Root/kernel/events/uprobes.c

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 <pzijlstr@redhat.com>
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/rmap.h> /* anon_vma_prepare */
31#include <linux/mmu_notifier.h> /* set_pte_at_notify */
32#include <linux/swap.h> /* try_to_free_swap */
33#include <linux/ptrace.h> /* user_enable_single_step */
34#include <linux/kdebug.h> /* notifier mechanism */
35
36#include <linux/uprobes.h>
37
38#define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
39#define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
40
41static struct srcu_struct uprobes_srcu;
42static struct rb_root uprobes_tree = RB_ROOT;
43
44static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
45
46#define UPROBES_HASH_SZ 13
47
48/* serialize (un)register */
49static struct mutex uprobes_mutex[UPROBES_HASH_SZ];
50
51#define uprobes_hash(v) (&uprobes_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
52
53/* serialize uprobe->pending_list */
54static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
55#define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
56
57/*
58 * uprobe_events allows us to skip the uprobe_mmap if there are no uprobe
59 * events active at this time. Probably a fine grained per inode count is
60 * better?
61 */
62static atomic_t uprobe_events = ATOMIC_INIT(0);
63
64/*
65 * Maintain a temporary per vma info that can be used to search if a vma
66 * has already been handled. This structure is introduced since extending
67 * vm_area_struct wasnt recommended.
68 */
69struct vma_info {
70    struct list_head probe_list;
71    struct mm_struct *mm;
72    loff_t vaddr;
73};
74
75struct uprobe {
76    struct rb_node rb_node; /* node in the rb tree */
77    atomic_t ref;
78    struct rw_semaphore consumer_rwsem;
79    struct list_head pending_list;
80    struct uprobe_consumer *consumers;
81    struct inode *inode; /* Also hold a ref to inode */
82    loff_t offset;
83    int flags;
84    struct arch_uprobe arch;
85};
86
87/*
88 * valid_vma: Verify if the specified vma is an executable vma
89 * Relax restrictions while unregistering: vm_flags might have
90 * changed after breakpoint was inserted.
91 * - is_register: indicates if we are in register context.
92 * - Return 1 if the specified virtual address is in an
93 * executable vma.
94 */
95static bool valid_vma(struct vm_area_struct *vma, bool is_register)
96{
97    if (!vma->vm_file)
98        return false;
99
100    if (!is_register)
101        return true;
102
103    if ((vma->vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)) == (VM_READ|VM_EXEC))
104        return true;
105
106    return false;
107}
108
109static loff_t vma_address(struct vm_area_struct *vma, loff_t offset)
110{
111    loff_t vaddr;
112
113    vaddr = vma->vm_start + offset;
114    vaddr -= vma->vm_pgoff << PAGE_SHIFT;
115
116    return vaddr;
117}
118
119/**
120 * __replace_page - replace page in vma by new page.
121 * based on replace_page in mm/ksm.c
122 *
123 * @vma: vma that holds the pte pointing to page
124 * @page: the cowed page we are replacing by kpage
125 * @kpage: the modified page we replace page by
126 *
127 * Returns 0 on success, -EFAULT on failure.
128 */
129static int __replace_page(struct vm_area_struct *vma, struct page *page, struct page *kpage)
130{
131    struct mm_struct *mm = vma->vm_mm;
132    pgd_t *pgd;
133    pud_t *pud;
134    pmd_t *pmd;
135    pte_t *ptep;
136    spinlock_t *ptl;
137    unsigned long addr;
138    int err = -EFAULT;
139
140    addr = page_address_in_vma(page, vma);
141    if (addr == -EFAULT)
142        goto out;
143
144    pgd = pgd_offset(mm, addr);
145    if (!pgd_present(*pgd))
146        goto out;
147
148    pud = pud_offset(pgd, addr);
149    if (!pud_present(*pud))
150        goto out;
151
152    pmd = pmd_offset(pud, addr);
153    if (!pmd_present(*pmd))
154        goto out;
155
156    ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
157    if (!ptep)
158        goto out;
159
160    get_page(kpage);
161    page_add_new_anon_rmap(kpage, vma, addr);
162
163    if (!PageAnon(page)) {
164        dec_mm_counter(mm, MM_FILEPAGES);
165        inc_mm_counter(mm, MM_ANONPAGES);
166    }
167
168    flush_cache_page(vma, addr, pte_pfn(*ptep));
169    ptep_clear_flush(vma, addr, ptep);
170    set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
171
172    page_remove_rmap(page);
173    if (!page_mapped(page))
174        try_to_free_swap(page);
175    put_page(page);
176    pte_unmap_unlock(ptep, ptl);
177    err = 0;
178
179out:
180    return err;
181}
182
183/**
184 * is_swbp_insn - check if instruction is breakpoint instruction.
185 * @insn: instruction to be checked.
186 * Default implementation of is_swbp_insn
187 * Returns true if @insn is a breakpoint instruction.
188 */
189bool __weak is_swbp_insn(uprobe_opcode_t *insn)
190{
191    return *insn == UPROBE_SWBP_INSN;
192}
193
194/*
195 * NOTE:
196 * Expect the breakpoint instruction to be the smallest size instruction for
197 * the architecture. If an arch has variable length instruction and the
198 * breakpoint instruction is not of the smallest length instruction
199 * supported by that architecture then we need to modify read_opcode /
200 * write_opcode accordingly. This would never be a problem for archs that
201 * have fixed length instructions.
202 */
203
204/*
205 * write_opcode - write the opcode at a given virtual address.
206 * @auprobe: arch breakpointing information.
207 * @mm: the probed process address space.
208 * @vaddr: the virtual address to store the opcode.
209 * @opcode: opcode to be written at @vaddr.
210 *
211 * Called with mm->mmap_sem held (for read and with a reference to
212 * mm).
213 *
214 * For mm @mm, write the opcode at @vaddr.
215 * Return 0 (success) or a negative errno.
