init: make the command-line rewrite optional

When launched as PID 1 and after parsing its arguments, init wipes all
all of them except argv[0] and rewrites argv[0] to contain only "init",
so that its command-line appears solely as "init" in tools such as ps.

This patch adds the FEATURE_INIT_MODIFY_CMDLINE which, if set to n, will
make init preserve all its arguments including argv[0], be they parsed or
ignored.
The original command-line used to launch init can then be retrieved in
/proc/1/cmdline on Linux, for example.

Signed-off-by: Nicolas Carrier <nicolas.carrier@parrot.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 22 insertions, 5 deletions

diff --git a/init/init.c b/init/init.c
index 2040a59e8..25bfaec8c 100644
--- a/init/init.c
+++ b/init/init.c
@@ -102,6 +102,21 @@
 //config:
 //config:         Note that on Linux, init attempts to detect serial terminal and
 //config:         sets TERM to "vt102" if one is found.
+//config:
+//config:config FEATURE_INIT_MODIFY_CMDLINE
+//config:       bool "Modify the command-line to \"init\""
+//config:       default y
+//config:       depends on INIT
+//config:       help
+//config:         When launched as PID 1 and after parsing its arguments, init
+//config:         wipes all the arguments but argv[0] and rewrites argv[0] to
+//config:         contain only "init", so that its command-line appears solely as
+//config:         "init" in tools such as ps.
+//config:         If this option is set to Y, init will keep its original behavior,
+//config:         otherwise, all the arguments including argv[0] will be preserved,
+//config:         be they parsed or ignored by init.
+//config:         The original command-line used to launch init can then be
+//config:         retrieved in /proc/1/cmdline on Linux, for example.
 
 //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
 //applet:IF_FEATURE_INITRD(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
@@ -1138,11 +1153,13 @@ int init_main(int argc UNUSED_PARAM, char **argv)
         }
 #endif
 
-        /* Make the command line just say "init"  - thats all, nothing else */
-        strncpy(argv[0], "init", strlen(argv[0]));
-        /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
-        while (*++argv)
-                nuke_str(*argv);
+        if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) {
+                /* Make the command line just say "init"  - that's all, nothing else */
+                strncpy(argv[0], "init", strlen(argv[0]));
+                /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
+                while (*++argv)
+                        nuke_str(*argv);
+        }
 
         /* Set up signal handlers */
         if (!DEBUG_INIT) {