Add torture test for zipos file descriptors

This change hardens the code for opening /zip/ files using the system
call interface. Thread safety and signal safety has been improved for
file descriptors in general. We now document fixed addresses that are
needed for low level allocations.

tool/viz/memplan.c

@@ -0,0 +1,94 @@
+#if 0
+/*─────────────────────────────────────────────────────────────────╗
+│ To the extent possible under law, Justine Tunney has waived      │
+│ all copyright and related or neighboring rights to this file,    │
+│ as it is written in the following disclaimers:                   │
+│   • http://unlicense.org/                                        │
+│   • http://creativecommons.org/publicdomain/zero/1.0/            │
+╚─────────────────────────────────────────────────────────────────*/
+#endif
+#include "libc/bits/bits.h"
+#include "libc/calls/internal.h"
+#include "libc/fmt/itoa.h"
+#include "libc/macros.internal.h"
+#include "libc/runtime/memtrack.internal.h"
+#include "libc/stdio/stdio.h"
+// clang-format off
+
+struct WinArgs {
+  char *argv[4096];
+  char *envp[4092];
+  intptr_t auxv[2][2];
+  char argblock[ARG_MAX / 2];
+  char envblock[ARG_MAX / 2];
+};
+
+//#define INCREMENT roundup2pow(kAutomapSize/16)
+#define INCREMENT (64L*1024*1024*1024)
+
+uint64_t last;
+
+void plan2(uint64_t addr, uint64_t end, const char *name) {
+  char sz[32];
+  FormatMemorySize(sz, end-addr+1);
+  printf("%08x-%08x %-6s %s\n", addr>>16, end>>16, sz, name);
+}
+
+void plan(uint64_t addr, uint64_t end, const char *name) {
+  uint64_t incr, next;
+  while (addr > last) {
+    if ((incr = last % INCREMENT)) {
+      incr = INCREMENT - incr;
+    } else {
+      incr = INCREMENT;
+    }
+    plan2(last,MIN(last+incr,addr)-1,"free");
+    last = MIN(last+incr,addr);
+  }
+  while (addr <= end) {
+    if (end-addr+1 <= INCREMENT) {
+      plan2(addr,end,name);
+      last = end + 1;
+      break;
+    }
+    if (!(addr % INCREMENT)) {
+      plan2(addr, addr + INCREMENT - 1, name);
+      last = addr + INCREMENT;
+      addr += INCREMENT;
+    } else {
+      next = INCREMENT - addr % INCREMENT + addr;
+      plan2(addr, next - 1, name);
+      last = next;
+      addr = next;
+    }
+  }
+}
+
+int main(int argc, char *argv[]) {
+  uint64_t x, y;
+
+  plan(0x00000000, 0x00200000-1, "null");
+  plan(0x00200000, 0x00400000-1, "loader");
+  if (!IsWindows() || IsAtLeastWindows10()) {
+    plan(0x00400000, 0x50000000-1, "image");
+    plan(0x50000000, 0x7ffdffff, "arena");
+    plan(0x7fff0000, 0x10007fffffff, "asan");
+  } else {
+    plan(0x00400000, 0x01000000-1, "image");
+  }
+  plan(kAutomapStart, kAutomapStart + kAutomapSize - 1, "automap");
+  plan(kMemtrackStart, kMemtrackStart + kMemtrackSize - 1, "memtrack");
+  plan(kFixedmapStart, kFixedmapStart + kFixedmapSize - 1, "fixedmap");
+  if (IsWindows() && !IsAtLeastWindows10()) {
+    plan(0x50000000, 0x7ffdffff, "arena");
+  }
+  x = (intptr_t)GetStaticStackAddr(0);
+  y = ROUNDUP(sizeof(struct WinArgs), FRAMESIZE);
+  plan(x - y, x - 1, "winargs");
+  plan(x, x + GetStackSize() - 1, "stack");
+  if (!IsWindows() || IsAtLeastWindows10()) {
+    plan(0x7f0000000000, 0x800000000000 - 1, "kernel");
+  }
+
+  return 0;
+}