rust_binder: avoid name mangling for get_work[_local]

Currently ps -A shows processes waiting on schedule() in functions with
names such as do_epoll_wait, wait_woken, and the impeccably named
_RNvMs2_NtCs8QPsHWIn21X_16rust_binder_main6threadNtB5_6Thread8get_work.

To improve how ps output looks, give explicit non-mangled names to the
functions where Rust Binder calls schedule(), since these are the most
likely places to show up on ps output.

The name of rust_binder_waitlcl is truncated instead of using _local
suffix because rust_binder_wait_local is sufficiently long that ps shows
unaligned output.

This is intended to be a temporary workaround until we find a better
solution. Adding #[export_name] to every Rust function that calls
schedule() is not a great long-term solution.

Suggested-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260219-rust-binder-ps-v2-1-773eca09c125@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder/process.rs

@@ -1442,6 +1442,9 @@ pub(crate) fn drop_outstanding_txn(&self) {
         }
     }
 
+    // #[export_name] is a temporary workaround so that ps output does not become unreadable from
+    // mangled symbol names.
+    #[export_name = "rust_binder_freeze"]
     pub(crate) fn ioctl_freeze(&self, info: &BinderFreezeInfo) -> Result {
         if info.enable == 0 {
             let msgs = self.prepare_freeze_messages()?;

drivers/android/binder/thread.rs

@@ -513,6 +513,9 @@ pub(crate) fn has_current_transaction(&self) -> bool {
     /// Attempts to fetch a work item from the thread-local queue. The behaviour if the queue is
     /// empty depends on `wait`: if it is true, the function waits for some work to be queued (or a
     /// signal); otherwise it returns indicating that none is available.
+    // #[export_name] is a temporary workaround so that ps output does not become unreadable from
+    // mangled symbol names.
+    #[export_name = "rust_binder_waitlcl"]
     fn get_work_local(self: &Arc<Self>, wait: bool) -> Result<Option<DLArc<dyn DeliverToRead>>> {
         {
             let mut inner = self.inner.lock();
@@ -551,6 +554,9 @@ fn get_work_local(self: &Arc<Self>, wait: bool) -> Result<Option<DLArc<dyn Deliv
     ///
     /// This must only be called when the thread is not participating in a transaction chain. If it
     /// is, the local version (`get_work_local`) should be used instead.
+    // #[export_name] is a temporary workaround so that ps output does not become unreadable from
+    // mangled symbol names.
+    #[export_name = "rust_binder_wait"]
     fn get_work(self: &Arc<Self>, wait: bool) -> Result<Option<DLArc<dyn DeliverToRead>>> {
         // Try to get work from the thread's work queue, using only a local lock.
         {