Merge "Aligns UART API with Rust Read and Write"

GitOrigin-RevId: df407ae4bddb75b1bc43c35062947679c2b10c3a

apps/system/components/DebugConsole/DebugConsole.camkes

@@ -10,12 +10,10 @@ component DebugConsole {
   control;
 
   dataport Buf tx_dataport;
-  uses dataport_io_inf uart_tx;
-  has mutex tx_mutex;
+  uses rust_write_inf uart_write;
 
   dataport Buf rx_dataport;
-  uses dataport_io_inf uart_rx;
-  has mutex rx_mutex;
+  uses rust_read_inf uart_read;
 
   provides LoggerInterface logger;
   uses ProcessControlInterface proc_ctrl;

apps/system/components/DebugConsole/kata-debug-console/src/run.rs

@@ -44,7 +44,7 @@ pub extern "C" fn pre_init() {
 #[no_mangle]
 pub extern "C" fn run() -> ! {
     trace!("run");
-    let mut tx = kata_uart_client::Tx {};
-    let mut rx = kata_uart_client::Rx {};
+    let mut tx = kata_uart_client::Tx::new();
+    let mut rx = kata_uart_client::Rx::new();
     kata_shell::repl(&mut tx, &mut rx);
 }

apps/system/components/DebugConsole/kata-uart-client/src/lib.rs

@@ -4,19 +4,6 @@ use core::fmt::Write;
 use cstr_core::CStr;
 use kata_io as io;
 
-// C interface to external UART driver.
-extern "C" {
-    static rx_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(level: u8, msg: *const cstr_core::c_char) {
@@ -30,44 +17,83 @@ pub extern "C" fn logger_log(level: u8, msg: *const cstr_core::c_char) {
     };
     if l <= log::max_level() {
         // TODO(sleffler): is the uart driver ok w/ multiple writers?
-        let output: &mut dyn io::Write = &mut self::Tx {};
+        let output: &mut dyn io::Write = &mut self::Tx::new();
         unsafe {
             let _ = writeln!(output, "{}", CStr::from_ptr(msg).to_str().unwrap());
         }
     }
 }
 
-pub struct Rx {}
+const DATAPORT_SIZE: usize = 4096;
+
+pub struct Rx {
+    dataport: &'static [u8],
+}
+
+impl Rx {
+    pub fn new() -> Rx {
+        extern "C" {
+            static rx_dataport: *mut cty::c_uchar;
+        }
+        Rx {
+            dataport: unsafe { core::slice::from_raw_parts(rx_dataport, DATAPORT_SIZE) },
+        }
+    }
+}
 
 impl io::Read for Rx {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        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();
+        extern "C" {
+            fn uart_read_read(limit: cty::size_t) -> cty::c_int;
+        }
+        let n = unsafe { uart_read_read(buf.len()) };
+        if n >= 0 {
+            let s = n as usize;
+            buf[..s].copy_from_slice(&self.dataport[..s]);
+            Ok(s)
+        } else {
+            Err(io::Error)
         }
-        Ok(buf.len())
     }
 }
 
-pub struct Tx {}
+pub struct Tx {
+    dataport: &'static mut [u8],
+}
+
+impl Tx {
+    pub fn new() -> Tx {
+        extern "C" {
+            static tx_dataport: *mut cty::c_uchar;
+        }
+        Tx {
+            dataport: unsafe { core::slice::from_raw_parts_mut(tx_dataport, DATAPORT_SIZE) },
+        }
+    }
+}
 
 impl io::Write for Tx {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        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();
+        extern "C" {
+            fn uart_write_write(available: cty::size_t) -> cty::c_int;
+        }
+        self.dataport[..buf.len()].copy_from_slice(buf);
+        let n = unsafe { uart_write_write(buf.len()) };
+        if n >= 0 {
+            Ok(n as usize)
+        } else {
+            Err(io::Error)
         }
-        Ok(buf.len())
     }
 
     fn flush(&mut self) -> io::Result<()> {
-        // Do nothing. This implementation has no internal buffering.
-        Ok(())
+        extern "C" {
+            fn uart_write_flush() -> cty::c_int;
+        }
+        if unsafe { uart_write_flush() } == 0 {
+            Ok(())
+        } else {
+            Err(io::Error)
+        }
     }
 }

apps/system/components/OpenTitanUARTDriver/OpenTitanUARTDriver.camkes

@@ -1,27 +1,23 @@
 /*
- * Copyright 2017, Data61
- * Commonwealth Scientific and Industrial Research Organisation (CSIRO)
- * ABN 41 687 119 230.
+ * CAmkES component accessing an OpenTitan UART.
  *
- * This software may be distributed and modified according to the terms of
- * the BSD 2-Clause license. Note that NO WARRANTY is provided.
- * See "LICENSE_BSD2.txt" for details.
- *
- * @TAG(DATA61_BSD)
+ * Copyright 2021, Google LLC
+ * Apache License 2.0
  */
 
