Re: [PATCH] arm64/cpufeature: Validate feature bits spacing in arm64_ftr_regs[]

[Suzuki K Poulose]

On 06/30/2020 02:49 AM, Anshuman Khandual wrote:
> On 06/29/2020 04:12 PM, Suzuki K Poulose wrote:
> > On 06/16/2020 03:25 AM, Anshuman Khandual wrote:
> > > arm64_feature_bits for a register in arm64_ftr_regs[] are in a descending
> > > order as per their shift values. Validate that these features bits are
> > > defined correctly and do not overlap with each other. This check protects
> > > against any inadvertent erroneous changes to the register definitions.
> > >
> > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > > Cc: Will Deacon <will@xxxxxxxxxx>
> > > Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > > Cc: Mark Brown <broonie@xxxxxxxxxx>
> > > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > > ---
> > > Applies on 5.8-rc1.
> > >
> > >  Â arch/arm64/kernel/cpufeature.c | 45 +++++++++++++++++++++++++++++++---
> > >  Â 1 file changed, 42 insertions(+), 3 deletions(-)

> > > +ÂÂÂÂÂÂÂ }
> > >  Â -ÂÂÂ /* Check that the array is sorted so that we can do the binary search */
> > > -ÂÂÂ for (i = 1; i < ARRAY_SIZE(arm64_ftr_regs); i++)
> > > +ÂÂÂÂÂÂÂ /*
> > > +ÂÂÂÂÂÂÂÂ * Skip the first register. There is nothing to
> > > +ÂÂÂÂÂÂÂÂ * compare against for now.
> > > +ÂÂÂÂÂÂÂÂ */
> > > +ÂÂÂÂÂÂÂ if (i == 0)
> > > +ÂÂÂÂÂÂÂÂÂÂÂ continue;
> >
> > You are starting at 1 already, so you may skip this check.
>
> Actually, now we are starting with 0 instead for both i and j.
> Hence this check would be required.

Sorry, ignore that.

Suzuki