Re: [PATCH v6 02/18] arm64: cpufeature: add pointer auth meta-capabilities

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

On 3/6/20 6:35 AM, Amit Daniel Kachhap wrote:
> From: Kristina Martsenko <kristina.martsenko@arm.com>
> 
> To enable pointer auth for the kernel, we're going to need to check for
> the presence of address auth and generic auth using alternative_if. We
> currently have two cpucaps for each, but alternative_if needs to check a
> single cpucap. So define meta-capabilities that are present when either
> of the current two capabilities is present.
> 
> Leave the existing four cpucaps in place, as they are still needed to
> check for mismatched systems where one CPU has the architected algorithm
> but another has the IMP DEF algorithm.
> 
> Note, the meta-capabilities were present before but were removed in
> commit a56005d32105 ("arm64: cpufeature: Reduce number of pointer auth
> CPU caps from 6 to 4") and commit 1e013d06120c ("arm64: cpufeature: Rework
> ptr auth hwcaps using multi_entry_cap_matches"), as they were not needed
> then. Note, unlike before, the current patch checks the cpucap values
> directly, instead of reading the CPU ID register value.
>

Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>

> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
> [Amit: commit message and macro rebase, use __system_matches_cap]
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> ---
>  arch/arm64/include/asm/cpucaps.h    |  4 +++-
>  arch/arm64/include/asm/cpufeature.h |  6 ++----
>  arch/arm64/kernel/cpufeature.c      | 25 ++++++++++++++++++++++++-
>  3 files changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
> index 865e025..72e4e05 100644
> --- a/arch/arm64/include/asm/cpucaps.h
> +++ b/arch/arm64/include/asm/cpucaps.h
> @@ -58,7 +58,9 @@
>  #define ARM64_WORKAROUND_SPECULATIVE_AT_NVHE	48
>  #define ARM64_HAS_E0PD				49
>  #define ARM64_HAS_RNG				50
> +#define ARM64_HAS_ADDRESS_AUTH			51
> +#define ARM64_HAS_GENERIC_AUTH			52
>  
> -#define ARM64_NCAPS				51
> +#define ARM64_NCAPS				53
>  
>  #endif /* __ASM_CPUCAPS_H */
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 2a746b9..0fd1feb 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -590,15 +590,13 @@ static __always_inline bool system_supports_cnp(void)
>  static inline bool system_supports_address_auth(void)
>  {
>  	return IS_ENABLED(CONFIG_ARM64_PTR_AUTH) &&
> -		(cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH_ARCH) ||
> -		 cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH_IMP_DEF));
> +		cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH);
>  }
>  
>  static inline bool system_supports_generic_auth(void)
>  {
>  	return IS_ENABLED(CONFIG_ARM64_PTR_AUTH) &&
> -		(cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_ARCH) ||
> -		 cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_IMP_DEF));
> +		cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH);
>  }
>  
>  static inline bool system_uses_irq_prio_masking(void)
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 3818685..b12e386 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1323,6 +1323,20 @@ static void cpu_enable_address_auth(struct arm64_cpu_capabilities const *cap)
>  	sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ENIA | SCTLR_ELx_ENIB |
>  				       SCTLR_ELx_ENDA | SCTLR_ELx_ENDB);
>  }
> +
> +static bool has_address_auth(const struct arm64_cpu_capabilities *entry,
> +			     int __unused)
> +{
> +	return __system_matches_cap(ARM64_HAS_ADDRESS_AUTH_ARCH) ||
> +	       __system_matches_cap(ARM64_HAS_ADDRESS_AUTH_IMP_DEF);
> +}
> +
> +static bool has_generic_auth(const struct arm64_cpu_capabilities *entry,
> +			     int __unused)
> +{
> +	return __system_matches_cap(ARM64_HAS_GENERIC_AUTH_ARCH) ||
> +	       __system_matches_cap(ARM64_HAS_GENERIC_AUTH_IMP_DEF);
> +}
>  #endif /* CONFIG_ARM64_PTR_AUTH */
>  
>  #ifdef CONFIG_ARM64_E0PD
> @@ -1600,7 +1614,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.field_pos = ID_AA64ISAR1_APA_SHIFT,
>  		.min_field_value = ID_AA64ISAR1_APA_ARCHITECTED,
>  		.matches = has_cpuid_feature,
> -		.cpu_enable = cpu_enable_address_auth,
>  	},
>  	{
>  		.desc = "Address authentication (IMP DEF algorithm)",
> @@ -1611,6 +1624,11 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.field_pos = ID_AA64ISAR1_API_SHIFT,
>  		.min_field_value = ID_AA64ISAR1_API_IMP_DEF,
>  		.matches = has_cpuid_feature,
> +	},
> +	{
> +		.capability = ARM64_HAS_ADDRESS_AUTH,
> +		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
> +		.matches = has_address_auth,
>  		.cpu_enable = cpu_enable_address_auth,
>  	},
>  	{
> @@ -1633,6 +1651,11 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.min_field_value = ID_AA64ISAR1_GPI_IMP_DEF,
>  		.matches = has_cpuid_feature,
>  	},
> +	{
> +		.capability = ARM64_HAS_GENERIC_AUTH,
> +		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
> +		.matches = has_generic_auth,
> +	},
>  #endif /* CONFIG_ARM64_PTR_AUTH */
>  #ifdef CONFIG_ARM64_PSEUDO_NMI
>  	{
> 

-- 
Regards,
Vincenzo

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