/* * Userspace Probes (UProbes) * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Copyright (C) IBM Corporation, 2008-2011 * Authors: * Srikar Dronamraju * Jim Keniston */ #include #include #include /* read_mapping_page */ #include #include #include /* anon_vma_prepare */ #include /* set_pte_at_notify */ #include /* try_to_free_swap */ #include static struct rb_root uprobes_tree = RB_ROOT; static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */ #define UPROBES_HASH_SZ 13 /* serialize (un)register */ static struct mutex uprobes_mutex[UPROBES_HASH_SZ]; #define uprobes_hash(v) (&uprobes_mutex[((unsigned long)(v)) %\ UPROBES_HASH_SZ]) /* serialize uprobe->pending_list */ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ]; #define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) %\ UPROBES_HASH_SZ]) /* * uprobe_events allows us to skip the mmap_uprobe if there are no uprobe * events active at this time. Probably a fine grained per inode count is * better? */ static atomic_t uprobe_events = ATOMIC_INIT(0); /* * Maintain a temporary per vma info that can be used to search if a vma * has already been handled. This structure is introduced since extending * vm_area_struct wasnt recommended. */ struct vma_info { struct list_head probe_list; struct mm_struct *mm; loff_t vaddr; }; /* * valid_vma: Verify if the specified vma is an executable vma * Relax restrictions while unregistering: vm_flags might have * changed after breakpoint was inserted. * - is_register: indicates if we are in register context. * - Return 1 if the specified virtual address is in an * executable vma. */ static bool valid_vma(struct vm_area_struct *vma, bool is_register) { if (!vma->vm_file) return false; if (!is_register) return true; if ((vma->vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)) == (VM_READ|VM_EXEC)) return true; return false; } static loff_t vma_address(struct vm_area_struct *vma, loff_t offset) { loff_t vaddr; vaddr = vma->vm_start + offset; vaddr -= vma->vm_pgoff << PAGE_SHIFT; return vaddr; } /** * __replace_page - replace page in vma by new page. * based on replace_page in mm/ksm.c * * @vma: vma that holds the pte pointing to page * @page: the cowed page we are replacing by kpage * @kpage: the modified page we replace page by * * Returns 0 on success, -EFAULT on failure. */ static int __replace_page(struct vm_area_struct *vma, struct page *page, struct page *kpage) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; pud_t *pud; pmd_t *pmd; pte_t *ptep; spinlock_t *ptl; unsigned long addr; int err = -EFAULT; addr = page_address_in_vma(page, vma); if (addr == -EFAULT) goto out; pgd = pgd_offset(mm, addr); if (!pgd_present(*pgd)) goto out; pud = pud_offset(pgd, addr); if (!pud_present(*pud)) goto out; pmd = pmd_offset(pud, addr); if (!pmd_present(*pmd)) goto out; ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); if (!ptep) goto out; get_page(kpage); page_add_new_anon_rmap(kpage, vma, addr); flush_cache_page(vma, addr, pte_pfn(*ptep)); ptep_clear_flush(vma, addr, ptep); set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); page_remove_rmap(page); if (!page_mapped(page)) try_to_free_swap(page); put_page(page); pte_unmap_unlock(ptep, ptl); err = 0; out: return err; } /** * is_bkpt_insn - check if instruction is breakpoint instruction. * @insn: instruction to be checked. * Default implementation of is_bkpt_insn * Returns true if @insn is a breakpoint instruction. */ bool __weak is_bkpt_insn(uprobe_opcode_t *insn) { return (*insn == UPROBES_BKPT_INSN); } /* * NOTE: * Expect the breakpoint instruction to be the smallest size instruction for * the architecture. If an