Enable argv[0] tests in more places (#1061)

Now we do them for assimilated binaries (except on OpenBSD or XNU
non-Silicon), for XnuSilicon, and for binaries with the preserve-
argv[0] auxv flag set. We check whether to pass the argv[0] value
at the test site rather than the Child site. We move a lot of the
test initialization into Child in the non-child case, in order to
get at the pre-init value of `__program_executable_name`. Finally,
we print out info about what we are skipping.

ape/loader.c

@@ -947,6 +947,7 @@ EXTERN_C __attribute__((__noreturn__)) void ApeLoader(long di, long *sp,
     } else if (SupportsNetbsd() && !os && ap[0] == AT_EXECFN_NETBSD) {
       os = NETBSD;
     } else if (SupportsLinux() && ap[0] == AT_FLAGS) {
+      // TODO(mrdomino): maybe set/insert this when we are called as "ape -".
       arg0 = !!(ap[1] & AT_FLAGS_PRESERVE_ARGV0);
     }
   }

libc/calls/getprogramexecutablename.greg.c

@@ -25,6 +25,7 @@
 #include "libc/errno.h"
 #include "libc/fmt/libgen.h"
 #include "libc/intrin/getenv.internal.h"
+#include "libc/intrin/strace.internal.h"
 #include "libc/limits.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/runtime.h"
@@ -260,5 +261,6 @@ static void InitProgramExecutableName(void) {
  */
 char *GetProgramExecutableName(void) {
   cosmo_once(&g_prog.once, InitProgramExecutableName);
+  STRACE("GetProgramExecutableName() → %#s", __program_executable_name);
   return __program_executable_name;
 }

libc/sysv/consts/auxv.h

@@ -10,6 +10,8 @@
 #define AT_PAGESZ                   6
 #define AT_BASE                     7
 #define AT_FLAGS                    8
+#define AT_FLAGS_PRESERVE_ARGV0_BIT 0
+#define AT_FLAGS_PRESERVE_ARGV0     (1 << AT_FLAGS_PRESERVE_ARGV0_BIT)
 #define AT_ENTRY                    9
 
 COSMOPOLITAN_C_START_

test/libc/calls/getprogramexecutablename_test.c

@@ -27,6 +27,7 @@
 #include "libc/serialize.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
+#include "libc/sysv/consts/auxv.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/ok.h"
 #include "libc/testlib/ezbench.h"
@@ -34,14 +35,16 @@
 #include "libc/testlib/testlib.h"
 
 static char *self;
-static bool skiptests;
+static bool loaded, skiptests, skiparg0;
 
 void SetUpOnce(void) {
   self = GetProgramExecutableName();
   testlib_enable_tmp_setup_teardown();
   if (IsMetal()) {
     skiptests = true;
-  } else if (IsOpenbsd() || (IsXnu() && !IsXnuSilicon())) {
+  } else if (IsWindows()) {
+    /* do all tests */
+  } else if (!loaded) {
     ASSERT_STRNE(self, "");
     ASSERT_SYS(0, 3, open(self, O_RDONLY));
     char buf[8];
@@ -50,15 +53,24 @@ void SetUpOnce(void) {
     if (READ64LE(buf) != READ64LE("MZqFpD='") &&
         READ64LE(buf) != READ64LE("jartsr='") &&
         READ64LE(buf) != READ64LE("APEDBG='")) {
-      fprintf(stderr,
-              "we appear to be running as an assimilated binary on OpenBSD or "
-              "x86_64 XNU;\nGetProgramExecutableName is unreliable here\n");
-      skiptests = true;
+      // GetProgramExecutableName does not work reliably for assimilated
+      // OpenBSD or XNU binaries.
+      skiptests = IsOpenbsd() || (IsXnu() && !IsXnuSilicon());
     }
+  } else {
+    skiparg0 =
+        !(IsXnuSilicon() || (getauxval(AT_FLAGS) & AT_FLAGS_PRESERVE_ARGV0));
+  }
+  fprintf(stderr, loaded ? "loaded\n" : "not loaded\n");
+  if (skiptests) {
+    fprintf(stderr, "skipping most GetProgramExecutableName tests\n");
+  } else if (skiparg0) {
+    fprintf(stderr, "skipping argv[0] tests\n");
   }
 }
 
 __attribute__((__constructor__)) static void Child(int argc, char *argv[]) {
+  loaded = !!__program_executable_name;
   if (argc >= 2 && !strcmp(argv[1], "Child")) {
     int rc;
     if (!IsWindows()) {
@@ -72,15 +84,11 @@ __attribute__((__constructor__)) static void Child(int argc, char *argv[]) {
     if (strcmp(argv[2], GetProgramExecutableName())) {
       exit(123);
     }
-    if (!IsXnuSilicon()) exit(0);
-    /* TODO(mrdomino): argv[0] tests only pass on XnuSilicon right now because
-                       __sys_execve fails there, so the ape loader is used.
-                       the correct check is "we have been invoked either as an
-                       assimilated binary or via the ape loader, and not via a
-                       raw __sys_execve." */
+    if (argc >= 4) {
       if (strcmp(argv[3], argv[0])) {
         exit(124);
       }
+    }
     exit(0);
   }
 }
@@ -98,7 +106,8 @@ TEST(GetProgramExecutableName, ofThisFile) {
 TEST(GetProgramExecutableName, nullEnv) {
   if (skiptests) return;
   SPAWN(fork);
-  execve(self, (char *[]){self, "Child", self, self, 0}, (char *[]){0});
+  execve(self, (char *[]){self, "Child", self, skiparg0 ? 0 : self, 0},
+         (char *[]){0});
   abort();
   EXITS(0);
 }
@@ -106,7 +115,8 @@ TEST(GetProgramExecutableName, nullEnv) {
 TEST(GetProramExecutableName, weirdArgv0NullEnv) {
   if (skiptests) return;
   SPAWN(fork);
-  execve(self, (char *[]){"hello", "Child", self, "hello", 0}, (char *[]){0});
+  execve(self, (char *[]){"hello", "Child", self, skiparg0 ? 0 : "hello", 0},
+         (char *[]){0});
   abort();
   EXITS(0);
 }
@@ -133,11 +143,12 @@ TEST(GetProgramExecutableName, movedSelf) {
   ASSERT_NE(NULL, getcwd(buf, BUFSIZ - 5));
   stpcpy(buf + strlen(buf), "/test");
   SPAWN(fork);
-  execve(buf, (char *[]){"hello", "Child", buf, "hello", 0}, (char *[]){0});
+  execve(buf, (char *[]){"hello", "Child", buf, skiparg0 ? 0 : "hello", 0},
+         (char *[]){0});
   abort();
   EXITS(0);
   SPAWN(fork);
-  execve("./test", (char *[]){"hello", "Child", buf, "hello", 0},
+  execve("./test", (char *[]){"hello", "Child", buf, skiparg0 ? 0 : "hello", 0},
          (char *[]){0});
   abort();
   EXITS(0);