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.

36 files changed, 379 insertions, 221 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..0b8d3e8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+*.o
+*.a
+work/
+toolchain/
diff --git a/bsp/env/common.mk b/bsp/env/common.mk
index 8d91805..0f5e9a1 100644
--- a/bsp/env/common.mk
+++ b/bsp/env/common.mk
@@ -1,5 +1,13 @@
 # See LICENSE for license details.
 
+ifndef _SIFIVE_MK_COMMON
+_SIFIVE_MK_COMMON := # defined
+
+.PHONY: all
+all: $(TARGET)
+
+include $(BSP_BASE)/libwrap/libwrap.mk
+
 BOARD ?= freedom-e300-hifive1
 ENV_DIR = $(BSP_BASE)/env
 PLATFORM_DIR = $(ENV_DIR)/$(BOARD)
@@ -7,28 +15,32 @@ PLATFORM_DIR = $(ENV_DIR)/$(BOARD)
 ASM_SRCS += $(PLATFORM_DIR)/start.S
 ASM_SRCS += $(PLATFORM_DIR)/entry.S
 C_SRCS += $(PLATFORM_DIR)/init.c
-C_SRCS += $(ENV_DIR)/syscall.c
 
 LINKER_SCRIPT := $(PLATFORM_DIR)/link.lds
 
-INCLUDES += -I.
 INCLUDES += -I$(BSP_BASE)/include
 INCLUDES += -I$(ENV_DIR)
 INCLUDES += -I$(PLATFORM_DIR)
 
-CC := $(BSP_BASE)/../toolchain/bin/riscv32-unknown-elf-gcc
+TOOL_DIR = $(BSP_BASE)/../toolchain/bin
 
-LDFLAGS += -T $(LINKER_SCRIPT) -nostdlib -nostartfiles -lc -lgcc
+CC := $(TOOL_DIR)/riscv32-unknown-elf-gcc
+AR := $(TOOL_DIR)/riscv32-unknown-elf-ar
+
+LDFLAGS += -T $(LINKER_SCRIPT) -nostartfiles
 LDFLAGS += -L$(ENV_DIR)
 
-ASM_OBJS := $(patsubst %.S,%.o,$(ASM_SRCS))
-C_OBJS := $(patsubst %.c,%.o,$(C_SRCS))
+ASM_OBJS := $(ASM_SRCS:.S=.o)
+C_OBJS := $(C_SRCS:.c=.o)
 
 LINK_OBJS += $(ASM_OBJS) $(C_OBJS)
+LINK_DEPS += $(LINKER_SCRIPT)
+
+CLEAN_OBJS += $(TARGET) $(LINK_OBJS)
 
 CFLAGS += -g
 
-$(TARGET): $(LINK_OBJS) $(LINKER_SCRIPT)
+$(TARGET): $(LINK_OBJS) $(LINK_DEPS)
 	$(CC) $(CFLAGS) $(INCLUDES) $(LINK_OBJS) -o $@ $(LDFLAGS)
 
 $(ASM_OBJS): %.o: %.S $(HEADERS)
@@ -37,9 +49,8 @@ $(ASM_OBJS): %.o: %.S $(HEADERS)
 $(C_OBJS): %.o: %.c $(HEADERS)
 	$(CC) $(CFLAGS) $(INCLUDES) -c -o $@ $<
 
-all: $(TARGET)
-
+.PHONY: clean
 clean:
-	rm -f $(TARGET) $(LINK_OBJS)
+	rm -f $(CLEAN_OBJS)
 
-.PHONY: all clean
+endif # _SIFIVE_MK_COMMON
diff --git a/bsp/env/freedom-e300-arty/init.c b/bsp/env/freedom-e300-arty/init.c
index 1f26b19..a7e368e 100644
--- a/bsp/env/freedom-e300-arty/init.c
+++ b/bsp/env/freedom-e300-arty/init.c
@@ -1,5 +1,6 @@
 //See LICENSE for license details.
 #include <stdint.h>
+#include <stdio.h>
 #include <unistd.h>
 
 #include "platform.h"
diff --git a/bsp/env/freedom-e300-hifive1/init.c b/bsp/env/freedom-e300-hifive1/init.c
index 268d41e..c088079 100644
--- a/bsp/env/freedom-e300-hifive1/init.c
+++ b/bsp/env/freedom-e300-hifive1/init.c
@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include <stdio.h>
 #include <unistd.h>
 
