diff --git a/os/include/blit/blit.h b/os/include/blit/blit.h
index c22ff2c44..03a111667 100644
--- a/os/include/blit/blit.h
+++ b/os/include/blit/blit.h
@@ -28,8 +28,7 @@
  * If the source and destination overlap, the result
  * of the copy operation is not defined.
  */
-extern "C" void blit(void *src, unsigned src_w,
-                     void *dst, unsigned dst_w,
-                     int w, int h);
+extern "C" void blit(void const *src, unsigned src_w,
+                     void *dst, unsigned dst_w, int w, int h);
 
 #endif /* _INCLUDE__BLIT__BLIT_H_ */
diff --git a/os/src/lib/blit/arm/blit_helper.h b/os/src/lib/blit/arm/blit_helper.h
index 4c7cea1d4..33e86d510 100644
--- a/os/src/lib/blit/arm/blit_helper.h
+++ b/os/src/lib/blit/arm/blit_helper.h
@@ -19,11 +19,11 @@
 /**
  * Copy single 16bit column
  */
-static inline void copy_16bit_column(char *src, int src_w,
+static inline void copy_16bit_column(char const *src, int src_w,
                                      char *dst, int dst_w, int h)
 {
 	for (; h-- > 0; src += src_w, dst += dst_w)
-		*(short *)dst = *(short *)src;
+		*(short *)dst = *(short const *)src;
 }
 
 
@@ -37,7 +37,7 @@ static inline void copy_16bit_column(char *src, int src_w,
  * \param src_w  width of source buffer in bytes
  * \param dst_w  width of destination buffer in bytes
  */
-static void copy_block_32bit(char *src, int src_w,
+static void copy_block_32bit(char const *src, int src_w,
                              char *dst, int dst_w,
                              int w, int h)
 {
@@ -45,7 +45,7 @@ static void copy_block_32bit(char *src, int src_w,
 	dst_w -= w*4;
 	for (; h--; src += src_w, dst += dst_w) {
 		for (int i = w; i--; src += 4, dst += 4)
-			*((int *)dst) = *((int *)src);
+			*((int *)dst) = *((int const *)src);
 	}
 }
 
@@ -56,7 +56,7 @@ static void copy_block_32bit(char *src, int src_w,
  * \param w  width in 32 byte chunks to copy per line
  * \param h  number of lines of copy
  */
-static inline void copy_block_32byte(char *src, int src_w,
+static inline void copy_block_32byte(char const *src, int src_w,
                                      char *dst, int dst_w,
                                      int w, int h)
 {
diff --git a/os/src/lib/blit/blit.cc b/os/src/lib/blit/blit.cc
index 0736308b7..515b3b3f9 100644
--- a/os/src/lib/blit/blit.cc
+++ b/os/src/lib/blit/blit.cc
@@ -15,11 +15,12 @@
 #include <blit_helper.h>
 
 
-extern "C" void blit(void *s, unsigned src_w,
+extern "C" void blit(void const *s, unsigned src_w,
                      void *d, unsigned dst_w,
                      int w, int h)
 {
-	char *src = (char *)s, *dst = (char *)d;
+	char const *src = (char const *)s;
+	char       *dst = (char       *)d;
 
 	if (w <= 0 || h <= 0) return;
 
diff --git a/os/src/lib/blit/blit_helper.h b/os/src/lib/blit/blit_helper.h
index d997f19e6..da34c6678 100644
--- a/os/src/lib/blit/blit_helper.h
+++ b/os/src/lib/blit/blit_helper.h
@@ -19,7 +19,7 @@
 /**
  * Copy single 16bit column
  */
-static inline void copy_16bit_column(char *src, int src_w,
+static inline void copy_16bit_column(char const *src, int src_w,
                                      char *dst, int dst_w, int h)
 {
 	for (; h-- > 0; src += src_w, dst += dst_w)
@@ -37,7 +37,7 @@ static inline void copy_16bit_column(char *src, int src_w,
  * \param src_w  width of source buffer in bytes
  * \param dst_w  width of destination buffer in bytes
  */
-static void copy_block_32bit(char *src, int src_w,
+static void copy_block_32bit(char const *src, int src_w,
                              char *dst, int dst_w,
                              int w, int h)
 {
@@ -46,15 +46,13 @@ static void copy_block_32bit(char *src, int src_w,
 }
 
 
-
-
 /**
  * Copy block with a size of multiple of 32 bytes
  *
  * \param w  width in 32 byte chunks to copy per line
  * \param h  number of lines of copy
  */
-static inline void copy_block_32byte(char *src, int src_w,
+static inline void copy_block_32byte(char const *src, int src_w,
                                      char *dst, int dst_w,
                                      int w, int h)
 {
diff --git a/os/src/lib/blit/x86/blit_helper.h b/os/src/lib/blit/x86/blit_helper.h
index 33472556c..0cdf9a4f2 100644
--- a/os/src/lib/blit/x86/blit_helper.h
+++ b/os/src/lib/blit/x86/blit_helper.h
@@ -20,11 +20,11 @@
 /**
  * Copy single 16bit column
  */
-static inline void copy_16bit_column(char *src, int src_w,
+static inline void copy_16bit_column(char const *src, int src_w,
                                      char *dst, int dst_w, int h)
 {
 	for (; h-- > 0; src += src_w, dst += dst_w)
-		*(short *)dst = *(short *)src;
+		*(short *)dst = *(short const *)src;
 }
 
 
@@ -38,7 +38,7 @@ static inline void copy_16bit_column(char *src, int src_w,
  * \param src_w  width of source buffer in bytes
  * \param dst_w  width of destination buffer in bytes
  */
-static inline void copy_block_32bit(char *src, int src_w,
+static inline void copy_block_32bit(char const *src, int src_w,
                                     char *dst, int dst_w,
                                     int w, int h)
 {
@@ -58,7 +58,7 @@ static inline void copy_block_32bit(char *src, int src_w,
  * \param w  width in 32 byte chunks to copy per line
  * \param h  number of lines of copy
  */
-static inline void copy_block_32byte(char *src, int src_w,
+static inline void copy_block_32byte(char const *src, int src_w,
                                      char *dst, int dst_w,
                                      int w, int h)
 {
diff --git a/os/src/lib/blit/x86/x86_32/mmx.h b/os/src/lib/blit/x86/x86_32/mmx.h
index afce6e497..50c40f048 100644
--- a/os/src/lib/blit/x86/x86_32/mmx.h
+++ b/os/src/lib/blit/x86/x86_32/mmx.h
@@ -18,7 +18,7 @@
 /**
  * Copy 32byte chunks via MMX
  */
-static inline void copy_32byte_chunks(void *src, void *dst, int size)
+static inline void copy_32byte_chunks(void const *src, void *dst, int size)
 {
 	asm volatile (
 		"emms                             \n\t"
diff --git a/os/src/lib/blit/x86/x86_64/mmx.h b/os/src/lib/blit/x86/x86_64/mmx.h
index dc152b394..e1c28eaf2 100644
--- a/os/src/lib/blit/x86/x86_64/mmx.h
+++ b/os/src/lib/blit/x86/x86_64/mmx.h
@@ -17,7 +17,7 @@
 /**
  * Copy 32byte chunks via MMX
  */
-static inline void copy_32byte_chunks(void *src, void *dst, int size)
+static inline void copy_32byte_chunks(void const *src, void *dst, int size)
 {
 	asm volatile (
 		"emms                             \n\t"