/* * User-space 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, 2008-2012 * Authors: * Srikar Dronamraju * Jim Keniston * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra */ #include #include #include /* read_mapping_page */ #include #include #include /* anon_vma_prepare */ #include /* set_pte_at_notify */ #include /* try_to_free_swap */ #include /* user_enable_single_step */ #include /* notifier mechanism */ #include #define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES) #define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE static struct srcu_struct uprobes_srcu; 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 uprobe_mmap 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; }; struct uprobe { struct rb_node rb_node; /* node in the rb tree */ atomic_t ref; struct rw_semaphore consumer_rwsem; struct list_head pending_list; struct uprobe_consumer *consumers; struct inode *inode; /* Also hold a ref to inode */ loff_t offset; int flags; struct arch_uprobe arch; }; /* * 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); if (!PageAnon(page)) { dec_mm_counter(mm, MM_FILEPAGES); inc_mm_counter(mm, MM_ANONPAGES); } 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_swbp_insn - check if instruction is breakpoint instruction. * @insn: instruction to be checked. * Default implementation of is_swbp_insn * Returns true if @insn is a breakpoint instruction. */ bool __weak is_swbp_insn(uprobe_opcode_t *insn) { return *insn == UPROBE_SWBP_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. * @auprobe: arch breakpointing information. * @mm: the probed process address space. * @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 arch_uprobe *auprobe, struct mm_struct *mm, 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; struct uprobe *uprobe; 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_swbp_insn(&opcode))) goto put_out; uprobe = container_of(auprobe, struct uprobe, arch); 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_SWBP_INSN_SIZE > PAGE_SIZE); memcpy(vaddr_new + vaddr, &opcode, UPROBE_SWBP_INSN_SIZE); 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); 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, 1, &page, NULL); if (ret <= 0) return ret; lock_page(page); vaddr_new = kmap_atomic(page); vaddr &= ~PAGE_MASK; memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE); kunmap_atomic(vaddr_new); unlock_page(page); put_page(page); return 0; } static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr) { uprobe_opcode_t opcode; int result; if (current->mm == mm) { pagefault_disable(); result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr, sizeof(opcode)); pagefault_enable(); if (likely(result == 0)) goto out; } result = read_opcode(mm, vaddr, &opcode); if (result) return result; out: if (is_swbp_insn(&opcode)) return 1; return 0; } /** * set_swbp - store breakpoint at a given address. * @auprobe: arch specific probepoint information. * @mm: the probed process address space. * @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_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr) { int result; result = is_swbp_at_addr(mm, vaddr); if (result == 1) return -EEXIST; if (result) return result; return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN); } /** * set_orig_insn - Restore the original instruction. * @mm: the probed process address space. * @auprobe: arch specific 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 arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, bool verify) { if (verify) { int result; result = is_swbp_at_addr(mm, vaddr); if (!result) return -EINVAL; if (result != 1) return result; } return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->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; 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; } /* * Acquire 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); /* For now assume that the instruction need not be single-stepped */ uprobe->flags |= UPROBE_SKIP_SSTEP; 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; } static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) { struct uprobe_consumer *uc; if (!