arch has variable length instruction and the * breakpoint instruction is not of the smallest length instruction * supported by that architecture then we need to modify read_opcode / * write_opcode accordingly. This would never be a problem for archs that * have fixed length instructions. */ /* * write_opcode - write the opcode at a given virtual address. * @mm: the probed process address space. * @uprobe: the breakpointing information. * @vaddr: the virtual address to store the opcode. * @opcode: opcode to be written at @vaddr. * * Called with mm->mmap_sem held (for read and with a reference to * mm). * * For mm @mm, write the opcode at @vaddr. * Return 0 (success) or a negative errno. */ static int write_opcode(struct mm_struct *mm, struct uprobe *uprobe, unsigned long vaddr, uprobe_opcode_t opcode) { struct page *old_page, *new_page; struct address_space *mapping; void *vaddr_old, *vaddr_new; struct vm_area_struct *vma; loff_t addr; int ret; /* Read the page with vaddr into memory */ ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma); if (ret <= 0) return ret; ret = -EINVAL; /* * We are interested in text pages only. Our pages of interest * should be mapped for read and execute only. We desist from * adding probes in write mapped pages since the breakpoints * might end up in the file copy. */ if (!valid_vma(vma, is_bkpt_insn(&opcode))) goto put_out; mapping = uprobe->inode->i_mapping; if (mapping != vma->vm_file->f_mapping) goto put_out; addr = vma_address(vma, uprobe->offset); if (vaddr != (unsigned long)addr) goto put_out; ret = -ENOMEM; new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr); if (!new_page) goto put_out; __SetPageUptodate(new_page); /* * lock page will serialize against do_wp_page()'s * PageAnon() handling */ lock_page(old_page); /* copy the page now that we've got it stable */ vaddr_old = kmap_atomic(old_page); vaddr_new = kmap_atomic(new_page); memcpy(vaddr_new, vaddr_old, PAGE_SIZE); /* poke the new insn in, ASSUMES we don't cross page boundary */ vaddr &= ~PAGE_MASK; BUG_ON(vaddr + uprobe_opcode_sz > PAGE_SIZE); memcpy(vaddr_new + vaddr, &opcode, uprobe_opcode_sz); kunmap_atomic(vaddr_new); kunmap_atomic(vaddr_old); ret = anon_vma_prepare(vma); if (ret) goto unlock_out; lock_page(new_page); ret = __replace_page(vma, old_page, new_page); unlock_page(new_page); unlock_out: unlock_page(old_page); page_cache_release(new_page); put_out: put_page(old_page); /* we did a get_page in the beginning */ return ret; } /** * read_opcode - read the opcode at a given virtual address. * @mm: the probed process address space. * @vaddr: the virtual address to read the opcode. * @opcode: location to store the read opcode. * * Called with mm->mmap_sem held (for read and with a reference to * mm. * * For mm @mm, read the opcode at @vaddr and store it in @opcode. * Return 0 (success) or a negative errno. */ static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode) { struct page *page; void *vaddr_new; int ret; ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL); if (ret <= 0) return ret; lock_page(page); vaddr_new = kmap_atomic(page); vaddr &= ~PAGE_MASK; memcpy(opcode, vaddr_new + vaddr, uprobe_opcode_sz); kunmap_atomic(vaddr_new); unlock_page(page); put_page(page); /* we did a get_user_pages in the beginning */ return 0; } static int is_bkpt_at_addr(struct mm_struct *mm, unsigned long vaddr) { uprobe_opcode_t opcode; int result = read_opcode(mm, vaddr, &opcode); if (result) return result; if (is_bkpt_insn(&opcode)) return 1; return 0; } /** * set_bkpt - store breakpoint at a given address. * @mm: the probed process address space. * @uprobe: the probepoint