lkml.org 
[lkml]   [2011]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v4 3.0-rc2-tip 4/22] 4: Uprobes: register/unregister probes.

    Hi Srikar,

    Just a few questions/comments inline below.

    On Tue, Jun 07, 2011 at 06:29:00PM +0530, Srikar Dronamraju wrote:
    > +int register_uprobe(struct inode *inode, loff_t offset,
    > + struct uprobe_consumer *consumer)
    > +{
    > + struct prio_tree_iter iter;
    > + struct list_head try_list, success_list;
    > + struct address_space *mapping;
    > + struct mm_struct *mm, *tmpmm;
    > + struct vm_area_struct *vma;
    > + struct uprobe *uprobe;
    > + int ret = -1;
    > +
    > + if (!inode || !consumer || consumer->next)
    > + return -EINVAL;
    > +
    > + if (offset > inode->i_size)
    > + return -EINVAL;
    > +
    > + uprobe = alloc_uprobe(inode, offset);
    > + if (!uprobe)
    > + return -ENOMEM;
    > +
    > + INIT_LIST_HEAD(&try_list);
    > + INIT_LIST_HEAD(&success_list);
    > + mapping = inode->i_mapping;
    > +
    > + mutex_lock(&uprobes_mutex);
    > + if (uprobe->consumers) {
    > + ret = 0;
    > + goto consumers_add;
    > + }
    > +
    > + mutex_lock(&mapping->i_mmap_mutex);
    > + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, 0) {
    > + loff_t vaddr;
    > + struct task_struct *tsk;
    > +
    > + if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
    > + continue;
    > +
    > + mm = vma->vm_mm;
    > + if (!valid_vma(vma)) {
    > + mmput(mm);
    > + continue;
    > + }
    > +
    > + vaddr = vma->vm_start + offset;
    > + vaddr -= vma->vm_pgoff << PAGE_SHIFT;
    > + if (vaddr < vma->vm_start || vaddr > vma->vm_end) {

    This check looks like it is off by one? vma->vm_end is already one byte
    past the last valid address in the vma, so we should compare using ">="
    here I think.

    > + /* Not in this vma */
    > + mmput(mm);
    > + continue;
    > + }
    > + tsk = get_mm_owner(mm);
    > + if (tsk && vaddr > TASK_SIZE_OF(tsk)) {
    > + /*
    > + * We cannot have a virtual address that is
    > + * greater than TASK_SIZE_OF(tsk)
    > + */
    > + put_task_struct(tsk);
    > + mmput(mm);
    > + continue;
    > + }
    > + put_task_struct(tsk);
    > + mm->uprobes_vaddr = (unsigned long) vaddr;
    > + list_add(&mm->uprobes_list, &try_list);
    > + }
    > + mutex_unlock(&mapping->i_mmap_mutex);
    > +
    > + if (list_empty(&try_list)) {
    > + ret = 0;
    > + goto consumers_add;
    > + }
    > + list_for_each_entry_safe(mm, tmpmm, &try_list, uprobes_list) {
    > + down_read(&mm->mmap_sem);
    > + ret = install_breakpoint(mm, uprobe);
    > +
    > + if (ret && (ret != -ESRCH || ret != -EEXIST)) {
    > + up_read(&mm->mmap_sem);
    > + break;
    > + }
    > + if (!ret)
    > + list_move(&mm->uprobes_list, &success_list);
    > + else {
    > + /*
    > + * install_breakpoint failed as there are no active
    > + * threads for the mm; ignore the error.
    > + */
    > + list_del(&mm->uprobes_list);
    > + mmput(mm);
    > + }
    > + up_read(&mm->mmap_sem);
    > + }
    > +
    > + if (list_empty(&try_list)) {
    > + /*
    > + * All install_breakpoints were successful;
    > + * cleanup successful entries.
    > + */
    > + ret = 0;
    > + list_for_each_entry_safe(mm, tmpmm, &success_list,
    > + uprobes_list) {
    > + list_del(&mm->uprobes_list);
    > + mmput(mm);
    > + }
    > + goto consumers_add;
    > + }
    > +
    > + /*
    > + * Atleast one unsuccessful install_breakpoint;
    > + * remove successful probes and cleanup untried entries.
    > + */
    > + list_for_each_entry_safe(mm, tmpmm, &success_list, uprobes_list)
    > + remove_breakpoint(mm, uprobe);
    > + list_for_each_entry_safe(mm, tmpmm, &try_list, uprobes_list) {
    > + list_del(&mm->uprobes_list);
    > + mmput(mm);
    > + }
    > + delete_uprobe(uprobe);
    > + goto put_unlock;
    > +
    > +consumers_add:
    > + add_consumer(uprobe, consumer);
    > +
    > +put_unlock:
    > + mutex_unlock(&uprobes_mutex);
    > + put_uprobe(uprobe); /* drop access ref */
    > + return ret;
    > +}
    > +
    > +/*
    > + * unregister_uprobe - unregister a already registered probe.
    > + * @inode: the file in which the probe has to be removed.
    > + * @offset: offset from the start of the file.
    > + * @consumer: identify which probe if multiple probes are colocated.
    > + */
    > +void unregister_uprobe(struct inode *inode, loff_t offset,
    > + struct uprobe_consumer *consumer)
    > +{
    > + struct prio_tree_iter iter;
    > + struct list_head tmp_list;
    > + struct address_space *mapping;
    > + struct mm_struct *mm, *tmpmm;
    > + struct vm_area_struct *vma;
    > + struct uprobe *uprobe;
    > +
    > + if (!inode || !consumer)
    > + return;
    > +
    > + uprobe = find_uprobe(inode, offset);
    > + if (!uprobe) {
    > + pr_debug("No uprobe found with inode:offset %p %lld\n",
    > + inode, offset);
    > + return;
    > + }
    > +
    > + if (!del_consumer(uprobe, consumer)) {
    > + pr_debug("No uprobe found with consumer %p\n",
    > + consumer);
    > + return;
    > + }

