Re: [PATCH] x86/tdx: Do not corrupt frame-pointer in __tdx_hypercall()

[Kirill A. Shutemov]

On Tue, Jan 31, 2023 at 09:34:12AM +0100, Peter Zijlstra wrote:
> On Mon, Jan 30, 2023 at 04:53:54PM +0300, Kirill A. Shutemov wrote:
> > If compiled with CONFIG_FRAME_POINTER=y, objtool in not happy that
> > __tdx_hypercall() messes up RBP.
> > 
> >   objtool: __tdx_hypercall+0x7f: return with modified stack frame
> > 
> > Rework the function to store TDX_HCALL_ flags on stack instead of RBP.
> 
> Also, on IRC you mentioned that per TDX spec, BP is a valid argument
> register too and you were going to raise this and get it fixed, TDX
> hypercalls must not use BP to pass data.

I've raised the question yesterday. No progress so far. It will take time
to get it into the public spec.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov