[PATCH] fix 2.4.x incorrect argv[0] for init

[PATCH] fix 2.4.x incorrect argv[0] for init

[Erik Andersen]

In both 2.4.x and in 2.6.x, when someone specifies "init=" to
select an alternative binary to run instead of /sbin/init,
argv[0] is not set correctly.  This is a problem for programs
such as busybox that multiplex applications based on the value of
argv[0].  For example, even if you specify init=/bin/sh" on the
kernel command line, busybox will still receive "/sbin/init" as
argv[0], and will therefore run init rather than /bin/sh...

This patch fixes it.  Please apply,

 -Erik

--
Erik B. Andersen             http://codepoet-consulting.com/
--This message was written using 73% post-consumer electrons--


--- orig/init/main.c	2003-08-30 10:50:15.000000000 -0600
+++ linux-2.4.22/init/main.c	2003-08-30 10:50:15.000000000 -0600
@@ -545,6 +545,12 @@
 #endif
 }
 
+static void run_init_process(char *init_filename)
+{
+	argv_init[0] = init_filename;
+	execve(init_filename, argv_init, envp_init);
+}
+
 extern void prepare_namespace(void);
 
 static int init(void * unused)
@@ -587,10 +593,12 @@
 	 */
 
 	if (execute_command)
-		execve(execute_command,argv_init,envp_init);
-	execve("/sbin/init",argv_init,envp_init);
-	execve("/etc/init",argv_init,envp_init);
-	execve("/bin/init",argv_init,envp_init);
-	execve("/bin/sh",argv_init,envp_init);
+		run_init_process(execute_command);
+
+	run_init_process("/sbin/init");
+	run_init_process("/etc/init");
+	run_init_process("/bin/init");
+	run_init_process("/bin/sh");
+
 	panic("No init found.  Try passing init= option to kernel.");
 }

[PATCH] fix 2.4.x incorrect argv[0] for init

[Erik Andersen]

In 2.4.x when someone specifies "init=/bin/foo" to select an
alternative binary to run instead of /sbin/init, argv[0] is not
to the correct value.  This is a problem for programs such as
busybox that multiplex applications based on the value of
argv[0].  For example, even if you specify init=/bin/sh" on the
kernel command line, busybox will still receive "/sbin/init" as
argv[0], and will therefore run init rather than /bin/sh...

This problem was recently fixed in 2.6.x.  This patch applies
the same fix to 2.4.x.

 -Erik

--
Erik B. Andersen             http://codepoet-consulting.com/
--This message was written using 73% post-consumer electrons--


--- orig/init/main.c	2003-08-30 10:50:15.000000000 -0600
+++ linux-2.4.22/init/main.c	2003-08-30 10:50:15.000000000 -0600
@@ -545,6 +545,12 @@
 #endif
 }
 
+static void run_init_process(char *init_filename)
+{
+	argv_init[0] = init_filename;
+	execve(init_filename, argv_init, envp_init);
+}
+
 extern void prepare_namespace(void);
 
 static int init(void * unused)
@@ -587,10 +593,12 @@
 	 */
 
 	if (execute_command)
-		execve(execute_command,argv_init,envp_init);
-	execve("/sbin/init",argv_init,envp_init);
-	execve("/etc/init",argv_init,envp_init);
-	execve("/bin/init",argv_init,envp_init);
-	execve("/bin/sh",argv_init,envp_init);
+		run_init_process(execute_command);
+
+	run_init_process("/sbin/init");
+	run_init_process("/etc/init");
+	run_init_process("/bin/init");
+	run_init_process("/bin/sh");
+
 	panic("No init found.  Try passing init= option to kernel.");
 }

Re: [PATCH] fix 2.4.x incorrect argv[0] for init

[jhf]

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On Wed, Oct 01, 2003 at 12:56:13PM -0600, Erik Andersen wrote:
> In 2.4.x when someone specifies "init=/bin/foo" to select an
> alternative binary to run instead of /sbin/init, argv[0] is not
> to the correct value.  This is a problem for programs such as
> busybox that multiplex applications based on the value of
> argv[0].  For example, even if you specify init=/bin/sh" on the
> kernel command line, busybox will still receive "/sbin/init" as
> argv[0], and will therefore run init rather than /bin/sh...
> 
> This problem was recently fixed in 2.6.x.  This patch applies
> the same fix to 2.4.x.

    I didn't know that got merged.  Great!

    Debian users running 2.6: go install busybox-static, then make a
link from /sbin/sh to /bin/busybox.  If something bad happens to your
file system or libc or something like that, you can still boot with
init=/sbin/sh and get a shell prompt and all the important utilities
as long as /bin/busybox is okay.  It's a nice failsafe, especially
when testing kernels or running an unstable distribution.

   If this patch gets merged in 2.4, 2.4 users will be able to do this
too.

-- 
Joseph Fannin
jhf@rivenstone.net

"That's all I have to say about that." -- Forrest Gump.

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