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Date: Tue, 11 Dec 2012 12:15:03 +0100
From: Christian Borntraeger <borntraeger@de.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH 1/3] s390: Fix empty kernel command line
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To: Alexander Graf <agraf@suse.de>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>, Jens Freimann <jfrei@linux.vnet.ibm.com>, Heinz Graalfs <graalfs@linux.vnet.ibm.com>, qemu-devel <qemu-devel@nongnu.org>, Einar Lueck <elelueck@linux.vnet.ibm.com>

On 11/12/12 11:34, Alexander Graf wrote:
> 
> On 07.12.2012, at 14:55, Jens Freimann wrote:
> 
>> From: Christian Borntraeger <borntraeger@de.ibm.com>
>>
>> Since commit 967c0da73a7b0da186baba6632301d83644a570c
>>    vl.c: Avoid segfault when started with no arguments
>>
>> the user can specify a kernel without a command line. Lets not
>> overwrite the default command line with \0 in that case.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
>> ---
>> hw/s390-virtio.c |    2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/hw/s390-virtio.c b/hw/s390-virtio.c
>> index ca1bb09..d77871a 100644
>> --- a/hw/s390-virtio.c
>> +++ b/hw/s390-virtio.c
>> @@ -290,7 +290,7 @@ static void s390_init(QEMUMachineInitArgs *args)
>>         stq_p(rom_ptr(INITRD_PARM_SIZE), initrd_size);
>>     }
>>
>> -    if (rom_ptr(KERN_PARM_AREA)) {
>> +    if (rom_ptr(KERN_PARM_AREA) && strlen(kernel_cmdline)) {
> 
> why strlen()? If no -append option was passed, kernel_cmdline should be NULL. If -append "" was passed, the user wants to command line to be overwritten with "\0".

Nope. kernel_cmdline is always a valid pointer.

vl.c:

[..]
    if (!kernel_cmdline) {
        kernel_cmdline = "";
    }

[..]