(uprobe->flags & UPROBE_RUN_HANDLER)) return; down_read(&uprobe->consumer_rwsem); for (uc = uprobe->consumers; uc; uc = uc->next) { if (!uc->filter || uc->filter(uc, current)) uc->handler(uc, regs); } up_read(&uprobe->consumer_rwsem); } /* Returns the previous consumer */ static struct uprobe_consumer * consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) { down_write(&uprobe->consumer_rwsem); uc->next = uprobe->consumers; uprobe->consumers = uc; up_write(&uprobe->consumer_rwsem); return uc->next; } /* * For uprobe @uprobe, delete the consumer @uc. * Return true if the @uc is deleted successfully * or return false. */ static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc) { struct uprobe_consumer **con; bool ret = false; down_write(&uprobe->consumer_rwsem); for (con = &uprobe->consumers; *con; con = &(*con)->next) { if (*con == uc) { *con = uc->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; unsigned long nbytes; int bytes; 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->arch.insn + nbytes, bytes - nbytes, uprobe->offset + nbytes)) return -ENOMEM; bytes = nbytes; } return __copy_insn(mapping, vma, uprobe->arch.insn, bytes, uprobe->offset); } /* * How mm->uprobes_state.count gets updated * uprobe_mmap() increments the count if * - it successfully adds a breakpoint. * - it cannot add a breakpoint, but sees that there is a underlying * breakpoint (via a is_swbp_at_addr()). * * uprobe_munmap() decrements the count if * - it sees a underlying breakpoint, (via is_swbp_at_addr) * (Subsequent uprobe_unregister wouldnt find the breakpoint * unless a uprobe_mmap kicks in, since the old vma would be * dropped just after uprobe_munmap.) * * uprobe_register increments the count if: * - it successfully adds a breakpoint. * * uprobe_unregister decrements the count if: * - it sees a underlying breakpoint and removes successfully. * (via is_swbp_at_addr) * (Subsequent uprobe_munmap wouldnt find the breakpoint * since there is no underlying breakpoint after the * breakpoint removal.) */ static int install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, 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 & UPROBE_COPY_INSN)) { ret = copy_insn(uprobe, vma, addr); if (ret) return ret; if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn)) return -EEXIST; ret = arch_uprobe_analyze_insn(&uprobe->arch, mm); if (ret) return ret; uprobe->flags |= UPROBE_COPY_INSN; } /* * Ideally, should be updating the probe count after the breakpoint * has been successfully inserted. However a thread could hit the * breakpoint we just inserted even before the probe count is * incremented. If this is the first breakpoint placed, breakpoint * notifier might ignore uprobes and pass the trap to the thread. * Hence increment before and decrement on failure. */ atomic_inc(&mm->uprobes_state.count); ret = set_swbp(&uprobe->arch, mm, addr); if (ret) atomic_dec(&mm->uprobes_state.count); return ret; } static void remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, loff_t vaddr) { if (!set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true)) atomic_dec(&mm->uprobes_state.count); } /* * There could be threads that have hit the breakpoint and are entering the * notifier code and trying to acquire the uprobes_treelock. The thread * calling delete_uprobe() that is removing the uprobe from the rb_tree can * race with these threads and might acquire the uprobes_treelock compared * to some of the breakpoint hit threads. In such a case, the breakpoint * hit threads will not find the uprobe. The current unregistering thread * waits till all other threads have hit a breakpoint, to acquire the * uprobes_treelock before the uprobe is removed from the rbtree. */ static void delete_uprobe(struct uprobe *uprobe) { unsigned long flags; synchronize_srcu(&uprobes_srcu); 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 address_space *mapping, struct list_head *head, struct vma_info *vi, loff_t offset, bool is_register) { struct prio_tree_iter iter; struct vm_area_struct *vma; struct vma_info *tmpvi; unsigned long pgoff; int existing_vma; loff_t vaddr; pgoff = offset >> PAGE_SHIFT; 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 address_space *mapping, struct list_head *head, loff_t offset, 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(mapping, head, vi, offset, 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; mapping = uprobe->inode->i_mapping; INIT_LIST_HEAD(&try_list); ret = 0; for (;;) { vi = find_next_vma_info(mapping, &try_list, uprobe->offset, is_register); if (!vi) break; if (IS_ERR(vi)) { ret = PTR_ERR(vi); break; } mm = vi->mm; down_write(&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_write(&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_write(&mm->mmap_sem); mmput(mm); continue; } if (is_register) ret = install_breakpoint(uprobe, mm, vma, vi->vaddr); else remove_breakpoint(uprobe, mm, vi->vaddr); up_write(&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 __uprobe_register(struct uprobe *uprobe) { return register_for_each_vma(uprobe, true); } static void __uprobe_unregister(struct uprobe *uprobe) { if (!register_for_each_vma(uprobe, false)) delete_uprobe(uprobe); /* TODO : cant unregister? schedule a worker thread */ } /* * uprobe_register - register a probe * @inode: the file in which the probe has to be placed. * @offset: offset from the start of the file. * @uc: information on howto handle the