216 */
217static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
218            unsigned long vaddr, uprobe_opcode_t opcode)
219{
220    struct page *old_page, *new_page;
221    struct address_space *mapping;
222    void *vaddr_old, *vaddr_new;
223    struct vm_area_struct *vma;
224    struct uprobe *uprobe;
225    loff_t addr;
226    int ret;
227
228    /* Read the page with vaddr into memory */
229    ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
230    if (ret <= 0)
231        return ret;
232
233    ret = -EINVAL;
234
235    /*
236     * We are interested in text pages only. Our pages of interest
237     * should be mapped for read and execute only. We desist from
238     * adding probes in write mapped pages since the breakpoints
239     * might end up in the file copy.
240     */
241    if (!valid_vma(vma, is_swbp_insn(&opcode)))
242        goto put_out;
243
244    uprobe = container_of(auprobe, struct uprobe, arch);
245    mapping = uprobe->inode->i_mapping;
246    if (mapping != vma->vm_file->f_mapping)
247        goto put_out;
248
249    addr = vma_address(vma, uprobe->offset);
250    if (vaddr != (unsigned long)addr)
251        goto put_out;
252
253    ret = -ENOMEM;
254    new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
255    if (!new_page)
256        goto put_out;
257
258    __SetPageUptodate(new_page);
259
260    /*
261     * lock page will serialize against do_wp_page()'s
262     * PageAnon() handling
263     */
264    lock_page(old_page);
265    /* copy the page now that we've got it stable */
266    vaddr_old = kmap_atomic(old_page);
267    vaddr_new = kmap_atomic(new_page);
268
269    memcpy(vaddr_new, vaddr_old, PAGE_SIZE);
270
271    /* poke the new insn in, ASSUMES we don't cross page boundary */
272    vaddr &= ~PAGE_MASK;
273    BUG_ON(vaddr + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
274    memcpy(vaddr_new + vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
275
276    kunmap_atomic(vaddr_new);
277    kunmap_atomic(vaddr_old);
278
279    ret = anon_vma_prepare(vma);
280    if (ret)
281        goto unlock_out;
282
283    lock_page(new_page);
284    ret = __replace_page(vma, old_page, new_page);
285    unlock_page(new_page);
286
287unlock_out:
288    unlock_page(old_page);
289    page_cache_release(new_page);
290
291put_out:
292    put_page(old_page);
293
294    return ret;
295}
296
297/**
298 * read_opcode - read the opcode at a given virtual address.
299 * @mm: the probed process address space.
300 * @vaddr: the virtual address to read the opcode.
301 * @opcode: location to store the read opcode.
302 *
303 * Called with mm->mmap_sem held (for read and with a reference to
304 * mm.
305 *
306 * For mm @mm, read the opcode at @vaddr and store it in @opcode.
307 * Return 0 (success) or a negative errno.
308 */
309static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode)
310{
311    struct page *page;
312    void *vaddr_new;
313    int ret;
314
315    ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
316    if (ret <= 0)
317        return ret;
318
319    lock_page(page);
320    vaddr_new = kmap_atomic(page);
321    vaddr &= ~PAGE_MASK;
322    memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
323    kunmap_atomic(vaddr_new);
324    unlock_page(page);
325
326    put_page(page);
327
328    return 0;
329}
330
331static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
332{
333    uprobe_opcode_t opcode;
334    int result;
335
336    result = read_opcode(mm, vaddr, &opcode);
337    if (result)
338        return result;
339
340    if (is_swbp_insn(&opcode))
341        return 1;
342
343    return 0;
344}
345
346/**
347 * set_swbp - store breakpoint at a given address.
348 * @auprobe: arch specific probepoint information.
349 * @mm: the probed process address space.
350 * @vaddr: the virtual address to insert the opcode.
351 *
352 * For mm @mm, store the breakpoint instruction at @vaddr.
353 * Return 0 (success) or a negative errno.
354 */
355int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
356{
357    int result;
358
359    result = is_swbp_at_addr(mm, vaddr);
360    if (result == 1)
361        return -EEXIST;
362
363    if (result)
364        return result;
365
366    return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
367}
368
369/**
370 * set_orig_insn - Restore the original instruction.
371 * @mm: the probed process address space.
372 * @auprobe: arch specific probepoint information.
373 * @vaddr: the virtual address to insert the opcode.
374 * @verify: if true, verify existance of breakpoint instruction.
375 *
376 * For mm @mm, restore the original opcode (opcode) at @vaddr.
377 * Return 0 (success) or a negative errno.
378 */
379int __weak
380set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, bool verify)
381{
382    if (verify) {
383        int result;
384
385        result = is_swbp_at_addr(mm, vaddr);
386        if (!result)
387            return -EINVAL;
388
389        if (result != 1)
390            return result;
391    }
392    return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
393}
394
395static int match_uprobe(struct uprobe *l, struct uprobe *r)
396{
397    if (l->inode < r->inode)
398        return -1;
399
400    if (l->inode > r->inode)
401        return 1;
402
403    if (l->offset < r->offset)
404        return -1;
405
406    if (l->offset > r->offset)
407        return 1;
408
409    return 0;
410}
411
412static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
413{
414    struct uprobe u = { .inode = inode, .offset = offset };
415    struct rb_node *n = uprobes_tree.rb_node;
416    struct uprobe *uprobe;
417    int match;
418
419    while (n) {
420        uprobe = rb_entry(n, struct uprobe, rb_node);
421        match = match_uprobe(&u, uprobe);
422        if (!match) {
423            atomic_inc(&uprobe->ref);
424            return uprobe;
425        }
426
427        if (match < 0)
428            n = n->rb_left;
429        else
430            n = n->rb_right;
431    }
432    return NULL;
433}
434
435/*
436 * Find a uprobe corresponding to a given inode:offset
437 * Acquires uprobes_treelock
438 */
439static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
440{
441    struct uprobe *uprobe;
442    unsigned long flags;
443
444    spin_lock_irqsave(&uprobes_treelock, flags);
445    uprobe = __find_uprobe(inode, offset);
446    spin_unlock_irqrestore(&uprobes_treelock, flags);
447
448    return uprobe;
449}
450
451static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
452{
453    struct rb_node **p = &uprobes_tree.rb_node;
454    struct rb_node *parent = NULL;
455    struct uprobe *u;
456    int match;
457
458    while (*p) {
459        parent = *p;
460        u = rb_entry(parent, struct uprobe, rb_node);
461        match = match_uprobe(uprobe, u);
462        if (!match) {
463            atomic_inc(&u->ref);
464            return u;
465        }
466
467        if (match < 0)
468            p = &parent->rb_left;
469        else
470            p = &parent->rb_right;
471
472    }
473
474    u = NULL;
475    rb_link_node(&uprobe->rb_node, parent, p);
476    rb_insert_color(&uprobe->rb_node, &uprobes_tree);
477    /* get access + creation ref */
478    atomic_set(&uprobe->ref, 2);
479
480    return u;
481}
482
483/*
484 * Acquire uprobes_treelock.
