Subject: Re: [PATCH v1 1/8] powerpc/lib/code-patching: Enhance code patching

From: Balbir Singh <[email-masked]>
Date: Mon, 29 May 2017 08:58:45 +1000

On Sun, 2017-05-28 at 16:29 +0200, christophe leroy wrote:
> 
> Le 25/05/2017 à 05:36, Balbir Singh a écrit :
> > Today our patching happens via direct copy and
> > patch_instruction. The patching code is well
> > contained in the sense that copying bits are limited.
> > 
> > While considering implementation of CONFIG_STRICT_RWX,
> > the first requirement is to a create another mapping
> > that will allow for patching. We create the window using
> > text_poke_area, allocated via get_vm_area(), which might
> > be an overkill. We can do per-cpu stuff as well. The
> > downside of these patches that patch_instruction is
> > now synchornized using a lock. Other arches do similar
> > things, but use fixmaps. The reason for not using
> > fixmaps is to make use of any randomization in the
> > future. The code also relies on set_pte_at and pte_clear
> > to do the appropriate tlb flushing.
> > 
> > Signed-off-by: Balbir Singh <[email-masked]>
> 
> [...]
> 
> > +static int kernel_map_addr(void *addr)
> > +{
> > +	unsigned long pfn;
> >  	int err;
> > 
> > -	__put_user_size(instr, addr, 4, err);
> > +	if (is_vmalloc_addr(addr))
> > +		pfn = vmalloc_to_pfn(addr);
> > +	else
> > +		pfn = __pa_symbol(addr) >> PAGE_SHIFT;
> > +
> > +	err = map_kernel_page((unsigned long)text_poke_area->addr,
> > +			(pfn << PAGE_SHIFT), _PAGE_KERNEL_RW | _PAGE_PRESENT);
> 
> map_kernel_page() doesn't exist on powerpc32, so compilation fails.
> 
> However a similar function exists and is called map_page()
> 
> Maybe the below modification could help (not tested yet)
> 
> Christophe
>

Thanks, I'll try and get a compile, as an alternative how about

#ifdef CONFIG_PPC32
#define map_kernel_page map_page
#endif

Balbir Singh.