diff options
Diffstat (limited to 'kernel/events/uprobes.c')
| -rw-r--r-- | kernel/events/uprobes.c | 1667 |
1 files changed, 1667 insertions, 0 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c new file mode 100644 index 0000000..985be4d --- /dev/null +++ b/kernel/events/uprobes.c @@ -0,0 +1,1667 @@ +/* + * 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> + +#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, 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); +} + +/* + * 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_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, 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; +} + +/* + * 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); + 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); |