    When del_consumer() fails dont we still need to do a put_uprobe(uprobe)
    to drop the extra access ref?

    > +
    > + INIT_LIST_HEAD(&tmp_list);
    > +
    > + mapping = inode->i_mapping;
    > +
    > + mutex_lock(&uprobes_mutex);
    > + if (uprobe->consumers)
    > + goto put_unlock;
    > +
    > + mutex_lock(&mapping->i_mmap_mutex);
    > + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, 0) {
    > + struct task_struct *tsk;
    > +
    > + if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
    > + continue;
    > +
    > + mm = vma->vm_mm;
    > +
    > + if (!atomic_read(&mm->uprobes_count)) {
    > + mmput(mm);
    > + continue;
    > + }
    > +
    > + if (valid_vma(vma)) {
    > + loff_t vaddr;
    > +
    > + vaddr = vma->vm_start + offset;
    > + vaddr -= vma->vm_pgoff << PAGE_SHIFT;
    > + if (vaddr < vma->vm_start || vaddr > vma->vm_end) {

    Same issue with the comparison against vma->vm_end here as well.


    Thanks,

    > + /* Not in this vma */
    > + mmput(mm);
    > + continue;
    > + }
    > + tsk = get_mm_owner(mm);
    > + if (tsk && vaddr > TASK_SIZE_OF(tsk)) {
    > + /*
    > + * We cannot have a virtual address that is
    > + * greater than TASK_SIZE_OF(tsk)
    > + */
    > + put_task_struct(tsk);
    > + mmput(mm);
    > + continue;
    > + }
    > + put_task_struct(tsk);
    > + mm->uprobes_vaddr = (unsigned long) vaddr;
    > + list_add(&mm->uprobes_list, &tmp_list);
    > + } else
    > + mmput(mm);
    > + }
    > + mutex_unlock(&mapping->i_mmap_mutex);
    > + list_for_each_entry_safe(mm, tmpmm, &tmp_list, uprobes_list)
    > + remove_breakpoint(mm, uprobe);
    > +
    > + delete_uprobe(uprobe);
    > +
    > +put_unlock:
    > + mutex_unlock(&uprobes_mutex);
    > + put_uprobe(uprobe); /* drop access ref */
    > +}

    --
    steve



    \
     
     \ /
      Last update: 2011-06-09 00:15    [W:0.037 / U:0.872 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site