[BUG][PATCH v8 4/6] arm64: Make _midr_in_range_list() an exported function

[Ada Couprie Diaz]

Hello,

I discovered that this patch breaks boot for some CPUs when building the 
default defconfig plus KASAN. This is still the case in v6.15-rc1 and rc2.

This patch marks `is_midr_in_range_list` as position independent but it 
isn't, breaking early boot when instrumented with KASAN and 
`CONFIG_RANDOMIZE_BASE` enabled.

The breaking usage seems to be in `kaslr_requires_kpti()` called in 
`early_map_kernel()`.
My testing on an AMD Seattle board does crash, but newer machines 
implementing E0PD do not crash as they do not need to check MIDRs in 
`kaslr_requires_kpti()`.
`is_mdr_in_range_list` did work in PI code previously because it was 
`inline`, which this patch changes.

Best regards,
Ada Couprie Diaz

On 21/02/2025 14:02, Shameer Kolothum wrote:
> Subsequent patch will add target implementation CPU support and that
> will require _midr_in_range_list() to access new data. To avoid
> exporting the data make _midr_in_range_list() a normal function and
> export it.
>
> No functional changes intended.
>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
> ---
>   arch/arm64/include/asm/cputype.h | 15 +--------------
>   arch/arm64/kernel/cpu_errata.c   | 15 +++++++++++++++
>   arch/arm64/kernel/image-vars.h   |  1 +
>   3 files changed, 17 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
> index 2a76f0e30006..ccb4a155d118 100644
> --- a/arch/arm64/include/asm/cputype.h
> +++ b/arch/arm64/include/asm/cputype.h
> @@ -276,20 +276,7 @@ static inline bool midr_is_cpu_model_range(u32 midr, u32 model, u32 rv_min,
>   	return _model == model && rv >= rv_min && rv <= rv_max;
>   }
>   
> -static inline bool is_midr_in_range(struct midr_range const *range)
> -{
> -	return midr_is_cpu_model_range(read_cpuid_id(), range->model,
> -				       range->rv_min, range->rv_max);
> -}
> -
> -static inline bool
> -is_midr_in_range_list(struct midr_range const *ranges)
> -{
> -	while (ranges->model)
> -		if (is_midr_in_range(ranges++))
> -			return true;
> -	return false;
> -}
> +bool is_midr_in_range_list(struct midr_range const *ranges);
>   
>   static inline u64 __attribute_const__ read_cpuid_mpidr(void)
>   {
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 99b55893fc4e..1f51cf6378c5 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -14,6 +14,21 @@
>   #include <asm/kvm_asm.h>
>   #include <asm/smp_plat.h>
>   
> +static inline bool is_midr_in_range(struct midr_range const *range)
> +{
> +	return midr_is_cpu_model_range(read_cpuid_id(), range->model,
> +				       range->rv_min, range->rv_max);
> +}
> +
> +bool is_midr_in_range_list(struct midr_range const *ranges)
> +{
> +	while (ranges->model)
> +		if (is_midr_in_range(ranges++))
> +			return true;
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(is_midr_in_range_list);
> +
>   static bool __maybe_unused
>   __is_affected_midr_range(const struct arm64_cpu_capabilities *entry,
>   			 u32 midr, u32 revidr)
> diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
> index ef3a69cc398e..de3d081e5a57 100644
> --- a/arch/arm64/kernel/image-vars.h
> +++ b/arch/arm64/kernel/image-vars.h
> @@ -49,6 +49,7 @@ PROVIDE(__pi_arm64_sw_feature_override	= arm64_sw_feature_override);
>   PROVIDE(__pi_arm64_use_ng_mappings	= arm64_use_ng_mappings);
>   #ifdef CONFIG_CAVIUM_ERRATUM_27456
>   PROVIDE(__pi_cavium_erratum_27456_cpus	= cavium_erratum_27456_cpus);
> +PROVIDE(__pi_is_midr_in_range_list	= is_midr_in_range_list);
>   #endif
>   PROVIDE(__pi__ctype			= _ctype);
>   PROVIDE(__pi_memstart_offset_seed	= memstart_offset_seed);