Re: Build errors in v4.4-stable-queue (i386)

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On Thu, 2018-01-18 at 19:10 +0100, Greg Kroah-Hartman wrote:
> On Thu, Jan 18, 2018 at 08:41:58AM -0800, Guenter Roeck wrote:
> > 
> > Building i386:defconfig ... failed
> > --------------
> > Error log:
> > arch/x86/entry/entry_32.S: Assembler messages:
> > arch/x86/entry/entry_32.S:230: Error: too many memory references
> > for `mov'
> Ick, no good, 0-day has pointed this out as well.
> 
> Razvan and David, any ideas?


	CALL_NOSPEC PT_EBX(%esp)

That turns into a retpoline with

        mov PT_EBX(%esp), 0(%esp)

Which is doubly wrong, because not only can't you have two memory
operands to a 'mov' but %esp has already *moved* by the time we get
here so we'd be using the wrong source anyway.

We need to pick a victim register and load PT_EBX(%esp) into it, then
CALL_NOSPEC %\reg.

We'll fix this and also the RSP-clobbering in context switch that you
just sent a "fails to apply" message for.

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