Re: [Qemu-devel] [PATCH] linux-user: Add binfmt wrapper

[Alexander Graf <agraf@suse.de>]

On 14.07.14 18:51, Joakim Tjernlund wrote:
> Alexander Graf <agraf@suse.de> wrote on 2014/07/14 18:34:34:
>>
>> On 14.07.14 18:32, Joakim Tjernlund wrote:
>>> Alexander Graf <agraf@suse.de> wrote on 2014/07/14 18:00:35:
>>> You think everyone feel OK with new defaults like OP ?
>>>> Yes.
>>> hmm, with current qemu it works to boot a LXC with just O flag.
>>> Why would we then want to complicate things by adding OP which
>>> then requires some version of my patch?
>> How does current QEMU boot anything with the 0 flag? It doesn't know how
>> to handle it and will misinterpret the argument, no?
> Playing some, one could possibly do both:
>
> -    if (i > 0 && strcmp(binfmt, "-binfmt-wrapper") == 0) {
> +    execfd = qemu_getauxval(AT_EXECFD);
> +    if (execfd > 0 || i > 0 && strcmp(binfmt, "-binfmt-wrapper") == 0) {

0 is a valid fd :). And yes, this would work, but I don't see why we 
should introduce the -binfmt-wrapper logic to upstream QEMU. It's never 
been there. And the AT_EXECFD evaluation is a lot cleaner.

While we're at it - should we also pass the C flag to binfmt_misc?


Alex