On Fri, Oct 30, 2020 at 4:07 AM KP Singh <kpsingh@xxxxxxxxxxxx> wrote: > > " > > On Fri, Oct 30, 2020 at 12:28 AM Song Liu <song@xxxxxxxxxx> wrote: > > > > On Wed, Oct 28, 2020 at 9:17 AM KP Singh <kpsingh@xxxxxxxxxxxx> wrote: > > > > > > From: KP Singh <kpsingh@xxxxxxxxxx> > > > > > > Similar to bpf_local_storage for sockets and inodes add local storage > > > for task_struct. > > > > > > The life-cycle of storage is managed with the life-cycle of the > > > task_struct. i.e. the storage is destroyed along with the owning task > > > with a callback to the bpf_task_storage_free from the task_free LSM > > > hook. > > > > It looks like task local storage is tightly coupled to LSM. As we discussed, > > it will be great to use task local storage in tracing programs. Would you > > like to enable it from the beginning? Alternatively, I guess we can also do > > follow-up patches. > > > > I would prefer if we do it in follow-up patches. > > > > > > > The BPF LSM allocates an __rcu pointer to the bpf_local_storage in > > > the security blob which are now stackable and can co-exist with other > > > LSMs. > > > > > > The userspace map operations can be done by using a pid fd as a key > > > passed to the lookup, update and delete operations. > > > > While testing task local storage, I noticed a limitation of pid fd: > > > > /* Currently, the process identified by > > * @pid must be a thread-group leader. This restriction currently exists > > * for all aspects of pidfds including pidfd creation (CLONE_PIDFD cannot > > * be used with CLONE_THREAD) and pidfd polling (only supports thread group > > * leaders). > > */ > > > > This could be a problem for some use cases. How about we try to remove > > this restriction (maybe with a new flag to pidfd_open) as part of this set? > > I would appreciate it if we could also do this in a follow-up patch. > > I do see that there is a comment in fork.c: > > "CLONE_THREAD is blocked until someone really needs it." > > But I don't understand the requirements well enough and would thus prefer > to do this in a follow-up series. Sounds good. Let's work on these in follow-up patches. Thanks, Song