 #include "platform.h"
diff --git a/bsp/env/syscall.c b/bsp/env/syscall.c
deleted file mode 100644
index 1b5de50..0000000
--- a/bsp/env/syscall.c
+++ /dev/null
@@ -1,190 +0,0 @@
-// See LICENSE for license details.
-
-/* This is an incomplete version of a syscall library, 
- * which really only supports simple reads and writes over UART.
- */
-
-#include <stdint.h>
-#include <stdlib.h>
-#include <stddef.h>
-#include <unistd.h>
-#include <errno.h>
-#include <sys/stat.h>
-#include <sys/times.h>
-#include <stdio.h>
-#include <string.h>
-
-#include "platform.h"
-
-void write_hex(int fd, uint32_t hex)
-{
-  uint8_t ii;
-  uint8_t jj;
-  char towrite;
-  write(fd , "0x", 2);
-  for (ii = 8 ; ii > 0; ii--) {
-    jj = ii - 1;
-    uint8_t digit = ((hex & (0xF << (jj*4))) >> (jj*4));
-    towrite = digit < 0xA ? ('0' + digit) : ('A' +  (digit - 0xA));
-    write(fd, &towrite, 1);
-  }
-}
-
-void _exit(int code)
-{
-  //volatile uint32_t* leds = (uint32_t*) (GPIO_BASE_ADDR + GPIO_OUT_OFFSET);
-  const char * message = "\nProgam has exited with code:";
-  
-  //*leds = (~(code));
-
-  write(STDERR_FILENO, message, strlen(message));
-  write_hex(STDERR_FILENO, code);
-  write(STDERR_FILENO, "\n", 1);
-
-  while (1) ;
-}
-
-void *sbrk(ptrdiff_t incr)
-{
-  extern char _end[];
-  extern char _heap_end[];
-  static char *curbrk = _end;
-
-  if ((curbrk + incr < _end) || (curbrk + incr > _heap_end))
-    return NULL - 1;
-
-  curbrk += incr;
-  return curbrk - incr;
-}
-
-static int stub(int err)
-{
-  return -1;
-}
-
-int open(const char* name, int flags, int mode)
-{
-  return stub(ENOENT);
-}
-
-int openat(int dirfd, const char* name, int flags, int mode)
-{
-  return stub(ENOENT);
-}
-
-int close(int fd)
-{
-  return stub(EBADF);
-}
-
-int execve(const char* name, char* const argv[], char* const env[])
-{
-  return stub(ENOMEM);
-}
-
-int fork()
-{
-  return stub(EAGAIN);
-}
-
-int fstat(int fd, struct stat *st)
-{
-  if (isatty(fd)) {
-    st->st_mode = S_IFCHR;
-    return 0;
-  }
-
-  return stub(EBADF);
-}
-
-int getpid()
-{
-  return 1;
-}
-
-int isatty(int fd)
-{
-  if (fd == STDOUT_FILENO || fd == STDERR_FILENO)
-    return 1;
-
-  return 0;
-}
-
-int kill(int pid, int sig)
-{
-  return stub(EINVAL);
-}
-
-int link(const char *old_name, const char *new_name)
-{
-  return stub(EMLINK);
-}
-
-off_t lseek(int fd, off_t ptr, int dir)
-{
-  if (isatty(fd))
-    return 0;
-
-  return stub(EBADF);
-}
-
-ssize_t 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);
-}
-
-int stat(const char* file, struct stat* st)
-{
-  return stub(EACCES);
-}
-
-clock_t times(struct tms* buf)
-{
-  return stub(EACCES);
-}
-
-int unlink(const char* name)
-{
-  return stub(ENOENT);
-}
-
-int wait(int* status)
-{
-  return stub(ECHILD);
-}
-
-ssize_t write(int fd, const void* ptr, size_t len)
-{
-  const uint8_t * current = (const char *)ptr;
-
-  if (isatty(fd)) {
-    for (size_t jj = 0; jj < len; jj++) {
-      while (UART0_REG(UART_REG_TXFIFO) & 0x80000000) ;
-      UART0_REG(UART_REG_TXFIFO) = current[jj];
-
-      if (current[jj] == '\n') {
-        while (UART0_REG(UART_REG_TXFIFO) & 0x80000000) ;
-        UART0_REG(UART_REG_TXFIFO) = '\r';
-      }
-    }
-    return len;
-  } 
-
