Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754817AbZJUTJu (ORCPT ); Wed, 21 Oct 2009 15:09:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754663AbZJUTJt (ORCPT ); Wed, 21 Oct 2009 15:09:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1026 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754495AbZJUTJt (ORCPT ); Wed, 21 Oct 2009 15:09:49 -0400 Message-ID: <4ADF5C6B.80605@redhat.com> Date: Wed, 21 Oct 2009 14:09:31 -0500 From: Eric Sandeen User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Arjan van de Ven CC: Ingo Molnar , Dave Jones , Linux Kernel , Thomas Gleixner , esandeen@redhat.com, cebbert@redhat.com, "H. Peter Anvin" Subject: Re: Unnecessary overhead with stack protector. References: <20091015183540.GA8098@redhat.com> <20091015190720.GA19467@elte.hu> <4ADF2DAA.9030604@redhat.com> <20091021110053.26ab9982@infradead.org> <4ADF59F8.7010205@redhat.com> In-Reply-To: <4ADF59F8.7010205@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1889 Lines: 54 Eric Sandeen wrote: > Arjan van de Ven wrote: ... >> do you have any indication that SP actually increases the stack >> footprint by that much? it's only a few bytes.... >> >> > > Here's a sample of some of the largest xfs stack users, > and the effect stack-protector had on them. This was just > done with objdump -d xfs.ko | scripts/checkstack.pl; I don't > know if there's extra runtime stack overhead w/ stackprotector? > > -Eric > > function nostack stackprot delta delta % > xfs_bmapi 376 408 32 9% > xfs_bulkstat 328 344 16 5% > _xfs_trans_commit 296 312 16 5% > xfs_iomap_write_delay 264 280 16 6% > xfs_file_ioctl 248 312 64 26% > xfs_symlink 248 264 16 6% > xfs_bunmapi 232 280 48 21% > xlog_do_recovery_pass 232 248 16 7% > xfs_trans_unreserve_and_mod_sb 224 240 16 7% > xfs_bmap_del_extent 216 248 32 15% > xfs_cluster_write 216 232 16 7% > xfs_file_compat_ioctl 216 296 80 37% > xfs_attr_set_int 200 216 16 8% > xfs_bmap_add_extent_delay_real 200 248 48 24% > but maybe more to Dave's original point, xfs on x86_64 in my tree had 243 functions with minimal stack usage of 8 bytes. w/ CC_STACKPROTECTOR_ALL in force, I end up with these sizes for those functions: count bytes 3 16 236 24 1 32 5 40 8->24 bytes is pretty significant too, w/ a 200% increase, if you add a few up... -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/