hush: fix exec builtin in a better way (+ "glob in exec" bug fixed)

function                                             old     new   delta
execvp_or_die                                          -      50     +50
static.pseudo_null_str                                 3       -      -3
builtin_exec                                          83      57     -26
pseudo_exec_argv                                     200     163     -37
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 0/2 up/down: 50/-66)            Total: -16 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 19 insertions, 27 deletions

diff --git a/shell/hush.c b/shell/hush.c
index ae08c7326..5edcdb844 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -3322,6 +3322,16 @@ static void exec_builtin(char ***to_free,
 }
 
 
+static void execvp_or_die(char **argv) NORETURN;
+static void execvp_or_die(char **argv)
+{
+        debug_printf_exec("execing '%s'\n", argv[0]);
+        sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
+        execvp(argv[0], argv);
+        bb_perror_msg("can't execute '%s'", argv[0]);
+        _exit(127); /* bash compat */
+}
+
 #if BB_MMU
 #define pseudo_exec_argv(nommu_save, argv, assignment_cnt, argv_expanded) \
         pseudo_exec_argv(argv, assignment_cnt, argv_expanded)
@@ -3337,7 +3347,7 @@ static void exec_builtin(char ***to_free,
 static void pseudo_exec_argv(nommu_save_t *nommu_save,
                 char **argv, int assignment_cnt,
                 char **argv_expanded) NORETURN;
-static void pseudo_exec_argv(nommu_save_t *nommu_save,
+static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save,
                 char **argv, int assignment_cnt,
                 char **argv_expanded)
 {
@@ -3421,11 +3431,7 @@ static void pseudo_exec_argv(nommu_save_t *nommu_save,
 #if ENABLE_FEATURE_SH_STANDALONE || BB_MMU
  skip:
 #endif
-        debug_printf_exec("execing '%s'\n", argv[0]);
-        sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
-        execvp(argv[0], argv);
-        bb_perror_msg("can't execute '%s'", argv[0]);
-        _exit(127); /* bash compat */
+        execvp_or_die(argv);
 }
 
 /* Called after [v]fork() in run_pipe
@@ -6985,32 +6991,19 @@ static int FAST_FUNC builtin_cd(char **argv)
 
 static int FAST_FUNC builtin_exec(char **argv)
 {
-        static const char pseudo_null_str[] = { SPECIAL_VAR_SYMBOL, SPECIAL_VAR_SYMBOL, '\0' };
-        char **pp;
-#if !BB_MMU
-        nommu_save_t dummy;
-#endif
-
         if (*++argv == NULL)
                 return EXIT_SUCCESS; /* bash does this */
 
-        /* Make sure empty arguments aren't ignored */
-        /* Example: exec ls '' */
-        pp = argv;
-        while (*pp) {
-                if ((*pp)[0] == '\0')
-                        *pp = (char*)pseudo_null_str;
-                pp++;
-        }
-
         /* Careful: we can end up here after [v]fork. Do not restore
          * tty pgrp then, only top-level shell process does that */
         if (G_saved_tty_pgrp && getpid() == G.root_pid)
                 tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
 
-        /* TODO: if exec fails, bash does NOT exit! We do... */
-        pseudo_exec_argv(&dummy, argv, 0, NULL);
-        /* never returns */
+        /* TODO: if exec fails, bash does NOT exit! We do.
+         * We'll need to undo sigprocmask (it's inside execvp_or_die)
+         * and tcsetpgrp, and this is inherently racy.
+         */
+        execvp_or_die(argv);
 }
 
 static int FAST_FUNC builtin_exit(char **argv)
diff --git a/shell/hush_test/hush-vars/param_glob.tests b/shell/hush_test/hush-vars/param_glob.tests
index 0173fd771..4d74fee02 100755
--- a/shell/hush_test/hush-vars/param_glob.tests
+++ b/shell/hush_test/hush-vars/param_glob.tests
@@ -1,7 +1,6 @@
 if test $# = 0; then
-    # UNFIXED BUG in builtin_exec! will glob param!
-    #exec "$THIS_SH" "$0" 'param_glob.t*'
-    "$THIS_SH" "$0" 'param_glob.t*'
+    exec "$THIS_SH" "$0" 'param_glob.t*'
+    echo NOT SHOWN
     exit
 fi
 echo $*