485 * Matching uprobe already exists in rbtree;
486 * increment (access refcount) and return the matching uprobe.
487 *
488 * No matching uprobe; insert the uprobe in rb_tree;
489 * get a double refcount (access + creation) and return NULL.
490 */
491static struct uprobe *insert_uprobe(struct uprobe *uprobe)
492{
493    unsigned long flags;
494    struct uprobe *u;
495
496    spin_lock_irqsave(&uprobes_treelock, flags);
497    u = __insert_uprobe(uprobe);
498    spin_unlock_irqrestore(&uprobes_treelock, flags);
499
500    /* For now assume that the instruction need not be single-stepped */
501    uprobe->flags |= UPROBE_SKIP_SSTEP;
502
503    return u;
504}
505
506static void put_uprobe(struct uprobe *uprobe)
507{
508    if (atomic_dec_and_test(&uprobe->ref))
509        kfree(uprobe);
510}
511
512static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
513{
514    struct uprobe *uprobe, *cur_uprobe;
515
516    uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
517    if (!uprobe)
518        return NULL;
519
520    uprobe->inode = igrab(inode);
521    uprobe->offset = offset;
522    init_rwsem(&uprobe->consumer_rwsem);
523    INIT_LIST_HEAD(&uprobe->pending_list);
524
525    /* add to uprobes_tree, sorted on inode:offset */
526    cur_uprobe = insert_uprobe(uprobe);
527
528    /* a uprobe exists for this inode:offset combination */
529    if (cur_uprobe) {
530        kfree(uprobe);
531        uprobe = cur_uprobe;
532        iput(inode);
533    } else {
534        atomic_inc(&uprobe_events);
535    }
536
537    return uprobe;
538}
539
540static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
541{
542    struct uprobe_consumer *uc;
543
544    if (!(uprobe->flags & UPROBE_RUN_HANDLER))
545        return;
546
547    down_read(&uprobe->consumer_rwsem);
548    for (uc = uprobe->consumers; uc; uc = uc->next) {
549        if (!uc->filter || uc->filter(uc, current))
550            uc->handler(uc, regs);
551    }
552    up_read(&uprobe->consumer_rwsem);
553}
554
555/* Returns the previous consumer */
556static struct uprobe_consumer *
557consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
558{
559    down_write(&uprobe->consumer_rwsem);
560    uc->next = uprobe->consumers;
561    uprobe->consumers = uc;
562    up_write(&uprobe->consumer_rwsem);
563
564    return uc->next;
565}
566
567/*
568 * For uprobe @uprobe, delete the consumer @uc.
569 * Return true if the @uc is deleted successfully
570 * or return false.
571 */
572static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc)
573{
574    struct uprobe_consumer **con;
575    bool ret = false;
576
577    down_write(&uprobe->consumer_rwsem);
578    for (con = &uprobe->consumers; *con; con = &(*con)->next) {
579        if (*con == uc) {
580            *con = uc->next;
581            ret = true;
582            break;
583        }
584    }
585    up_write(&uprobe->consumer_rwsem);
586
587    return ret;
588}
589
590static int
591__copy_insn(struct address_space *mapping, struct vm_area_struct *vma, char *insn,
592            unsigned long nbytes, unsigned long offset)
593{
594    struct file *filp = vma->vm_file;
595    struct page *page;
596    void *vaddr;
597    unsigned long off1;
598    unsigned long idx;
599
600    if (!filp)
601        return -EINVAL;
602
603    idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT);
604    off1 = offset &= ~PAGE_MASK;
605
606    /*
607     * Ensure that the page that has the original instruction is
608     * populated and in page-cache.
609     */
610    page = read_mapping_page(mapping, idx, filp);
611    if (IS_ERR(page))
612        return PTR_ERR(page);
613
614    vaddr = kmap_atomic(page);
615    memcpy(insn, vaddr + off1, nbytes);
616    kunmap_atomic(vaddr);
617    page_cache_release(page);
618
619    return 0;
620}
621
622static int
623copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long addr)
624{
625    struct address_space *mapping;
626    unsigned long nbytes;
627    int bytes;
628
629    addr &= ~PAGE_MASK;
630    nbytes = PAGE_SIZE - addr;
631    mapping = uprobe->inode->i_mapping;
632
633    /* Instruction at end of binary; copy only available bytes */
634    if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
635        bytes = uprobe->inode->i_size - uprobe->offset;
636    else
637        bytes = MAX_UINSN_BYTES;
638
639    /* Instruction at the page-boundary; copy bytes in second page */
640    if (nbytes < bytes) {
641        if (__copy_insn(mapping, vma, uprobe->arch.insn + nbytes,
642                bytes - nbytes, uprobe->offset + nbytes))
643            return -ENOMEM;
644
645        bytes = nbytes;
646    }
647    return __copy_insn(mapping, vma, uprobe->arch.insn, bytes, uprobe->offset);
648}
649
650/*
651 * How mm->uprobes_state.count gets updated
652 * uprobe_mmap() increments the count if
653 * - it successfully adds a breakpoint.
654 * - it cannot add a breakpoint, but sees that there is a underlying
655 * breakpoint (via a is_swbp_at_addr()).
656 *
657 * uprobe_munmap() decrements the count if
658 * - it sees a underlying breakpoint, (via is_swbp_at_addr)
659 * (Subsequent uprobe_unregister wouldnt find the breakpoint
660 * unless a uprobe_mmap kicks in, since the old vma would be
661 * dropped just after uprobe_munmap.)
