libc: malloc: store the global heap in a fixed region of virtual memory

lib/libc/malloc/CMakeLists.txt

@@ -30,5 +30,5 @@ sysroot_add_library(
 	HEADER_DIR /usr/include
 	LIB_DIR /usr/lib)
 
-target_compile_definitions(libc-malloc PRIVATE ENABLE_GLOBAL_HEAP=1)
+target_compile_definitions(libc-malloc PRIVATE LIBC_STATIC=1 ENABLE_GLOBAL_HEAP=1)
 target_link_libraries(libc-malloc libc-core libmagenta)

lib/libc/malloc/heap.c

@@ -8,6 +8,12 @@
 #include <magenta/vm.h>
 #include <stdio.h>
 
+#if defined(LIBC_STATIC)
+#define HEAP_REGION_BASE 0x20000000000
+#else
+#define HEAP_REGION_BASE 0x60000000000
+#endif
+
 #define HEAP_REGION_SIZE      0x40000000
 #define HEAP_EXPAND_INCREMENT 0x100000
 
@@ -40,7 +46,7 @@ static kern_status_t init_heap_region(heap_t *heap)
 
 	kern_status_t status = address_space_reserve(
 		address_space,
-		MAP_ADDRESS_ANY,
+		HEAP_REGION_BASE,
 		HEAP_REGION_SIZE,
 		&heap->heap_base);