probe.. * * Apart from the access refcount, uprobe_register() 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 uprobe_unregister from freeing the * @uprobe even before the register operation is complete. Creation * refcount is released when the last @uc for the @uprobe * unregisters. * * Return errno if it cannot successully install probes * else return 0 (success) */ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc) { struct uprobe *uprobe; int ret; if (!inode || !uc || uc->next) return -EINVAL; if (offset > i_size_read(inode)) return -EINVAL; ret = 0; mutex_lock(uprobes_hash(inode)); uprobe = alloc_uprobe(inode, offset); if (uprobe && !consumer_add(uprobe, uc)) { ret = __uprobe_register(uprobe); if (ret) { uprobe->consumers = NULL; __uprobe_unregister(uprobe); } else { uprobe->flags |= UPROBE_RUN_HANDLER; } } mutex_unlock(uprobes_hash(inode)); put_uprobe(uprobe); return ret; } /* * uprobe_unregister - unregister a already registered probe. * @inode: the file in which the probe has to be removed. * @offset: offset from the start of the file. * @uc: identify which probe if multiple probes are colocated. */ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc) { struct uprobe *uprobe; if (!inode || !uc) return; uprobe = find_uprobe(inode, offset); if (!uprobe) return; mutex_lock(uprobes_hash(inode)); if (consumer_del(uprobe, uc)) { if (!uprobe->consumers) { __uprobe_unregister(uprobe); uprobe->flags &= ~UPROBE_RUN_HANDLER; } } 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; unsigned long flags; struct rb_node *n; 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 uprobe_mmap(struct vm_area_struct *vma) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct inode *inode; int ret, count; if (!atomic_read(&uprobe_events) || !valid_vma(vma, true)) return 0; inode = vma->vm_file->f_mapping->host; if (!inode) return 0; INIT_LIST_HEAD(&tmp_list); mutex_lock(uprobes_mmap_hash(inode)); build_probe_list(inode, &tmp_list); ret = 0; count = 0; 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(uprobe, vma->vm_mm, vma, vaddr); /* Ignore double add: */ if (ret == -EEXIST) { ret = 0; if (!is_swbp_at_addr(vma->vm_mm, vaddr)) continue; /* * Unable to insert a breakpoint, but * breakpoint lies underneath. Increment the * probe count. */ atomic_inc(&vma->vm_mm->uprobes_state.count); } if (!ret) count++; } put_uprobe(uprobe); } mutex_unlock(uprobes_mmap_hash(inode)); if (ret) atomic_sub(count, &vma->vm_mm->uprobes_state.count); return ret; } /* * Called in context of a munmap of a vma. */ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct inode *inode; if (!atomic_read(&uprobe_events) || !valid_vma(vma, false)) return; if (!atomic_read(&vma->vm_mm->uprobes_state.count)) return; inode = vma->vm_file->f_mapping->host; if (!inode) return; 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); vaddr = vma_address(vma, uprobe->offset); if (vaddr >= start && vaddr < end) { /* * An unregister could have removed the probe before * unmap. So check before we decrement the count. */ if (is_swbp_at_addr(vma->vm_mm, vaddr) == 1) atomic_dec(&vma->vm_mm->uprobes_state.count); } put_uprobe(uprobe); } mutex_unlock(uprobes_mmap_hash(inode)); } /* Slot allocation for XOL */ static int xol_add_vma(struct xol_area *area) { struct mm_struct *mm; int ret; area->page = alloc_page(GFP_HIGHUSER); if (!area->page) return -ENOMEM; ret = -EALREADY; mm = current->mm; down_write(&mm->mmap_sem); if (mm->uprobes_state.xol_area) goto fail; ret = -ENOMEM; /* Try to map as high as possible, this is only a hint. */ area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0); if (area->vaddr & ~PAGE_MASK) { ret = area->vaddr; goto fail; } ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE, VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page); if (ret) goto fail; smp_wmb(); /* pairs with get_xol_area() */ mm->uprobes_state.xol_area = area; ret = 0; fail: up_write(&mm->mmap_sem); if (ret) __free_page(area->page); return ret; } static struct xol_area *get_xol_area(struct mm_struct *mm) { struct xol_area *area; area = mm->uprobes_state.xol_area; smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */ return area; } /* * xol_alloc_area - Allocate process's xol_area. * This area will be used for storing instructions for execution out of * line. * * Returns the allocated area or NULL. */ static struct xol_area *xol_alloc_area(void) { struct xol_area *area; area = kzalloc(sizeof(*area), GFP_KERNEL); if (unlikely(!area)) return NULL; area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL); if (!area->bitmap) goto fail; init_waitqueue_head(&area->wq); if (!xol_add_vma(area)) return area; fail: kfree(area->bitmap); kfree(area); return get_xol_area(current->mm); } /* * uprobe_clear_state - Free the area allocated for slots. */ void