+import "../../interfaces/RustIO.idl4";
+
 component OpenTitanUARTDriver {
   dataport Buf mmio_region;
 
   dataport Buf tx_dataport;
-  provides dataport_io_inf tx;
+  provides rust_write_inf write;
   consumes Interrupt tx_watermark;
   consumes Interrupt tx_empty;
-  has semaphore tx_semaphore;
   has mutex tx_mutex;
 
   dataport Buf rx_dataport;
-  provides dataport_io_inf rx;
+  provides rust_read_inf read;
   consumes Interrupt rx_watermark;
   has semaphore rx_semaphore;
   has mutex rx_mutex;

apps/system/components/OpenTitanUARTDriver/include/uart_driver_error.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2021, Google LLC
+ *
+ * Error codes for the OpenTitanUARTDriver.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+// Return codes for errors on read() and write().
+//
+// Normally these functions return the number of bytes actually read or written,
+// with 0 indicating the end of the stream. If something goes wrong, the
+// functions will return one of these negative values.
+typedef enum UARTDriverError {
+  UARTDriver_AssertionFailed = -1,
+  UARTDriver_OutOfDataportBounds = -2,
+} uart_driver_error_t;

apps/system/components/OpenTitanUARTDriver/src/driver.c

@@ -15,6 +15,7 @@
 
 #include "circular_buffer.h"
 #include "opentitan/uart.h"
+#include "uart_driver_error.h"
 
 // Referenced by macros in the generated file opentitan/uart.h.
 #define UART0_BASE_ADDR (void *)mmio_region
@@ -46,6 +47,13 @@
   ((value & UART_##regname##_##subfield##_MASK)     \
    << UART_##regname##_##subfield##_OFFSET)
 
+#define LOCK(lockname) seL4_Assert(lockname##_lock() == 0);
+#define UNLOCK(lockname) seL4_Assert(lockname##_unlock() == 0);
+#define ASSERT_OR_RETURN(x)            \
+  if (!(bool)(x)) {                    \
+    return UARTDriver_AssertionFailed; \
+  }
+
 // Driver-owned buffer to receive more than the FIFO size before the received
 // data is consumed by rx_update.
 static circular_buffer rx_buf;  // guarded by rx_mutex
@@ -84,7 +92,7 @@ static void uart_putchar(char c) {
 // This stops when the transmit FIFO is full or when tx_buf is empty, whichever
 // comes first.
 static void fill_tx_fifo() {
-  seL4_Assert(tx_mutex_lock() == 0);
+  LOCK(tx_mutex);
   while (tx_fifo_level() < UART_FIFO_CAPACITY) {
     char c;
     if (!circular_buffer_pop_front(&tx_buf, &c)) {
@@ -93,10 +101,7 @@ static void fill_tx_fifo() {
     }
     uart_putchar(c);
   }
-  if (circular_buffer_remaining(&tx_buf) > 0) {
-    seL4_Assert(tx_semaphore_post() == 0);
-  }
-  seL4_Assert(tx_mutex_unlock() == 0);
+  UNLOCK(tx_mutex);
 }
 
 // CAmkES initialization hook.
@@ -157,62 +162,86 @@ void pre_init() {
        BIT(UART_INTR_COMMON_TX_EMPTY));
 }
 
-// Implements the update method of the CAmkES dataport_inf rx.
+// Implements Rust Read::read().
 //
-// Reads a given number of bytes from rx_buf into the CAmkES rx_dataport,
-// blocking the RPC until the entire requested byte count has been read.
-void rx_update(uint32_t num_to_read) {
-  // TODO(mattharvey): Error return value for num_to_read >
-  // TX_RX_DATAPORT_CAPACITY.
-  seL4_Assert(num_to_read <= TX_RX_DATAPORT_CAPACITY);
+// Reads up to a given limit of bytes into the CAmkES rx_dataport, blocking
+// until at least one byte is available.
+int read_read(size_t limit) {
+  if (limit > TX_RX_DATAPORT_CAPACITY) {
+    return UARTDriver_OutOfDataportBounds;
+  }
+  char *cursor = (char *)rx_dataport;
+  char *const cursor_begin = cursor;
+  char *const cursor_limit = cursor_begin + limit;
 
