Messages in this thread | | | Subject | Re: [PATCH] arm64/cpufeature: Validate feature bits spacing in arm64_ftr_regs[] | From | Suzuki K Poulose <> | Date | Mon, 29 Jun 2020 11:42:36 +0100 |
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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@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Suzuki K Poulose <suzuki.poulose@arm.com> > Cc: Mark Brown <broonie@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > Applies on 5.8-rc1. > > arch/arm64/kernel/cpufeature.c | 45 +++++++++++++++++++++++++++++++--- > 1 file changed, 42 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 4ae41670c2e6..2270eda9a7fb 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -697,11 +697,50 @@ static s64 arm64_ftr_safe_value(const struct arm64_ftr_bits *ftrp, s64 new, > > static void __init sort_ftr_regs(void) > { > - int i; > + const struct arm64_ftr_reg *ftr_reg; > + const struct arm64_ftr_bits *ftr_bits; > + unsigned int i, j, width, shift, prev_shift; > + > + for (i = 0; i < ARRAY_SIZE(arm64_ftr_regs); i++) { > + /* > + * Features here must be sorted in descending order with respect > + * to their shift values and should not overlap with each other. > + */ > + ftr_reg = arm64_ftr_regs[i].reg; > + for (ftr_bits = ftr_reg->ftr_bits, j = 0; > + ftr_bits->width != 0; ftr_bits++, j++) { > + if (WARN_ON(ftr_bits->shift + ftr_bits->width > 64)) > + pr_err("%s has invalid feature at shift %d\n", > + ftr_reg->name, ftr_bits->shift);
nit:
WARN((ftr_bits->shift + ftr_bits->width) > 64, "%s......);?
> + > + /* > + * Skip the first feature. There is nothing to > + * compare against for now. > + */ > + if (j == 0) > + continue; > + > + prev_shift = ftr_reg->ftr_bits[j - 1].shift; > + width = ftr_reg->ftr_bits[j].width; > + shift = ftr_reg->ftr_bits[j].shift; > + if (WARN_ON(prev_shift < shift + width)) > + pr_err("%s has feature overlap at shift %d\n", > + ftr_reg->name, ftr_bits->shift);
same as above ?
> + } > > - /* Check that the array is sorted so that we can do the binary search */ > - for (i = 1; i < ARRAY_SIZE(arm64_ftr_regs); i++) > + /* > + * Skip the first register. There is nothing to > + * compare against for now. > + */ > + if (i == 0) > + continue;
You are starting at 1 already, so you may skip this check.
> + /* > + * Registers here must be sorted in ascending order with respect > + * to sys_id for subsequent binary search in get_arm64_ftr_reg() > + * to work correctly. > + */ > BUG_ON(arm64_ftr_regs[i].sys_id < arm64_ftr_regs[i - 1].sys_id); > + } > } > > /*
Otherwise looks good to me.
Suzuki
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