From patchwork Fri Oct 30 18:26:55 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andre Przywara X-Patchwork-Id: 538471 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 5F4D114139B for ; Sat, 31 Oct 2015 05:26:48 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966007AbbJ3S0g (ORCPT ); Fri, 30 Oct 2015 14:26:36 -0400 Received: from foss.arm.com ([217.140.101.70]:45259 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759775AbbJ3S0c (ORCPT ); Fri, 30 Oct 2015 14:26:32 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9B9433FB; Fri, 30 Oct 2015 11:26:23 -0700 (PDT) Received: from e104803-lin.lan (unknown [10.1.203.153]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E51C93F308; Fri, 30 Oct 2015 11:26:30 -0700 (PDT) From: Andre Przywara To: will.deacon@arm.com, kvm@vger.kernel.org Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm-ppc@vger.kernel.org Subject: [PATCH 2/7] provide generic read_file() implementation Date: Fri, 30 Oct 2015 18:26:55 +0000 Message-Id: <1446229620-28088-3-git-send-email-andre.przywara@arm.com> X-Mailer: git-send-email 2.5.1 In-Reply-To: <1446229620-28088-1-git-send-email-andre.przywara@arm.com> References: <1446229620-28088-1-git-send-email-andre.przywara@arm.com> Sender: kvm-ppc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@vger.kernel.org In various parts of kvmtool we simply try to read files into memory, but fail to do so in a safe way. The read(2) syscall can return early having only parts of the file read, or it may return -1 due to being interrupted by a signal (in which case we should simply retry). The ARM code seems to provide the only safe implementation, so take that as an inspiration to provide a generic read_file() function usable by every part of kvmtool. Signed-off-by: Andre Przywara --- include/kvm/read-write.h | 2 ++ util/read-write.c | 21 +++++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/include/kvm/read-write.h b/include/kvm/read-write.h index 67571f9..acbd6f0 100644 --- a/include/kvm/read-write.h +++ b/include/kvm/read-write.h @@ -12,6 +12,8 @@ ssize_t xread(int fd, void *buf, size_t count); ssize_t xwrite(int fd, const void *buf, size_t count); +ssize_t read_file(int fd, char *buf, size_t max_size); + ssize_t read_in_full(int fd, void *buf, size_t count); ssize_t write_in_full(int fd, const void *buf, size_t count); diff --git a/util/read-write.c b/util/read-write.c index 44709df..bf6fb2f 100644 --- a/util/read-write.c +++ b/util/read-write.c @@ -32,6 +32,27 @@ restart: return nr; } +/* + * Read in the whole file while not exceeding max_size bytes of the buffer. + * Returns -1 (with errno set) in case of an error (ENOMEM if buffer was + * too small) or the filesize if the whole file could be read. + */ +ssize_t read_file(int fd, char *buf, size_t max_size) +{ + ssize_t ret; + char dummy; + + errno = 0; + ret = read_in_full(fd, buf, max_size); + + /* Probe whether we reached EOF. */ + if (xread(fd, &dummy, 1) == 0) + return ret; + + errno = ENOMEM; + return -1; +} + ssize_t read_in_full(int fd, void *buf, size_t count) { ssize_t total = 0;