From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755554AbaCZOB1 (ORCPT ); Wed, 26 Mar 2014 10:01:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2582 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755505AbaCZOBY (ORCPT ); Wed, 26 Mar 2014 10:01:24 -0400 From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: Prarit Bhargava , Rob Landley , Andrew Morton , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Frederic Weisbecker , linux-doc@vger.kernel.org Subject: [PATCH] Add initcall_blacklist kernel parameter Date: Wed, 26 Mar 2014 10:00:41 -0400 Message-Id: <1395842441-17923-1-git-send-email-prarit@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a module is built into the kernel, the modules's module_init() function becomes an initcall. 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 is a wasteful time consuming process as it may be repeated several times before determining precisely what caused the problem. This patch has been useful in identifying problems with built-in modules and initcalls. It allows a user to skip an initcall to see if the kernel would continue to boot properly without requiring recompiles. Usage: initcall_blacklist= ex) added "initcall_blacklist=sgi_uv_sysfs_init" as a kernel parameter and the log contains: blacklisted initcall sgi_uv_sysfs_init ... ... function sgi_uv_sysfs_init returning without executing Cc: Rob Landley Cc: Andrew Morton Cc: Steven Rostedt Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: linux-doc@vger.kernel.org Signed-off-by: Prarit Bhargava --- Documentation/kernel-parameters.txt | 4 ++++ init/main.c | 16 ++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 7116fda..dadc43b 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1268,6 +1268,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. for working out where the kernel is dying during startup. + initcall_blacklist= [KNL] Stop executing the specified initcall + function. 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 9c7fd4c..a34677c 100644 --- a/init/main.c +++ b/init/main.c @@ -666,6 +666,15 @@ static void __init do_ctors(void) bool initcall_debug; core_param(initcall_debug, initcall_debug, bool, 0644); +static char blacklist_buf[128] = "\0"; +static int initcall_blacklist(char *str) +{ + snprintf(blacklist_buf, 127, "%s", str); + pr_debug("blacklisted initcall %s\n", blacklist_buf); + return 0; +} +__setup("initcall_blacklist=", initcall_blacklist); + static int __init_or_module do_one_initcall_debug(initcall_t fn) { ktime_t calltime, delta, rettime; @@ -689,6 +698,13 @@ int __init_or_module do_one_initcall(initcall_t fn) int count = preempt_count(); int ret; char msgbuf[64]; + char fn_name[128] = "\0"; + + snprintf(fn_name, 127, "%pf", fn); + if (!strcmp(fn_name, blacklist_buf)) { + pr_debug("function %pf returning without executing\n", fn); + return -EPERM; + } if (initcall_debug) ret = do_one_initcall_debug(fn); -- 1.7.9.3