hush: pass $! thru re-execution; try harder on re-exec; give error

 msg if re-exec didn't work; other tweaks in main()

function                                             old     new   delta
hush_main                                           1144    1199     +55
re_execute_shell                                     237     286     +49
file_get                                             240     260     +20
clean_up_after_re_execute                             58      66      +8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 132/0)             Total: 132 bytes

1 files changed, 57 insertions, 41 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 39d3c01de..eba7a86df 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -487,7 +487,8 @@ struct globals {
         int global_argc;
         char **global_argv;
 #if !BB_MMU
-        char **argv_for_re_execing;
+        char *argv0_for_re_execing;
+        char **argv_from_re_execing;
 #endif
 #if ENABLE_HUSH_LOOPS
         unsigned depth_break_continue;
@@ -2356,18 +2357,19 @@ static void re_execute_shell(const char *s)
         char **argv, **pp, **pp2;
         unsigned cnt;
 
-        /* 1:hush 2:-$<pid> 3:-?<exitcode> 4:-D<depth> <vars...>
-         * 5:-c 6:<cmd> <argN...> 7:NULL
+        /* 1:hush 2:-$<pid> 3:-!<pid> 4:-?<exitcode> 5:-D<depth> <vars...>
+         * 6:-c 7:<cmd> <argN...> 8:NULL
          */
-        cnt = 7 + G.global_argc;
+        cnt = 8 + G.global_argc;
         for (cur = G.top_var; cur; cur = cur->next) {
                 if (!cur->flg_export || cur->flg_read_only)
                         cnt += 2;
         }
-        G.argv_for_re_execing = pp = xzalloc(sizeof(argv[0]) * cnt);
-        *pp++ = (char *) applet_name;
-        *pp++ = xasprintf("-$%u", G.root_pid);
-        *pp++ = xasprintf("-?%u", G.last_return_code);
+        G.argv_from_re_execing = pp = xzalloc(sizeof(argv[0]) * cnt);
+        *pp++ = (char *) G.argv0_for_re_execing;
+        *pp++ = xasprintf("-$%u", (unsigned) G.root_pid);
+        *pp++ = xasprintf("-!%u", (unsigned) G.last_bg_pid);
+        *pp++ = xasprintf("-?%u", (unsigned) G.last_return_code);
 #if ENABLE_HUSH_LOOPS
         *pp++ = xasprintf("-D%u", G.depth_of_loop);
 #endif
@@ -2392,23 +2394,27 @@ static void re_execute_shell(const char *s)
 
         debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s);
         sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
-        execv(bb_busybox_exec_path, G.argv_for_re_execing);
-//TODO: fallback for init=/bin/hush?
-        _exit(127);
+        execv(bb_busybox_exec_path, G.argv_from_re_execing);
+        /* Fallback. Useful for init=/bin/hush usage etc */
+        if (G.argv0_for_re_execing[0] == '/')
+                execv(G.argv0_for_re_execing, G.argv_from_re_execing);
+        xfunc_error_retval = 127;
+        bb_error_msg_and_die("can't re-execute the shell");
 }
 
 static void clean_up_after_re_execute(void)
 {
-        char **pp = G.argv_for_re_execing;
+        char **pp = G.argv_from_re_execing;
         if (pp) {
                 /* Must match re_execute_shell's allocations */
                 free(pp[1]);
                 free(pp[2]);
-#if ENABLE_HUSH_LOOPS
                 free(pp[3]);
+#if ENABLE_HUSH_LOOPS
+                free(pp[4]);
 #endif
                 free(pp);
-                G.argv_for_re_execing = NULL;
+                G.argv_from_re_execing = NULL;
         }
 }
 #else
@@ -3001,8 +3007,8 @@ static void debug_print_tree(struct pipe *pi, int lvl)
                 [RES_SNTX ] = "SNTX" ,
         };
         static const char *const GRPTYPE[] = {
-                "()",
                 "{}",
+                "()",
 #if ENABLE_HUSH_FUNCTIONS
                 "func()",
 #endif
@@ -4990,14 +4996,15 @@ int hush_main(int argc, char **argv)
         };
 
         int opt;
-        FILE *input;
         char **e;
         struct variable *cur_var;
 
         INIT_G();
-
-        G.root_pid = getpid();
-
+        if (EXIT_SUCCESS) /* if EXIT_SUCCESS == 0, is already done */
+                G.last_return_code = EXIT_SUCCESS;
+#if !BB_MMU
+        G.argv0_for_re_execing = argv[0];
+#endif
         /* Deal with HUSH_VERSION */
         G.shell_ver = const_shell_ver; /* copying struct here */
         G.top_var = &G.shell_ver;
@@ -5020,11 +5027,9 @@ int hush_main(int argc, char **argv)
         }
         debug_printf_env("putenv '%s'\n", hush_version_str);
         putenv((char *)hush_version_str); /* reinstate HUSH_VERSION */
-
 #if ENABLE_FEATURE_EDITING
         G.line_input_state = new_line_input_t(FOR_SHELL);
 #endif
-        /* XXX what should these be while sourcing /etc/profile? */
         G.global_argc = argc;
         G.global_argv = argv;
         /* Initialize some more globals to non-zero values */
@@ -5035,31 +5040,19 @@ int hush_main(int argc, char **argv)
         G.PS2 = "> ";
 #endif
 
