Refactor libc stubs into libwrap

The --wrap feature of GNU ld supports a cleaner framework for linking in
alternative implementations of libc functions without cpp hacks.
Place wrappers in separate object files to reduce static code size.

1 files changed, 30 insertions, 0 deletions

diff --git a/bsp/libwrap/sys/read.c b/bsp/libwrap/sys/read.c
new file mode 100644
index 0000000..4e57f08
--- /dev/null
+++ b/bsp/libwrap/sys/read.c
@@ -0,0 +1,30 @@
+/* See LICENSE of license details. */
+
+#include <stdint.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#include "platform.h"
+#include "stub.h"
+
+ssize_t __wrap_read(int fd, void* ptr, size_t len)
+{
+  uint8_t * current = (uint8_t *)ptr;
+  volatile uint32_t * uart_rx = (uint32_t *)(UART0_BASE_ADDR + UART_REG_RXFIFO);
+  volatile uint8_t * uart_rx_cnt = (uint8_t *)(UART0_BASE_ADDR + UART_REG_RXCTRL + 2);
+
+  ssize_t result = 0;
+
+  if (isatty(fd)) {
+    for (current = (uint8_t *)ptr;
+        (current < ((uint8_t *)ptr) + len) && (*uart_rx_cnt > 0);
+        current ++) {
+      *current = *uart_rx;
+      result++;
+    }
+    return result;
+  }
+
+  return _stub(EBADF);
+}