From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754242AbcBHSZE (ORCPT ); Mon, 8 Feb 2016 13:25:04 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:35937 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752267AbcBHSZC (ORCPT ); Mon, 8 Feb 2016 13:25:02 -0500 Message-ID: <56B8DD7A.1010303@gmail.com> Date: Mon, 08 Feb 2016 10:24:58 -0800 From: David Daney User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Harvey Hunt CC: David Daney , linux-mips@linux-mips.org, ralf@linux-mips.org, David Daney , Paul Burton , James Hogan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] MIPS: Always page align TASK_SIZE References: <1454954723-24887-1-git-send-email-harvey.hunt@imgtec.com> <56B8DA56.9020108@caviumnetworks.com> <56B8DB2D.3070604@imgtec.com> In-Reply-To: <56B8DB2D.3070604@imgtec.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/08/2016 10:15 AM, Harvey Hunt wrote: > Hi David, > > On 02/08/2016 10:11 AM, David Daney wrote: >> On 02/08/2016 10:05 AM, Harvey Hunt wrote: >>> STACK_TOP_MAX is aligned on a 32k boundary. When __bprm_mm_init() >>> creates an >>> initial stack for a process, it does so using STACK_TOP_MAX as the end >>> of the >>> vma. A process's arguments and environment information are placed on >>> the stack >>> and then the stack is relocated and aligned on a page boundary. When >>> using a 32 >>> bit kernel with 64k pages, the relocated stack has the process's args >>> erroneously stored in the middle of the stack. This means that processes >>> receive no arguments or environment variables, preventing them from >>> running >>> correctly. >>> >>> Fix this by aligning TASK_SIZE on a page boundary. >>> >>> Signed-off-by: Harvey Hunt >>> Cc: David Daney >>> Cc: Paul Burton >>> Cc: James Hogan >>> Cc: linux-kernel@vger.kernel.org >>> --- >>> arch/mips/include/asm/processor.h | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/arch/mips/include/asm/processor.h >>> b/arch/mips/include/asm/processor.h >>> index 3f832c3..b618b40 100644 >>> --- a/arch/mips/include/asm/processor.h >>> +++ b/arch/mips/include/asm/processor.h >>> @@ -39,13 +39,13 @@ extern unsigned int vced_count, vcei_count; >>> #ifdef CONFIG_32BIT >>> #ifdef CONFIG_KVM_GUEST >>> /* User space process size is limited to 1GB in KVM Guest Mode */ >>> -#define TASK_SIZE 0x3fff8000UL >>> +#define TASK_SIZE (0x40000000UL - PAGE_SIZE) >>> #else >>> /* >>> * User space process size: 2GB. This is hardcoded into a few places, >>> * so don't change it unless you know what you are doing. >>> */ >>> -#define TASK_SIZE 0x7fff8000UL >>> +#define TASK_SIZE (0x7fff8000UL & PAGE_SIZE) >> >> Can you check your math here. This doesn't seem correct. > > Thanks for spotting that - it should have been: > > (0x7fff8000UL & PAGE_MASK) This brings up an interesting point. How was this tested? Please note that in the change log. Also look at the definition of PAGE_MASK in page.h Is that correct? Most of the other related symbols have an "_AC(1,UL)" in them. Why is this not also appropriate for PAGE_MASK? It may also be a good idea to prepare and test a patch that defines PAGE_MASK much in the same way HPAGE_MASK is defined. David Daney > > I'll do a v2 now. > >> >>> #endif >>> >>> #define STACK_TOP_MAX TASK_SIZE >>> @@ -62,7 +62,7 @@ extern unsigned int vced_count, vcei_count; >>> * support 16TB; the architectural reserve for future expansion is >>> * 8192EB ... >>> */ >>> -#define TASK_SIZE32 0x7fff8000UL >>> +#define TASK_SIZE32 (0x7fff8000UL & PAGE_SIZE) >> >> Same here. > > As above. > >> >>> #define TASK_SIZE64 0x10000000000UL >>> #define TASK_SIZE (test_thread_flag(TIF_32BIT_ADDR) ? TASK_SIZE32 : >>> TASK_SIZE64) >>> #define STACK_TOP_MAX TASK_SIZE64 >>> >> > > Thanks, > > Harvey