Improve signals and memory protection

- Document sigaction()
- Simplify New Technology fork() code
- Testing and many bug fixes for mprotect()
- Distribute Intel Xed ILD in the amalgamation
- Turn Xed enums into defines to avoid DWARF bloat
- Improve polyfilling of SA_SIGINFO on BSDs and fix bugs
- setpgid(getpid(), getpid()) on Windows will ignore CTRL-C
- Work around issues relating to NT mappings being executable
- Permit automatic executable stack override via `ape_stack_pf`

libc/intrin/describemapflags.greg.c

@@ -0,0 +1,44 @@
+/*-*- 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 2022 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/intrin/describeflags.internal.h"
+#include "libc/macros.internal.h"
+#include "libc/nt/enum/consolemodeflags.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/prot.h"
+
+const char *DescribeMapFlags(int x) {
+  static char mapflags[256];
+  const struct DescribeFlags kMapFlags[] = {
+      {MAP_ANONYMOUS, "ANONYMOUS"},              //
+      {MAP_PRIVATE, "PRIVATE"},                  //
+      {MAP_SHARED, "SHARED"},                    //
+      {MAP_FIXED, "FIXED"},                      //
+      {MAP_FIXED_NOREPLACE, "FIXED_NOREPLACE"},  //
+      {MAP_GROWSDOWN, "GROWSDOWN"},              //
+      {MAP_CONCEAL, "CONCEAL"},                  //
+      {MAP_HUGETLB, "HUGETLB"},                  //
+      {MAP_LOCKED, "LOCKED"},                    //
+      {MAP_NORESERVE, "NORESERVE"},              //
+      {MAP_NONBLOCK, "NONBLOCK"},                //
+      {MAP_POPULATE, "POPULATE"},                //
+      {MAP_STACK, "STACK"},                      // order matters
+  };
+  return DescribeFlags(mapflags, sizeof(mapflags), kMapFlags,
+                       ARRAYLEN(kMapFlags), "MAP_", x);
+}