-  char *dataport_cursor = (char *)rx_dataport;
-  char *const dataport_end = dataport_cursor + num_to_read;
-  while (dataport_cursor < dataport_end) {
-    seL4_Assert(rx_mutex_lock() == 0);
+  LOCK(rx_mutex);
+  {
     while (circular_buffer_empty(&rx_buf)) {
-      seL4_Assert(rx_mutex_unlock() == 0);
+      UNLOCK(rx_mutex);
       seL4_Assert(rx_semaphore_wait() == 0);
-      seL4_Assert(rx_mutex_lock() == 0);
+      LOCK(rx_mutex);
     }
-    for (; dataport_cursor < dataport_end; ++dataport_cursor) {
-      if (!circular_buffer_pop_front(&rx_buf, dataport_cursor)) {
+    while (cursor < cursor_limit) {
+      if (!circular_buffer_pop_front(&rx_buf, cursor)) {
         // The buffer is empty.
         break;
       }
+      ++cursor;
     }
-    seL4_Assert(rx_mutex_unlock() == 0);
   }
+  UNLOCK(rx_mutex);
+
+  int num_read = cursor - cursor_begin;
+  ASSERT_OR_RETURN(num_read > 0);
+  return num_read;
 }
 
-// Implements the update method of the CAmkES dataport_inf tx.
+// Implements Rust Write::write().
 //
-// Writes the contents of the CAmkES tx_dataport to the UART, one at a time,
-// blocking the RPC until the entire requested number of bytes has been written.
-void tx_update(uint32_t num_valid_dataport_bytes) {
-  // TODO(mattharvey): Error return value for num_valid_dataport_bytes >
-  // TX_RX_DATAPORT_CAPACITY.
-  seL4_Assert(num_valid_dataport_bytes <= TX_RX_DATAPORT_CAPACITY);
+// Writes as many bytes from tx_dataport as the hardware will accept, but not
+// more than the number available (specified by the argument). Returns the
+// number of bytes written or a negative value if there is any error.
+int write_write(size_t available) {
+  if (available > TX_RX_DATAPORT_CAPACITY) {
+    return UARTDriver_OutOfDataportBounds;
+  }
+  const char *cursor = (const char *)tx_dataport;
+  const char *const cursor_begin = cursor;
+  const char *const cursor_limit = cursor_begin + available;
 
-  const char *dataport_cursor = (const char *)tx_dataport;
-  const char *const dataport_end = dataport_cursor + num_valid_dataport_bytes;
-  while (dataport_cursor < dataport_end) {
-    seL4_Assert(tx_mutex_lock() == 0);
-    while (circular_buffer_remaining(&tx_buf) == 0) {
-      seL4_Assert(tx_mutex_unlock() == 0);
-      seL4_Assert(tx_semaphore_wait() == 0);
-      seL4_Assert(tx_mutex_lock() == 0);
-    }
-    for (; dataport_cursor < dataport_end; ++dataport_cursor) {
-      if (!circular_buffer_push_back(&tx_buf, *dataport_cursor)) {
-        // The buffer is full.
+  while (cursor < cursor_limit) {
+    LOCK(tx_mutex);
+    {
+      if (circular_buffer_remaining(&tx_buf) == 0) {
         break;
       }
+      for (; cursor < cursor_limit; ++cursor) {
+        if (!circular_buffer_push_back(&tx_buf, *cursor)) {
+          // The buffer is full.
+          break;
+        }
+      }
     }
-    seL4_Assert(tx_mutex_unlock() == 0);
+    UNLOCK(tx_mutex);
   }
 
   fill_tx_fifo();
+
+  int num_written = cursor - cursor_begin;
+  ASSERT_OR_RETURN(num_written > 0);
+  return num_written;
+}
+
+// Implements Rust Write::flush().
+//
+// Drains tx_buf and TX_FIFO. Returns a negative value if there is any error.
+int write_flush() {
+  LOCK(tx_mutex);
+  while (circular_buffer_remaining(&tx_buf)) {
+    fill_tx_fifo();
+  }
+  UNLOCK(tx_mutex);
+  return 0;
 }
 
 // Handles a tx_watermark interrupt.
@@ -247,7 +276,7 @@ void rx_watermark_handle(void) {
   }
 
   uint32_t num_read = 0;
-  seL4_Assert(rx_mutex_lock() == 0);
+  LOCK(rx_mutex);
   while (num_read < num_to_read) {
     if (!circular_buffer_push_back(&rx_buf, uart_getchar())) {
       // The buffer is full.
@@ -255,7 +284,7 @@ void rx_watermark_handle(void) {
     }
     ++num_read;
   }
-  seL4_Assert(rx_mutex_unlock() == 0);
+  UNLOCK(rx_mutex);
 
   if (num_read > 0) {
     seL4_Assert(rx_semaphore_post() == 0);
@@ -275,14 +304,16 @@ void rx_watermark_handle(void) {
 void tx_empty_handle(void) {
   fill_tx_fifo();
 
