Re: [PATCH v5 5/6] kprobes: Use text_alloc() and text_free()

[Masami Hiramatsu]

On Fri, 24 Jul 2020 13:27:48 +0300
Mike Rapoport <rppt@xxxxxxxxxx> wrote:

> On Fri, Jul 24, 2020 at 08:05:52AM +0300, Jarkko Sakkinen wrote:
> > Use text_alloc() and text_free() instead of module_alloc() and
> > module_memfree() when an arch provides them.
> > 
> > Cc: linux-mm@xxxxxxxxx
> > Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> > ---
> >  kernel/kprobes.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 4e46d96d4e16..611fcda9f6bf 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -40,6 +40,7 @@
> >  #include <asm/cacheflush.h>
> >  #include <asm/errno.h>
> >  #include <linux/uaccess.h>
> > +#include <linux/vmalloc.h>
> >  
> >  #define KPROBE_HASH_BITS 6
> >  #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
> > @@ -111,12 +112,20 @@ enum kprobe_slot_state {
> >  
> >  void __weak *alloc_insn_page(void)
> >  {
> > +#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
> > +	return text_alloc(PAGE_SIZE);
> > +#else
> >  	return module_alloc(PAGE_SIZE);
> > +#endif
> >  }
> >  
> >  void __weak free_insn_page(void *page)
> >  {
> > +#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
> > +	text_free(page);
> > +#else
> >  	module_memfree(page);
> > +#endif
> >  }
> 
> Both alloc_insn_page() and free_insn_page() are __weak and can be simple
> overriden in arch/x86 code.

No, we can't use module_alloc/memfree() without CONFIG_MODULES, so
we can not escape from this #ifdefs. (and I think this is not so bad.)

Thank you,

-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>