diff --git a/CMakeLists.txt b/CMakeLists.txt
index ea01580..fc8e32c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,6 +51,7 @@ add_executable(skl_tunnel
 
     app/src/app_logging.cpp
     main.cpp
+    syscalls.c
 )
 
 target_include_directories(skl_tunnel
diff --git a/arm-none-eabi.cmake b/arm-none-eabi.cmake
index 5550eda..662327b 100644
--- a/arm-none-eabi.cmake
+++ b/arm-none-eabi.cmake
@@ -34,9 +34,9 @@ set(CMAKE_CXX_COMPILER             arm-none-eabi-g++)
 set(CMAKE_ASM_COMPILER             arm-none-eabi-as)
 set(CMAKE_RANLIB                   arm-none-eabi-ranlib)
 
-set(COMMON_C_FLAGS                 "-mcpu=cortex-m0plus -mfloat-abi=soft -mthumb -mlong-calls -fdata-sections -ffunction-sections -Wall -Wextra -O2")
+set(COMMON_C_FLAGS                 "-mcpu=cortex-m0plus -mfloat-abi=soft -mthumb -mlong-calls -fdata-sections -ffunction-sections -Wall -Wextra -Wswitch-enum -Og")
 
 set(CMAKE_C_FLAGS_INIT             "${COMMON_C_FLAGS}")
-set(CMAKE_CXX_FLAGS_INIT           "${COMMON_C_FLAGS} -fno-exceptions -fno-rtti")
+set(CMAKE_CXX_FLAGS_INIT           "${COMMON_C_FLAGS} -fno-exceptions -fno-rtti -fno-use-cxa-atexit")
 set(CMAKE_ASM_FLAGS_INIT           "${COMMON_C_FLAGS}")
-set(CMAKE_EXE_LINKER_FLAGS_INIT    "${COMMON_C_FLAGS} -specs=nosys.specs")
+set(CMAKE_EXE_LINKER_FLAGS_INIT    "${COMMON_C_FLAGS} -specs=nano.specs -specs=nosys.specs")
diff --git a/syscalls.c b/syscalls.c
new file mode 100644
index 0000000..85741f5
--- /dev/null
+++ b/syscalls.c
@@ -0,0 +1,38 @@
+//
+// Created by erki on 10.07.22.
+//
+
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stdio.h>
+#include <signal.h>
+#include <time.h>
+#include <sys/time.h>
+#include <sys/times.h>
+
+extern int __io_putchar(int ch) __attribute__((weak));
+extern int __io_getchar(void) __attribute__((weak));
+
+__attribute__((weak)) int _read(int file, char *ptr, int len)
+{
+  int DataIdx;
+
+  for (DataIdx = 0; DataIdx < len; DataIdx++)
+  {
+    *ptr++ = __io_getchar();
+  }
+
+  return len;
+}
+
+__attribute__((weak)) int _write(int file, char *ptr, int len)
+{
+  int DataIdx;
+
+  for (DataIdx = 0; DataIdx < len; DataIdx++)
+  {
+    __io_putchar(*ptr++);
+  }
+  return len;
+}