662 *
663 * uprobe_register increments the count if:
664 * - it successfully adds a breakpoint.
665 *
666 * uprobe_unregister decrements the count if:
667 * - it sees a underlying breakpoint and removes successfully.
668 * (via is_swbp_at_addr)
669 * (Subsequent uprobe_munmap wouldnt find the breakpoint
670 * since there is no underlying breakpoint after the
671 * breakpoint removal.)
672 */
673static int
674install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
675            struct vm_area_struct *vma, loff_t vaddr)
676{
677    unsigned long addr;
678    int ret;
679
680    /*
681     * If probe is being deleted, unregister thread could be done with
682     * the vma-rmap-walk through. Adding a probe now can be fatal since
683     * nobody will be able to cleanup. Also we could be from fork or
684     * mremap path, where the probe might have already been inserted.
685     * Hence behave as if probe already existed.
686     */
687    if (!uprobe->consumers)
688        return -EEXIST;
689
690    addr = (unsigned long)vaddr;
691
692    if (!(uprobe->flags & UPROBE_COPY_INSN)) {
693        ret = copy_insn(uprobe, vma, addr);
694        if (ret)
695            return ret;
696
697        if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
698            return -EEXIST;
699
700        ret = arch_uprobe_analyze_insn(&uprobe->arch, mm);
701        if (ret)
702            return ret;
703
704        uprobe->flags |= UPROBE_COPY_INSN;
705    }
706
707    /*
708     * Ideally, should be updating the probe count after the breakpoint
709     * has been successfully inserted. However a thread could hit the
710     * breakpoint we just inserted even before the probe count is
711     * incremented. If this is the first breakpoint placed, breakpoint
712     * notifier might ignore uprobes and pass the trap to the thread.
713     * Hence increment before and decrement on failure.
714     */
715    atomic_inc(&mm->uprobes_state.count);
716    ret = set_swbp(&uprobe->arch, mm, addr);
717    if (ret)
718        atomic_dec(&mm->uprobes_state.count);
719
720    return ret;
721}
722
723static void
724remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, loff_t vaddr)
725{
726    if (!set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true))
727        atomic_dec(&mm->uprobes_state.count);
728}
729
730/*
731 * There could be threads that have hit the breakpoint and are entering the
732 * notifier code and trying to acquire the uprobes_treelock. The thread
733 * calling delete_uprobe() that is removing the uprobe from the rb_tree can
734 * race with these threads and might acquire the uprobes_treelock compared
735 * to some of the breakpoint hit threads. In such a case, the breakpoint
736 * hit threads will not find the uprobe. The current unregistering thread
737 * waits till all other threads have hit a breakpoint, to acquire the
738 * uprobes_treelock before the uprobe is removed from the rbtree.
739 */
740static void delete_uprobe(struct uprobe *uprobe)
741{
742    unsigned long flags;
743
744    synchronize_srcu(&uprobes_srcu);
745    spin_lock_irqsave(&uprobes_treelock, flags);
746    rb_erase(&uprobe->rb_node, &uprobes_tree);
747    spin_unlock_irqrestore(&uprobes_treelock, flags);
748    iput(uprobe->inode);
749    put_uprobe(uprobe);
750    atomic_dec(&uprobe_events);
751}
752
753static struct vma_info *
754__find_next_vma_info(struct address_space *mapping, struct list_head *head,
755            struct vma_info *vi, loff_t offset, bool is_register)
756{
757    struct prio_tree_iter iter;
758    struct vm_area_struct *vma;
759    struct vma_info *tmpvi;
760    unsigned long pgoff;
761    int existing_vma;
762    loff_t vaddr;
763
764    pgoff = offset >> PAGE_SHIFT;
765
766    vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
767        if (!valid_vma(vma, is_register))
768            continue;
769
770        existing_vma = 0;
771        vaddr = vma_address(vma, offset);
772
773        list_for_each_entry(tmpvi, head, probe_list) {
774            if (tmpvi->mm == vma->vm_mm && tmpvi->vaddr == vaddr) {
775                existing_vma = 1;
776                break;
777            }
778        }
779
780        /*
781         * Another vma needs a probe to be installed. However skip
782         * installing the probe if the vma is about to be unlinked.
783         */
784        if (!existing_vma && atomic_inc_not_zero(&vma->vm_mm->mm_users)) {
785            vi->mm = vma->vm_mm;
786            vi->vaddr = vaddr;
787            list_add(&vi->probe_list, head);
788
789            return vi;
790        }
791    }
792
793    return NULL;
794}
795
796/*
797 * Iterate in the rmap prio tree and find a vma where a probe has not
798 * yet been inserted.
799 */
800static struct vma_info *
801find_next_vma_info(struct address_space *mapping, struct list_head *head,
802        loff_t offset, bool is_register)
803{
804    struct vma_info *vi, *retvi;
805
806    vi = kzalloc(sizeof(struct vma_info), GFP_KERNEL);
807    if (!vi)
808        return ERR_PTR(-ENOMEM);
809
810    mutex_lock(&mapping->i_mmap_mutex);
811    retvi = __find_next_vma_info(mapping, head, vi, offset, is_register);
812    mutex_unlock(&mapping->i_mmap_mutex);
813
814    if (!retvi)
815        kfree(vi);
816
817    return retvi;
818}
819
820static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
821{
822    struct list_head try_list;
823    struct vm_area_struct *vma;
824    struct address_space *mapping;
825    struct vma_info *vi, *tmpvi;
826    struct mm_struct *mm;
827    loff_t vaddr;
828    int ret;
829
830    mapping = uprobe->inode->i_mapping;
831    INIT_LIST_HEAD(&try_list);
832
833    ret = 0;
834
835    for (;;) {
836        vi = find_next_vma_info(mapping, &try_list, uprobe->offset, is_register);
837        if (!vi)
838            break;
839
840        if (IS_ERR(vi)) {
841            ret = PTR_ERR(vi);
842            break;
843        }
844
845        mm = vi->mm;
846        down_read(&mm->mmap_sem);
847        vma = find_vma(mm, (unsigned long)vi->vaddr);
848        if (!vma || !valid_vma(vma, is_register)) {
849            list_del(&vi->probe_list);
850            kfree(vi);
851            up_read(&mm->mmap_sem);
852            mmput(mm);
853            continue;
854        }
855        vaddr = vma_address(vma, uprobe->offset);
856        if (vma->vm_file->f_mapping->host != uprobe->inode ||
857                        vaddr != vi->vaddr) {
858            list_del(&vi->probe_list);
859            kfree(vi);
860            up_read(&mm->mmap_sem);
861            mmput(mm);
862            continue;
863        }
864
865        if (is_register)
866            ret = install_breakpoint(uprobe, mm, vma, vi->vaddr);
867        else
868            remove_breakpoint(uprobe, mm, vi->vaddr);
869
870        up_read(&mm->mmap_sem);
871        mmput(mm);
872        if (is_register) {
873            if (ret && ret == -EEXIST)
874                ret = 0;
875            if (ret)
876                break;
877        }
878    }
879
880    list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
881        list_del(&vi->probe_list);
882        kfree(vi);
883    }
884
885    return ret;
886}
887
888static int __uprobe_register(struct uprobe *uprobe)
889{
890    return register_for_each_vma(uprobe, true);
891}
892
893static void __uprobe_unregister(struct uprobe *uprobe)
894{
895    if (!register_for_each_vma(uprobe, false))
896        delete_uprobe(uprobe);
897
898    /* TODO : cant unregister? schedule a worker thread */
899}
900
901/*
902 * uprobe_register - register a probe
903 * @inode: the file in which the probe has to be placed.
