trying to get VGA fb mode to work..

rocklibc/include/syscall.h

@@ -9,6 +9,8 @@
 #define SYS_WRITE   4
 #define SYS_OPEN    5
 #define SYS_CLOSE   6
+#define SYS_BRK     12
+#define SYS_SBRK    13
 #define SYS_PTY     20
 #define SYS_FORK    21
 #define SYS_EXEC    22
@@ -25,7 +27,7 @@ int lseek(int fd, size_t offset, int whence);
 
 void exit(int status) __attribute__((noreturn));
 
-void *sbrk(intptr_t increment);
+void* sbrk(int32_t increment);
 int brk(void *addr);
 
 int pty(int* slave);