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

Peter Zijlstra
2011-06-16T18:26:10Z

On Thu, 2011-06-16 at 20:23 +0200, Peter Zijlstra wrote:
> int __register_uprobe(...)
> {
> uprobe = alloc_uprobe(...); // find or insert in tree
>
> vma_prio_tree_foreach(..) {
> // get mm ref, add to list blah blah
> }
>
> list_for_each_entry_safe() {
> // del from list etc..
> down_read(mm->mmap_sem);
> ret = install_breakpoint();
> if (ret && (ret != -ESRCH || ret != -EEXIST)) {
> up_read(..);
> goto fail;
> }
>
> return 0;
>
> fail:
> list_for_each_entry_safe() {
> // del from list, put mm
> }
>
> return ret;
> }
>
> void __unregister_uprobe(...)
> {
> uprobe = find_uprobe(); // ref++
> if (delete_consumer(...)); // includes tree removal on last consumer
> // implies we own the last ref
> return; // consumers
>
> vma_prio_tree_foreach() {
> // create list
> }
>
> list_for_each_entry_safe() {
> // remove from list
> remove_breakpoint(); // unconditional, if it wasn't there
> // its a nop anyway, can't get any new
> // new probes on account of holding
> // uprobes_mutex and mmap() doesn't see
> // it due to tree removal.
> }

put_uprobe(); // last ref, *poof*
> }
>
> int register_uprobe(...)
> {
> int ret;
>
> mutex_lock(&uprobes_mutex);
> ret = __register_uprobe(...);
> if (!ret)
> __unregister_uprobe(...);
> mutex_unlock(&uprobes_mutex);
>
> ret;
> }
>
> int mmap_uprobe(...)
> {
> spin_lock(&uprobes_treelock);
> for_each_probe_in_inode() {
> // create list;
> }
> spin_unlock(..);
>
> list_for_each_entry_safe() {
> // remove from list
> ret = install_breakpoint();
> if (ret)
> goto fail;
> if (!uprobe_still_there()) // takes treelock
> remove_breakpoint();
> }
>
> return 0;
>
> fail:
> list_for_each_entry_safe() {
> // destroy list
> }
> return ret;
> }