Re: [Xen-devel] [PATCH v2 for-4.7 5/6] xen/xsplice: add ELFOSABI_FREEBSD as a supported OSABI for payloads

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.05.16 at 18:35, <roger.pau@xxxxxxxxxx> wrote:
> On Wed, May 04, 2016 at 04:34:26AM -0600, Jan Beulich wrote:
>> >>> On 04.05.16 at 11:48, <roger.pau@xxxxxxxxxx> wrote:
>> > On Tue, May 03, 2016 at 08:17:15AM -0600, Jan Beulich wrote:
>> >> >>> On 03.05.16 at 12:55, <roger.pau@xxxxxxxxxx> wrote:
>> >> > The calling convention used by the FreeBSD ELF OSABI is exactly the 
>> >> > same 
> as
>> >> > the the one defined by System V, so payloads with a FreeBSD OSABI 
>> >> > should 
> be
>> >> > accepted by the xsplice machinery.
>> >> 
>> >> Well, you realize that the ABI is more than just the calling convention?
>> >> I.e. your patch basically says ELFOSABI_NONE == ELFOSABI_FREEBSD,
>> >> in which case I wonder why the latter exists in the first place. Is there
>> >> a proper document somewhere describing everything the latter implies,
>> >> so that one can check whether for xSplice purposes such similar
>> >> treatment is indeed okay? Until then I'm afraid I'm opposed to this going
>> >> in.
>> > 
>> > The FreeBSD elf OSABI only has a meaning for userspace applications, it's 
>> > used by FreeBSD in order to detect if an application is native or if it 
>> > needs to be run in the linuxator (the Linux emulator, or any other 
>> > emulator 
> 
>> > that is available and matches the ELF OSABI specified in the binary FWIW).
>> > 
>> > THe only difference from SYSV to FreeBSD OSABI is the sysentvec that's 
>> > selected inside of the FreeBSD kernel (the ABI between the kernel and the 
>> > user-space application), but of course this doesn't apply to kernel code, 
>> > which is what Xen and the xsplice payloads are. Sadly this is not written 
>> > anywhere.
>> 
>> Well, okay, in that case I agree the patch should be fine.
> 
> Would you like me to resend this with a more expanded commit message, or are 
> you going to squash my explanation in the commit message?

I'd be fine folding it in, but I may not be the one ending up
committing it - it needs an xSplice maintainer's ack first, and
it may well be that Konrad then would apply it.

Jan


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