Add mmap kernel syscall. Needed for large malloc

src/kernel/memory/kbrk.c

@@ -2,6 +2,7 @@
 #include <debug.h>
 
 static long _brk = KERNEL_BRK0;
+static long _mmap = KERNEL_MMAP;
 
 long k_brk(long brk, long, long, long, long, long)
 {
@@ -15,4 +16,22 @@ long k_brk(long brk, long, long, long, long, long)
     } else {
         return _brk;
     }
+}
+
+long k_mmap(long addr, long length, long prot, long flags, long fd, long offset)
+{
+    (void)addr;
+    (void)prot;
+    (void)flags;
+    (void)offset;
+    if(fd != -1)
+        PANIC("Unknown mmap request\n");
+    long retval = _mmap;
+    while(length > 0)
+    {
+        vmm_set_page(kernel_P4, _mmap, pmm_alloc(), PAGE_WRITE | PAGE_PRESENT);
+        _mmap += PAGE_SIZE;
+        length -= PAGE_SIZE;
+    }
+    return retval;
 }