Re: [PATCH 3/6] x86/entry/64/compat: Fix Xen PV SYSENTER frame setup

[Boris Ostrovsky]

On 6/26/20 1:21 PM, Andy Lutomirski wrote:
> The SYSENTER frame setup was nonsense.  It worked by accident
> because the normal code into which the Xen asm jumped
> (entry_SYSENTER_32/compat) threw away SP without touching the stack.
> entry_SYSENTER_compat was recently modified such that it relied on
> having a valid stack pointer, so now the Xen asm needs to invoke it
> with a valid stack.
>
> Fix it up like SYSCALL: use the Xen-provided frame and skip the bare
> metal prologue.
>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Fixes: 1c3e5d3f60e2 ("x86/entry: Make entry_64_compat.S objtool clean")
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>