Commit 7b0b73d7 authored by Prarit Bhargava's avatar Prarit Bhargava Committed by Linus Torvalds
Browse files

init/main.c: add initcall_blacklist kernel parameter 



When a module is built into the kernel the module_init() function
becomes an initcall.  Sometimes debugging through dynamic debug can
help, however, debugging built in kernel modules is typically done by
changing the .config, recompiling, and booting the new kernel in an
effort to determine exactly which module caused a problem.

This patchset can be useful stand-alone or combined with initcall_debug.
There are cases where some initcalls can hang the machine before the
console can be flushed, which can make initcall_debug output inaccurate.
Having the ability to skip initcalls can help further debugging of these
scenarios.

Usage: initcall_blacklist=<list of comma separated initcalls>

ex) added "initcall_blacklist=sgi_uv_sysfs_init" as a kernel parameter and
the log contains:

	blacklisting initcall sgi_uv_sysfs_init
	...
	...
	initcall sgi_uv_sysfs_init blacklisted

ex) added "initcall_blacklist=foo_bar,sgi_uv_sysfs_init" as a kernel parameter
and the log contains:

	blacklisting initcall foo_bar
	blacklisting initcall sgi_uv_sysfs_init
	...
	...
	initcall sgi_uv_sysfs_init blacklisted

[akpm@linux-foundation.org: tweak printk text]
Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
Cc: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: Rob Landley <rob@landley.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d62cf815

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -1312,6 +1312,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			for working out where the kernel is dying during

			startup.



	initcall_blacklist=  [KNL] Do not execute a comma-separated list of

			initcall functions.  Useful for debugging built-in

			modules and initcalls.



	initrd=		[BOOT] Specify the location of the initial ramdisk



	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver

init/main.c

+68 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ 
#include <linux/sched_clock.h>

#include <linux/context_tracking.h>

#include <linux/random.h>

#include <linux/list.h>



#include <asm/io.h>

#include <asm/bugs.h>
@@ -665,6 +666,70 @@ static void __init do_ctors(void) 
bool initcall_debug;

core_param(initcall_debug, initcall_debug, bool, 0644);



#ifdef CONFIG_KALLSYMS

struct blacklist_entry {

	struct list_head next;

	char *buf;

};



static __initdata_or_module LIST_HEAD(blacklisted_initcalls);



static int __init initcall_blacklist(char *str)

{

	char *str_entry;

	struct blacklist_entry *entry;



	/* str argument is a comma-separated list of functions */

	do {

		str_entry = strsep(&str, ",");

		if (str_entry) {

			pr_debug("blacklisting initcall %s\n", str_entry);

			entry = alloc_bootmem(sizeof(*entry));

			entry->buf = alloc_bootmem(strlen(str_entry) + 1);

			strcpy(entry->buf, str_entry);

			list_add(&entry->next, &blacklisted_initcalls);

		}

	} while (str_entry);



	return 0;

}



static bool __init_or_module initcall_blacklisted(initcall_t fn)

{

	struct list_head *tmp;

	struct blacklist_entry *entry;

	char *fn_name;



	fn_name = kasprintf(GFP_KERNEL, "%pf", fn);

	if (!fn_name)

		return false;



	list_for_each(tmp, &blacklisted_initcalls) {

		entry = list_entry(tmp, struct blacklist_entry, next);

		if (!strcmp(fn_name, entry->buf)) {

			pr_debug("initcall %s blacklisted\n", fn_name);

			kfree(fn_name);

			return true;

		}

	}



	kfree(fn_name);

	return false;

}

#else

static int __init initcall_blacklist(char *str)

{

	pr_warn("initcall_blacklist requires CONFIG_KALLSYMS\n");

	return 0;

}



static bool __init_or_module initcall_blacklisted(initcall_t fn)

{

	return false;

}

#endif

__setup("initcall_blacklist=", initcall_blacklist);



static int __init_or_module do_one_initcall_debug(initcall_t fn)

{

	ktime_t calltime, delta, rettime;
@@ -689,6 +754,9 @@ int __init_or_module do_one_initcall(initcall_t fn) 
	int ret;

	char msgbuf[64];



	if (initcall_blacklisted(fn))

		return -EPERM;



	if (initcall_debug)

		ret = do_one_initcall_debug(fn);

	else

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