From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH v2] xen/arch/x86: Fix early boot command line parsing Date: Wed, 04 Dec 2013 07:16:41 +0000 Message-ID: References: <529E3FD0.1030906@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <529E3FD0.1030906@citrix.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: Andrew Cooper , Daniel Kiper Cc: xen-devel@lists.xensource.com, keir@xen.org, jbeulich@suse.com List-Id: xen-devel@lists.xenproject.org On 03/12/2013 20:32, "Andrew Cooper" wrote: > 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 Acked-by: Keir Fraser >> --- >> 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 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel