Re: [PATCH 3/4] ARM: Support KFENCE for ARM

[Kefeng Wang]

On 2021/8/25 21:18, ownia wrote:
> On 2021/8/25 17:21, Kefeng Wang wrote:
> > Add architecture specific implementation details for KFENCE and enable
> > KFENCE on ARM. In particular, this implements the required interface in
> >   <asm/kfence.h>.
> >
> > KFENCE requires that attributes for pages from its memory pool can
> > individually be set. Therefore, force the kfence pool to be mapped
> > at page granularity.
> >
> > Testing this patch using the testcases in kfence_test.c and all passed
> > with or without ARM_LPAE.
> >
> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
...
> > +#endif /* __ASM_ARM_KFENCE_H */
> > diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> > index f7ab6dabe89f..9fa221ffa1b9 100644
> > --- a/arch/arm/mm/fault.c
> > +++ b/arch/arm/mm/fault.c
> > @@ -17,6 +17,7 @@
> >   #include <linux/sched/debug.h>
> >   #include <linux/highmem.h>
> >   #include <linux/perf_event.h>
> > +#include <linux/kfence.h>
> >   
> >   #include <asm/system_misc.h>
> >   #include <asm/system_info.h>
> > @@ -131,10 +132,14 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
> >   	/*
> >   	 * No handler, we'll have to terminate things with extreme prejudice.
> >   	 */
> > -	if (addr < PAGE_SIZE)
> > +	if (addr < PAGE_SIZE) {
> >   		msg = "NULL pointer dereference";
> > -	else
> > +	} else {
> > +		if (kfence_handle_page_fault(addr, is_write_fault(fsr), regs))
> > +			return;
> > +
> >   		msg = "paging request";
> > +	}
>
> I think here should do some fixup to follow upstream mainline code.

Yes, the fixup is still there, as the cover-letter said,

NOTE:
The context of patch2/3 changes in arch/arm/mm/fault.c is based on link[1],
which make some refactor and cleanup about page fault.

...

[1]https://lore.kernel.org/linux-arm-kernel/20210610123556.171328-1-wangkefeng.wang@xxxxxxxxxx/

> >   
> >   	die_kernel_fault(msg, mm, addr, fsr, regs);
> >   }
> .