-  return stub(EBADF);
-}
diff --git a/bsp/libwrap/libwrap.mk b/bsp/libwrap/libwrap.mk
new file mode 100644
index 0000000..313ed00
--- /dev/null
+++ b/bsp/libwrap/libwrap.mk
@@ -0,0 +1,54 @@
+# See LICENSE for license details.
+
+ifndef _SIFIVE_MK_LIBWRAP
+_SIFIVE_MK_LIBWRAP := # defined
+
+LIBWRAP_DIR := $(dir $(lastword $(MAKEFILE_LIST)))
+LIBWRAP_DIR := $(LIBWRAP_DIR:/=)
+
+LIBWRAP_SRCS := \
+	stdlib/malloc.c \
+	sys/open.c \
+	sys/lseek.c \
+	sys/read.c \
+	sys/write.c \
+	sys/fstat.c \
+	sys/stat.c \
+	sys/close.c \
+	sys/link.c \
+	sys/unlink.c \
+	sys/execve.c \
+	sys/fork.c \
+	sys/getpid.c \
+	sys/kill.c \
+	sys/wait.c \
+	sys/isatty.c \
+	sys/times.c \
+	sys/sbrk.c \
+	sys/_exit.c \
+	misc/write_hex.c
+
+LIBWRAP_SRCS := $(foreach f,$(LIBWRAP_SRCS),$(LIBWRAP_DIR)/$(f))
+LIBWRAP_OBJS := $(LIBWRAP_SRCS:.c=.o)
+
+LIBWRAP_SYMS := malloc free \
+	open lseek read write fstat stat close link unlink \
+	execve fork getpid kill wait \
+	isatty times sbrk _exit
+
+LIBWRAP := libwrap.a
+
+LINK_DEPS += $(LIBWRAP)
+
+LDFLAGS += $(foreach s,$(LIBWRAP_SYMS),-Wl,--wrap=$(s))
+LDFLAGS += -L. -Wl,--start-group -lwrap -lc -Wl,--end-group
+
+CLEAN_OBJS += $(LIBWRAP_OBJS)
+
+$(LIBWRAP_OBJS): %.o: %.c $(HEADERS)
+	$(CC) $(CFLAGS) $(INCLUDES) -c -o $@ $<
+
+$(LIBWRAP): $(LIBWRAP_OBJS)
+	$(AR) rcs $@ $^
+
+endif # _SIFIVE_MK_LIBWRAP
diff --git a/bsp/libwrap/misc/write_hex.c b/bsp/libwrap/misc/write_hex.c
new file mode 100644
index 0000000..e678bdc
--- /dev/null
+++ b/bsp/libwrap/misc/write_hex.c
@@ -0,0 +1,19 @@
+/* See LICENSE of license details. */
+
+#include <stdint.h>
+#include <unistd.h>
+#include "platform.h"
+
+void write_hex(int fd, uint32_t hex)
+{
+  uint8_t ii;
+  uint8_t jj;
+  char towrite;
+  write(fd , "0x", 2);
+  for (ii = 8 ; ii > 0; ii--) {
+    jj = ii - 1;
+    uint8_t digit = ((hex & (0xF << (jj*4))) >> (jj*4));
+    towrite = digit < 0xA ? ('0' + digit) : ('A' +  (digit - 0xA));
+    write(fd, &towrite, 1);
+  }
+}
diff --git a/bsp/libwrap/stdlib/malloc.c b/bsp/libwrap/stdlib/malloc.c
new file mode 100644
index 0000000..8f4f432
--- /dev/null
+++ b/bsp/libwrap/stdlib/malloc.c
@@ -0,0 +1,17 @@
+/* See LICENSE for license details. */
+
+/* These functions are intended for embedded RV32 systems and are
+   obviously incorrect in general. */
+
+void* __wrap_malloc(unsigned long sz)
+{
+  extern void* sbrk(long);
+  void* res = sbrk(sz);
+  if ((long)res == -1)
+    return 0;
+  return res;
+}
+
+void __wrap_free(void* ptr)
+{
+}
diff --git a/bsp/libwrap/sys/_exit.c b/bsp/libwrap/sys/_exit.c
new file mode 100644
index 0000000..7261891
--- /dev/null
+++ b/bsp/libwrap/sys/_exit.c
@@ -0,0 +1,17 @@
+/* See LICENSE of license details. */
+
+#include <unistd.h>
+#include "platform.h"
+
+void __wrap__exit(int code)
+{
+//volatile uint32_t* leds = (uint32_t*) (GPIO_BASE_ADDR + GPIO_OUT_OFFSET);
+  const char message[] = "\nProgam has exited with code:";
+//*leds = (~(code));
+
+  write(STDERR_FILENO, message, sizeof(message) - 1);
+  write_hex(STDERR_FILENO, code);
+  write(STDERR_FILENO, "\n", 1);
+
+  for (;;);
+}
diff --git a/bsp/libwrap/sys/close.c b/bsp/libwrap/sys/close.c
new file mode 100644
index 0000000..e4f8e14
--- /dev/null