information. * @vaddr: the virtual address to insert the opcode. * * For mm @mm, store the breakpoint instruction at @vaddr. * Return 0 (success) or a negative errno. */ int __weak set_bkpt(struct mm_struct *mm, struct uprobe *uprobe, unsigned long vaddr) { int result = is_bkpt_at_addr(mm, vaddr); if (result == 1) return -EEXIST; if (result) return result; return write_opcode(mm, uprobe, vaddr, UPROBES_BKPT_INSN); } /** * set_orig_insn - Restore the original instruction. * @mm: the probed process address space. * @uprobe: the probepoint information. * @vaddr: the virtual address to insert the opcode. * @verify: if true, verify existance of breakpoint instruction. * * For mm @mm, restore the original opcode (opcode) at @vaddr. * Return 0 (success) or a negative errno. */ int __weak set_orig_insn(struct mm_struct *mm, struct uprobe *uprobe, unsigned long vaddr, bool verify) { if (verify) { int result = is_bkpt_at_addr(mm, vaddr); if (!result) return -EINVAL; if (result != 1) return result; } return write_opcode(mm, uprobe, vaddr, *(uprobe_opcode_t *)uprobe->insn); } static int match_uprobe(struct uprobe *l, struct uprobe *r) { if (l->inode < r->inode) return -1; if (l->inode > r->inode) return 1; else { if (l->offset < r->offset) return -1; if (l->offset > r->offset) return 1; } return 0; } static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset) { struct uprobe u = { .inode = inode, .offset = offset }; struct rb_node *n = uprobes_tree.rb_node; struct uprobe *uprobe; int match; while (n) { uprobe = rb_entry(n, struct uprobe, rb_node); match = match_uprobe(&u, uprobe); if (!match) { atomic_inc(&uprobe->ref); return uprobe; } if (match < 0) n = n->rb_left; else n = n->rb_right; } return NULL; } /* * Find a uprobe corresponding to a given inode:offset * Acquires uprobes_treelock */ static struct uprobe *find_uprobe(struct inode *inode, loff_t offset) { struct uprobe *uprobe; unsigned long flags; spin_lock_irqsave(&uprobes_treelock, flags); uprobe = __find_uprobe(inode, offset); spin_unlock_irqrestore(&uprobes_treelock, flags); return uprobe; } static struct uprobe *__insert_uprobe(struct uprobe *uprobe) { struct rb_node **p = &uprobes_tree.rb_node; struct rb_node *parent = NULL; struct uprobe *u; int match; while (*p) { parent = *p; u = rb_entry(parent, struct uprobe, rb_node); match = match_uprobe(uprobe, u); if (!match) { atomic_inc(&u->ref); return u; } if (match < 0) p = &parent->rb_left; else p = &parent->rb_right; } u = NULL; rb_link_node(&uprobe->rb_node, parent, p); rb_insert_color(&uprobe->rb_node, &uprobes_tree); /* get access + creation ref */ atomic_set(&uprobe->ref, 2); return u; } /* * Acquires uprobes_treelock. * Matching uprobe already exists in rbtree; * increment (access refcount) and return the matching uprobe. * * No matching uprobe; insert the uprobe in rb_tree; * get a double refcount (access + creation) and return NULL. */ static struct uprobe *insert_uprobe(struct uprobe *uprobe) { unsigned long flags; struct uprobe *u; spin_lock_irqsave(&uprobes_treelock, flags); u = __insert_uprobe(uprobe); spin_unlock_irqrestore(&uprobes_treelock, flags); return u; } static void put_uprobe(struct uprobe *uprobe) { if (atomic_dec_and_test(&uprobe->ref)) kfree(uprobe); } static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset) { struct uprobe *uprobe, *cur_uprobe; uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL); if (!uprobe) return NULL; uprobe->inode = igrab(inode); uprobe->offset = offset; init_rwsem(&uprobe->consumer_rwsem); INIT_LIST_HEAD(&uprobe->pending_list); /* add to uprobes_tree, sorted on inode:offset */ cur_uprobe = insert_uprobe(uprobe); /* a