Support malloc() on bare metal

Your Actually Portable Executables now contains a simple virtual memory
that works similarly to the Linux Kernel in the sense that it maps your
physical memory to negative addresses. This is needed to support mmap()
and malloc(). This functionality has zero code size impact. For example
the MODE=tiny LIFE.COM executable is still only 12KB in size.

The APE bootloader code has also been simplified to improve readibility
and further elevate the elegance by which we're able to support so many
platforms thereby enhancing verifiability so that we may engender trust
in this bootloading process.

libc/runtime/directmap-nt.c

@@ -0,0 +1,87 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/internal.h"
+#include "libc/macros.h"
+#include "libc/nt/enum/filemapflags.h"
+#include "libc/nt/enum/pageflags.h"
+#include "libc/nt/memory.h"
+#include "libc/nt/runtime.h"
+#include "libc/nt/struct/overlapped.h"
+#include "libc/runtime/directmap.internal.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/prot.h"
+
+textwindows noasan struct DirectMap sys_mmap_nt(void *addr, size_t size,
+                                                int prot, int flags,
+                                                int64_t handle, int64_t off) {
+  uint32_t got;
+  size_t i, upsize;
+  struct DirectMap dm;
+  struct NtOverlapped op;
+  if ((prot & PROT_WRITE) && (flags & MAP_PRIVATE) && handle != -1) {
+    /*
+     * WIN32 claims it can do COW mappings but we still haven't found a
+     * combination of flags, that'll cause Windows to actually do this!
+     */
+    upsize = ROUNDUP(size, FRAMESIZE);
+    if ((dm.maphandle = CreateFileMappingNuma(
+             -1, &kNtIsInheritable, kNtPageExecuteReadwrite, upsize >> 32,
+             upsize, NULL, kNtNumaNoPreferredNode))) {
+      if ((dm.addr = MapViewOfFileExNuma(
+               dm.maphandle, kNtFileMapWrite | kNtFileMapExecute, 0, 0, upsize,
+               addr, kNtNumaNoPreferredNode))) {
+        for (i = 0; i < size; i += got) {
+          got = 0;
+          op.Internal = 0;
+          op.InternalHigh = 0;
+          op.Pointer = (void *)(uintptr_t)i;
+          op.hEvent = 0;
+          if (!ReadFile(handle, (char *)dm.addr + i, size - i, &got, &op)) {
+            break;
+          }
+        }
+        if (i == size) {
+          return dm;
+        }
+        UnmapViewOfFile(dm.addr);
+      }
+      CloseHandle(dm.maphandle);
+    }
+  } else {
+    if ((dm.maphandle = CreateFileMappingNuma(
+             handle, &kNtIsInheritable,
+             (prot & PROT_WRITE) ? kNtPageExecuteReadwrite : kNtPageExecuteRead,
+             handle != -1 ? 0 : size >> 32, handle != -1 ? 0 : size, NULL,
+             kNtNumaNoPreferredNode))) {
+      if ((dm.addr = MapViewOfFileExNuma(
+               dm.maphandle,
+               (prot & PROT_WRITE) ? kNtFileMapWrite | kNtFileMapExecute
+                                   : kNtFileMapRead | kNtFileMapExecute,
+               off >> 32, off, size, addr, kNtNumaNoPreferredNode))) {
+        return dm;
+      } else {
+        CloseHandle(dm.maphandle);
+      }
+    }
+  }
+  dm.maphandle = kNtInvalidHandleValue;
+  dm.addr = (void *)(intptr_t)__winerr();
+  return dm;
+}