Re: [PATCH 4/5] powerpc/lib: Add LKDTM accessor for patching addr

["Christopher M. Riedl" <cmr@informatik.wtf>]

On Wed Jun 3, 2020 at 9:14 AM, Christophe Leroy wrote:
>
> 
>
> 
> Le 03/06/2020 à 07:19, Christopher M. Riedl a écrit :
> > When live patching a STRICT_RWX kernel, a mapping is installed at a
> > "patching address" with temporary write permissions. Provide a
> > LKDTM-only accessor function for this address in preparation for a LKDTM
> > test which attempts to "hijack" this mapping by writing to it from
> > another CPU.
> > 
> > Signed-off-by: Christopher M. Riedl <cmr@informatik.wtf>
> > ---
> >   arch/powerpc/lib/code-patching.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> > 
> > diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> > index df0765845204..c23453049116 100644
> > --- a/arch/powerpc/lib/code-patching.c
> > +++ b/arch/powerpc/lib/code-patching.c
> > @@ -52,6 +52,13 @@ int raw_patch_instruction(struct ppc_inst *addr, struct ppc_inst instr)
> >   static struct mm_struct *patching_mm __ro_after_init;
> >   static unsigned long patching_addr __ro_after_init;
> >   
> > +#ifdef CONFIG_LKDTM
> > +unsigned long read_cpu_patching_addr(unsigned int cpu)
>
> 
> If this fonction is not static, it means it is intended to be used from
> some other C file, so it should be declared in a .h too.
>
Yup agreed. This was left-over from the RFC to simplify using the LKDTM
test on a tree without this series. Will fix this in the next spin.
> 
> Christophe
>
> 
> > +{
> > +	return patching_addr;
> > +}
> > +#endif
> > +
> >   void __init poking_init(void)
> >   {
> >   	spinlock_t *ptl; /* for protecting pte table */
> > 
>
> 
>
>