uprobe exists for this inode:offset combination */ if (cur_uprobe) { kfree(uprobe); uprobe = cur_uprobe; iput(inode); } else atomic_inc(&uprobe_events); return uprobe; } /* Returns the previous consumer */ static struct uprobe_consumer *add_consumer(struct uprobe *uprobe, struct uprobe_consumer *consumer) { down_write(&uprobe->consumer_rwsem); consumer->next = uprobe->consumers; uprobe->consumers = consumer; up_write(&uprobe->consumer_rwsem); return consumer->next; } /* * For uprobe @uprobe, delete the consumer @consumer. * Return true if the @consumer is deleted successfully * or return false. */ static bool del_consumer(struct uprobe *uprobe, struct uprobe_consumer *consumer) { struct uprobe_consumer **con; bool ret = false; down_write(&uprobe->consumer_rwsem); for (con = &uprobe->consumers; *con; con = &(*con)->next) { if (*con == consumer) { *con = consumer->next; ret = true; break; } } up_write(&uprobe->consumer_rwsem); return ret; } static int __copy_insn(struct address_space *mapping, struct vm_area_struct *vma, char *insn, unsigned long nbytes, unsigned long offset) { struct file *filp = vma->vm_file; struct page *page; void *vaddr; unsigned long off1; unsigned long idx; if (!filp) return -EINVAL; idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT); off1 = offset &= ~PAGE_MASK; /* * Ensure that the page that has the original instruction is * populated and in page-cache. */ page = read_mapping_page(mapping, idx, filp); if (IS_ERR(page)) return PTR_ERR(page); vaddr = kmap_atomic(page); memcpy(insn, vaddr + off1, nbytes); kunmap_atomic(vaddr); page_cache_release(page); return 0; } static int copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long addr) { struct address_space *mapping; int bytes; unsigned long nbytes; addr &= ~PAGE_MASK; nbytes = PAGE_SIZE - addr; mapping = uprobe->inode->i_mapping; /* Instruction at end of binary; copy only available bytes */ if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size) bytes = uprobe->inode->i_size - uprobe->offset; else bytes = MAX_UINSN_BYTES; /* Instruction at the page-boundary; copy bytes in second page */ if (nbytes < bytes) { if (__copy_insn(mapping, vma, uprobe->insn + nbytes, bytes - nbytes, uprobe->offset + nbytes)) return -ENOMEM; bytes = nbytes; } return __copy_insn(mapping, vma, uprobe->insn, bytes, uprobe->offset); } static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe, struct vm_area_struct *vma, loff_t vaddr) { unsigned long addr; int ret; /* * If probe is being deleted, unregister thread could be done with * the vma-rmap-walk through. Adding a probe now can be fatal since * nobody will be able to cleanup. Also we could be from fork or * mremap path, where the probe might have already been inserted. * Hence behave as if probe already existed. */ if (!uprobe->consumers) return -EEXIST; addr = (unsigned long)vaddr; if (!(uprobe->flags & UPROBES_COPY_INSN)) { ret = copy_insn(uprobe, vma, addr); if (ret) return ret; if (is_bkpt_insn((uprobe_opcode_t *)uprobe->insn)) return -EEXIST; ret = analyze_insn(mm, uprobe); if (ret) return ret; uprobe->flags |= UPROBES_COPY_INSN; } ret = set_bkpt(mm, uprobe, addr); return ret; } static void remove_breakpoint(struct mm_struct *mm, struct uprobe *uprobe, loff_t vaddr) { set_orig_insn(mm, uprobe, (unsigned long)vaddr, true); } static void delete_uprobe(struct uprobe *uprobe) { unsigned long flags; spin_lock_irqsave(&uprobes_treelock, flags); rb_erase(&uprobe->rb_node, &uprobes_tree); spin_unlock_irqrestore(&uprobes_treelock, flags); iput(uprobe->inode); put_uprobe(uprobe); atomic_dec(&uprobe_events); } static struct vma_info *__find_next_vma_info(struct