Make terminal ui binaries work well everywhere

Here's some screenshots of an emulator tui program that was compiled on
Linux, then scp'd it to Windows, Mac, and FreeBSD.

https://justine.storage.googleapis.com/blinkenlights-cmdexe.png
https://justine.storage.googleapis.com/blinkenlights-imac.png
https://justine.storage.googleapis.com/blinkenlights-freebsd.png
https://justine.storage.googleapis.com/blinkenlights-lisp.png

How is this even possible that we have a nontrivial ui binary that just
works on Mac, Windows, Linux, and BSD? Surely a first ever achievement.

Fixed many bugs. Bootstrapped John McCarthy's metacircular evaluator on
bare metal in half the size of Altair BASIC (about 2.5kb) and ran it in
emulator for fun and profit.

tool/build/lib/memorymalloc.c

@@ -17,35 +17,167 @@
 │ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
 │ 02110-1301 USA                                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/calls/calls.h"
+#include "libc/log/check.h"
+#include "libc/log/log.h"
 #include "libc/mem/mem.h"
+#include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
+#include "libc/sysv/errfuns.h"
+#include "libc/x/x.h"
+#include "tool/build/lib/buffer.h"
+#include "tool/build/lib/endian.h"
 #include "tool/build/lib/machine.h"
 #include "tool/build/lib/memory.h"
 #include "tool/build/lib/pml4t.h"
 
-void *MallocPage(void) {
-  void *p;
-  size_t n;
-  if ((p = memalign(4096, 4096))) {
-    memset(p, 0, 4096);
-  }
-  return p;
-}
-
-int RegisterMemory(struct Machine *m, int64_t v, void *r, size_t n) {
-  return RegisterPml4t(m->cr3, v, (int64_t)(intptr_t)r, n, MallocPage);
-}
-
-void ResetRam(struct Machine *m) {
-  FreePml4t(m->cr3, -0x800000000000, 0x800000000000, free, munmap);
-}
-
 struct Machine *NewMachine(void) {
   struct Machine *m;
-  m = memalign(alignof(struct Machine), sizeof(struct Machine));
-  memset(m, 0, sizeof(struct Machine));
+  m = xmemalignzero(alignof(struct Machine), sizeof(struct Machine));
   m->mode = XED_MACHINE_MODE_LONG_64;
-  InitMachine(m);
+  ResetCpu(m);
+  ResetMem(m);
   return m;
 }
+
+static void FreeMachineRealFree(struct Machine *m) {
+  struct MachineRealFree *rf;
+  while ((rf = m->realfree)) {
+    m->realfree = rf->next;
+    free(rf);
+  }
+}
+
+void FreeMachine(struct Machine *m) {
+  if (m) {
+    FreeMachineRealFree(m);
+    free(m->real.p);
+    free(m);
+  }
+}
+
+void ResetMem(struct Machine *m) {
+  FreeMachineRealFree(m);
+  ResetTlb(m);
+  m->real.i = 0;
+  m->cr3 = AllocateLinearPage(m);
+}
+
+long AllocateLinearPage(struct Machine *m) {
+  uint8_t *p;
+  size_t i, n;
+  struct MachineRealFree *rf;
+  if ((rf = m->realfree)) {
+    DCHECK(rf->n);
+    DCHECK_EQ(0, rf->i & 0xfff);
+    DCHECK_EQ(0, rf->n & 0xfff);
+    DCHECK_LE(rf->i + rf->n, m->real.i);
+    i = rf->i;
+    rf->i += 0x1000;
+    if (!(rf->n -= 0x1000)) {
+      m->realfree = rf->next;
+      free(rf);
+    }
+  } else {
+    i = m->real.i;
+    n = m->real.n;
+    p = m->real.p;
+    if (i == n) {
+      if (n) {
+        n += n >> 1;
+      } else {
+        n = 0x10000;
+      }
+      n = ROUNDUP(n, 0x1000);
+      if ((p = realloc(p, n))) {
+        m->real.p = p;
+        m->real.n = n;
+        ResetTlb(m);
+      } else {
+        return -1;
+      }
+    }
+    DCHECK_EQ(0, i & 0xfff);
+    DCHECK_EQ(0, n & 0xfff);
+    DCHECK_LE(i + 0x1000, n);
+    m->real.i += 0x1000;
+  }
+  memset(m->real.p + i, 0, 0x1000); /* TODO: lazy page clearing */
+  return i;
+}
+
+static uint64_t MachineRead64(struct Machine *m, unsigned long i) {
+  CHECK_LE(i + 8, m->real.n);
+  return Read64(m->real.p + i);
+}
+
+static void MachineWrite64(struct Machine *m, unsigned long i, uint64_t x) {
+  CHECK_LE(i + 8, m->real.n);
+  Write64(m->real.p + i, x);
+}
+
+int ReserveVirtual(struct Machine *m, int64_t virt, size_t size) {
+  int64_t level, pt, ti, mi, end;
+  for (end = virt + size; virt < end; virt += 0x1000) {
+    for (pt = m->cr3, level = 39; level >= 12; level -= 9) {
+      pt = pt & 0x00007ffffffff000;
+      ti = (virt >> level) & 511;
+      DEBUGF("reserve %p level %d table %p index %ld", virt, level, pt, ti);
+      mi = pt + ti * 8;
+      pt = MachineRead64(m, mi);
+      if (!(pt & 1)) {
+        if ((pt = AllocateLinearPage(m)) == -1) return -1;
+        MachineWrite64(m, mi, pt | 7);
+      }
+    }
+  }
+  return 0;
+}
+
+int64_t FindVirtual(struct Machine *m, int64_t virt, size_t size) {
+  uint64_t i, pt, got;
+  got = 0;
+  do {
+    if (virt >= 0x800000000000) return enomem();
+    for (pt = m->cr3, i = 39; i >= 12; i -= 9) {
+      pt = MachineRead64(m, (pt & 0x7ffffffff000) + ((virt >> i) & 511) * 8);
+      if (!(pt & 1)) break;
+    }
+    if (i >= 12) {
+      got += 1ull << i;
+    } else {
+      virt += 0x1000;
+      got = 0;
+    }
+  } while (got < size);
+  return virt;
+}
+
+int FreeVirtual(struct Machine *m, int64_t base, size_t size) {
+  struct MachineRealFree *rf;
+  uint64_t i, mi, pt, la, end, virt;
+  for (virt = base, end = virt + size; virt < end;) {
+    for (pt = m->cr3, i = 39;; i -= 9) {
+      mi = (pt & 0x7ffffffff000) + ((virt >> i) & 511) * 8;
+      pt = MachineRead64(m, mi);
+      if (!(pt & 1)) {
+        break;
+      } else if (i == 12) {
+        MachineWrite64(m, mi, 0);
+        la = pt & 0x7ffffffff000;
+        if (m->realfree && la == m->realfree->i + m->realfree->n) {
+          m->realfree->n += 0x1000;
+        } else if ((rf = malloc(sizeof(struct MachineRealFree)))) {
+          rf->i = la;
+          rf->n = 0x1000;
+          rf->next = m->realfree;
+          m->realfree = rf;
+        }
+        break;
+      }
+    }
+    virt += 1ull << i;
+  }
+  return 0;
+}