+++ b/bsp/libwrap/sys/close.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_close(int fd)
+{
+  return _stub(EBADF);
+}
diff --git a/bsp/libwrap/sys/execve.c b/bsp/libwrap/sys/execve.c
new file mode 100644
index 0000000..6178a01
--- /dev/null
+++ b/bsp/libwrap/sys/execve.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_execve(const char* name, char* const argv[], char* const env[])
+{
+  return _stub(ENOMEM);
+}
diff --git a/bsp/libwrap/sys/fork.c b/bsp/libwrap/sys/fork.c
new file mode 100644
index 0000000..13a3e65
--- /dev/null
+++ b/bsp/libwrap/sys/fork.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int fork(void)
+{
+  return _stub(EAGAIN);
+}
diff --git a/bsp/libwrap/sys/fstat.c b/bsp/libwrap/sys/fstat.c
new file mode 100644
index 0000000..6ea3e6a
--- /dev/null
+++ b/bsp/libwrap/sys/fstat.c
@@ -0,0 +1,16 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include "stub.h"
+
+int __wrap_fstat(int fd, struct stat* st)
+{
+  if (isatty(fd)) {
+    st->st_mode = S_IFCHR;
+    return 0;
+  }
+
+  return _stub(EBADF);
+}
diff --git a/bsp/libwrap/sys/getpid.c b/bsp/libwrap/sys/getpid.c
new file mode 100644
index 0000000..5aa510b
--- /dev/null
+++ b/bsp/libwrap/sys/getpid.c
@@ -0,0 +1,6 @@
+/* See LICENSE of license details. */
+
+int __wrap_getpid(void)
+{
+  return 1;
+}
diff --git a/bsp/libwrap/sys/isatty.c b/bsp/libwrap/sys/isatty.c
new file mode 100644
index 0000000..55eab0a
--- /dev/null
+++ b/bsp/libwrap/sys/isatty.c
@@ -0,0 +1,11 @@
+/* See LICENSE of license details. */
+
+#include <unistd.h>
+
+int __wrap_isatty(int fd)
+{
+  if (fd == STDOUT_FILENO || fd == STDERR_FILENO)
+    return 1;
+
+  return 0;
+}
diff --git a/bsp/libwrap/sys/kill.c b/bsp/libwrap/sys/kill.c
new file mode 100644
index 0000000..9c56632
--- /dev/null
+++ b/bsp/libwrap/sys/kill.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_kill(int pid, int sig)
+{
+  return _stub(EINVAL);
+}
diff --git a/bsp/libwrap/sys/link.c b/bsp/libwrap/sys/link.c
new file mode 100644
index 0000000..9340cad
--- /dev/null
+++ b/bsp/libwrap/sys/link.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_link(const char *old_name, const char *new_name)
+{
+  return _stub(EMLINK);
+}
diff --git a/bsp/libwrap/sys/lseek.c b/bsp/libwrap/sys/lseek.c
new file mode 100644
index 0000000..46f58fa
--- /dev/null
+++ b/bsp/libwrap/sys/lseek.c
@@ -0,0 +1,14 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include "stub.h"
+
+off_t __wrap_lseek(int fd, off_t ptr, int dir)
+{
+  if (isatty(fd))
+    return 0;
+
+  return _stub(EBADF);
+}
diff --git a/bsp/libwrap/sys/open.c b/bsp/libwrap/sys/open.c
new file mode 100644
index 0000000..d1871f9
--- /dev/null
+++ b/bsp/libwrap/sys/open.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_open(const char* name, int flags, int mode)
+{
+  return _stub(ENOENT);
+}
diff --git a/bsp/libwrap/sys/openat.c b/bsp/libwrap/sys/openat.c
new file mode 100644
index 0000000..7f1c945
--- /dev/null
+++ b/bsp/libwrap/sys/openat.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_openat(int dirfd, const char* name, int flags, int mode)
+{
+  return _stub(ENOENT);
+}
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);
+}
diff --git a/bsp/libwrap/sys/sbrk.c b/bsp/libwrap/sys/sbrk.c
new file mode 100644
index 0000000..6e6b36a
