Don't relocate file descriptor memory

This change fixes #496 where ASAN spotted a race condition that could
happen in multithreaded programs, with more than OPEN_MAX descriptors
when using ZipOS or Windows NT, which require tracking open file info
and this change fixes that table so it never relocates, thus allowing
us to continue to enjoy the benefits of avoiding locks while reading.

libc/zipos/free.c

@@ -23,11 +23,6 @@
 #include "libc/str/str.h"
 #include "libc/zipos/zipos.internal.h"
 
-/**
- * Frees ZipOS handle.
- * @asyncsignalsafe
- * @threadsafe
- */
 void __zipos_free(struct Zipos *z, struct ZiposHandle *h) {
   if (IsAsan()) {
     __asan_poison((char *)h + sizeof(struct ZiposHandle),

libc/zipos/open.c

@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/extend.internal.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/state.internal.h"
 #include "libc/calls/struct/sigset.h"
@@ -42,47 +43,19 @@
 #include "libc/zip.h"
 #include "libc/zipos/zipos.internal.h"
 
-static volatile size_t maptotal;
-
-static pureconst size_t __zipos_granularity(void) {
-  return FRAMESIZE * (IsAsan() ? 8 : 1);
-}
+static char *mapend;
+static size_t maptotal;
 
 static void *__zipos_mmap(size_t mapsize) {
+  char *start;
   size_t offset;
-  struct DirectMap dm;
-  int rc, prot, flags;
-  uint64_t addr, addr2, addr3;
   assert(mapsize);
-  do offset = maptotal;
-  while (!_cmpxchg(&maptotal, offset, maptotal + mapsize));
-  if (offset + mapsize <= kMemtrackZiposSize) {
-    prot = PROT_READ | PROT_WRITE;
-    flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED;
-    addr = kMemtrackZiposStart + offset;
-    if ((dm = sys_mmap((void *)addr, mapsize, prot, flags, -1, 0)).addr !=
-        MAP_FAILED) {
-      rc = TrackMemoryInterval(&_mmi, addr >> 16, (addr + mapsize - 1) >> 16,
-                               dm.maphandle, prot, flags, false, false, 0,
-                               mapsize);
-      assert(!rc);
-      if (IsAsan()) {
-        addr2 = (addr >> 3) + 0x7fff8000;
-        addr3 = ((addr + mapsize) >> 3) + 0x7fff8000;
-        assert(!(addr2 & (FRAMESIZE - 1)));
-        assert(!(addr3 & (FRAMESIZE - 1)));
-        dm = sys_mmap((void *)addr2, mapsize >> 3, prot, flags, -1, 0);
-        assert(dm.addr != MAP_FAILED);
-        rc = TrackMemoryInterval(&_mmi, addr2 >> 16, (addr3 >> 16) - 1,
-                                 dm.maphandle, prot, flags, false, false, 0,
-                                 mapsize >> 3);
-        assert(!rc);
-      }
-      return (void *)addr;
-    }
-  }
-  enomem();
-  return 0;
+  offset = maptotal;
+  maptotal += mapsize;
+  start = (char *)0x6fd000040000;
+  if (!mapend) mapend = start;
+  mapend = _extend(start, maptotal, mapend, 0x6fdfffff0000);
+  return start + offset;
 }
 
 static struct ZiposHandle *__zipos_alloc(struct Zipos *zipos, size_t size) {
@@ -90,7 +63,7 @@ static struct ZiposHandle *__zipos_alloc(struct Zipos *zipos, size_t size) {
   struct ZiposHandle *h, **ph;
   __zipos_lock();
   mapsize = sizeof(struct ZiposHandle) + size;
-  mapsize = ROUNDUP(mapsize, __zipos_granularity());
+  mapsize = ROUNDUP(mapsize, 4096);
 StartOver:
   ph = &zipos->freelist;
   while ((h = *ph)) {

libc/zipos/zipos.internal.h

@@ -1,6 +1,5 @@
 #ifndef COSMOPOLITAN_LIBC_ZIPOS_ZIPOS_H_
 #define COSMOPOLITAN_LIBC_ZIPOS_ZIPOS_H_
-#include "libc/calls/calls.h"
 #include "libc/intrin/nopl.h"
 #include "libc/nexgen32e/threaded.h"
 #if !(__ASSEMBLER__ + __LINKER__ + 0)