ash: more changes to noexec applets

- Change the 'flags' argument to shellexec()/tryexec() so it only
  indicates that it's permissible to run ash_main() directly.  The
  flag is only set TRUE in forkshell_shellexec().

- The check for a script with an interpreter which is an applet is
  now performed for all calls to tryexec(), not just those that
  originate from evalcommand().

Saves 64-80 bytes.

GitHub issue #461.

1 files changed, 16 insertions, 30 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 3865b72d4..679846574 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -9090,28 +9090,24 @@ static struct tblentry **cmdtable;
 static int builtinloc = -1;     /* index in path of %builtin, or -1 */
 
 
-#if ENABLE_PLATFORM_MINGW32
-# define EXEC_FLAG 2
-
 static void
-tryexec(IF_FEATURE_SH_STANDALONE(int applet_no, const char *nfpath, int flags,)
+#if ENABLE_PLATFORM_MINGW32
+tryexec(IF_FEATURE_SH_STANDALONE(int applet_no, const char *path, int noexec,)
                         const char *cmd, char **argv, char **envp)
 #else
-static void
 tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, char **envp)
 #endif
 {
 #if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
-        struct forkshell *fs = (struct forkshell *)sticky_mem_start;
         interp_t interp;
 #endif
 #if ENABLE_FEATURE_SH_STANDALONE
         if (applet_no >= 0) {
 # if ENABLE_PLATFORM_MINGW32
                 /* Treat all applets as NOEXEC, including the shell itself
-                 * unless it was invoked by the exec builtin. */
-                if (applet_main[applet_no] != ash_main || !(flags & EXEC_FLAG)) {
+                 * if we were called from forkshell_shellexec(). */
  run_noexec:
+                if (applet_main[applet_no] != ash_main || noexec) {
                         /* mingw-w64's getopt() uses __argv[0] as the program name */
                         __argv[0] = (char *)cmd;
                         /* 'which' wants to know if it was invoked from a standalone
@@ -9154,17 +9150,10 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
         add_win32_extension((char *)cmd);
 
 # if ENABLE_FEATURE_SH_STANDALONE
-        /* If nfpath is non-NULL evalcommand() has determined this
-         * command doesn't need a fork().  Even it's NULL we can
-         * possibly avoid a fork if this is a FS_SHELLEXEC shell. */
-        if (nfpath == NULL && (fs && fs->fpid == FS_SHELLEXEC))
-                nfpath = pathval();
-
-        /* If nfpath is non-NULL and the command is a script with an
-         * interpreter which is an applet, we can run it as if it
-         * were a noexec applet. */
-        if (nfpath && parse_interpreter(cmd, &interp)) {
-                applet_no = find_applet_by_name_for_sh(interp.name, nfpath);
+        /* If the command is a script with an interpreter which is an
+         * applet, we can run it as if it were a noexec applet. */
+        if (parse_interpreter(cmd, &interp)) {
+                applet_no = find_applet_by_name_for_sh(interp.name, path);
                 if (applet_no >= 0) {
                         argv[0] = (char *)cmd;
                         /* evalcommand()/spawn_forkshell() add two elements before argv */
@@ -9233,18 +9222,15 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
  */
 static struct builtincmd *find_builtin(const char *name);
 static void shellexec(char *prog, char **argv, const char *path, int idx,
-                                                int nofork) NORETURN;
+                                                int noexec) NORETURN;
 static void shellexec(char *prog, char **argv, const char *path, int idx,
-                                                int nofork)
+                                                int noexec)
 {
         char *cmdname;
         int e;
         char **envp;
         int exerrno;
         int applet_no = -1; /* used only by FEATURE_SH_STANDALONE */
-#if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
-        const char *nfpath = (nofork & ~EXEC_FLAG) ? path : NULL;
-#endif
 
         envp = listvars(VEXPORT, VUNSET, /*strlist:*/ NULL, /*end:*/ NULL);
 #if ENABLE_FEATURE_SH_STANDALONE && ENABLE_PLATFORM_MINGW32 && defined(_UCRT)
@@ -9266,7 +9252,7 @@ static void shellexec(char *prog, char **argv, const char *path, int idx,
         ) {
 #if ENABLE_PLATFORM_MINGW32
                 char *progext = stack_add_ext_space(prog);
-                tryexec(IF_FEATURE_SH_STANDALONE(applet_no, nfpath, nofork,)
+                tryexec(IF_FEATURE_SH_STANDALONE(applet_no, path, noexec,)
                                 progext, argv, envp);
 #else
                 tryexec(IF_FEATURE_SH_STANDALONE(applet_no,) prog, argv, envp);
@@ -9284,7 +9270,7 @@ static void shellexec(char *prog, char **argv, const char *path, int idx,
                         const char *name = bb_basename(prog);
 # if ENABLE_FEATURE_SH_STANDALONE
                         if ((applet_no = find_applet_by_name_for_sh(name, path)) >= 0) {
-                                tryexec(applet_no, nfpath, nofork, name, argv, envp);
+                                tryexec(applet_no, path, noexec, name, argv, envp);
                                 e = errno;
                         }
 # endif
@@ -9301,7 +9287,7 @@ static void shellexec(char *prog, char **argv, const char *path, int idx,
                         cmdname = stackblock();
                         if (--idx < 0 && pathopt == NULL) {
 #if ENABLE_PLATFORM_MINGW32
-                                tryexec(IF_FEATURE_SH_STANDALONE(-1, nfpath, nofork,)
+                                tryexec(IF_FEATURE_SH_STANDALONE(-1, path, noexec,)
                                                 cmdname, argv, envp);
 #else
                                 tryexec(IF_FEATURE_SH_STANDALONE(-1,) cmdname, argv, envp);
@@ -11278,7 +11264,7 @@ execcmd(int argc UNUSED_PARAM, char **argv)
                 prog = argv[0];
                 if (optionarg)
                         argv[0] = optionarg;
-                shellexec(prog, argv, pathval(), 0, EXEC_FLAG);
+                shellexec(prog, argv, pathval(), 0, FALSE);
                 /* NOTREACHED */
         }
         return 0;
@@ -11834,7 +11820,7 @@ evalcommand(union node *cmd, int flags)
                         /* fall through to exec'ing external program */
                 }
 #endif
-                shellexec(argv[0], argv, path, cmdentry.u.index, TRUE);
+                shellexec(argv[0], argv, path, cmdentry.u.index, FALSE);
                 /* NOTREACHED */
         } /* default */
         case CMDBUILTIN:
@@ -16554,7 +16540,7 @@ forkshell_shellexec(struct forkshell *fs)
         char *path = fs->path;
 
         FORCE_INT_ON;
-        shellexec(argv[0], argv, path, idx, FALSE);
+        shellexec(argv[0], argv, path, idx, TRUE);
 }
 
 static void