--- /dev/null
+++ b/bsp/libwrap/sys/sbrk.c
@@ -0,0 +1,16 @@
+/* See LICENSE of license details. */
+
+#include <stddef.h>
+
+void *__wrap_sbrk(ptrdiff_t incr)
+{
+  extern char _end[];
+  extern char _heap_end[];
+  static char *curbrk = _end;
+
+  if ((curbrk + incr < _end) || (curbrk + incr > _heap_end))
+    return NULL - 1;
+
+  curbrk += incr;
+  return curbrk - incr;
+}
diff --git a/bsp/libwrap/sys/stat.c b/bsp/libwrap/sys/stat.c
new file mode 100644
index 0000000..1ccc2f4
--- /dev/null
+++ b/bsp/libwrap/sys/stat.c
@@ -0,0 +1,10 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <sys/stat.h>
+#include "stub.h"
+
+int __wrap_stat(const char* file, struct stat* st)
+{
+  return _stub(EACCES);
+}
diff --git a/bsp/libwrap/sys/stub.h b/bsp/libwrap/sys/stub.h
new file mode 100644
index 0000000..fb5e5be
--- /dev/null
+++ b/bsp/libwrap/sys/stub.h
@@ -0,0 +1,10 @@
+/* See LICENSE of license details. */
+#ifndef _SIFIVE_SYS_STUB_H
+#define _SIFIVE_SYS_STUB_H
+
+static inline int _stub(int err)
+{
+  return -1;
+}
+
+#endif /* _SIFIVE_SYS_STUB_H */
diff --git a/bsp/libwrap/sys/times.c b/bsp/libwrap/sys/times.c
new file mode 100644
index 0000000..26a9566
--- /dev/null
+++ b/bsp/libwrap/sys/times.c
@@ -0,0 +1,10 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include <sys/times.h>
+#include "stub.h"
+
+clock_t __wrap_times(struct tms* buf)
+{
+  return _stub(EACCES);
+}
diff --git a/bsp/libwrap/sys/unlink.c b/bsp/libwrap/sys/unlink.c
new file mode 100644
index 0000000..b62b1ba
--- /dev/null
+++ b/bsp/libwrap/sys/unlink.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int __wrap_unlink(const char* name)
+{
+  return _stub(ENOENT);
+}
diff --git a/bsp/libwrap/sys/wait.c b/bsp/libwrap/sys/wait.c
new file mode 100644
index 0000000..ea3225b
--- /dev/null
+++ b/bsp/libwrap/sys/wait.c
@@ -0,0 +1,9 @@
+/* See LICENSE of license details. */
+
+#include <errno.h>
+#include "stub.h"
+
+int wait(int* status)
+{
+  return _stub(ECHILD);
+}
diff --git a/bsp/libwrap/sys/write.c b/bsp/libwrap/sys/write.c
new file mode 100644
index 0000000..d00eb17
--- /dev/null
+++ b/bsp/libwrap/sys/write.c
@@ -0,0 +1,29 @@
+/* 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_write(int fd, const void* ptr, size_t len)
+{
+  const uint8_t * current = (const char *)ptr;
+
+  if (isatty(fd)) {
+    for (size_t jj = 0; jj < len; jj++) {
+      while (UART0_REG(UART_REG_TXFIFO) & 0x80000000) ;
+      UART0_REG(UART_REG_TXFIFO) = current[jj];
+
+      if (current[jj] == '\n') {
+        while (UART0_REG(UART_REG_TXFIFO) & 0x80000000) ;
+        UART0_REG(UART_REG_TXFIFO) = '\r';
+      }
+    }
+    return len;
+  }
+
+  return _stub(EBADF);
+}
diff --git a/software/demo_gpio/.gitignore b/software/demo_gpio/.gitignore
new file mode 100644
index 0000000..35566c7
--- /dev/null
+++ b/software/demo_gpio/.gitignore
@@ -0,0 +1 @@
+demo_gpio
diff --git a/software/demo_gpio/Makefile b/software/demo_gpio/Makefile
index 0a0b148..04a11b7 100644
--- a/software/demo_gpio/Makefile
+++ b/software/demo_gpio/Makefile
@@ -1,7 +1,7 @@
 TARGET = demo_gpio
 C_SRCS += demo_gpio.c
 C_SRCS += plic_driver.c
-CFLAGS += -fno-builtin-printf -DUSE_PLIC -DUSE_M_TIME
+CFLAGS += -O2 -fno-builtin-printf -DUSE_PLIC -DUSE_M_TIME
 
