2 files changed, 32 insertions, 4 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 3d5cd7a09b2f..d2f0c67ba1fb 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1174,6 +1174,11 @@ running once the system is up.
                         New name for the ramdisk parameter.
                         See Documentation/ramdisk.txt.
 
+        rdinit=         [KNL]
+                        Format: <full_path>
+                        Run specified binary instead of /init from the ramdisk,
+                        used for early userspace startup. See initrd.
+
         reboot=         [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
                         Format: <reboot_mode>[,<reboot_mode2>[,...]]
                         See arch/*/kernel/reboot.c.
diff --git a/init/main.c b/init/main.c
index e4dbcbcd26cf..f142d4035341 100644
--- a/init/main.c
+++ b/init/main.c
@@ -123,6 +123,7 @@ extern void softirq_init(void);
 char saved_command_line[COMMAND_LINE_SIZE];
 
 static char *execute_command;
+static char *ramdisk_execute_command;
 
 /* Setup configured maximum number of CPUs to activate */
 static unsigned int max_cpus = NR_CPUS;
@@ -297,6 +298,18 @@ static int __init init_setup(char *str)
 }
 __setup("init=", init_setup);
 
+static int __init rdinit_setup(char *str)
+{
+        unsigned int i;
+
+        ramdisk_execute_command = str;
+        /* See "auto" comment in init_setup */
+        for (i = 1; i < MAX_INIT_ARGS; i++)
+                argv_init[i] = NULL;
+        return 1;
+}
+__setup("rdinit=", rdinit_setup);
+
 extern void setup_arch(char **);
 
 #ifndef CONFIG_SMP
@@ -681,10 +694,14 @@ static int init(void * unused)
          * check if there is an early userspace init.  If yes, let it do all
          * the work
          */
-        if (sys_access((const char __user *) "/init", 0) == 0)
-                execute_command = "/init";
-        else
+
+        if (!ramdisk_execute_command)
+                ramdisk_execute_command = "/init";
+
+        if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
+                ramdisk_execute_command = NULL;
                 prepare_namespace();
+        }
 
         /*
          * Ok, we have completed the initial bootup, and
@@ -701,7 +718,13 @@ static int init(void * unused)
 
         (void) sys_dup(0);
         (void) sys_dup(0);
-        
+
+        if (ramdisk_execute_command) {
+                run_init_process(ramdisk_execute_command);
+                printk(KERN_WARNING "Failed to execute %s\n",
+                                ramdisk_execute_command);
+        }
+
         /*
          * We try each of these until one succeeds.
          *