From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754541Ab0CIQNI (ORCPT ); Tue, 9 Mar 2010 11:13:08 -0500 Received: from smtp.gentoo.org ([140.211.166.183]:60601 "EHLO smtp.gentoo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751719Ab0CIQNH (ORCPT ); Tue, 9 Mar 2010 11:13:07 -0500 From: Mike Frysinger To: uclinux-dev@uclinux.org, David Howells , David McCullough , Greg Ungerer , Paul Mundt Cc: uclinux-dist-devel@blackfin.uclinux.org, linux-kernel@vger.kernel.org, Bernd Schmidt Subject: [PATCH] NOMMU: allow private mappings of read-only devices Date: Tue, 9 Mar 2010 11:16:22 -0500 Message-Id: <1268151382-28469-1-git-send-email-vapier@gentoo.org> X-Mailer: git-send-email 1.7.0.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Bernd Schmidt Slightly rearrange the logic that determines capabilities and vm_flags. Disable BDI_CAP_MAP_DIRECT in all cases if the device can't support the protections. Allow private readonly mappings of readonly backing devices. Signed-off-by: Bernd Schmidt Signed-off-by: Mike Frysinger --- mm/nommu.c | 32 ++++++++++++++++++-------------- 1 files changed, 18 insertions(+), 14 deletions(-) diff --git a/mm/nommu.c b/mm/nommu.c index 61a68d5..5767237 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -930,14 +930,6 @@ static int validate_mmap_request(struct file *file, if (!(capabilities & BDI_CAP_MAP_DIRECT)) return -ENODEV; - if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) || - ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) || - ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP)) - ) { - printk("MAP_SHARED not completely supported on !MMU\n"); - return -EINVAL; - } - /* we mustn't privatise shared mappings */ capabilities &= ~BDI_CAP_MAP_COPY; } @@ -953,6 +945,20 @@ static int validate_mmap_request(struct file *file, capabilities &= ~BDI_CAP_MAP_DIRECT; } + if (capabilities & BDI_CAP_MAP_DIRECT) { + if (((prot & PROT_READ) && !(capabilities & BDI_CAP_READ_MAP)) || + ((prot & PROT_WRITE) && !(capabilities & BDI_CAP_WRITE_MAP)) || + ((prot & PROT_EXEC) && !(capabilities & BDI_CAP_EXEC_MAP)) + ) { + capabilities &= ~BDI_CAP_MAP_DIRECT; + if (flags & MAP_SHARED) { + printk(KERN_WARNING + "MAP_SHARED not completely supported on !MMU\n"); + return -EINVAL; + } + } + } + /* handle executable mappings and implied executable * mappings */ if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) { @@ -1008,22 +1014,20 @@ static unsigned long determine_vm_flags(struct file *file, unsigned long vm_flags; vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags); - vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; /* vm_flags |= mm->def_flags; */ if (!(capabilities & BDI_CAP_MAP_DIRECT)) { /* attempt to share read-only copies of mapped file chunks */ + vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; if (file && !(prot & PROT_WRITE)) vm_flags |= VM_MAYSHARE; - } - else { + } else { /* overlay a shareable mapping on the backing device or inode * if possible - used for chardevs, ramfs/tmpfs/shmfs and * romfs/cramfs */ + vm_flags |= VM_MAYSHARE | (capabilities & BDI_CAP_VMFLAGS); if (flags & MAP_SHARED) - vm_flags |= VM_MAYSHARE | VM_SHARED; - else if ((((vm_flags & capabilities) ^ vm_flags) & BDI_CAP_VMFLAGS) == 0) - vm_flags |= VM_MAYSHARE; + vm_flags |= VM_SHARED; } /* refuse to let anyone share private mappings with this process if -- 1.7.0.2