904 * @offset: offset from the start of the file.
905 * @uc: information on howto handle the probe..
906 *
907 * Apart from the access refcount, uprobe_register() takes a creation
908 * refcount (thro alloc_uprobe) if and only if this @uprobe is getting
909 * inserted into the rbtree (i.e first consumer for a @inode:@offset
910 * tuple). Creation refcount stops uprobe_unregister from freeing the
911 * @uprobe even before the register operation is complete. Creation
912 * refcount is released when the last @uc for the @uprobe
913 * unregisters.
914 *
915 * Return errno if it cannot successully install probes
916 * else return 0 (success)
917 */
918int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
919{
920    struct uprobe *uprobe;
921    int ret;
922
923    if (!inode || !uc || uc->next)
924        return -EINVAL;
925
926    if (offset > i_size_read(inode))
927        return -EINVAL;
928
929    ret = 0;
930    mutex_lock(uprobes_hash(inode));
931    uprobe = alloc_uprobe(inode, offset);
932
933    if (uprobe && !consumer_add(uprobe, uc)) {
934        ret = __uprobe_register(uprobe);
935        if (ret) {
936            uprobe->consumers = NULL;
937            __uprobe_unregister(uprobe);
938        } else {
939            uprobe->flags |= UPROBE_RUN_HANDLER;
940        }
941    }
942
943    mutex_unlock(uprobes_hash(inode));
944    put_uprobe(uprobe);
945
946    return ret;
947}
948
949/*
950 * uprobe_unregister - unregister a already registered probe.
951 * @inode: the file in which the probe has to be removed.
952 * @offset: offset from the start of the file.
953 * @uc: identify which probe if multiple probes are colocated.
954 */
955void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
956{
957    struct uprobe *uprobe;
958
959    if (!inode || !uc)
960        return;
961
962    uprobe = find_uprobe(inode, offset);
963    if (!uprobe)
964        return;
965
966    mutex_lock(uprobes_hash(inode));
967
968    if (consumer_del(uprobe, uc)) {
969        if (!uprobe->consumers) {
970            __uprobe_unregister(uprobe);
971            uprobe->flags &= ~UPROBE_RUN_HANDLER;
972        }
973    }
974
975    mutex_unlock(uprobes_hash(inode));
976    if (uprobe)
977        put_uprobe(uprobe);
978}
979
980/*
981 * Of all the nodes that correspond to the given inode, return the node
982 * with the least offset.
983 */
984static struct rb_node *find_least_offset_node(struct inode *inode)
985{
986    struct uprobe u = { .inode = inode, .offset = 0};
987    struct rb_node *n = uprobes_tree.rb_node;
988    struct rb_node *close_node = NULL;
989    struct uprobe *uprobe;
990    int match;
991
992    while (n) {
993        uprobe = rb_entry(n, struct uprobe, rb_node);
994        match = match_uprobe(&u, uprobe);
995
996        if (uprobe->inode == inode)
997            close_node = n;
998
999        if (!match)
1000            return close_node;
1001
1002        if (match < 0)
1003            n = n->rb_left;
1004        else
1005            n = n->rb_right;
1006    }
1007
1008    return close_node;
1009}
1010
1011/*
1012 * For a given inode, build a list of probes that need to be inserted.
1013 */
1014static void build_probe_list(struct inode *inode, struct list_head *head)
1015{
1016    struct uprobe *uprobe;
1017    unsigned long flags;
1018    struct rb_node *n;
1019
1020    spin_lock_irqsave(&uprobes_treelock, flags);
1021
1022    n = find_least_offset_node(inode);
1023
1024    for (; n; n = rb_next(n)) {
1025        uprobe = rb_entry(n, struct uprobe, rb_node);
1026        if (uprobe->inode != inode)
1027            break;
1028
1029        list_add(&uprobe->pending_list, head);
1030        atomic_inc(&uprobe->ref);
1031    }
1032
1033    spin_unlock_irqrestore(&uprobes_treelock, flags);
1034}
1035
1036/*
1037 * Called from mmap_region.
1038 * called with mm->mmap_sem acquired.
1039 *
1040 * Return -ve no if we fail to insert probes and we cannot
1041 * bail-out.
1042 * Return 0 otherwise. i.e:
1043 *
1044 * - successful insertion of probes
1045 * - (or) no possible probes to be inserted.
1046 * - (or) insertion of probes failed but we can bail-out.
