From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751853AbXBVUil (ORCPT ); Thu, 22 Feb 2007 15:38:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751856AbXBVUil (ORCPT ); Thu, 22 Feb 2007 15:38:41 -0500 Received: from ruby.spiritone.com ([216.99.193.130]:37789 "EHLO ruby.spiritone.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751853AbXBVUik (ORCPT ); Thu, 22 Feb 2007 15:38:40 -0500 X-Greylist: delayed 458 seconds by postgrey-1.27 at vger.kernel.org; Thu, 22 Feb 2007 15:38:40 EST Message-ID: <45DDFD98.4080300@BitWagon.com> Date: Thu, 22 Feb 2007 12:31:20 -0800 From: John Reiser Organization: - User-Agent: Mozilla Thunderbird 1.0.8-1.1.fc4 (X11/20060501) X-Accept-Language: en-us, en MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: fully honor vdso_enabled [i386, sh; x86_64?] X-Enigmail-Version: 0.92.0.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Architectures such as i386, sh, x86_64 have a flag /proc/sys/vm/vdso_enabled to choose whether the kernel should setup a process to use vdso after execve(). Informing the user code via AT_SYSINFO* is controlled by macro ARCH_DLINFO in fs/binfmt_elf.c and include/asm-$ARCH/elf.h, but the vdso page is established always via arch_setup_additonal_pages() called from load_elf_binary(). If vdso_enabled is off, then current code wastes kernel time during execve() and fragments the address space unnecessarily. This patch changes arch_setup_additonal_pages() to honor vdso_enabled. For i386 it also allows the option of a fixed addresss to avoid fragmenting the address space. Compiles and runs on i386. x86_64 [IA32 support] and sh maintainers also please comment. For some related history, including interaction with exec-shield, see: http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=229304 and also 207020 and 162797. Signed-off-by: John Reiser diff --git a/arch/i386/kernel/sysenter.c b/arch/i386/kernel/sysenter.c index 13ca54a..f8c4d76 100644 --- a/arch/i386/kernel/sysenter.c +++ b/arch/i386/kernel/sysenter.c @@ -22,6 +22,8 @@ #include #include #include +#include +#include /* * Should the kernel map a VDSO page into processes and pass its @@ -105,10 +107,25 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack) { struct mm_struct *mm = current->mm; unsigned long addr; + unsigned long flags; int ret; + switch (vdso_enabled) { + case 0: /* none */ + return 0; + default: + case 1: /* vdso in random available page */ + addr = 0ul; + flags = 0ul; + break; + case 2: /* out of user's way */ + addr = STACK_TOP; + flags = MAP_FIXED; + break; + } + down_write(&mm->mmap_sem); - addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); + addr = get_unmapped_area(NULL, addr, PAGE_SIZE, 0, flags); if (IS_ERR_VALUE(addr)) { ret = addr; goto up_fail; diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c index 7b0f66f..2b789fb 100644 --- a/arch/sh/kernel/vsyscall/vsyscall.c +++ b/arch/sh/kernel/vsyscall/vsyscall.c @@ -64,6 +64,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, unsigned long addr; int ret; + if (!vdso_enabled) + return 0; + down_write(&mm->mmap_sem); addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); if (IS_ERR_VALUE(addr)) { diff --git a/include/asm-i386/a.out.h b/include/asm-i386/a.out.h index ab17bb8..9894f73 100644 --- a/include/asm-i386/a.out.h +++ b/include/asm-i386/a.out.h @@ -19,7 +19,7 @@ struct exec #ifdef __KERNEL__ -#define STACK_TOP TASK_SIZE +#define STACK_TOP (TASK_SIZE - PAGE_SIZE) /* 1 page optional for vdso */ #endif --