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

[Peter Zijlstra]

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.