1047 */
1048int uprobe_mmap(struct vm_area_struct *vma)
1049{
1050    struct list_head tmp_list;
1051    struct uprobe *uprobe, *u;
1052    struct inode *inode;
1053    int ret, count;
1054
1055    if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
1056        return 0;
1057
1058    inode = vma->vm_file->f_mapping->host;
1059    if (!inode)
1060        return 0;
1061
1062    INIT_LIST_HEAD(&tmp_list);
1063    mutex_lock(uprobes_mmap_hash(inode));
1064    build_probe_list(inode, &tmp_list);
1065
1066    ret = 0;
1067    count = 0;
1068
1069    list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1070        loff_t vaddr;
1071
1072        list_del(&uprobe->pending_list);
1073        if (!ret) {
1074            vaddr = vma_address(vma, uprobe->offset);
1075
1076            if (vaddr < vma->vm_start || vaddr >= vma->vm_end) {
1077                put_uprobe(uprobe);
1078                continue;
1079            }
1080
1081            ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
1082
1083            /* Ignore double add: */
1084            if (ret == -EEXIST) {
1085                ret = 0;
1086
1087                if (!is_swbp_at_addr(vma->vm_mm, vaddr))
1088                    continue;
1089
1090                /*
1091                 * Unable to insert a breakpoint, but
1092                 * breakpoint lies underneath. Increment the
1093                 * probe count.
1094                 */
1095                atomic_inc(&vma->vm_mm->uprobes_state.count);
1096            }
1097
1098            if (!ret)
1099                count++;
1100        }
1101        put_uprobe(uprobe);
1102    }
1103
1104    mutex_unlock(uprobes_mmap_hash(inode));
1105
1106    if (ret)
1107        atomic_sub(count, &vma->vm_mm->uprobes_state.count);
1108
1109    return ret;
1110}
1111
1112/*
1113 * Called in context of a munmap of a vma.
1114 */
1115void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
1116{
1117    struct list_head tmp_list;
1118    struct uprobe *uprobe, *u;
1119    struct inode *inode;
1120
1121    if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
1122        return;
1123
1124    if (!atomic_read(&vma->vm_mm->uprobes_state.count))
1125        return;
1126
1127    inode = vma->vm_file->f_mapping->host;
1128    if (!inode)
1129        return;
1130
1131    INIT_LIST_HEAD(&tmp_list);
1132    mutex_lock(uprobes_mmap_hash(inode));
1133    build_probe_list(inode, &tmp_list);
1134
1135    list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
1136        loff_t vaddr;
1137
1138        list_del(&uprobe->pending_list);
1139        vaddr = vma_address(vma, uprobe->offset);
1140
1141        if (vaddr >= start && vaddr < end) {
1142            /*
1143             * An unregister could have removed the probe before
1144             * unmap. So check before we decrement the count.
1145             */
1146            if (is_swbp_at_addr(vma->vm_mm, vaddr) == 1)
1147                atomic_dec(&vma->vm_mm->uprobes_state.count);
1148        }
1149        put_uprobe(uprobe);
1150    }
1151    mutex_unlock(uprobes_mmap_hash(inode));
1152}
1153
1154/* Slot allocation for XOL */
1155static int xol_add_vma(struct xol_area *area)
1156{
1157    struct mm_struct *mm;
1158    int ret;
1159
1160    area->page = alloc_page(GFP_HIGHUSER);
1161    if (!area->page)
1162        return -ENOMEM;
1163
1164    ret = -EALREADY;
1165    mm = current->mm;
1166
1167    down_write(&mm->mmap_sem);
1168    if (mm->uprobes_state.xol_area)
1169        goto fail;
1170
1171    ret = -ENOMEM;
1172
1173    /* Try to map as high as possible, this is only a hint. */
1174    area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0);
1175    if (area->vaddr & ~PAGE_MASK) {
1176        ret = area->vaddr;
1177        goto fail;
1178    }
1179
1180    ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
1181                VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page);
1182    if (ret)
1183        goto fail;
1184
1185    smp_wmb(); /* pairs with get_xol_area() */
1186    mm->uprobes_state.xol_area = area;
1187    ret = 0;
1188
1189fail:
1190    up_write(&mm->mmap_sem);
1191    if (ret)
1192        __free_page(area->page);
1193
1194    return ret;
1195}
1196
1197static struct xol_area *get_xol_area(struct mm_struct *mm)
1198{
1199    struct xol_area *area;
1200
1201    area = mm->uprobes_state.xol_area;
1202    smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
1203
1204    return area;
1205}
1206
1207/*
1208 * xol_alloc_area - Allocate process's xol_area.
1209 * This area will be used for storing instructions for execution out of
1210 * line.
1211 *
1212 * Returns the allocated area or NULL.
1213 */
1214static struct xol_area *xol_alloc_area(void)
1215{
1216    struct xol_area *area;
1217
1218    area = kzalloc(sizeof(*area), GFP_KERNEL);
1219    if (unlikely(!area))
1220        return NULL;
1221
1222    area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL);
1223
1224    if (!area->bitmap)
1225        goto fail;
1226
1227    init_waitqueue_head(&area->wq);
1228    if (!xol_add_vma(area))
1229        return area;
1230
1231fail:
1232    kfree(area->bitmap);
1233    kfree(area);
1234
1235    return get_xol_area(current->mm);
1236}
1237
1238/*
1239 * uprobe_clear_state - Free the area allocated for slots.
1240 */
1241void 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->page);
1249    kfree(area->bitmap);
1250    kfree(area);
1251}
1252
1253/*
1254 * uprobe_reset_state - Free the area allocated for slots.
1255 */
1256void uprobe_reset_state(struct mm_struct *mm)
1257{
1258    mm->uprobes_state.xol_area = NULL;
1259    atomic_set(&mm->uprobes_state.count, 0);
1260}
1261
1262/*
1263 * - search for a free slot.
1264 */
1265static unsigned long xol_take_insn_slot(struct xol_area *area)
1266{
1267    unsigned long slot_addr;
1268    int slot_nr;
1269
1270    do {
1271        slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
1272        if (slot_nr < UINSNS_PER_PAGE) {
1273            if (!test_and_set_bit(slot_nr, area->bitmap))
1274                break;
1275
1276            slot_nr = UINSNS_PER_PAGE;
1277            continue;
1278        }
1279        wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
1280    } while (slot_nr >= UINSNS_PER_PAGE);
1281
1282    slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
1283    atomic_inc(&area->slot_count);
1284
1285    return slot_addr;
1286}
1287
1288/*
1289 * xol_get_insn_slot - If was not allocated a slot, then
1290 * allocate a slot.
1291 * Returns the allocated slot address or 0.
1292 */
1293static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot_addr)
1294{
1295    struct xol_area *area;
1296    unsigned long offset;
1297    void *vaddr;
1298
1299    area = get_xol_area(current->mm);
1300    if (!area) {
1301        area = xol_alloc_area();
1302        if (!area)
1303            return 0;
1304    }
1305    current->utask->xol_vaddr = xol_take_insn_slot(area);
1306
1307    /*
1308     * Initialize the slot if xol_vaddr points to valid
1309     * instruction slot.
1310     */
1311    if (unlikely(!current->utask->xol_vaddr))
1312        return 0;
1313
1314    current->utask->vaddr = slot_addr;
1315    offset = current->utask->xol_vaddr & ~PAGE_MASK;
1316    vaddr = kmap_atomic(area->page);
1317    memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
1318    kunmap_atomic(vaddr);
1319
1320    return current->utask->xol_vaddr;
1321}
1322
1323/*
1324 * xol_free_insn_slot - If slot was earlier allocated by
1325 * @xol_get_insn_slot(), make the slot available for
1326 * subsequent requests.
1327 */
1328static void xol_free_insn_slot(struct task_struct *tsk)
1329{
1330    struct xol_area *area;
1331    unsigned long vma_end;
1332    unsigned long slot_addr;
1333
1334    if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask)
1335        return;
1336
1337    slot_addr = tsk->utask->xol_vaddr;
1338
1339    if (unlikely(!slot_addr || IS_ERR_VALUE(slot_addr)))
1340        return;
1341
1342    area = tsk->mm->uprobes_state.xol_area;
1343    vma_end = area->vaddr + PAGE_SIZE;
1344    if (area->vaddr <= slot_addr && slot_addr < vma_end) {
1345        unsigned long offset;
1346        int slot_nr;
1347
1348        offset = slot_addr - area->vaddr;
1349        slot_nr = offset / UPROBE_XOL_SLOT_BYTES;
1350        if (slot_nr >= UINSNS_PER_PAGE)
1351            return;
1352
1353        clear_bit(slot_nr, area->bitmap);
1354        atomic_dec(&area->slot_count);
1355        if (waitqueue_active(&area->wq))
1356            wake_up(&area->wq);
1357
1358        tsk->utask->xol_vaddr = 0;
1359    }
1360}
1361
1362/**
1363 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
1364 * @regs: Reflects the saved state of the task after it has hit a breakpoint
1365 * instruction.
1366 * Return the address of the breakpoint instruction.
1367 */
1368unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
1369{
1370    return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
1371}
1372
1373/*
1374 * Called with no locks held.
1375 * Called in context of a exiting or a exec-ing thread.
1376 */
1377void uprobe_free_utask(struct task_struct *t)
1378{
1379    struct uprobe_task *utask = t->utask;
1380
1381    if (t->uprobe_srcu_id != -1)
1382        srcu_read_unlock_raw(&uprobes_srcu, t->uprobe_srcu_id);
1383
1384    if (!utask)
1385        return;
1386
1387    if (utask->active_uprobe)
1388        put_uprobe(utask->active_uprobe);
1389
1390    xol_free_insn_slot(t);
1391    kfree(utask);
1392    t->utask = NULL;
1393}
1394
1395/*
1396 * Called in context of a new clone/fork from copy_process.
1397 */
1398void uprobe_copy_process(struct task_struct *t)
1399{
1400    t->utask = NULL;
1401    t->uprobe_srcu_id = -1;
1402}
1403
1404/*
1405 * Allocate a uprobe_task object for the task.
1406 * Called when the thread hits a breakpoint for the first time.
1407 *
1408 * Returns:
1409 * - pointer to new uprobe_task on success
1410 * - NULL otherwise
1411 */
1412static struct uprobe_task *add_utask(void)
1413{
1414    struct uprobe_task *utask;
1415
1416    utask = kzalloc(sizeof *utask, GFP_KERNEL);
1417    if (unlikely(!utask))
1418        return NULL;
1419
1420    utask->active_uprobe = NULL;
1421    current->utask = utask;
1422    return utask;
1423}
1424
1425/* Prepare to single-step probed instruction out of line. */
1426static int
1427pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr)
1428{
1429    if (xol_get_insn_slot(uprobe, vaddr) && !arch_uprobe_pre_xol(&uprobe->arch, regs))
1430        return 0;
1431
1432    return -EFAULT;
1433}
1434
1435/*
1436 * If we are singlestepping, then ensure this thread is not connected to
1437 * non-fatal signals until completion of singlestep. When xol insn itself
1438 * triggers the signal, restart the original insn even if the task is
1439 * already SIGKILL'ed (since coredump should report the correct ip). This
1440 * is even more important if the task has a handler for SIGSEGV/etc, The
1441 * _same_ instruction should be repeated again after return from the signal
1442 * handler, and SSTEP can never finish in this case.
1443 */
1444bool uprobe_deny_signal(void)
1445{
1446    struct task_struct *t = current;
1447    struct uprobe_task *utask = t->utask;
1448
1449    if (likely(!utask || !utask->active_uprobe))
1450        return false;
1451
1452    WARN_ON_ONCE(utask->state != UTASK_SSTEP);
1453
1454    if (signal_pending(t)) {
1455        spin_lock_irq(&t->sighand->siglock);
1456        clear_tsk_thread_flag(t, TIF_SIGPENDING);
1457        spin_unlock_irq(&t->sighand->siglock);
1458
1459        if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
1460            utask->state = UTASK_SSTEP_TRAPPED;
1461            set_tsk_thread_flag(t, TIF_UPROBE);
1462            set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
1463        }
1464    }
1465
1466    return true;
1467}
1468
1469/*
1470 * Avoid singlestepping the original instruction if the original instruction
1471 * is a NOP or can be emulated.
