Re: [PATCH] x86/sev: Add ENCODE_FRAME_POINTER after stack changed for #VC

[Lai Jiangshan]

On Fri, Mar 18, 2022 at 6:19 AM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
>
> On Wed, Mar 16, 2022 at 12:16:12PM +0800, Lai Jiangshan wrote:
> > From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
> >
> > In idtentry_vc(), the real frame is changed after it switches to new
> > stack, ENCODE_FRAME_POINTER should be called in case for unwinder.
> >
> > Cc: Joerg Roedel <jroedel@xxxxxxx>
> > Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
> > ---
> >  arch/x86/entry/entry_64.S | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> > index e20eabaa56b8..f99f2881ed83 100644
> > --- a/arch/x86/entry/entry_64.S
> > +++ b/arch/x86/entry/entry_64.S
> > @@ -540,6 +540,7 @@ SYM_CODE_START(\asmsym)
> >       call    vc_switch_off_ist
> >       movq    %rax, %rsp              /* Switch to new stack */
> >
> > +     ENCODE_FRAME_POINTER
> >       UNWIND_HINT_REGS
> >
> >       /* Update pt_regs */
>
> Looks right to me.  Any chance you have the ability to test this
> scenario by unwinding from #VC with CONFIG_FRAME_POINTER?
>

I don't have the hardware to test it.  Actually, it was you to
inspire me to find this in the conversation of my patchset when
I tried to search all the code of switching of %rsp to see how
ENCODE_FRAME_POINTER and UNWIND_HINT_REGS are used once more.

> --
> Josh
>