should kernel support "rdinit=" parm without initrd support?

Robert P. J. Day
2009-07-08T09:00:50Z

wasn't sure if this was an LKML or newbies list question, so i
flipped a coin. you lost.

from init/main.c:

=====

static int __init init_setup(char *str)
{
unsigned int i;

execute_command = str;
/*
* In case LILO is going to boot us with default command line,
* it prepends "auto" before the whole cmdline which makes
* the shell think it should execute a script with such name.
* So we ignore all arguments entered _before_ init=... [MJ]
*/
for (i = 1; i < MAX_INIT_ARGS; i++)
argv_init[i] = NULL;
return 1;
}
__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);

=====

so, as i read it (and i might be wrong), "rdinit=" is used to
override the initial program in *early* userspace, while "init=" is
typically used to override the initial program in the final root
filesystem. is that a fairly accurate way to put it?

however, if you don't configure initramfs support *at all* (by not
selecting BLK_DEV_INITRD), notice what happens in init_post():

=====

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.
*
* The Bourne shell can be used instead of init if we are
* trying to recover a really broken machine.
*/
if (execute_command) {
run_init_process(execute_command);
printk(KERN_WARNING "Failed to execute %s. Attempting "
"defaults...\n", execute_command);
}
run_init_process("/sbin/init");
run_init_process("/etc/init");
run_init_process("/bin/init");
run_init_process("/bin/sh");

=====

even without BLK_DEV_INITRD initramfs support, the code will still
try to process a "rdinit=" command line parm (possibly overriding a
simultaneous "init=" parm). does that make sense? is there some
value to still processing "rdinit=" when you have no initramfs
support? or would it make more sense to simply preprocess that code
away thusly:

=====

#ifdef CONFIG_BLK_DEV_INITRD
if (ramdisk_execute_command) {
run_init_process(ramdisk_execute_command);
printk(KERN_WARNING "Failed to execute %s\n",
ramdisk_execute_command);
}
#endif

=====

or am i misreading this entirely?

rday
--

========================================================================
Robert P. J. Day Waterloo, Ontario, CANADA

Linux Consulting, Training and Annoying Kernel Pedantry.

Web page: http://crashcourse.ca
Linked In: http://www.linkedin.com/in/rpjday
Twitter: http://twitter.com/rpjday
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