Re: [PATCH v4 3.0-rc2-tip 7/22] 7: uprobes: mmap and fork hooks.

Stephen Wilson
2011-06-08T22:14:09Z

On Tue, Jun 07, 2011 at 06:29:31PM +0530, Srikar Dronamraju wrote:
> +static void add_to_temp_list(struct vm_area_struct *vma, struct inode *inode,
> + struct list_head *tmp_list)
> +{
> + struct uprobe *uprobe;
> + struct rb_node *n;
> + unsigned long flags;
> +
> + n = uprobes_tree.rb_node;
> + spin_lock_irqsave(&uprobes_treelock, flags);
> + uprobe = __find_uprobe(inode, 0, &n);

It is valid for a uprobe offset to be zero I guess, so perhaps we need
to do a put_uprobe() here when the result of __find_uprobe() is
non-null.

> + for (; n; n = rb_next(n)) {
> + uprobe = rb_entry(n, struct uprobe, rb_node);
> + if (uprobe->inode != inode)
> + break;
> + list_add(&uprobe->pending_list, tmp_list);
> + continue;
> + }
> + spin_unlock_irqrestore(&uprobes_treelock, flags);
> +}
> +
> +/*
> + * Called from dup_mmap.
> + * called with mm->mmap_sem and old_mm->mmap_sem acquired.
> + */
> +void dup_mmap_uprobe(struct mm_struct *old_mm, struct mm_struct *mm)
> +{
> + atomic_set(&old_mm->uprobes_count,
> + atomic_read(&mm->uprobes_count));
> +}
> +
> +/*
> + * 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
> + * - no possible probes to be inserted.
> + * - insertion of probes failed but we can bail-out.
> + */
> +int mmap_uprobe(struct vm_area_struct *vma)
> +{
> + struct list_head tmp_list;
> + struct uprobe *uprobe, *u;
> + struct mm_struct *mm;
> + struct inode *inode;
> + unsigned long start, pgoff;
> + int ret = 0;
> +
> + if (!valid_vma(vma))
> + return ret; /* Bail-out */
> +
> + INIT_LIST_HEAD(&tmp_list);
> +
> + mm = vma->vm_mm;
> + inode = vma->vm_file->f_mapping->host;
> + start = vma->vm_start;
> + pgoff = vma->vm_pgoff;
> + __iget(inode);
> +
> + up_write(&mm->mmap_sem);
> + mutex_lock(&uprobes_mutex);
> + down_read(&mm->mmap_sem);
> +
> + vma = find_vma(mm, start);
> + /* Not the same vma */
> + if (!vma || vma->vm_start != start ||
> + vma->vm_pgoff != pgoff || !valid_vma(vma) ||
> + inode->i_mapping != vma->vm_file->f_mapping)
> + goto mmap_out;
> +
> + add_to_temp_list(vma, inode, &tmp_list);
> + list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
> + loff_t vaddr;
> +
> + list_del(&uprobe->pending_list);
> + if (ret)
> + continue;
> +
> + vaddr = vma->vm_start + uprobe->offset;
> + vaddr -= vma->vm_pgoff << PAGE_SHIFT;
> + if (vaddr < vma->vm_start || vaddr > vma->vm_end)

Another place where the check should be "vaddr >= vma->vm_end" I think?

Thanks,

> + /* Not in this vma */
> + continue;
> + if (vaddr > TASK_SIZE)
> + /*
> + * We cannot have a virtual address that is
> + * greater than TASK_SIZE
> + */
> + continue;
> + mm->uprobes_vaddr = (unsigned long)vaddr;
> + ret = install_breakpoint(mm, uprobe);
> + if (ret && (ret == -ESRCH || ret == -EEXIST))
> + ret = 0;
> + }
> +
> +mmap_out:
> + mutex_unlock(&uprobes_mutex);
> + iput(inode);
> + up_read(&mm->mmap_sem);
> + down_write(&mm->mmap_sem);
> + return ret;
> +}

--
steve