ash: minimise work when a forkshell process is started

There's no need to create or initialise the global data structures
when a forkshell is being started:  they'll soon be replaced by
data from the forkshell data block.

Move the call to forkshell_init() to the top of ash_main() along
with some initialisation that's common to forkshell shells and
ordinary shells.  Add the minimum necessary initialisation to
forkshell_init().

1 files changed, 27 insertions, 19 deletions

diff --git a/shell/ash.c b/shell/ash.c
index f57819810..e21131b01 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -391,7 +391,6 @@ enum {
 
 static struct forkshell* forkshell_prepare(struct forkshell *fs);
 static void forkshell_init(const char *idstr);
-static void forkshell_child(struct forkshell *fs);
 static void sticky_free(void *p);
 # define free(p) sticky_free(p)
 #if !JOBS
@@ -15254,12 +15253,27 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
         int login_sh;
 #if ENABLE_PLATFORM_MINGW32
         char *sd;
-        int is_forkshell;
+
+        INIT_G_memstack();
+
+        /* from init() */
+        basepf.next_to_pgetc = basepf.buf = ckmalloc(IBUFSIZ);
+        basepf.linno = 1;
+
+        hSIGINT = CreateEvent(NULL, TRUE, FALSE, NULL);
+
+        if (argc == 3 && !strcmp(argv[1], "--fs")) {
+                forkshell_init(argv[2]);
+                /* only reached in case of error */
+                bb_error_msg_and_die("forkshell failed");
+        }
 #endif
 
         /* Initialize global data */
         INIT_G_misc();
+#if !ENABLE_PLATFORM_MINGW32
         INIT_G_memstack();
+#endif
         INIT_G_var();
 #if ENABLE_ASH_ALIAS
         INIT_G_alias();
@@ -15303,27 +15317,13 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
         rootpid = getpid();
 
 #if ENABLE_PLATFORM_MINGW32
-        /* we will never free this */
-        basepf.next_to_pgetc = basepf.buf = ckmalloc(IBUFSIZ);
-        basepf.linno = 1;
-
         winxp = (argv[1] != NULL && strcmp(argv[1], "-X") == 0);
-        is_forkshell = (argc == 3 && !strcmp(argv[1], "--fs"));
-        if (!is_forkshell)
 #endif
         init();
         setstackmark(&smark);
 
 #if ENABLE_PLATFORM_MINGW32
-        hSIGINT = CreateEvent(NULL, TRUE, FALSE, NULL);
         SetConsoleCtrlHandler(ctrl_handler, TRUE);
-
-        if (is_forkshell) {
-                forkshell_init(argv[2]);
-
-                /* only reached in case of error */
-                bb_error_msg_and_die("forkshell failed");
-        }
 #endif
 
 #if NUM_SCRIPTS > 0
@@ -16301,7 +16301,6 @@ forkshell_prepare(struct forkshell *fs)
         return new;
 }
 
-#undef exception_handler
 #undef trap
 #undef trap_ptr
 static void *sticky_mem_start, *sticky_mem_end;
@@ -16316,6 +16315,7 @@ forkshell_init(const char *idstr)
         int i;
         char **ptr;
         char *lrelocate;
+        struct jmploc jmploc;
 
         if (sscanf(idstr, "%p", &map_handle) != 1)
                 return;
@@ -16348,11 +16348,10 @@ forkshell_init(const char *idstr)
                         e = e->next;
                 }
         }
-        fs->gmp->exception_handler = ash_ptr_to_globals_misc->exception_handler;
         memset(fs->gmp->trap, 0, sizeof(fs->gmp->trap[0])*NSIG);
         /* fs->gmp->trap_ptr = fs->gmp->trap; */
 
-        /* Switch global variables */
+        /* Set global variables */
         gvpp = (struct globals_var **)&ash_ptr_to_globals_var;
         *gvpp = fs->gvp;
         gmpp = (struct globals_misc **)&ash_ptr_to_globals_misc;
@@ -16374,6 +16373,12 @@ forkshell_init(const char *idstr)
 
         reinitvar();
 
+        if (setjmp(jmploc.loc)) {
+                exitreset();
+                exitshell();
+        }
+        exception_handler = &jmploc;
+
         shlvl++;
         if (fs->mode == FORK_BG) {
                 SetConsoleCtrlHandler(NULL, TRUE);
@@ -16383,6 +16388,9 @@ forkshell_init(const char *idstr)
                                 ash_msg_and_raise_perror("can't open '%s'", bb_dev_null);
                 }
         }
+        else {
+                SetConsoleCtrlHandler(ctrl_handler, TRUE);
+        }
         forkshell_child(fs);
 }