Messages in this thread | | | Date | Fri, 24 Jun 2011 07:36:59 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH v4 3.0-rc2-tip 7/22] 7: uprobes: mmap and fork hooks. |
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> > so I am thinking of a solution that includes most of your ideas along > with using i_mmap_mutex in mmap_uprobe path. >
Addressing Peter's comments given on irc wrt i_mmap_mutex.
/* Changes: 1. Uses inode->i_mutex instead of uprobes_mutex. 2. Now along with vma rma walk, i_mmap_mutex is even held when we do deletion of uprobes into RB tree. 3. mmap_uprobe takes i_mmap_mutex.
Advantages: 1. No need to drop mmap_sem. 2. Now register/unregister can run in parallel. 3. */
void _unregister_uprobe(...) { if (!del_consumer(...)) { // includes tree removal on last consumer return; } if (uprobe->consumers) return;
mutex_lock(&mapping->i_mmap_mutex); //sync with mmap. vma_prio_tree_foreach() { // create list }
mutex_unlock(&mapping->i_mmap_mutex);
list_for_each_entry_safe() { // remove from list down_read(&mm->mmap_sem); remove_breakpoint(); // unconditional, if it wasn't there up_read(&mm->mmap_sem); }
mutex_lock(&mapping->i_mmap_mutex); delete_uprobe(uprobe); mutex_unlock(&mapping->i_mmap_mutex);
inode->uprobes_count--; mutex_unlock(&inode->i_mutex); }
int register_uprobe(...) { uprobe = alloc_uprobe(...); // find or insert in tree
mutex_lock(&inode->i_mutex); // sync with register/unregister if (uprobe->consumers) { add_consumer(); goto put_unlock; } add_consumer(); inode->uprobes_count++; mutex_lock(&mapping->i_mmap_mutex); //sync with mmap. vma_prio_tree_foreach(..) { // get mm ref, add to list blah blah }
mutex_unlock(&mapping->i_mmap_mutex); list_for_each_entry_safe() { if (ret) { // del from list etc.. // continue; } down_read(mm->mmap_sem); ret = install_breakpoint(); up_read(..); // del from list etc.. // if (ret && (ret == -ESRCH || ret == -EEXIST)) ret = 0; }
if (ret) _unregister_uprobe();
put_unlock: mutex_unlock(&inode->i_mutex); put_uprobe(uprobe); return ret; }
void unregister_uprobe(...) { mutex_lock(&inode->i_mutex); // sync with register/unregister uprobe = find_uprobe(); // ref++ _unregister_uprobe(); mutex_unlock(&inode->i_mutex); put_uprobe(uprobe); }
int mmap_uprobe(struct vm_area_struct *vma) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct mm_struct *mm; struct inode *inode; int ret = 0;
if (!valid_vma(vma)) return ret; /* Bail-out */
mm = vma->vm_mm; inode = vma->vm_file->f_mapping->host; if (inode->uprobes_count) return ret; __iget(inode);
INIT_LIST_HEAD(&tmp_list);
mutex_lock(&mapping->i_mmap_mutex); 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; ret = install_breakpoint(mm, uprobe, vaddr);
if (ret && (ret == -ESRCH || ret == -EEXIST)) ret = 0; }
mutex_unlock(&mapping->i_mmap_mutex); iput(inode); return ret; }
int munmap_uprobe(struct vm_area_struct *vma) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct mm_struct *mm; struct inode *inode; int ret = 0;
if (!valid_vma(vma)) return ret; /* Bail-out */
mm = vma->vm_mm; inode = vma->vm_file->f_mapping->host; if (inode->uprobes_count) return ret;
// walk thro RB tree and decrement mm->uprobes_count walk_rbtree_and_dec_uprobes_count(); //hold treelock.
return ret; }
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