more alloc stuff

kernel/kmain.c

@@ -136,7 +136,7 @@ void kmain(uint32_t magic, multiboot_info* mbi)  {
   init_page_tables();
   kprintf("Page tables initialized\n");
 
-  kheap_init();
+  kgrow(1);
   kprintf("Allocated 4kb for kernel heap\n");
 
   kprintf("scanning for drives\n");

kernel/lib/memory.c

@@ -1,6 +1,12 @@
 #include "lib/memory.h"
 #include "memory/mm.h"
 
+#define KHEAP_START 0xE0000000
+
+typedef struct __attribute__((packed)) {
+    uint8_t free;
+    uint32_t next_blk;
+} alloc_header_t;
 
 void memcpy(const void* src, void* dst, size_t sz) {
     for (size_t i = 0; i < sz; i++) {
@@ -31,16 +37,58 @@ int strlen(const char* str) {
     return len;
 }
 
-static void* kernel_heap = (void*)0xE0000000;
+static void* kernel_heap_start = (void*)KHEAP_START;
-static size_t kernel_heap_sz = 0;
+static void* kernel_heap_end = (void*)KHEAP_START;
+alloc_header_t* blk_list = NULL;
 
-void kheap_init() {
+void kgrow(size_t pages) {
-    if (kernel_heap_sz == 0) {
+    if (kernel_heap_end == kernel_heap_start) {
+        // probaably not great, but if we don't have a heap yet, allocate the first (or only) frame requested.
+        // Then initialize the first block header for the allocator
         void* frame = p_alloc_frame();
-        map_page((uint32_t)kernel_heap, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
+        map_page((uint32_t)kernel_heap_end, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
+        kernel_heap_end = (void*)((uint32_t)kernel_heap_end + PAGE_SIZE);
+        pages--;
+        blk_list = kernel_heap_start;
+        blk_list->free = 1;
+        blk_list->next_blk = 0;
+    }
+
+    for (size_t p = 0; p < pages; p++) {
+        void* frame = p_alloc_frame();
+        map_page((uint32_t)kernel_heap_end, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
+        kernel_heap_end = (void*)((uint32_t)kernel_heap_end + PAGE_SIZE); 
     }
 }
 
-void* alloc(size_t sz) {
+void* kalloc(size_t sz) {
+    if (sz == 0) {
+        return NULL;
+    }
 
+    alloc_header_t* header = blk_list;
+    while (!header->free) {
+        if (header->next_blk == 0) {
+            return NULL;
+        }
+        header = (alloc_header_t*)header->next_blk;
+    }
+
+    uint32_t data_ptr = (uint32_t)header + sizeof(alloc_header_t);
+    if (data_ptr >= (uint32_t)kernel_heap_end) {
+        return NULL;
+    } // if the start of the data is already at the end, we don't have room
+
+    uint32_t end_of_blk = data_ptr + sz;
+    if (end_of_blk > (uint32_t)kernel_heap_end) {
+        return NULL;
+    } // if the end of the data is past the end, we don't have room
+
+    if (end_of_blk != header->next_blk && end_of_blk < ((uint32_t)kernel_heap_end - sizeof(alloc_header_t))) {
+        header->next_blk = end_of_blk;
+        alloc_header_t* next_header = (alloc_header_t*)header->next_blk;
+        next_header->f
+    } // see if we have room to place the next header and at least 1 byte of data
+
+    return (void*)data_ptr;
 }

kernel/lib/memory.h

@@ -10,7 +10,7 @@ void memset(const uint8_t* dst, uint8_t val, size_t sz);
 int strcmp(const char *s1, const char *s2);
 int strlen(const char* str);
 
-void kheap_init();
+void kgrow(size_t pages);
 void* alloc(size_t sz);