From: Keir Fraser <keir.xen@gmail.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Daniel Kiper <daniel.kiper@oracle.com>
Cc: xen-devel@lists.xensource.com, keir@xen.org, jbeulich@suse.com
Subject: Re: [PATCH v2] xen/arch/x86: Fix early boot command line parsing
Date: Wed, 04 Dec 2013 07:16:41 +0000 [thread overview]
Message-ID: <CEC48759.690C8%keir.xen@gmail.com> (raw)
In-Reply-To: <529E3FD0.1030906@citrix.com>
On 03/12/2013 20:32, "Andrew Cooper" <andrew.cooper3@citrix.com> 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 <daniel.kiper@oracle.com>
>
> 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 <andrew.cooper3@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
>> ---
>> 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
prev parent reply other threads:[~2013-12-04 7:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-03 20:28 [PATCH v2] xen/arch/x86: Fix early boot command line parsing Daniel Kiper
2013-12-03 20:32 ` Andrew Cooper
2013-12-04 7:16 ` Keir Fraser [this message]
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