From: Prarit Bhargava <prarit@redhat.com>
Date: Thu, 22 May 2014 00:43:45 +0000 (+1000)
Subject: init/main.c: add initcall_blacklist kernel parameter
X-Git-Tag: next-20140530~2^2~143
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=3e6b7cc259bcf9ea097eea7227258c4c409ba7dd;p=karo-tx-linux.git

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

Signed-off-by: Prarit 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: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 12ffbf1c372f..5a0c56ff3ef4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1290,6 +1290,10 @@ 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
diff --git a/init/main.c b/init/main.c
index 9d3a7b84de5c..6b275a2ea05b 100644
--- a/init/main.c
+++ b/init/main.c
@@ -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("initcall blacklisted %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