list_head *head, loff_t offset, struct address_space *mapping, struct vma_info *vi, bool is_register) { struct prio_tree_iter iter; struct vm_area_struct *vma; struct vma_info *tmpvi; loff_t vaddr; unsigned long pgoff = offset >> PAGE_SHIFT; int existing_vma; vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { if (!valid_vma(vma, is_register)) continue; existing_vma = 0; vaddr = vma_address(vma, offset); list_for_each_entry(tmpvi, head, probe_list) { if (tmpvi->mm == vma->vm_mm && tmpvi->vaddr == vaddr) { existing_vma = 1; break; } } /* * Another vma needs a probe to be installed. However skip * installing the probe if the vma is about to be unlinked. */ if (!existing_vma && atomic_inc_not_zero(&vma->vm_mm->mm_users)) { vi->mm = vma->vm_mm; vi->vaddr = vaddr; list_add(&vi->probe_list, head); return vi; } } return NULL; } /* * Iterate in the rmap prio tree and find a vma where a probe has not * yet been inserted. */ static struct vma_info *find_next_vma_info(struct list_head *head, loff_t offset, struct address_space *mapping, bool is_register) { struct vma_info *vi, *retvi; vi = kzalloc(sizeof(struct vma_info), GFP_KERNEL); if (!vi) return ERR_PTR(-ENOMEM); mutex_lock(&mapping->i_mmap_mutex); retvi = __find_next_vma_info(head, offset, mapping, vi, is_register); mutex_unlock(&mapping->i_mmap_mutex); if (!retvi) kfree(vi); return retvi; } static int register_for_each_vma(struct uprobe *uprobe, bool is_register) { struct list_head try_list; struct vm_area_struct *vma; struct address_space *mapping; struct vma_info *vi, *tmpvi; struct mm_struct *mm; loff_t vaddr; int ret = 0; mapping = uprobe->inode->i_mapping; INIT_LIST_HEAD(&try_list); while ((vi = find_next_vma_info(&try_list, uprobe->offset, mapping, is_register)) != NULL) { if (IS_ERR(vi)) { ret = PTR_ERR(vi); break; } mm = vi->mm; down_read(&mm->mmap_sem); vma = find_vma(mm, (unsigned long)vi->vaddr); if (!vma || !valid_vma(vma, is_register)) { list_del(&vi->probe_list); kfree(vi); up_read(&mm->mmap_sem); mmput(mm); continue; } vaddr = vma_address(vma, uprobe->offset); if (vma->vm_file->f_mapping->host != uprobe->inode || vaddr != vi->vaddr) { list_del(&vi->probe_list); kfree(vi); up_read(&mm->mmap_sem); mmput(mm); continue; } if (is_register) ret = install_breakpoint(mm, uprobe, vma, vi->vaddr); else remove_breakpoint(mm, uprobe, vi->vaddr); up_read(&mm->mmap_sem); mmput(mm); if (is_register) { if (ret && ret == -EEXIST) ret = 0; if (ret) break; } } list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) { list_del(&vi->probe_list); kfree(vi); } return ret; } static int __register_uprobe(struct uprobe *uprobe) { return register_for_each_vma(uprobe, true); } static void __unregister_uprobe(struct uprobe *uprobe) { if (!register_for_each_vma(uprobe, false)) delete_uprobe(uprobe); /* TODO : cant unregister? schedule a worker thread */ } /* * register_uprobe - register a probe * @inode: the file in which the probe has to be placed. * @offset: offset from the start of the file. * @consumer: information on howto handle the probe.. * * Apart from the access refcount, register_uprobe() takes a creation * refcount (thro alloc_uprobe) if and only if this @uprobe is getting * inserted into the rbtree (i.e first consumer for a @inode:@offset * tuple). Creation refcount stops unregister_uprobe from freeing the * @uprobe even before the register operation is complete. Creation * refcount is released when the last @consumer for the @uprobe * unregisters. * * Return errno if it cannot successully install probes * else return 0 (success) */ int register_uprobe(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer) { struct