From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + ftrace-remove-direct-reference-to-mcount-in-trace-code.patch added to -mm tree Date: Thu, 28 Aug 2008 17:02:25 -0700 Message-ID: <200808290002.m7T02PUe021305@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:53311 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753219AbYH2AD3 (ORCPT ); Thu, 28 Aug 2008 20:03:29 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org Cc: rostedt@goodmis.org, srostedt@redhat.com The patch titled ftrace: remove direct reference to mcount in trace code has been added to the -mm tree. Its filename is ftrace-remove-direct-reference-to-mcount-in-trace-code.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: ftrace: remove direct reference to mcount in trace code From: Steven Rostedt The mcount record method of ftrace scans objdump for references to mcount. Using mcount as the reference to test if the calls to mcount being replaced are indeed calls to mcount, this use of mcount was also caught as a location to change. Using a variable that points to the mcount address moves this reference into the data section that is not scanned, and we do not use a false location to try and modify. The warn on code was what was used to detect this bug. Signed-off-by: Steven Rostedt Signed-off-by: Andrew Morton --- kernel/trace/ftrace.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff -puN kernel/trace/ftrace.c~ftrace-remove-direct-reference-to-mcount-in-trace-code kernel/trace/ftrace.c --- a/kernel/trace/ftrace.c~ftrace-remove-direct-reference-to-mcount-in-trace-code +++ a/kernel/trace/ftrace.c @@ -37,6 +37,14 @@ int ftrace_enabled __read_mostly; static int last_ftrace_enabled; /* + * Since MCOUNT_ADDR may point to mcount itself, we do not want + * to get it confused by reading a reference in the code as we + * are parsing on objcopy output of text. Use a variable for + * it instead. + */ +static unsigned long mcount_addr = MCOUNT_ADDR; + +/* * ftrace_disabled is set when an anomaly is discovered. * ftrace_disabled is much stronger than ftrace_enabled. */ @@ -596,7 +604,7 @@ ftrace_code_disable(struct dyn_ftrace *r ip = rec->ip; nop = ftrace_nop_replace(); - call = ftrace_call_replace(ip, MCOUNT_ADDR); + call = ftrace_call_replace(ip, mcount_addr); failed = ftrace_modify_code(ip, call, nop); if (failed) { _ Patches currently in -mm which might be from rostedt@goodmis.org are origin.patch linux-next.patch kbuild-ftrace-dont-assume-that-scripts-recordmcountpl-is-executable.patch ftrace-warn-on-failure-to-disable-mcount-callers.patch ftrace-remove-direct-reference-to-mcount-in-trace-code.patch