feat(loader, kernel): impl part of loader and initialize kernel structure

arch/x86_64/mem.zig

@@ -0,0 +1,43 @@
+pub const PAGE_SHIFT: usize = 12;
+pub const PAGE_SIZE: usize = 1 << PAGE_SHIFT;
+
+pub const PTE_SHIFT: u32 = 12;
+pub const PMD_SHIFT: u32 = 21;
+pub const PUD_SHIFT: u32 = 30;
+pub const PGD_SHIFT: u32 = 39;
+
+pub const PTE_SIZE: usize = 1 << PTE_SHIFT;
+pub const PMD_SIZE: usize = 1 << PMD_SHIFT;
+pub const PUD_SIZE: usize = 1 << PUD_SHIFT;
+pub const PGD_SIZE: usize = 1 << PGD_SHIFT;
+
+pub const PTE_MASK: usize = 1 << PTE_SHIFT - 1;
+pub const PMD_MASK: usize = 1 << PMD_SHIFT - 1;
+pub const PUD_MASK: usize = 1 << PUD_SHIFT - 1;
+pub const PGD_MASK: usize = 1 << PGD_SHIFT - 1;
+
+pub const ENTRIES_PER_TABLE: usize = PAGE_SIZE / 64;
+
+pub const PFType = struct{
+    pub const PROT: usize = 0;
+    pub const WRITE: usize = 1<<1;
+    pub const USER: usize = 1<<2;
+    pub const RSVD: usize = 1<<3;
+    pub const INSTR: usize = 1<<4;
+    pub const PK: usize = 1<<5;
+    pub const SHSTK: usize = 1<<6;
+};
+
+pub const PGDEntry = packed struct {
+    present: u1,
+    write: u1,
+    supervisor: u1,
+    write_through: u1,
+    cache_disable: u1,
+    accessed: u1,
+    _padding_1: u6,
+    addr: u40,
+    pub fn getIndex(self: usize) usize {
+        return (self >> PGD_SHIFT) & 0x1FF;
+    }
+};