-        if (EXIT_SUCCESS) /* otherwise is already done */
-                G.last_return_code = EXIT_SUCCESS;
-
-        if (argv[0] && argv[0][0] == '-') {
-                debug_printf("sourcing /etc/profile\n");
-                input = fopen_for_read("/etc/profile");
-                if (input != NULL) {
-                        close_on_exec_on(fileno(input));
-                        parse_and_run_file(input);
-                        fclose(input);
-                }
-        }
-        input = stdin;
-
         /* http://www.opengroup.org/onlinepubs/9699919799/utilities/sh.html */
         while (1) {
                 opt = getopt(argc, argv, "c:xins"
 #if !BB_MMU
-                                "$:?:D:R:V:"
+                                "$:!:?:D:R:V:"
 #endif
                 );
                 if (opt <= 0)
                         break;
                 switch (opt) {
                 case 'c':
+                        if (!G.root_pid)
+                                G.root_pid = getpid();
                         G.global_argv = argv + optind;
                         if (!argv[optind]) {
                                 /* -c 'script' (no params): prevent empty $0 */
@@ -5082,6 +5075,9 @@ int hush_main(int argc, char **argv)
                 case '$':
                         G.root_pid = xatoi_u(optarg);
                         break;
+                case '!':
+                        G.last_bg_pid = xatoi_u(optarg);
+                        break;
                 case '?':
                         G.last_return_code = xatoi_u(optarg);
                         break;
@@ -5109,6 +5105,21 @@ int hush_main(int argc, char **argv)
 #endif
                 }
         }
+
+        if (!G.root_pid)
+                G.root_pid = getpid();
+        if (argv[0] && argv[0][0] == '-') {
+                FILE *input;
+                /* XXX what should argv be while sourcing /etc/profile? */
+                debug_printf("sourcing /etc/profile\n");
+                input = fopen_for_read("/etc/profile");
+                if (input != NULL) {
+                        close_on_exec_on(fileno(input));
+                        parse_and_run_file(input);
+                        fclose(input);
+                }
+        }
+
 #if ENABLE_HUSH_JOB
         /* A shell is interactive if the '-i' flag was given, or if all of
          * the following conditions are met:
@@ -5117,7 +5128,7 @@ int hush_main(int argc, char **argv)
          *    standard input is a terminal
          *    standard output is a terminal
          *    Refer to Posix.2, the description of the 'sh' utility. */
-        if (argv[optind] == NULL && input == stdin
+        if (argv[optind] == NULL
          && isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)
         ) {
                 G.saved_tty_pgrp = tcgetpgrp(STDIN_FILENO);
@@ -5132,8 +5143,8 @@ int hush_main(int argc, char **argv)
                                         /* give up */
                                         G_interactive_fd = 0;
                         }
-                        // TODO: track & disallow any attempts of user
-                        // to (inadvertently) close/redirect it
+// TODO: track & disallow any attempts of user
+// to (inadvertently) close/redirect it
                 }
         }
         init_signal_mask(); /* note: ensures SIGCHLD is not masked */
@@ -5152,7 +5163,7 @@ int hush_main(int argc, char **argv)
         }
 #elif ENABLE_HUSH_INTERACTIVE
 /* no job control compiled, only prompt/line editing */
-        if (argv[optind] == NULL && input == stdin
+        if (argv[optind] == NULL
          && isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)
         ) {
                 G_interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
@@ -5169,10 +5180,12 @@ int hush_main(int argc, char **argv)
         }
         init_signal_mask(); /* note: ensures SIGCHLD is not masked */
 #else
+//TODO: we didn't do it for -c or /etc/profile! Shouldn't we?
         init_signal_mask();
 #endif
         /* POSIX allows shell to re-enable SIGCHLD
          * even if it was SIG_IGN on entry */
+//TODO: we didn't do it for -c or /etc/profile! Shouldn't we?
 //      G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
         signal(SIGCHLD, SIG_DFL); // SIGCHLD_handler);
 
@@ -5186,18 +5199,21 @@ int hush_main(int argc, char **argv)
         if (argv[optind] == NULL) {
                 parse_and_run_file(stdin);
         } else {
+                FILE *input;
                 debug_printf("\nrunning script '%s'\n", argv[optind]);
                 G.global_argv = argv + optind;
                 G.global_argc = argc - optind;
                 input = xfopen_for_read(argv[optind]);
                 fcntl(fileno(input), F_SETFD, FD_CLOEXEC);
                 parse_and_run_file(input);
+#if ENABLE_FEATURE_CLEAN_UP
+                fclose(input);
+#endif
         }
 
  final_return:
 
 #if ENABLE_FEATURE_CLEAN_UP
-        fclose(input);
         if (G.cwd != bb_msg_unknown)
                 free((char*)G.cwd);
         cur_var = G.top_var->next;