Re: [PATCH v10 04/10] powerpc/kprobes: Mark newly allocated probes as ROX

[Jordan Niethe <jniethe5@gmail.com>]

On Tue, Mar 30, 2021 at 4:05 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 30/03/2021 à 06:51, Jordan Niethe a écrit :
> > From: Russell Currey <ruscur@russell.cc>
> >
> > Add the arch specific insn page allocator for powerpc. This allocates
> > ROX pages if STRICT_KERNEL_RWX is enabled. These pages are only written
> > to with patch_instruction() which is able to write RO pages.
> >
> > Reviewed-by: Daniel Axtens <dja@axtens.net>
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> > [jpn: Reword commit message, switch to __vmalloc_node_range()]
> > Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> > ---
> > v9: - vmalloc_exec() no longer exists
> >      - Set the page to RW before freeing it
> > v10: - use __vmalloc_node_range()
> > ---
> >   arch/powerpc/kernel/kprobes.c | 14 ++++++++++++++
> >   1 file changed, 14 insertions(+)
> >
> > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> > index 01ab2163659e..3ae27af9b094 100644
> > --- a/arch/powerpc/kernel/kprobes.c
> > +++ b/arch/powerpc/kernel/kprobes.c
> > @@ -25,6 +25,7 @@
> >   #include <asm/sections.h>
> >   #include <asm/inst.h>
> >   #include <linux/uaccess.h>
> > +#include <linux/vmalloc.h>
> >
> >   DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
> >   DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
> > @@ -103,6 +104,19 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
> >       return addr;
> >   }
> >
> > +void *alloc_insn_page(void)
> > +{
> > +     if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
> > +             return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
> > +                             GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
> > +                             NUMA_NO_NODE, __builtin_return_address(0));
> > +     } else {
> > +             return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
> > +                             GFP_KERNEL, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
> > +                             NUMA_NO_NODE, __builtin_return_address(0));
> > +     }
> > +}
> > +
>
> What about
>
> void *alloc_insn_page(void)
> {
>         pgprot_t prot = IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
>
>         return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
>                         GFP_KERNEL, prot, VM_FLUSH_RESET_PERMS,
>                         NUMA_NO_NODE, __builtin_return_address(0));
> }
Yes, that is better.
>
> >   int arch_prepare_kprobe(struct kprobe *p)
> >   {
> >       int ret = 0;
> >