From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v2] xen/arch/x86: Fix early boot command line parsing Date: Tue, 3 Dec 2013 20:32:16 +0000 Message-ID: <529E3FD0.1030906@citrix.com> References: <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: In-Reply-To: <1386102537-16527-1-git-send-email-daniel.kiper@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Daniel Kiper Cc: xen-devel@lists.xensource.com, keir@xen.org, jbeulich@suse.com List-Id: xen-devel@lists.xenproject.org On 03/12/13 20:28, Daniel Kiper wrote: > 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 I was thinking more along the lines of /* NULL check (as $'\0' == 0x30 in GAS) */ Either way, at least it is obvious. Reviewed-by: Andrew Cooper > --- > 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