Re: [PATCH V2 02/41] x86/traps: Remove stack-protector from traps.c

[Lai Jiangshan]

On 2021/9/27 18:19, Borislav Petkov wrote:
> On Sun, Sep 26, 2021 at 11:07:59PM +0800, Lai Jiangshan wrote:
> > diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> > index 8f4e8fa6ed75..0e054e2304c6 100644
> > --- a/arch/x86/kernel/Makefile
> > +++ b/arch/x86/kernel/Makefile
> > @@ -48,6 +48,9 @@ KCOV_INSTRUMENT		:= n
> >   
> >   CFLAGS_head$(BITS).o	+= -fno-stack-protector
> >   
> > +CFLAGS_REMOVE_traps.o		= -fstack-protector -fstack-protector-strong
>
> Why this too?
>
> > +CFLAGS_traps.o			+= -fno-stack-protector
>
> Isn't this enough to disable stack protector for this file?

I did not investigate deep enough.  I reviewed the generated code and
found %gs is accessed early for the C entry function and searched for
solution and I chose to copy the code that I thought is the most complete:
kernel/entry/Makefile

Using only "-fno-stack-protector" is enough to disable stack protector with
my .config, I'm not so sure about other configuration.

Thanks
Lai