1472 */
1473static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
1474{
1475    if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
1476        return true;
1477
1478    uprobe->flags &= ~UPROBE_SKIP_SSTEP;
1479    return false;
1480}
1481
1482/*
1483 * Run handler and ask thread to singlestep.
1484 * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
1485 */
1486static void handle_swbp(struct pt_regs *regs)
1487{
1488    struct vm_area_struct *vma;
1489    struct uprobe_task *utask;
1490    struct uprobe *uprobe;
1491    struct mm_struct *mm;
1492    unsigned long bp_vaddr;
1493
1494    uprobe = NULL;
1495    bp_vaddr = uprobe_get_swbp_addr(regs);
1496    mm = current->mm;
1497    down_read(&mm->mmap_sem);
1498    vma = find_vma(mm, bp_vaddr);
1499
1500    if (vma && vma->vm_start <= bp_vaddr && valid_vma(vma, false)) {
1501        struct inode *inode;
1502        loff_t offset;
1503
1504        inode = vma->vm_file->f_mapping->host;
1505        offset = bp_vaddr - vma->vm_start;
1506        offset += (vma->vm_pgoff << PAGE_SHIFT);
1507        uprobe = find_uprobe(inode, offset);
1508    }
1509
1510    srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);
1511    current->uprobe_srcu_id = -1;
1512    up_read(&mm->mmap_sem);
1513
1514    if (!uprobe) {
1515        /* No matching uprobe; signal SIGTRAP. */
1516        send_sig(SIGTRAP, current, 0);
1517        return;
1518    }
1519
1520    utask = current->utask;
1521    if (!utask) {
1522        utask = add_utask();
1523        /* Cannot allocate; re-execute the instruction. */
1524        if (!utask)
1525            goto cleanup_ret;
1526    }
1527    utask->active_uprobe = uprobe;
1528    handler_chain(uprobe, regs);
1529    if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
1530        goto cleanup_ret;
1531
1532    utask->state = UTASK_SSTEP;
1533    if (!pre_ssout(uprobe, regs, bp_vaddr)) {
1534        user_enable_single_step(current);
1535        return;
1536    }
1537
1538cleanup_ret:
1539    if (utask) {
1540        utask->active_uprobe = NULL;
1541        utask->state = UTASK_RUNNING;
1542    }
1543    if (uprobe) {
1544        if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
1545
1546            /*
1547             * cannot singlestep; cannot skip instruction;
1548             * re-execute the instruction.
1549             */
1550            instruction_pointer_set(regs, bp_vaddr);
1551
1552        put_uprobe(uprobe);
1553    }
1554}
1555
1556/*
1557 * Perform required fix-ups and disable singlestep.
1558 * Allow pending signals to take effect.
1559 */
1560static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
1561{
1562    struct uprobe *uprobe;
1563
1564    uprobe = utask->active_uprobe;
1565    if (utask->state == UTASK_SSTEP_ACK)
1566        arch_uprobe_post_xol(&uprobe->arch, regs);
1567    else if (utask->state == UTASK_SSTEP_TRAPPED)
1568        arch_uprobe_abort_xol(&uprobe->arch, regs);
1569    else
1570        WARN_ON_ONCE(1);
1571
1572    put_uprobe(uprobe);
1573    utask->active_uprobe = NULL;
1574    utask->state = UTASK_RUNNING;
1575    user_disable_single_step(current);
1576    xol_free_insn_slot(current);
1577
1578    spin_lock_irq(&current->sighand->siglock);
1579    recalc_sigpending(); /* see uprobe_deny_signal() */
1580    spin_unlock_irq(&current->sighand->siglock);
1581}
1582
1583/*
1584 * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on
1585 * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
1586 * allows the thread to return from interrupt.
1587 *
1588 * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
1589 * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from
1590 * interrupt.
1591 *
1592 * While returning to userspace, thread notices the TIF_UPROBE flag and calls
1593 * uprobe_notify_resume().
1594 */
1595void uprobe_notify_resume(struct pt_regs *regs)
1596{
1597    struct uprobe_task *utask;
1598
1599    utask = current->utask;
1600    if (!utask || utask->state == UTASK_BP_HIT)
1601        handle_swbp(regs);
1602    else
1603        handle_singlestep(utask, regs);
1604}
1605
1606/*
1607 * uprobe_pre_sstep_notifier gets called from interrupt context as part of
1608 * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
1609 */
1610int uprobe_pre_sstep_notifier(struct pt_regs *regs)
1611{
1612    struct uprobe_task *utask;
1613
1614    if (!current->mm || !atomic_read(&current->mm->uprobes_state.count))
1615        /* task is currently not uprobed */
1616        return 0;
1617
1618    utask = current->utask;
1619    if (utask)
1620        utask->state = UTASK_BP_HIT;
1621
1622    set_thread_flag(TIF_UPROBE);
1623    current->uprobe_srcu_id = srcu_read_lock_raw(&uprobes_srcu);
1624
1625    return 1;
1626}
1627
1628/*
1629 * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
1630 * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
1631 */
1632int uprobe_post_sstep_notifier(struct pt_regs *regs)
1633{
1634    struct uprobe_task *utask = current->utask;
1635
1636    if (!current->mm || !utask || !utask->active_uprobe)
1637        /* task is currently not uprobed */
1638        return 0;
1639
1640    utask->state = UTASK_SSTEP_ACK;
1641    set_thread_flag(TIF_UPROBE);
1642    return 1;
1643}
1644
1645static struct notifier_block uprobe_exception_nb = {
1646    .notifier_call = arch_uprobe_exception_notify,
1647    .priority = INT_MAX-1, /* notified after kprobes, kgdb */
1648};
1649
1650static int __init init_uprobes(void)
1651{
1652    int i;
1653
1654    for (i = 0; i < UPROBES_HASH_SZ; i++) {
1655        mutex_init(&uprobes_mutex[i]);
1656        mutex_init(&uprobes_mmap_mutex[i]);
1657    }
1658    init_srcu_struct(&uprobes_srcu);
1659
1660    return register_die_notifier(&uprobe_exception_nb);
1661}
1662module_init(init_uprobes);
1663
1664static void __exit exit_uprobes(void)
1665{
1666}
1667module_exit(exit_uprobes);
1668

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