[PATCH v7 3/5] powerpc: Rework and improve STRICT_KERNEL_RWX patching

[Jordan Niethe]

On Sat, Mar 12, 2022 at 6:30 PM Christophe Leroy
<christophe.leroy at csgroup.eu> wrote:
>
> Hi Jordan
>
> Le 10/11/2021 à 01:37, Jordan Niethe a écrit :
> > From: "Christopher M. Riedl" <cmr at bluescreens.de>
> >
> > Rework code-patching with STRICT_KERNEL_RWX to prepare for a later patch
> > which uses a temporary mm for patching under the Book3s64 Radix MMU.
> > Make improvements by adding a WARN_ON when the patchsite doesn't match
> > after patching and return the error from __patch_instruction() properly.
> >
> > Signed-off-by: Christopher M. Riedl <cmr at bluescreens.de>
> > Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
> > ---
> > v7: still pass addr to map_patch_area()
>
>
> This patch doesn-t apply, can you rebase the series ?
Yep, will do.
>
> Thanks
> Christophe
>
> > ---
> >   arch/powerpc/lib/code-patching.c | 20 ++++++++++----------
> >   1 file changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> > index 29a30c3068ff..d586bf9c7581 100644
> > --- a/arch/powerpc/lib/code-patching.c
> > +++ b/arch/powerpc/lib/code-patching.c
> > @@ -75,6 +75,7 @@ static inline void stop_using_temp_mm(struct temp_mm_state prev_state)
> >   }
> >
> >   static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
> > +static DEFINE_PER_CPU(unsigned long, cpu_patching_addr);
> >
> >   static int text_area_cpu_up(unsigned int cpu)
> >   {
> > @@ -87,6 +88,7 @@ static int text_area_cpu_up(unsigned int cpu)
> >               return -1;
> >       }
> >       this_cpu_write(text_poke_area, area);
> > +     this_cpu_write(cpu_patching_addr, (unsigned long)area->addr);
> >
> >       return 0;
> >   }
> > @@ -172,11 +174,10 @@ static inline int unmap_patch_area(unsigned long addr)
> >
> >   static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
> >   {
> > -     int err;
> > +     int err, rc = 0;
> >       u32 *patch_addr = NULL;
> >       unsigned long flags;
> >       unsigned long text_poke_addr;
> > -     unsigned long kaddr = (unsigned long)addr;
> >
> >       /*
> >        * During early early boot patch_instruction is called
> > @@ -188,15 +189,13 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
> >
> >       local_irq_save(flags);
> >
> > -     text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
> > -     if (map_patch_area(addr, text_poke_addr)) {
> > -             err = -1;
> > +     text_poke_addr = __this_cpu_read(cpu_patching_addr);
> > +     err = map_patch_area(addr, text_poke_addr);
> > +     if (err)
> >               goto out;
> > -     }
> > -
> > -     patch_addr = (u32 *)(text_poke_addr + (kaddr & ~PAGE_MASK));
> >
> > -     __patch_instruction(addr, instr, patch_addr);
> > +     patch_addr = (u32 *)(text_poke_addr | offset_in_page(addr));
> > +     rc = __patch_instruction(addr, instr, patch_addr);
> >
> >       err = unmap_patch_area(text_poke_addr);
> >       if (err)
> > @@ -204,8 +203,9 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
> >
> >   out:
> >       local_irq_restore(flags);
> > +     WARN_ON(!ppc_inst_equal(ppc_inst_read(addr), instr));
> >
> > -     return err;
> > +     return rc ? rc : err;
> >   }
> >   #else /* !CONFIG_STRICT_KERNEL_RWX */
> >