basic memory management and uart wait fix

[cortex-from-scratch] / mm.c

diff --git a/mm.c b/mm.c
index ba0cc2c..4f56459 100644 (file)
--- 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);
+       }
+               
 }