Re: [PATCH v2 13/16] powerpc/watchpoint: Prepare handler to handle more than one watcnhpoint

[Ravi Bangoria]

On 4/1/20 12:20 PM, Christophe Leroy wrote:
> Le 01/04/2020 Ã 08:13, Ravi Bangoria a ÃcritÂ:
> > Currently we assume that we have only one watchpoint supported by hw.
> > Get rid of that assumption and use dynamic loop instead. This should
> > make supporting more watchpoints very easy.
> >
> > With more than one watchpoint, exception handler need to know which
> > DAWR caused the exception, and hw currently does not provide it. So
> > we need sw logic for the same. To figure out which DAWR caused the
> > exception, check all different combinations of user specified range,
> > dawr address range, actual access range and dawrx constrains. For ex,
> > if user specified range and actual access range overlaps but dawrx is
> > configured for readonly watchpoint and the instruction is store, this
> > DAWR must not have caused exception.
> >
> > Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
> > ---
> > Â arch/powerpc/include/asm/processor.h |ÂÂ 2 +-
> > Â arch/powerpc/include/asm/sstep.hÂÂÂÂ |ÂÂ 2 +
> >  arch/powerpc/kernel/hw_breakpoint.c | 396 +++++++++++++++++++++------
> > Â arch/powerpc/kernel/process.cÂÂÂÂÂÂÂ |ÂÂ 3 -
> > Â 4 files changed, 313 insertions(+), 90 deletions(-)
>
> [...]
>
> > -static bool
> > -dar_range_overlaps(unsigned long dar, int size, struct arch_hw_breakpoint *info)
> > +static bool dar_user_range_overlaps(unsigned long dar, int size,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct arch_hw_breakpoint *info)
> > Â {
> > ÂÂÂÂÂ return ((dar <= info->address + info->len - 1) &&
> > ÂÂÂÂÂÂÂÂÂ (dar + size - 1 >= info->address));
> > Â }
>
> Here and several other places, I think it would be more clear if you could avoid the - 1 :
>
>  ÂÂÂÂreturn ((dar < info->address + info->len) &&
>  ÂÂÂÂÂÂÂ (dar + size > info->address));

Ok. see below...

> > +static bool dar_in_hw_range(unsigned long dar, struct arch_hw_breakpoint *info)
> > +{
> > +ÂÂÂ unsigned long hw_start_addr, hw_end_addr;
> > +
> > +ÂÂÂ hw_start_addr = ALIGN_DOWN(info->address, HW_BREAKPOINT_SIZE);
> > +ÂÂÂ hw_end_addr = ALIGN(info->address + info->len, HW_BREAKPOINT_SIZE) - 1;
> > +
> > +ÂÂÂ return ((hw_start_addr <= dar) && (hw_end_addr >= dar));
> > +}
>
>  ÂÂÂÂhw_end_addr = ALIGN(info->address + info->len, HW_BREAKPOINT_SIZE);
>
>  ÂÂÂÂreturn ((hw_start_addr <= dar) && (hw_end_addr > dar));

I'm using -1 while calculating end address is to make it
inclusive. If I don't use -1, the end address points to a
location outside of actual range, i.e. it's not really an
end address.

Ravi