ash: add FEATURE_SH_NOFORK support

2 files changed, 35 insertions, 0 deletions

diff --git a/shell/Config.in b/shell/Config.in
index 40e0217f4..94ffa09f8 100644
--- a/shell/Config.in
+++ b/shell/Config.in
@@ -287,6 +287,23 @@ config FEATURE_SH_STANDALONE
 #         that exact location with that exact name, this option will not work at
 #         all.
 
+config FEATURE_SH_NOFORK
+        bool "Run 'nofork' applets directly"
+        default n
+        depends on (MSH || LASH || HUSH || ASH) && FEATURE_PREFER_APPLETS
+        help
+          This option causes busybox shells [currently only ash]
+          to not execute typical fork/exec/wait sequence, but call <applet>_main
+          directly, if possible. (Sometimes it is not possible: for example,
+          this is not possible in pipes).
+
+          This will be done only for some applets (those which are marked
+          NOFORK in include/applets.h).
+
+          This may significantly speed up some shell scripts.
+
+          This feature is relatively new. Use with care.
+
 config CTTYHACK
         bool "cttyhack"
         default n
diff --git a/shell/ash.c b/shell/ash.c
index 0872e681a..cc61401d1 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -8747,6 +8747,24 @@ evalcommand(union node *cmd, int flags)
         /* Execute the command. */
         switch (cmdentry.cmdtype) {
         default:
+
+#if ENABLE_FEATURE_SH_NOFORK
+                {
+                /* TODO: don't rerun find_applet_by_name, find_command
+                 * already did it. Make it save applet_no somewhere */
+                int applet_no = find_applet_by_name(argv[0]);
+                if (applet_no >= 0 && APPLET_IS_NOFORK(applet_no)) {
+                        struct nofork_save_area nofork_save;
+
+                        listsetvar(varlist.list, VEXPORT|VSTACK);
+                        save_nofork_data(&nofork_save);
+                        /* run <applet>_main(), then restore nofork_save_area */
+                        exitstatus = run_nofork_applet_prime(&nofork_save, applet_no, argv) & 0xff;
+                        break;
+                }
+                }
+#endif
+
                 /* Fork off a child process if necessary. */
                 if (!(flags & EV_EXIT) || trap[0]) {
                         INT_OFF;