uprobe *uprobe; int ret = -EINVAL; if (!inode || !consumer || consumer->next) return ret; if (offset > i_size_read(inode)) return ret; ret = 0; mutex_lock(uprobes_hash(inode)); uprobe = alloc_uprobe(inode, offset); if (uprobe && !add_consumer(uprobe, consumer)) { ret = __register_uprobe(uprobe); if (ret) { uprobe->consumers = NULL; __unregister_uprobe(uprobe); } else uprobe->flags |= UPROBES_RUN_HANDLER; } mutex_unlock(uprobes_hash(inode)); put_uprobe(uprobe); return ret; } /* * unregister_uprobe - unregister a already registered probe. * @inode: the file in which the probe has to be removed. * @offset: offset from the start of the file. * @consumer: identify which probe if multiple probes are colocated. */ void unregister_uprobe(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer) { struct uprobe *uprobe = NULL; if (!inode || !consumer) return; uprobe = find_uprobe(inode, offset); if (!uprobe) return; mutex_lock(uprobes_hash(inode)); if (!del_consumer(uprobe, consumer)) goto unreg_out; if (!uprobe->consumers) { __unregister_uprobe(uprobe); uprobe->flags &= ~UPROBES_RUN_HANDLER; } unreg_out: mutex_unlock(uprobes_hash(inode)); if (uprobe) put_uprobe(uprobe); } /* * Of all the nodes that correspond to the given inode, return the node * with the least offset. */ static struct rb_node *find_least_offset_node(struct inode *inode) { struct uprobe u = { .inode = inode, .offset = 0}; struct rb_node *n = uprobes_tree.rb_node; struct rb_node *close_node = NULL; struct uprobe *uprobe; int match; while (n) { uprobe = rb_entry(n, struct uprobe, rb_node); match = match_uprobe(&u, uprobe); if (uprobe->inode == inode) close_node = n; if (!match) return close_node; if (match < 0) n = n->rb_left; else n = n->rb_right; } return close_node; } /* * For a given inode, build a list of probes that need to be inserted. */ static void build_probe_list(struct inode *inode, struct list_head *head) { struct uprobe *uprobe; struct rb_node *n; unsigned long flags; spin_lock_irqsave(&uprobes_treelock, flags); n = find_least_offset_node(inode); for (; n; n = rb_next(n)) { uprobe = rb_entry(n, struct uprobe, rb_node); if (uprobe->inode != inode) break; list_add(&uprobe->pending_list, head); atomic_inc(&uprobe->ref); } spin_unlock_irqrestore(&uprobes_treelock, flags); } /* * Called from mmap_region. * called with mm->mmap_sem acquired. * * Return -ve no if we fail to insert probes and we cannot * bail-out. * Return 0 otherwise. i.e : * - successful insertion of probes * - (or) no possible probes to be inserted. * - (or) insertion of probes failed but we can bail-out. */ int mmap_uprobe(struct vm_area_struct *vma) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct inode *inode; int ret = 0; if (!atomic_read(&uprobe_events) || !valid_vma(vma, true)) return ret; /* Bail-out */ inode = vma->vm_file->f_mapping->host; if (!inode) return ret; INIT_LIST_HEAD(&tmp_list); mutex_lock(uprobes_mmap_hash(inode)); build_probe_list(inode, &tmp_list); list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) { loff_t vaddr; list_del(&uprobe->pending_list); if (!ret) { vaddr = vma_address(vma, uprobe->offset); if (vaddr < vma->vm_start || vaddr >= vma->vm_end) { put_uprobe(uprobe); continue; } ret = install_breakpoint(vma->vm_mm, uprobe, vma, vaddr); if (ret == -EEXIST) ret = 0; } put_uprobe(uprobe); } mutex_unlock(uprobes_mmap_hash(inode)); return ret; } static int __init init_uprobes(void) { int i; for (i = 0; i < UPROBES_HASH_SZ; i++) { mutex_init(&uprobes_mutex[i]); mutex_init(&uprobes_mmap_mutex[i]); } return 0; } static void __exit exit_uprobes(void) { } module_init(init_uprobes); module_exit(exit_uprobes);