make busybox --install work even if /proc/self/exe doesn't exist

# size busybox_old busybox_unstripped
   text    data     bss     dec     hex filename
 680095    2704   15648  698447   aa84f busybox_old
 680099    2704   15648  698451   aa853 busybox_unstripped

8 files changed, 15 insertions, 21 deletions

diff --git a/applets/applets.c b/applets/applets.c
index bd3704394..f34124252 100644
--- a/applets/applets.c
+++ b/applets/applets.c
@@ -577,21 +577,13 @@ static int busybox_main(char **argv)
         }
 
         if (ENABLE_FEATURE_INSTALLER && strcmp(argv[1], "--install") == 0) {
-                int use_symbolic_links = 0;
-                char *busybox;
-
-                /* to use symlinks, or not to use symlinks... */
-                if (argv[2])
-                        if (strcmp(argv[2], "-s") == 0)
-                                use_symbolic_links = 1;
-
-                /* link */
-                busybox = xmalloc_readlink_or_warn("/proc/self/exe");
+                const char *busybox;
+                busybox = xmalloc_readlink_or_warn(bb_busybox_exec_path);
                 if (!busybox)
-                        return 1;
-                install_links(busybox, use_symbolic_links);
-                if (ENABLE_FEATURE_CLEAN_UP)
-                        free(busybox);
+                        busybox = bb_busybox_exec_path;
+                /* -s makes symlinks */
+                install_links(busybox,
+                                 argv[2] && strcmp(argv[2], "-s") == 0);
                 return 0;
         }
 
diff --git a/include/libbb.h b/include/libbb.h
index 1ba122a2d..a32a74253 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -952,6 +952,7 @@ extern const char bb_path_securetty_file[];
 extern const char bb_path_motd_file[];
 extern const char bb_path_wtmp_file[];
 extern const char bb_dev_null[];
+extern const char bb_busybox_exec_path[];
 
 extern const int const_int_0;
 extern const int const_int_1;
diff --git a/libbb/execable.c b/libbb/execable.c
index d84364753..f679108be 100644
--- a/libbb/execable.c
+++ b/libbb/execable.c
@@ -65,7 +65,7 @@ int exists_execable(const char *filename)
  */
 int bb_execvp(const char *file, char *const argv[])
 {
-        return execvp(find_applet_by_name(file) ? CONFIG_BUSYBOX_EXEC_PATH : file,
+        return execvp(find_applet_by_name(file) ? bb_busybox_exec_path : file,
                                         argv);
 }
 #endif
diff --git a/libbb/messages.c b/libbb/messages.c
index fbd882c43..16aaea553 100644
--- a/libbb/messages.c
+++ b/libbb/messages.c
@@ -37,8 +37,9 @@ const char bb_path_gshadow_file[] = "/etc/gshadow";
 const char bb_path_nologin_file[] = "/etc/nologin";
 const char bb_path_securetty_file[] = "/etc/securetty";
 const char bb_path_motd_file[] = "/etc/motd";
-const char bb_default_login_shell[] = LIBBB_DEFAULT_LOGIN_SHELL;
 const char bb_dev_null[] = "/dev/null";
+const char bb_busybox_exec_path[] = CONFIG_BUSYBOX_EXEC_PATH;
+const char bb_default_login_shell[] = LIBBB_DEFAULT_LOGIN_SHELL;
 
 const int const_int_0;
 const int const_int_1 = 1;
diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 349628796..cb4dee799 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -220,8 +220,8 @@ void forkexit_or_rexec(char **argv)
         /* high-order bit of first char in argv[0] is a hidden
          * "we have (alrealy) re-execed, don't do it again" flag */
         argv[0][0] |= 0x80;
-        execv(CONFIG_BUSYBOX_EXEC_PATH, argv);
-        bb_perror_msg_and_die("exec %s", CONFIG_BUSYBOX_EXEC_PATH);
+        execv(bb_busybox_exec_path, argv);
+        bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
 }
 #else
 /* Dance around (void)...*/
diff --git a/shell/ash.c b/shell/ash.c
index ea10a65cf..29d8713b7 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6471,7 +6471,7 @@ tryexec(char *cmd, char **argv, char **envp)
                                 run_current_applet_and_exit(argv);
                         }
                         /* re-exec ourselves with the new arguments */
-                        execve(CONFIG_BUSYBOX_EXEC_PATH, argv, envp);
+                        execve(bb_busybox_exec_path, argv, envp);
                         /* If they called chroot or otherwise made the binary no longer
                          * executable, fall through */
                 }
diff --git a/shell/hush.c b/shell/hush.c
index 2a4076ed2..40bcafdd9 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -1392,7 +1392,7 @@ static void pseudo_exec_argv(char **argv)
                         }
                         /* re-exec ourselves with the new arguments */
                         debug_printf_exec("re-execing applet '%s'\n", argv[0]);
-                        execvp(CONFIG_BUSYBOX_EXEC_PATH, argv);
+                        execvp(bb_busybox_exec_path, argv);
                         /* If they called chroot or otherwise made the binary no longer
                          * executable, fall through */
                 }
diff --git a/shell/msh.c b/shell/msh.c
index d81a00122..aab805ff5 100644
--- a/shell/msh.c
+++ b/shell/msh.c
@@ -3062,7 +3062,7 @@ static const char *rexecve(char *c, char **v, char **envp)
                         /* We have to exec here since we vforked.  Running
                          * run_applet_and_exit() won't work and bad things
                          * will happen. */
-                        execve(CONFIG_BUSYBOX_EXEC_PATH, v, envp);
+                        execve(bb_busybox_exec_path, v, envp);
                 }
         }