X-Git-Url: https://robinkrens.nl/gitweb/?p=cortex-from-scratch;a=blobdiff_plain;f=mm.c;h=4f564594789aa0e67df22697b2072ecf490b23e3;hp=ba0cc2c1846276bc02d7a16fc93158dc37e1d9b6;hb=3f9ee85c250250580f0ceb38525ddb99ebc6d36e;hpb=22c1abee1ad44eb88784fd7ff38ca669f41b6c01

diff --git a/mm.c b/mm.c
index ba0cc2c..4f56459 100644
--- a/mm.c
+++ b/mm.c
@@ -4,18 +4,98 @@
 #include <stm32.h>
 #include <mmap.h>
 
-uint32_t free_base;
+/* TOTAL SRAM MEMORY: 64kB 
+ * 64 chunks of 1kB 
+ * 128 chunks of 512 bytes
+ * SIMPLE BITMAP IMPLEMENTATION
+ * */
+
+#define CHUNKS  128
+#define FREE 	0x00
+#define ALLOC	0x01
+
+#define BASE 0x20000400
+
+#define SET_SIZE(s) 	(s << 8)
+#define SET_FLAGS(f) 	(f << 24)
+#define IS_ALLOC(c)   	((c >> 24) & 0x0F )
+#define PADDR(i)	(0x20000400 + (i * 0x200))
+#define I_OFFSET(p)     ((p  - 0x20000400))
+
+uint32_t chunk[CHUNKS];
+
+/* 
+ * | FLAGS | SIZE   | RESERVED	|
+ * | 0x00  | 0x0000 | 0x00     	|
+ *
+ * */
 
 
 void mm_init() {
 
-	free_base = MEM_SIZE;
+	// interrupt vector
+	chunk[0] = SET_SIZE(96) | SET_FLAGS(ALLOC); 
+
+	// test
+	/* uart_puts("ALLOC:\n");
+	int * p = mm_alloc(100);
+	*p = 0x12345678;
+
+	addrtohex(p);
+	addrtohex(*p);
+
+	uart_puts("FREE:\n");
+
+	int * p2 = mm_alloc(100);
+	*p2 = 0xFFFFAAAA;
+	addrtohex(p2);
+	addrtohex(*p2);
 
+	free(p);
+	free(p2); */
 }
 
-size_t mm_free() {
+ void test_memory(uint32_t * ptr) {
+
+	*ptr = 0xEEEEEEEE;
+	for (int i = 0; i < 100; i++) {
+		ptr++;
+		*ptr = 0xEEEEEEEE;
+	}
+
+} 
+
+
+void * mm_alloc(size_t size) { // in bytes
+
+	if (size > 512) {
+		uart_puts("SYSERROR: WE CAN'T ALLOCATE THAT MUCH!\n");
+		return NULL; 
+	}
+
+	/* check which chunk is free */
+	for (int i = 1; i < CHUNKS; i++) {
+		if (!IS_ALLOC(chunk[i])) {
+			chunk[i] = SET_SIZE(size) | SET_FLAGS(ALLOC);
+		       	return (void *) PADDR(i);
+		}
+	}
+	
+	uart_puts("SYSERROR: OUT OF MEMORY\n");
+	return NULL;
+}
+
+void free(void *ptr) {
+
+	uint32_t index = (uint32_t) I_OFFSET(ptr) / 0x200;
 
-	return MEM_SIZE; 
+	uint32_t tmp = chunk[index];
+	if (!IS_ALLOC(tmp))
+		uart_puts("SYSERROR: ALREADY FREED!\n");
 
+	else if(index < CHUNKS) {
+		chunk[index] = SET_FLAGS(FREE) | SET_SIZE(0);
+	}
+		
 }