mm: implemented mmio()

Author: jewelcodes

src/memory/mmio.c

@@ -29,5 +29,30 @@
  */
 
 uintptr_t mmio(Thread *t, uintptr_t addr, off_t count, int flags) {
+    off_t offset = addr & ~(PAGE_SIZE-1);
+    size_t pageCount = (count + PAGE_SIZE - 1) / PAGE_SIZE;
+    if(addr & ~(PAGE_SIZE-1)) pageCount++;
 
+    if(flags & MMIO_ENABLE) {
+        // creating a memory mapping
+        int pageFlags = PLATFORM_PAGE_PRESENT | PLATFORM_PAGE_USER;
+        if(flags & MMIO_W) pageFlags |= PLATFORM_PAGE_WRITE;
+        if(flags & MMIO_X) pageFlags |= PLATFORM_PAGE_EXEC;
+
+        uintptr_t virt = vmmAllocate(USER_MMIO_BASE, USER_LIMIT_ADDRESS, pageCount, VMM_USER);
+        if(!virt) return 0;
+
+        for(int i = 0; i < pageCount; i++)
+            platformMapPage(virt + (i*PAGE_SIZE), addr + (i*PAGE_SIZE), pageFlags);
+
+        return virt | offset;
+    } else {
+        // deleting a memory mapping
+        if(addr < USER_MMIO_BASE) return addr;
+
+        for(int i = 0; i < pageCount; i++)
+            platformMapPage(addr + (i * PAGE_SIZE), 0, 0);
+
+        return 0;
+    }
 }