bodge: sbrk impl stolen from newlib to get minimal libc working w/ microblaze

Signed-off-by: Alp Sayin <alpsayin@gmail.com>

Author: alpsayin

arch/microblaze/core/CMakeLists.txt

@@ -29,4 +29,8 @@ zephyr_library_sources(
 	thread.c
 )
 
+if (CONFIG_MINIMAL_LIBC)
+	zephyr_library_sources(sbrk.c)
+endif()
+
 zephyr_library_sources_ifdef(CONFIG_IRQ_OFFLOAD irq_offload.c)

arch/microblaze/core/sbrk.c

@@ -0,0 +1,32 @@
+
+#include <zephyr/devicetree.h>
+#include <zephyr/linker/linker-defs.h>
+
+#define _DDR_NODE          DT_CHOSEN(zephyr_sram)
+#define _LAYOUT_DDR_LOC	   DT_REG_ADDR(_DDR_NODE)
+#define _LAYOUT_DDR_SIZE   DT_REG_SIZE(_DDR_NODE)
+
+/* Current offset from HEAP_BASE of unused memory */
+__attribute__((section(".bss"), used)) static size_t heap_sz;
+
+#define HEAP_BASE ((uintptr_t) (&_end))
+#define MAX_HEAP_SIZE (_LAYOUT_DDR_LOC + _LAYOUT_DDR_SIZE - HEAP_BASE)
+
+/* Implementation stolen from newlib/libc-hooks.c */
+void *_sbrk(intptr_t count)
+{
+	void *ret, *ptr;
+
+	ptr = ((char *)HEAP_BASE) + heap_sz;
+
+	if ((heap_sz + count) < MAX_HEAP_SIZE) {
+		heap_sz += count;
+		ret = ptr;
+
+	} else {
+		ret = (void *)-1;
+	}
+
+	return ret;
+}
+__weak FUNC_ALIAS(_sbrk, sbrk, void *);