 BSP_BASE = ../../bsp
 include $(BSP_BASE)/env/common.mk
diff --git a/software/dhrystone/.gitignore b/software/dhrystone/.gitignore
new file mode 100644
index 0000000..eb51a6c
--- /dev/null
+++ b/software/dhrystone/.gitignore
@@ -0,0 +1 @@
+dhrystone
diff --git a/software/dhrystone/Makefile b/software/dhrystone/Makefile
index 2058ca1..a55b1ec 100644
--- a/software/dhrystone/Makefile
+++ b/software/dhrystone/Makefile
@@ -5,10 +5,11 @@ C_SRCS := dhry_stubs.c dhry_printf.c
 HEADERS := dhry.h
 
 DHRY_SRCS := dhry_1.c dhry_2.c
-DHRY_CFLAGS := -O2 -DTIME -fno-inline -Wno-implicit
+DHRY_CFLAGS := -O2 -DTIME -fno-inline -fno-builtin-printf -Wno-implicit
 
 XLEN ?= 32
-CFLAGS := -Dscanf=dhry_scanf -Dprintf=dhry_printf -Os -fno-common
+CFLAGS := -Os -fno-common
+LDFLAGS := -Wl,--wrap=scanf -Wl,--wrap=printf
 
 DHRY_OBJS := $(patsubst %.c,%.o,$(DHRY_SRCS))
 LINK_OBJS := $(DHRY_OBJS)
diff --git a/software/dhrystone/dhry_printf.c b/software/dhrystone/dhry_printf.c
index 1fdaac4..025d231 100644
--- a/software/dhrystone/dhry_printf.c
+++ b/software/dhrystone/dhry_printf.c
@@ -246,7 +246,7 @@ static void vprintfmt(void (*putch)(int, void**), void **putdat, const char *fmt
   }
 }
 
-int printf(const char* fmt, ...)
+int __wrap_printf(const char* fmt, ...)
 {
   va_list ap;
   va_start(ap, fmt);
@@ -257,7 +257,7 @@ int printf(const char* fmt, ...)
   return 0; // incorrect return value, but who cares, anyway?
 }
 
-int sprintf(char* str, const char* fmt, ...)
+int __wrap_sprintf(char* str, const char* fmt, ...)
 {
   va_list ap;
   char* str0 = str;
diff --git a/software/dhrystone/dhry_stubs.c b/software/dhrystone/dhry_stubs.c
index d384bf1..d3bd14c 100644
--- a/software/dhrystone/dhry_stubs.c
+++ b/software/dhrystone/dhry_stubs.c
@@ -12,20 +12,7 @@ long time(void)
 }
 
 // set the number of dhrystone iterations
-void scanf(const char* fmt, int* n)
+void __wrap_scanf(const char* fmt, int* n)
 {
   *n = 1500000;
 }
-
-// simple memory allocator
-void* malloc(unsigned long sz)
-{
-  extern void* sbrk(long);
-  void* res = sbrk(sz);
-  if ((long)res == -1)
-    return 0;
-  return res;
-}
-
-// simple memory deallocator
-void free(void* ptr) {}
diff --git a/software/hello/.gitignore b/software/hello/.gitignore
new file mode 100644
index 0000000..ce01362
--- /dev/null
+++ b/software/hello/.gitignore
@@ -0,0 +1 @@
+hello
diff --git a/software/hello/Makefile b/software/hello/Makefile
index c0c5c55..058621c 100644
--- a/software/hello/Makefile
+++ b/software/hello/Makefile
@@ -1,6 +1,6 @@
 TARGET = hello
 C_SRCS += hello.c
-CFLAGS += -fno-builtin-printf
+CFLAGS += -O2 -fno-builtin-printf
 
 BSP_BASE = ../../bsp
 include $(BSP_BASE)/env/common.mk