From 4043c8b5b751a94b7ee6acab3a230d623b6590f8 Mon Sep 17 00:00:00 2001
From: Matt Harvey <mattharvey@google.com>
Date: Fri, 13 Aug 2021 14:26:43 -0700
Subject: [PATCH] Mutex guards kata-uart-client read and write

Change-Id: I5757dcf68f64359b743f458f336a813aeb43c069
GitOrigin-RevId: 1c6c85f95c6509cc915df1b82076942cd540c441
---
 .../components/DebugConsole/DebugConsole.camkes      |  2 ++
 .../DebugConsole/kata-uart-client/src/lib.rs         | 12 ++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/apps/system/components/DebugConsole/DebugConsole.camkes b/apps/system/components/DebugConsole/DebugConsole.camkes
index 2ff735e..fb569a2 100644
--- a/apps/system/components/DebugConsole/DebugConsole.camkes
+++ b/apps/system/components/DebugConsole/DebugConsole.camkes
@@ -9,9 +9,11 @@ component DebugConsole {
 
   dataport Buf tx_dataport;
   uses dataport_io_inf uart_tx;
+  has mutex tx_mutex;
 
   dataport Buf rx_dataport;
   uses dataport_io_inf uart_rx;
+  has mutex rx_mutex;
 
   provides LoggerInterface logger;
   uses ProcessControlInterface proc_ctrl;
diff --git a/apps/system/components/DebugConsole/kata-uart-client/src/lib.rs b/apps/system/components/DebugConsole/kata-uart-client/src/lib.rs
index 2185a76..9f0c152 100644
--- a/apps/system/components/DebugConsole/kata-uart-client/src/lib.rs
+++ b/apps/system/components/DebugConsole/kata-uart-client/src/lib.rs
@@ -7,15 +7,19 @@ use kata_io as io;
 // C interface to external UART driver.
 extern "C" {
     static rx_dataport: *mut cty::c_uchar;
-    static tx_dataport: *mut cty::c_uchar;
     fn uart_rx_update(n: cty::size_t);
+    fn rx_mutex_lock();
+    fn rx_mutex_unlock();
+
+    static tx_dataport: *mut cty::c_uchar;
     fn uart_tx_update(n: cty::size_t);
+    fn tx_mutex_lock();
+    fn tx_mutex_unlock();
 }
 
 // Console logging interface.
 #[no_mangle]
 pub extern "C" fn logger_log(msg: *const cstr_core::c_char) {
-    // TODO(sleffler): is the uart driver ok w/ multiple writers?
     let output: &mut dyn io::Write = &mut self::Tx {};
     unsafe {
         let _ = writeln!(output, "{}", CStr::from_ptr(msg).to_str().unwrap());
@@ -27,9 +31,11 @@ pub struct Rx {}
 impl io::Read for Rx {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize, io::Error> {
         unsafe {
+            rx_mutex_lock();
             uart_rx_update(buf.len());
             let port = core::slice::from_raw_parts(rx_dataport, buf.len());
             buf.copy_from_slice(&port);
+            rx_mutex_unlock();
         }
         Ok(buf.len())
     }
@@ -40,9 +46,11 @@ pub struct Tx {}
 impl io::Write for Tx {
     fn write(&mut self, buf: &[u8]) -> Result<usize, io::Error> {
         unsafe {
+            tx_mutex_lock();
             let port = core::slice::from_raw_parts_mut(tx_dataport, buf.len());
             port.copy_from_slice(buf);
             uart_tx_update(buf.len());
+            tx_mutex_unlock();
         }
         Ok(buf.len())
     }