On Mon, 7 Mar 2016, Alan Stern wrote:
> > 319: 9c pushfq
> > 31a: 41 5c pop %r12
> > 31c: 48 89 df mov %rbx,%rdi
> > 31f: e8 00 00 00 00 callq 324 <usbhid_close+0x44>
> > 324: 41 54 push %r12
> > 326: 9d popfq
>
> spin_unlock_irq(&usbhid->lock); while attempting to preserve the Z
> flag. The problem is that this code sequence will also preserve the
> Interrupt Flag!
You are right Alan, thanks a lot, for reason I could not understand I
completely missed the pushf/popf last time I was looking at the generated
assembly!
OK, a little bit of googling revealed related discussion on LLVM
mailinglist:
http://lists.llvm.org/pipermail/llvm-dev/2015-July/088780.html
Seems like it has been reported already, but noone dared to fix it yet.
This basically makes LLVM unusable for compiling the kernel.
--
Jiri Kosina
SUSE Labs
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