Subject: Re: [PATCH v3 2/2] powerpc/64: add stack protector support

From: Segher Boessenkool <[email-masked]>
Date: Wed, 26 Sep 2018 12:37:44 -0500

On Wed, Sep 26, 2018 at 11:41:26AM +0200, Christophe LEROY wrote:
> Le 26/09/2018 à 11:28, Segher Boessenkool a écrit :
> >On Wed, Sep 26, 2018 at 09:58:30AM +0200, Christophe LEROY wrote:
> >>Segher, any idea about this problem ?
> >
> >>>>arch/powerpc/platforms/powermac/bootx_init.o: In function 
> >>>>`bootx_printf':
> >>>>/var/lib/jenkins-slave/workspace/snowpatch/snowpatch-linux-
> >>>>sparse/linux/arch/powerpc/platforms/powermac/bootx_init.c:88:
> >>>>undefined reference to `__stack_chk_fail_local'
> >
> >Are you building as PIC?  Are you linking libssp_nonshared.a?  Why not?
> 
> Spotted, thanks.
> 
> arch/powerpc/platforms/powermac/Makefile contains:
> 
> CFLAGS_bootx_init.o  		+= -fPIC
> 
> Does it mean we should add -lssp_nonshared to LDFLAGS_vmlinux ?

Something like that.

> Or maybe stack protection on bootx_init doesn't make much sense and we 
> could just do the following ?
> 
> CFLAGS_bootx_init.o  		+= -fPIC $(call cc-option, 
> -fno-stack-protector)

But more likely this.  Why does it use -fPIC?

If it is only boot-time init (which the name suggests) then disabling
ssp makes a lot of sense.

Segher