)
2037                 mutex_init(&uprobes_mmap_mutex[i]);
2038 
2039         if (percpu_init_rwsem(&dup_mmap_sem))
2040                 return -ENOMEM;
2041 
2042         return register_die_notifier(&uprobe_exception_nb);
2043 }
2044 __initcall(init_uprobes);
2045 

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