Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934289AbcKDNO5 (ORCPT ); Fri, 4 Nov 2016 09:14:57 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:60800 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933226AbcKDNOz (ORCPT ); Fri, 4 Nov 2016 09:14:55 -0400 DMARC-Filter: OpenDMARC Filter v1.3.1 smtp.codeaurora.org 459626043B Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=pass smtp.mailfrom=cov@codeaurora.org From: Christopher Covington To: linux-mm@vger.kernel.org, Jonathan Corbet , Andrew Morton , Michal Hocko , Vlastimil Babka , Hugh Dickins , Konstantin Khlebnikov , Naoya Horiguchi , "Kirill A. Shutemov" , Robert Foss , John Stultz , Robert Ho , Ross Zwisler , Jerome Marchand , Andy Lutomirski , Johannes Weiner , Kees Cook , Christopher Covington , Alexey Dobriyan , Jann Horn , Joe Perches , Andy Shevchenko , "Richard W.M. Jones" , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Christopher Covington Subject: [PATCH] procfs: Add mem_end to /proc//stat Date: Fri, 4 Nov 2016 09:14:06 -0400 Message-Id: <20161104131408.16886-1-cov@codeaurora.org> X-Mailer: git-send-email 2.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2673 Lines: 57 Applications such as Just-In-Time (JIT) compilers, Checkpoint/Restore In Userspace (CRIU), and User Mode Linux (UML) need to know the highest virtual address, TASK_SIZE, to implement pointer tagging or make a first educated guess at where to find a large, unused region of memory. Unfortunately the currently available mechanisms for determining TASK_SIZE are either convoluted and potentially error-prone, such as making repeated munmap() calls and checking the return code, or make use of hard-coded assumptions that limit an application's portability across kernels with different Kconfig options and multiple architectures. Therefore, expose TASK_SIZE to userspace. While PAGE_SIZE is exposed to userspace via an auxiliary vector, that approach is not used for TASK_SIZE in case run-time alterations to the usable virtual address range are one day implemented, such as through an extension to prctl(PR_SET_MM) or a flag to clone. There is no prctl(PR_GET_MM). Instead such information is expected to come from /proc//stat[m]. For the same extendability reason, use a per-pid proc entry rather than a system-wide entry like /proc/sys/vm/mmap_min_addr. Signed-off-by: Christopher Covington --- Documentation/filesystems/proc.txt | 1 + fs/proc/array.c | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 74329fd..b9c19cf 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -343,6 +343,7 @@ Table 1-4: Contents of the stat files (as of 2.6.30-rc7) env_start address above which program environment is placed env_end address below which program environment is placed exit_code the thread's exit_code in the form reported by the waitpid system call + end_mem address below which all regular program parts are placed (TASK_SIZE) .............................................................................. The /proc/PID/maps file containing the currently mapped memory regions and diff --git a/fs/proc/array.c b/fs/proc/array.c index 9a3ca9e..32b5002 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -561,6 +561,11 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, else seq_puts(m, " 0"); + if (mm && permitted) + seq_put_decimal_ull(m, " ", mm->task_size); + else + seq_puts(m, " 0"); + seq_putc(m, '\n'); if (mm) mmput(mm); -- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.