| /* |
| * 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 <pzijlstr@redhat.com> |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/highmem.h> |
| #include <linux/pagemap.h> /* read_mapping_page */ |
| #include <linux/slab.h> |
| #include <linux/sched.h> |
| #include <linux/rmap.h> /* anon_vma_prepare */ |
| #include <linux/mmu_notifier.h> /* set_pte_at_notify */ |
| #include <linux/swap.h> /* try_to_free_swap */ |
| #include <linux/ptrace.h> /* user_enable_single_step */ |
| #include <linux/kdebug.h> /* notifier mechanism */ |
| |
| #include <linux/uprobes.h> |
| |
| 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); |
| |
| 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, 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_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; |
| |
| result = read_opcode(mm, vaddr, &opcode); |
| if (result) |
| return result; |
| |
| 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); |
| } |
| |
| 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; |
| } |
| ret = set_swbp(&uprobe->arch, mm, addr); |
| |
| return ret; |
| } |
| |
| static void |
| remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, loff_t vaddr) |
| { |
| set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true); |
| } |
| |
| /* |
| * 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_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(uprobe, mm, vma, vi->vaddr); |
| else |
| remove_breakpoint(uprobe, mm, 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 __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; |
| |
| 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; |
| |
| 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) { |
| ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr); |
| /* Ignore double add: */ |
| if (ret == -EEXIST) |
| ret = 0; |
| } |
| } |
| put_uprobe(uprobe); |
| } |
| |
| mutex_unlock(uprobes_mmap_hash(inode)); |
| |
| return ret; |
| } |
| |
| /** |
| * 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); |
| |
| 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) |
| { |
| 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; |
| } |
| |
| /* |
| * 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 vm_area_struct *vma; |
| struct uprobe_task *utask; |
| struct uprobe *uprobe; |
| struct mm_struct *mm; |
| unsigned long bp_vaddr; |
| |
| uprobe = NULL; |
| bp_vaddr = uprobe_get_swbp_addr(regs); |
| mm = current->mm; |
| down_read(&mm->mmap_sem); |
| vma = find_vma(mm, bp_vaddr); |
| |
| if (vma && vma->vm_start <= bp_vaddr && 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); |
| } |
| |
| srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id); |
| current->uprobe_srcu_id = -1; |
| up_read(&mm->mmap_sem); |
| |
| 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); |
| |
| 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) |
| 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); |