Heap allocations now works.

--HG--
branch : dtrg-videocore

plat/rpi/build.mk

@@ -18,23 +18,23 @@ platform-headers := \
 
 platform-libsys := \
 	_hol0.s \
+	errno.s \
 	phys_to_user.s \
 	user_to_phys.s \
 	uart.s \
-	write.c \
-
-ifeq (x,y)
-	errno.s \
-	_sys_rawread.s \
-	_sys_rawwrite.s \
-	open.c \
 	creat.c \
 	close.c \
+	open.c \
 	read.c \
+	write.c \
+	isatty.c \
 	brk.c \
+
+ifeq (x,y)
+	_sys_rawread.s \
+	_sys_rawwrite.s \
 	getpid.c \
 	kill.c \
-	isatty.c \
 	lseek.c \
 	time.c \
 	signal.c

plat/rpi/libsys/brk.c

@@ -8,25 +8,25 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <unistd.h>
+#include <pi.h>
 
 #define	OUT_OF_MEMORY (void*)(-1)	/* sbrk returns this on failure */
-#define STACK_BUFFER 128 /* number of bytes to leave for stack */
+#define STACK_BUFFER 1024 /* number of bytes to leave for stack */
 
 extern char _end[1];
 static char* current = _end;
 
+/* Top of heap: we assume that the block of memory the binary is loaded in
+ * is 256kB long. Because user pointers are always relative to the beginning
+ * of the block, this makes the end address easy to calculate. */
+static char* max = (char*) (256*1024);
+
 int brk(void* newend)
 {
-	/* This variable is used to figure out the current stack pointer,
-	 * by taking its address. */
-	char dummy;
-	char* p = newend;
-	
-	if ((p > (&dummy - STACK_BUFFER)) ||
-	    (p < _end))	
+	if ((newend >= (void*)max) || (newend < (void*)_end))
 		return -1;
 
-	current = p;
+	current = newend;
 	return 0;
 }