-  seL4_Assert(tx_mutex_lock() == 0);
-  if (circular_buffer_empty(&tx_buf)) {
-    // Clears INTR_STATE for tx_empty. (INTR_STATE is write-1-to-clear.) We only
-    // do this if tx_buf is empty, since the TX FIFO might have become empty in
-    // the time from fill_tx_fifo having sent the last character until here. In
-    // that case, we want the interrupt to reassert.
-    REG(INTR_STATE) = BIT(UART_INTR_STATE_TX_EMPTY);
+  LOCK(tx_mutex);
+  {
+    if (circular_buffer_empty(&tx_buf)) {
+      // Clears INTR_STATE for tx_empty. (INTR_STATE is write-1-to-clear.) We
+      // only do this if tx_buf is empty, since the TX FIFO might have become
+      // empty in the time from fill_tx_fifo having sent the last character
+      // until here. In that case, we want the interrupt to reassert.
+      REG(INTR_STATE) = BIT(UART_INTR_STATE_TX_EMPTY);
+    }
+    seL4_Assert(tx_empty_acknowledge() == 0);
   }
-  seL4_Assert(tx_empty_acknowledge() == 0);
-  seL4_Assert(tx_mutex_unlock() == 0);
+  UNLOCK(tx_mutex);
 }

apps/system/interfaces/RustIO.idl4

@@ -0,0 +1,38 @@
+/*
+ * CAmkES backing for Rust Read and Write traits.
+ *
+ * Copyright 2021, Google LLC
+ * Apache License 2.0
+ *
+ * These CAmkES interfaces express the standard Rust read() and write()
+ * signatures, assuming two separate, externally defined, and implicitly
+ * associated dataports for each of read and write.
+ *
+ * It is intended that Rust code be able to use extern "C" declarations
+ * referencing the camkes.h that this will generate as the core of
+ * implementations of the Read and Write traits.
+ */
+
+procedure rust_read_inf {
+  // Reads up to limit bytes into the read dataport.
+  //
+  // Returns the number of bytes read or a negative value if there is any
+  // error.
+  int read(in size_t limit);
+};
+
+procedure rust_write_inf {
+  // Writes up to a given number of bytes from the write dataport.
+  //
+  // Returns the number of bytes actually written or a negative value if there
+  // is any error. For non-negative return values < available, the caller is
+  // reponsible for retrying with the remaining bytes at the beginning of the
+  // write dataport.
+  int write(in size_t available);
+
+  // Blocks until all bytes so far written have been pushed to the real sink.
+  //
+  // The semantics are the same as Rust's Write::flush. Returns 0 on success
+  // and a negative value if there is any error.
+  int flush();
+}

apps/system/interfaces/dataport_io.idl4

@@ -1,15 +0,0 @@
-/*
- * Copyright 2017, Data61
- * Commonwealth Scientific and Industrial Research Organisation (CSIRO)
- * ABN 41 687 119 230.
- *
- * This software may be distributed and modified according to the terms of
- * the BSD 2-Clause license. Note that NO WARRANTY is provided.
- * See "LICENSE_BSD2.txt" for details.
- *
- * @TAG(DATA61_BSD)
- */
-
-procedure dataport_io_inf {
-  void update(in size_t n);
-};

apps/system/system.camkes

@@ -13,7 +13,6 @@
 import <std_connector.camkes>;
 import <global-connectors.camkes>;
 
-import "interfaces/dataport_io.idl4";
 import "interfaces/VectorCoreInterface.camkes";
 import "interfaces/VectorCoreReturnInterface.camkes";
 import "components/OpenTitanUARTDriver/OpenTitanUARTDriver.camkes";
@@ -108,12 +107,12 @@ assembly {
         // Connect the DebugConsole to the OpenTitanUARTDriver.
         connection seL4SharedData tx_channel(
             from debug_console.tx_dataport, to uart_driver.tx_dataport);
-        connection seL4RPCCall tx_call(
-            from debug_console.uart_tx, to uart_driver.tx);
+        connection seL4RPCCall write_call(
+            from debug_console.uart_write, to uart_driver.write);
         connection seL4SharedData rx_channel(
             from debug_console.rx_dataport, to uart_driver.rx_dataport);
-        connection seL4RPCCall rx_call(
-            from debug_console.uart_rx, to uart_driver.rx);
+        connection seL4RPCCall read_call(
+            from debug_console.uart_read, to uart_driver.read);
 
         // Connect the LoggerInterface to each component that needs to log
         // to the console. Note this allocates a 4KB shared memory region to