Re: [PATCH v9 7/8] powerpc/mm: implement set_memory_attr()

[Jordan Niethe <jniethe5@gmail.com>]

On Tue, Mar 16, 2021 at 6:25 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 16/03/2021 à 04:17, Jordan Niethe a écrit :
> > From: Christophe Leroy <christophe.leroy@c-s.fr>
>
> Can you please update the whole series with my new email address: christophe.leroy@csgroup.eu
Of course, I shall do that.
>
>
>
> >
> > In addition to the set_memory_xx() functions which allows to change
> > the memory attributes of not (yet) used memory regions, implement a
> > set_memory_attr() function to:
> > - set the final memory protection after init on currently used
> > kernel regions.
> > - enable/disable kernel memory regions in the scope of DEBUG_PAGEALLOC.
> >
> > Unlike the set_memory_xx() which can act in three step as the regions
> > are unused, this function must modify 'on the fly' as the kernel is
> > executing from them. At the moment only PPC32 will use it and changing
> > page attributes on the fly is not an issue.
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> > Reported-by: kbuild test robot <lkp@intel.com>
> > [ruscur: cast "data" to unsigned long instead of int]
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> > ---
> >   arch/powerpc/include/asm/set_memory.h |  2 ++
> >   arch/powerpc/mm/pageattr.c            | 33 +++++++++++++++++++++++++++
> >   2 files changed, 35 insertions(+)
> >
> > diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h
> > index 64011ea444b4..b040094f7920 100644
> > --- a/arch/powerpc/include/asm/set_memory.h
> > +++ b/arch/powerpc/include/asm/set_memory.h
> > @@ -29,4 +29,6 @@ static inline int set_memory_x(unsigned long addr, int numpages)
> >       return change_memory_attr(addr, numpages, SET_MEMORY_X);
> >   }
> >
> > +int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot);
> > +
> >   #endif
> > diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
> > index 2da3fbab6ff7..2fde1b195c85 100644
> > --- a/arch/powerpc/mm/pageattr.c
> > +++ b/arch/powerpc/mm/pageattr.c
> > @@ -79,3 +79,36 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
> >       return apply_to_existing_page_range(&init_mm, start, sz,
> >                                           change_page_attr, (void *)action);
> >   }
> > +
> > +/*
> > + * Set the attributes of a page:
> > + *
> > + * This function is used by PPC32 at the end of init to set final kernel memory
> > + * protection. It includes changing the maping of the page it is executing from
> > + * and data pages it is using.
> > + */
> > +static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
> > +{
> > +     pgprot_t prot = __pgprot((unsigned long)data);
> > +
> > +     spin_lock(&init_mm.page_table_lock);
> > +
> > +     set_pte_at(&init_mm, addr, ptep, pte_modify(*ptep, prot));
> > +     flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
> > +
> > +     spin_unlock(&init_mm.page_table_lock);
> > +
> > +     return 0;
> > +}
> > +
> > +int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
> > +{
> > +     unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
> > +     unsigned long sz = numpages * PAGE_SIZE;
> > +
> > +     if (numpages <= 0)
> > +             return 0;
> > +
> > +     return apply_to_existing_page_range(&init_mm, start, sz, set_page_attr,
> > +                                         (void *)pgprot_val(prot));
> > +}
> >