(memory): zero out memory on free

src/kernel/memory.c

@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include "drivers/uart.h"
 #include "memory.h"
@@ -37,6 +38,7 @@ void page_init()
 	test_memory_integrity();
 	test_memory_alignment();
 	test_memory_stress();
+	test_memory_reuse();
 	// page_free((void *)23);
 }
 
@@ -143,6 +145,8 @@ void kfree(void *ptr)
 	}
 	header->is_free = 1;
 
+	memset(ptr,0,header->size);
+
 	HeapHeader *final_block = kcoalesce(header);
 	uintptr_t block_start = (uintptr_t)final_block;
 	uintptr_t block_end = block_start + sizeof(HeapHeader) + final_block->size;
@@ -306,6 +310,48 @@ void test_memory_integrity()
 	kfree(e);
 }
 
+void test_memory_reuse()
+{
+    kprint("Running Reuse Test...\n");
+
+    uint8_t *big = (uint8_t *)kmalloc(256);
+    if (!big) {
+        kprint("Allocation failed – aborting reuse test.\n");
+        return;
+    }
+
+    for (size_t i = 0; i < 256; ++i) {
+        big[i] = 0xAA;
+    }
+
+    kfree(big);
+    heap_stats();
+
+    uint8_t *small = (uint8_t *)kmalloc(32);
+    if (!small) {
+        kprint("Second allocation failed – aborting reuse test.\n");
+        return;
+    }
+
+    bool dirty = false;
+    for (size_t i = 0; i < 32; ++i) {
+        if (small[i] != 0) {
+			kprintf("bad value %x", small[i]);
+            dirty = true;
+            break;
+        }
+    }
+
+    if (dirty) {
+        kprint("FAIL: Reused block contains leftover data!\n");
+    } else {
+        kprint("PASS: Reused block is clean.\n");
+    }
+
+    kfree(small);
+    heap_stats();
+}
+
 void test_memory_alignment()
 {
 	kprint("Running Alignment Test...\n");

src/kernel/memory.h

@@ -30,6 +30,7 @@ void kheap_split(HeapHeader *header, size_t size);
 void kheap_insert_sorted(HeapHeader *new_block);
 void kfree(void *ptr);
 HeapHeader *kcoalesce(HeapHeader *header);
+void test_memory_reuse();
 void test_memory_integrity();
 void test_memory_alignment();
 void test_memory_stress();