first commit

kernel/src/mm/pmm.c

@@ -0,0 +1,114 @@
+#include "limine.h"
+#include <stddef.h>
+#include <mm/memop.h>
+#include <mm/pmm.h>
+#include <stdint.h>
+#include <sys/log.h>
+
+pmm_stack_t stack;
+struct limine_memmap_response *_memmap;
+
+uint64_t hhdm_offset = 0x0;
+
+__attribute__((used, section(".limine_requests")))
+struct limine_memmap_request mm_req = {
+    .id = LIMINE_MEMMAP_REQUEST,
+    .revision = 3
+};
+
+
+__attribute__((used, section(".limine_requests")))
+struct limine_hhdm_request hhdm_req = {
+    .id = LIMINE_HHDM_REQUEST,
+    .revision = 3
+};
+
+int pmm_init()
+{
+    uint64_t free_pages = 0;
+    hhdm_offset = hhdm_req.response->offset;
+
+    struct limine_memmap_response *memmap = mm_req.response;
+    _memmap = memmap;
+
+    //DEBUG("mm", "----- PMM //INFO -----");
+    int freemem = 0;
+    for (uint64_t i = 0; i < memmap->entry_count; i++)
+    {
+        if (memmap->entries[i]->type == LIMINE_MEMMAP_USABLE)
+        {
+            //DEBUG("mm", " - USABLE ENTRY\t\t@ 0x%.16llx, size: 0x%.16llx", memmap->entries[i]->base, memmap->entries[i]->length);
+            free_pages += DIV_ROUND_UP(memmap->entries[i]->length, PMM_PAGE_SIZE);
+            freemem += memmap->entries[i]->length;
+        }
+    }
+
+    uint64_t array_size = ALIGN_UP(free_pages * 8, PMM_PAGE_SIZE);
+
+    for (uint64_t i = 0; i < memmap->entry_count; i++)
+    {
+        struct limine_memmap_entry *entry = memmap->entries[i];
+        if (entry->length >= array_size && entry->type == LIMINE_MEMMAP_USABLE)
+        {
+            stack.pages = (uintptr_t*)HIGHER_HALF(entry->base);
+            entry->length -= array_size;
+            entry->base += array_size;
+            //DEBUG("mm", " - STACK START\t\t@ 0x%.16llx", stack.pages);
+            break;
+        }
+    }
+
+    for (uint64_t i = 0; i < memmap->entry_count; i++)
+    {
+        struct limine_memmap_entry *entry = memmap->entries[i];
+        if (entry->type == LIMINE_MEMMAP_USABLE)
+        {
+            for (uint64_t j = 0; j < entry->length; j += PMM_PAGE_SIZE)
+            {
+                stack.pages[stack.idx++] = entry->base + j;
+            }
+        }
+    }
+
+    stack.max = stack.idx;
+    //DEBUG("mm", " - MAX INDEX:\t\t%d", stack.max);
+    //DEBUG("mm", " - CURRENT INDEX:\t%d", stack.idx);
+    //DEBUG("mm", "--------------------");
+
+
+    log("pmm - %dmb is available to us.\n", freemem / (1024 * 1024));
+    return 0;
+}
+
+void *pmm_request_page()
+{
+    if (stack.idx == 0)
+    {
+        //ERROR("mm", "No more pages available.");
+        log("pmm - out of memory.\n");
+        asm("cli");
+        while (1) {
+            asm("hlt");
+        }
+        return NULL;
+    }
+
+    uint64_t page_addr = stack.pages[--stack.idx];
+    memset(HIGHER_HALF(page_addr), 0, PMM_PAGE_SIZE);
+    return (void *)page_addr;
+}
+
+void pmm_free_page(void *ptr)
+{
+    if (ptr == NULL)
+        return;
+
+    if (stack.idx >= stack.max)
+    {
+        //ERROR("mm", "Stack overflow attempt while freeing a page.");
+        log("pmm - could not free the page: stack overflow.\n");
+        return;
+    }
+
+    stack.pages[stack.idx++] = (uint64_t)ptr;
+}