[CRIU] [PATCH] compel/x86: Don't use pushq for a label

[Cyrill Gorcunov]

On Wed, Sep 11, 2019 at 12:12:33PM +0100, Dmitry Safonov wrote:
> On Wed, 11 Sep 2019 at 11:20, Cyrill Gorcunov <gorcunov at gmail.com> wrote:
> >
> > On Wed, Sep 11, 2019 at 11:13:51AM +0100, Dmitry Safonov wrote:
> > > `pushq` sign-extends the value. Which is a bummer as the label's address
> > > may be higher that 2Gb, which means that the sign-bit will be set.
> > >
> > > As it long-jumps with ia32 selector, %r11 can be scratched.
> > > Use %r11 register as a temporary to push the 32-bit address.
> > >
> > > Complements: a9a760278c1a ("arch/x86: push correct eip on the stack
> > > before lretq")
> > > Cc: Cyrill Gorcunov <gorcunov at gmail.com>
> > > Reported-by: Andrei Vagin <avagin at gmail.com>
> > > Signed-off-by: Dmitry Safonov <dima at arista.com>
> > > ---
> > >  compel/arch/x86/plugins/std/parasite-head.S | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/compel/arch/x86/plugins/std/parasite-head.S b/compel/arch/x86/plugins/std/parasite-head.S
> > > index a988de9d4218..465cd887b1f9 100644
> > > --- a/compel/arch/x86/plugins/std/parasite-head.S
> > > +++ b/compel/arch/x86/plugins/std/parasite-head.S
> > > @@ -25,7 +25,9 @@ ENTRY(__export_parasite_head_start_compat)
> > >  .code64
> > >       PARASITE_ENTRY 0
> > >       pushq   $__USER32_CS
> > > -     pushq   $2f
> > > +     xor     %r11, %r11
> > > +     movl    $2f, %r11d
> > > +     pushq   %r11
> > >       lretq
> > >  2:
> > >  .code32
> >
> > Wait, didn't Andrew already fixed it?
> 
> Yes, but as the guys who reviewed it hasn't noticed the same piece of code
> for threads curing... :)
> 
> Note, there is also feature-test.mak, but we don't care about correctness there
> as it's a test for compilation.

Thanks!