Fix fork() regression on Windows

Recent optimizations to fork() introduced a regression, that could cause
the subprocess to fail unexpectedly, when TlsAlloc() returns a different
index. This is because we were burning the indexes into the displacement
of x86 opcodes. So when fork() happened and the executable memory copied
it would use the old index. Right now the way this is being solved is to
not copy the executable on fork() and then re-apply code changes. If you
need to be able to preserve self-modified code on fork, reach out and we
can implement a better solution for you. This gets us unblocked quickly.

test/libc/proc/BUILD.mk

@@ -31,6 +31,7 @@ TEST_LIBC_PROC_DIRECTDEPS =						\
 	LIBC_NT_KERNEL32						\
 	LIBC_PROC							\
 	LIBC_RUNTIME							\
+	LIBC_LOG							\
 	LIBC_STDIO							\
 	LIBC_STR							\
 	LIBC_SYSV							\
@@ -90,6 +91,7 @@ o/$(MODE)/test/libc/proc/execve_test.dbg:				\
 		o/$(MODE)/test/libc/proc/execve_test.o			\
 		o/$(MODE)/test/libc/calls/life-nomod.zip.o		\
 		o/$(MODE)/test/libc/proc/execve_test_prog1.zip.o	\
+		o/$(MODE)/test/libc/proc/execve_test_prog2.zip.o	\
 		o/$(MODE)/test/libc/mem/prog/life.elf.zip.o		\
 		o/$(MODE)/test/libc/mem/prog/sock.elf.zip.o		\
 		o/$(MODE)/test/libc/proc/proc.pkg			\
@@ -119,6 +121,7 @@ o/$(MODE)/test/libc/proc/life.dbg:					\
 
 o/$(MODE)/test/libc/proc/life.zip.o					\
 o/$(MODE)/test/libc/proc/execve_test_prog1.zip.o			\
+o/$(MODE)/test/libc/proc/execve_test_prog2.zip.o			\
 o/$(MODE)/test/libc/proc/life-pe.zip.o: private				\
 		ZIPOBJ_FLAGS +=						\
 			-B

test/libc/proc/execve_test.c

@@ -53,6 +53,7 @@ TEST(execve, testArgPassing) {
   char ibuf[12], buf[8];
   const char *prog = "./execve_test_prog1";
   testlib_extract("/zip/execve_test_prog1", prog, 0755);
+  testlib_extract("/zip/execve_test_prog2", "execve_test_prog2", 0755);
   for (i = 0; i < N; ++i) {
     FormatInt32(ibuf, i);
     GenBuf(buf, i);

test/libc/proc/execve_test_prog1.c

@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/fmt/conv.h"
+#include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 
 void GenBuf(char buf[8], int x) {
@@ -40,5 +41,15 @@ int main(int argc, char *argv[]) {
     tinyprint(2, "error: buf check failed\n", NULL);
     return 10;
   }
+  const char *prog = "./execve_test_prog2";
+  if (!fork()) {
+    execl(prog, prog, NULL);
+    _Exit(127);
+  }
+  int ws;
+  if (wait(&ws) == -1)
+    return 30;
+  if (ws)
+    return 31;
   return 0;
 }

test/libc/proc/execve_test_prog2.c

@@ -0,0 +1,23 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2024 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/proc/proc.h"
+#include "libc/testlib/testlib.h"
+
+int main(int argc, char *argv[]) {
+}