From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753120Ab0E1GYK (ORCPT ); Fri, 28 May 2010 02:24:10 -0400 Received: from dalsmrelay2.nai.com ([205.227.136.216]:65202 "HELO dalsmrelay2.nai.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750988Ab0E1GYG (ORCPT ); Fri, 28 May 2010 02:24:06 -0400 Date: Fri, 28 May 2010 16:23:42 +1000 From: David McCullough To: Mike Frysinger CC: uclinux-dev@uclinux.org, David Howells , Greg Ungerer , Paul Mundt , uclinux-dist-devel@blackfin.uclinux.org, microblaze-uclinux@itee.uq.edu.au, Michal Simek , linux-m32r@ml.linux-m32r.org, Hirokazu Takata , linux-kernel@vger.kernel.org, Yoshinori Sato Subject: Re: [PATCH 1/2 v2] FLAT: split the stack & data alignments Message-ID: <20100528062342.GA20365@mcafee.com> References: <1274815467-14584-1-git-send-email-vapier@gentoo.org> <1274863506-14168-1-git-send-email-vapier@gentoo.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1274863506-14168-1-git-send-email-vapier@gentoo.org> User-Agent: Mutt/1.5.20 (2009-06-14) X-OriginalArrivalTime: 28 May 2010 06:23:43.0712 (UTC) FILETIME=[525AE600:01CAFE2E] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jivin Mike Frysinger lays it down ... > The stack and data have different alignment requirements, so don't force > them to wear the same shoe. Increase the data alignment to match that > which the elf2flt linker script has always been using: 0x20 bytes. Not > only does this bring the kernel loader in line with the toolchain, but > it also fixes a swath of gcc tests which try to force larger alignment > values but randomly fail when the FLAT loader fails to deliver. > > Signed-off-by: Mike Frysinger Acked-by: David McCullough Cheers, Davidm > --- > v2 > - split changes & document better > > fs/binfmt_flat.c | 23 +++++++++++++++-------- > 1 files changed, 15 insertions(+), 8 deletions(-) > > diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c > index 49566c1..b865622 100644 > --- a/fs/binfmt_flat.c > +++ b/fs/binfmt_flat.c > @@ -56,15 +56,22 @@ > #endif > > /* > - * User data (stack, data section and bss) needs to be aligned > - * for the same reasons as SLAB memory is, and to the same amount. > - * Avoid duplicating architecture specific code by using the same > - * macro as with SLAB allocation: > + * User data (data section and bss) needs to be aligned. > + * We pick 0x20 here because it is the max value elf2flt has always > + * used in producing FLAT files, and because it seems to be large > + * enough to make all the gcc alignment related tests happy. > + */ > +#define FLAT_DATA_ALIGN (0x20) > + > +/* > + * User data (stack) also needs to be aligned. > + * Here we can be a bit looser than the data sections since this > + * needs to only meet arch ABI requirements. > */ > #ifdef ARCH_SLAB_MINALIGN > -#define FLAT_DATA_ALIGN (ARCH_SLAB_MINALIGN) > +#define FLAT_STACK_ALIGN (ARCH_SLAB_MINALIGN) > #else > -#define FLAT_DATA_ALIGN (sizeof(void *)) > +#define FLAT_STACK_ALIGN (sizeof(void *)) > #endif > > #define RELOC_FAILED 0xff00ff01 /* Relocation incorrect somewhere */ > @@ -129,7 +136,7 @@ static unsigned long create_flat_tables( > > sp = (unsigned long *)p; > sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); > - sp = (unsigned long *) ((unsigned long)sp & -FLAT_DATA_ALIGN); > + sp = (unsigned long *) ((unsigned long)sp & -FLAT_STACK_ALIGN); > argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0); > envp = argv + (argc + 1); > > @@ -876,7 +883,7 @@ static int load_flat_binary(struct linux_binprm * bprm, struct pt_regs * regs) > stack_len = TOP_OF_ARGS - bprm->p; /* the strings */ > stack_len += (bprm->argc + 1) * sizeof(char *); /* the argv array */ > stack_len += (bprm->envc + 1) * sizeof(char *); /* the envp array */ > - stack_len += FLAT_DATA_ALIGN - 1; /* reserve for upcoming alignment */ > + stack_len += FLAT_STACK_ALIGN - 1; /* reserve for upcoming alignment */ > > res = load_flat_file(bprm, &libinfo, 0, &stack_len); > if (IS_ERR_VALUE(res)) > -- > 1.7.1 > > > -- David McCullough, david_mccullough@mcafee.com, Ph:+61 734352815 McAfee - SnapGear http://www.mcafee.com http://www.uCdot.org