From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751602AbeBUTdk (ORCPT ); Wed, 21 Feb 2018 14:33:40 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:45054 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbeBUTdj (ORCPT ); Wed, 21 Feb 2018 14:33:39 -0500 X-Google-Smtp-Source: AH8x225DU0QTxNO9xxvDmDG3EQTYUrfCPsTDK0v3BJxrSZGAzBj++gFEdQXjpR5Ds2K0N94dL5YYUw== Date: Wed, 21 Feb 2018 22:33:35 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 5/5] proc: deduplicate /proc/*/cmdline implementation Message-ID: <20180221193335.GB28678@avx2> References: <20180221192339.GA28548@avx2> <20180221192605.GB28548@avx2> <20180221192751.GC28548@avx2> <20180221193009.GA28678@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180221193009.GA28678@avx2> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Code can be sonsolidated if a dummy region of 0 length is used in normal case of \0-separated command line: 1) [arg_start, arg_end) + [dummy len=0] 2) [arg_start, arg_end) + [env_start, env_end) Signed-off-by: Alexey Dobriyan --- fs/proc/base.c | 53 ++++++++++++++++++++--------------------------------- 1 file changed, 20 insertions(+), 33 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -239,9 +239,12 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, char *page; unsigned long count = _count; unsigned long arg_start, arg_end, env_start, env_end; - unsigned long len1, len2, len; - unsigned long p; + unsigned long len1, len2; char __user *buf0 = buf; + struct { + unsigned long p; + unsigned long len; + } cmdline[2]; char c; int rv; @@ -283,43 +286,21 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, if (access_remote_vm(mm, arg_end - 1, &c, 1, 0) != 1) goto end; + cmdline[0].p = arg_start; + cmdline[0].len = len1; if (c == '\0') { /* Command line (set of strings) occupies whole ARGV. */ - if (len1 <= *pos) - goto end; - - p = arg_start + *pos; - len = len1 - *pos; - while (count > 0 && len > 0) { - unsigned int nr_read; - - nr_read = min3(count, len, PAGE_SIZE); - nr_read = access_remote_vm(mm, p, page, nr_read, 0); - if (nr_read == 0) - goto end; - - if (copy_to_user(buf, page, nr_read)) { - rv = -EFAULT; - goto out_free_page; - } - - p += nr_read; - len -= nr_read; - buf += nr_read; - count -= nr_read; - } + cmdline[1].len = 0; } else { /* * Command line (1 string) occupies ARGV and * extends into ENVP. */ - struct { - unsigned long p; - unsigned long len; - } cmdline[2] = { - { .p = arg_start, .len = len1 }, - { .p = env_start, .len = len2 }, - }; + cmdline[1].p = env_start; + cmdline[1].len = len2; + } + + { loff_t pos1 = *pos; unsigned int i; @@ -329,6 +310,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, i++; } while (i < 2) { + unsigned long p; + unsigned long len; + p = cmdline[i].p + pos1; len = cmdline[i].len - pos1; while (count > 0 && len > 0) { @@ -343,7 +327,10 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, * Command line can be shorter than whole ARGV * even if last "marker" byte says it is not. */ - nr_write = strnlen(page, nr_read); + if (c == '\0') + nr_write = nr_read; + else + nr_write = strnlen(page, nr_read); if (copy_to_user(buf, page, nr_write)) { rv = -EFAULT;