uprobe_clear_state(struct mm_struct *mm) { struct xol_area *area = mm->uprobes_state.xol_area; if (!area) return; put_page(area->page); kfree(area->bitmap); kfree(area); } /* * uprobe_reset_state - Free the area allocated for slots. */ void uprobe_reset_state(struct mm_struct *mm) { mm->uprobes_state.xol_area = NULL; atomic_set(&mm->uprobes_state.count, 0); } /* * - search for a free slot. */ static unsigned long xol_take_insn_slot(struct xol_area *area) { unsigned long slot_addr; int slot_nr; do { slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE); if (slot_nr < UINSNS_PER_PAGE) { if (!test_and_set_bit(slot_nr, area->bitmap)) break; slot_nr = UINSNS_PER_PAGE; continue; } wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE)); } while (slot_nr >= UINSNS_PER_PAGE); slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES); atomic_inc(&area->slot_count); return slot_addr; } /* * xol_get_insn_slot - If was not allocated a slot, then * allocate a slot. * Returns the allocated slot address or 0. */ static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot_addr) { struct xol_area *area; unsigned long offset; void *vaddr; area = get_xol_area(current->mm); if (!area) { area = xol_alloc_area(); if (!area) return 0; } current->utask->xol_vaddr = xol_take_insn_slot(area); /* * Initialize the slot if xol_vaddr points to valid * instruction slot. */ if (unlikely(!current->utask->xol_vaddr)) return 0; current->utask->vaddr = slot_addr; offset = current->utask->xol_vaddr & ~PAGE_MASK; vaddr = kmap_atomic(area->page); memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES); kunmap_atomic(vaddr); return current->utask->xol_vaddr; } /* * xol_free_insn_slot - If slot was earlier allocated by * @xol_get_insn_slot(), make the slot available for * subsequent requests. */ static void xol_free_insn_slot(struct task_struct *tsk) { struct xol_area *area; unsigned long vma_end; unsigned long slot_addr; if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask) return; slot_addr = tsk->utask->xol_vaddr; if (unlikely(!slot_addr || IS_ERR_VALUE(slot_addr))) return; area = tsk->mm->uprobes_state.xol_area; vma_end = area->vaddr + PAGE_SIZE; if (area->vaddr <= slot_addr && slot_addr < vma_end) { unsigned long offset; int slot_nr; offset = slot_addr - area->vaddr; slot_nr = offset / UPROBE_XOL_SLOT_BYTES; if (slot_nr >= UINSNS_PER_PAGE) return; clear_bit(slot_nr, area->bitmap); atomic_dec(&area->slot_count); if (waitqueue_active(&area->wq)) wake_up(&area->wq); tsk->utask->xol_vaddr = 0; } } /** * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs * @regs: Reflects the saved state of the task after it has hit a breakpoint * instruction. * Return the address of the breakpoint instruction. */ unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs) { return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE; } /* * Called with no locks held. * Called in context of a exiting or a exec-ing thread. */ void uprobe_free_utask(struct task_struct *t) { struct uprobe_task *utask = t->utask; if (t->uprobe_srcu_id != -1) srcu_read_unlock_raw(&uprobes_srcu, t->uprobe_srcu_id); if (!utask) return; if (utask->active_uprobe) put_uprobe(utask->active_uprobe); xol_free_insn_slot(t); kfree(utask); t->utask = NULL; } /* * Called in context of a new clone/fork from copy_process. */ void uprobe_copy_process(struct task_struct *t) { t->utask = NULL; t->uprobe_srcu_id = -1; } /* * Allocate a uprobe_task object for the task. * Called when the thread hits a breakpoint for the first time. * * Returns: * - pointer to new uprobe_task on success * - NULL otherwise */ static struct uprobe_task *add_utask(void) { struct uprobe_task *utask; utask = kzalloc(sizeof *utask, GFP_KERNEL); if (unlikely(!utask)) return NULL; utask->active_uprobe = NULL; current->utask = utask; return utask; } /* Prepare to single-step probed instruction out of line. */ static int pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr) { if (xol_get_insn_slot(uprobe, vaddr) && !arch_uprobe_pre_xol(&uprobe->arch, regs)) return 0; return -EFAULT; } /* * If we are singlestepping, then ensure this thread is not connected to * non-fatal signals until completion of singlestep. When xol insn itself * triggers the signal, restart the original insn even if the task is * already SIGKILL'ed (since coredump should report the correct ip). This * is even more important if the task has a handler for SIGSEGV/etc, The * _same_ instruction should be repeated again after return from the signal * handler, and SSTEP can never finish in this case. */ bool uprobe_deny_signal(void) { struct task_struct *t = current; struct uprobe_task *utask = t->utask; if (likely(!utask || !utask->active_uprobe)) return false; WARN_ON_ONCE(utask->state != UTASK_SSTEP); if (signal_pending(t)) { spin_lock_irq(&t->sighand->siglock); clear_tsk_thread_flag(t, TIF_SIGPENDING); spin_unlock_irq(&t->sighand->siglock); if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) { utask->state = UTASK_SSTEP_TRAPPED; set_tsk_thread_flag(t, TIF_UPROBE); set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); } } return true; } /* * Avoid singlestepping the original instruction if the original instruction * is a NOP or can be emulated. */ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs) { if (arch_uprobe_skip_sstep(&uprobe->arch, regs)) return true; uprobe->flags &= ~UPROBE_SKIP_SSTEP; return false; } static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp) { struct mm_struct *mm = current->mm; struct uprobe *uprobe = NULL; struct vm_area_struct *vma; down_read(&mm->mmap_sem); vma = find_vma(mm, bp_vaddr); if (vma && vma->vm_start <= bp_vaddr) { if (valid_vma(vma, false)) { struct inode *inode; loff_t offset; inode = vma->vm_file->f_mapping->host; offset = bp_vaddr - vma->vm_start; offset += (vma->vm_pgoff << PAGE_SHIFT); uprobe = find_uprobe(inode, offset); } if (!uprobe) *is_swbp = is_swbp_at_addr(mm, bp_vaddr); } else { *is_swbp = -EFAULT; } srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id); current->uprobe_srcu_id = -1; up_read(&mm->mmap_sem); return uprobe; } /* * Run handler and ask thread to singlestep. * Ensure all non-fatal signals cannot interrupt thread while it singlesteps. */ static void handle_swbp(struct pt_regs *regs) { struct uprobe_task *utask; struct uprobe *uprobe; unsigned long bp_vaddr; int is_swbp; bp_vaddr = uprobe_get_swbp_addr(regs); uprobe = find_active_uprobe(bp_vaddr, &is_swbp); if (!uprobe) { /* No matching uprobe; signal SIGTRAP. */ send_sig(SIGTRAP, current, 0); return; } utask = current->utask; if (!utask) { utask = add_utask(); /* Cannot allocate; re-execute the instruction. */ if (!utask) goto cleanup_ret; } utask->active_uprobe = uprobe; handler_chain(uprobe, regs); if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs)) goto cleanup_ret; utask->state = UTASK_SSTEP; if (!pre_ssout(uprobe, regs, bp_vaddr)) { user_enable_single_step(current); return; } cleanup_ret: if (utask) { utask->active_uprobe = NULL; utask->state = UTASK_RUNNING; } if (uprobe) { if (!(uprobe->flags & UPROBE_SKIP_SSTEP)) /* * cannot singlestep; cannot skip instruction; * re-execute the instruction. */ instruction_pointer_set(regs, bp_vaddr); put_uprobe(uprobe); } } /* * Perform required fix-ups and disable singlestep. * Allow pending signals to take effect. */ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) { struct uprobe *uprobe; uprobe = utask->active_uprobe; if (utask->state == UTASK_SSTEP_ACK) arch_uprobe_post_xol(&uprobe->arch, regs); else if (utask->state == UTASK_SSTEP_TRAPPED) arch_uprobe_abort_xol(&uprobe->arch, regs); else WARN_ON_ONCE(1); put_uprobe(uprobe); utask->active_uprobe = NULL; utask->state = UTASK_RUNNING; user_disable_single_step(current); xol_free_insn_slot(current); spin_lock_irq(¤t->sighand->siglock); recalc_sigpending(); /* see uprobe_deny_signal() */ spin_unlock_irq(¤t->sighand->siglock); } /* * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and * allows the thread to return from interrupt. * * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from * interrupt. * * While returning to userspace, thread notices the TIF_UPROBE flag and calls * uprobe_notify_resume(). */ void uprobe_notify_resume(struct pt_regs *regs) { struct uprobe_task *utask; utask = current->utask; if (!utask || utask->state == UTASK_BP_HIT) handle_swbp(regs); else handle_singlestep(utask, regs); } /* * uprobe_pre_sstep_notifier gets called from interrupt context as part of * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit. */ int uprobe_pre_sstep_notifier(struct pt_regs *regs) { struct uprobe_task *utask; if (!current->mm || !atomic_read(¤t->mm->uprobes_state.count)) /* task is currently not uprobed */ return 0; utask = current->utask; if (utask) utask->state = UTASK_BP_HIT; set_thread_flag(TIF_UPROBE); current->uprobe_srcu_id = srcu_read_lock_raw(&uprobes_srcu); return 1; } /* * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep. */ int uprobe_post_sstep_notifier(struct pt_regs *regs) { struct uprobe_task *utask = current->utask; if (!current->mm || !utask || !utask->active_uprobe) /* task is currently not uprobed */ return 0; utask->state = UTASK_SSTEP_ACK; set_thread_flag(TIF_UPROBE); return 1; } static struct notifier_block uprobe_exception_nb = { .notifier_call = arch_uprobe_exception_notify, .priority = INT_MAX-1, /* notified after kprobes, kgdb */ }; 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]); } init_srcu_struct(&uprobes_srcu); return register_die_notifier(&uprobe_exception_nb); } module_init(init_uprobes); static void __exit exit_uprobes(void) { } module_exit(exit_uprobes);