From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Kiper Subject: [PATCH v2] xen/arch/x86: Fix early boot command line parsing Date: Tue, 3 Dec 2013 21:28:57 +0100 Message-ID: <1386102537-16527-1-git-send-email-daniel.kiper@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: andrew.cooper3@citrix.com, jbeulich@suse.com, keir@xen.org, xen-devel@lists.xensource.com Cc: Daniel Kiper List-Id: xen-devel@lists.xenproject.org There is no reliable way to encode NUL character as a character so encode it as a number. Read: http://sourceware.org/binutils/docs/as/Characters.html. Octal and hex encoding do not work on at least one system (GNU assembler version 2.22 (x86_64-linux-gnu) using BFD version (GNU Binutils for Debian) 2.22). Without this fix e.g. no-real-mode option at the end of xen.gz command line is not detected. v2 - suggestions/fixes: - add relevant comment to assembly file (suggested by Andrew Cooper), - leave encoding of other characters as is for readability (suggested by Jan Beulich). Signed-off-by: Daniel Kiper --- xen/arch/x86/boot/cmdline.S | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/boot/cmdline.S b/xen/arch/x86/boot/cmdline.S index 05ffb94..b83975e 100644 --- a/xen/arch/x86/boot/cmdline.S +++ b/xen/arch/x86/boot/cmdline.S @@ -138,7 +138,15 @@ call .Lstrlen add $4,%esp xadd %eax,%ebx - cmpb $'\0',(%ebx) + /* + * There is no reliable way to encode NUL character as a character so encode + * it as a number. Read: http://sourceware.org/binutils/docs/as/Characters.html. + * Octal and hex encoding do not work on at least one system (GNU assembler + * version 2.22 (x86_64-linux-gnu) using BFD version (GNU Binutils for Debian) 2.22). + * Without this fix e.g. no-real-mode option at the end of xen.gz command line + * is not detected. + */ + cmpb $0,(%ebx) je 3f cmpb $' ',(%ebx) je 3f -- 1.7.10.4