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

arch/x86_64/boot/ident_map.zig

@@ -0,0 +1,62 @@
+const std = @import("std");
+const processor = @import("arch").processor;
+const mem = @import("arch").mem;
+const PFType = mem.PFType;
+const early_serial_console = @import("early_serial_console.zig");
+const assert = std.debug.assert;
+
+var pgtable_buffer: struct {
+    buffer: [*][mem.PAGE_SIZE]u8,
+    size: usize,
+    used_pages: usize,
+} = undefined;
+
+fn allocPgtablePage() error.OutOfMemory![4096]u8 {
+    // if (used + mem.PAGE_SIZE > size) {
+    //     early_serial_console.dprint("Out of page table memory!\n", .{});
+    //     return error.OutOfMemory;
+    // }
+    // const page = buffer + used;
+    // return page;
+}
+// fn pgdIdentInit() {
+
+// }
+
+// fn pudIdentInit() {
+
+// }
+
+fn kernelAddIdentityMap(pgdt_page: [*]mem.PGDEntry, start: u64, end: u64) void {
+    assert(start % mem.PMD_SIZE == 0);
+    assert(end % mem.PMD_SIZE == 0);
+    var address = start;
+    while (address < end) {
+        // var pgd = &pgdt_page[mem.PGDEntry.getIndex(address)];
+        // if ()
+        address += mem.PMD_SIZE;
+    }
+}
+export fn initializeIdentMap() void {
+    // var pgd_table = processor.readCr3();
+    // if (pgdtable == _pgtable) {
+
+    // }
+}
+fn printPF(msg: []const u8, errorCode: u64, faultAddress: u64, ip: u64) void {
+    early_serial_console.dprint(
+        \\{s}:
+        \\error code: 0x{x}
+        \\fault address: 0x{x}
+        \\instruction pointer: 0x{x}
+        \\
+        , .{msg, errorCode, faultAddress, ip});
+}
+export fn doBootPageFault(regs: processor.PtRegs, errorCode: u64) void {
+    const faultAddress = processor.readCr2();
+    if (errorCode & (PFType.PROT | PFType.USER | PFType.RSVD) == 0) {
+        printPF("Unexpected page fault", errorCode, faultAddress, regs.ip);
+    }
+    const address = faultAddress & mem.PMD_MASK;
+    kernelAddIdentityMap(address, address + mem.PMD_SIZE);
+}