[PATCHv4,05/10] arm64/cpufeature: detect pointer authentication

Message ID 20180503132031.25705-6-mark.rutland@arm.com
State New
Headers show
Series
  • ARMv8.3 pointer authentication userspace support
Related show

Commit Message

Mark Rutland May 3, 2018, 1:20 p.m.
So that we can dynamically handle the presence of pointer authentication
functionality, wire up probing code in cpufeature.c.

From ARMv8.3 onwards, ID_AA64ISAR1 is no longer entirely RES0, and now
has four fields describing the presence of pointer authentication
functionality:

* APA - address authentication present, using an architected algorithm
* API - address authentication present, using an IMP DEF algorithm
* GPA - generic authentication present, using an architected algorithm
* GPI - generic authentication present, using an IMP DEF algorithm

For the moment we only care about address authentication, so we only
need to check APA and API. It is assumed that if all CPUs support an IMP
DEF algorithm, the same algorithm is used across all CPUs.

Note that when we implement KVM support, we will also need to ensure
that CPUs have uniform support for GPA and GPI.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/cpucaps.h |  5 ++++-
 arch/arm64/kernel/cpufeature.c   | 47 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 1 deletion(-)

-- 
2.11.0

Comments

Suzuki K Poulose May 23, 2018, 8:48 a.m. | #1
Mark,

On 03/05/18 14:20, Mark Rutland wrote:
> So that we can dynamically handle the presence of pointer authentication

> functionality, wire up probing code in cpufeature.c.

> 

>  From ARMv8.3 onwards, ID_AA64ISAR1 is no longer entirely RES0, and now

> has four fields describing the presence of pointer authentication

> functionality:

> 

> * APA - address authentication present, using an architected algorithm

> * API - address authentication present, using an IMP DEF algorithm

> * GPA - generic authentication present, using an architected algorithm

> * GPI - generic authentication present, using an IMP DEF algorithm

> 

> For the moment we only care about address authentication, so we only

> need to check APA and API. It is assumed that if all CPUs support an IMP

> DEF algorithm, the same algorithm is used across all CPUs.

> 

> Note that when we implement KVM support, we will also need to ensure

> that CPUs have uniform support for GPA and GPI.

> 

> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

> Cc: Catalin Marinas <catalin.marinas@arm.com>

> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>

> Cc: Will Deacon <will.deacon@arm.com>

> ---

>   arch/arm64/include/asm/cpucaps.h |  5 ++++-

>   arch/arm64/kernel/cpufeature.c   | 47 ++++++++++++++++++++++++++++++++++++++++

>   2 files changed, 51 insertions(+), 1 deletion(-)

> 

> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h

> index bc51b72fafd4..9dcb4d1b14f5 100644

> --- a/arch/arm64/include/asm/cpucaps.h

> +++ b/arch/arm64/include/asm/cpucaps.h

> @@ -48,7 +48,10 @@

>   #define ARM64_HAS_CACHE_IDC			27

>   #define ARM64_HAS_CACHE_DIC			28

>   #define ARM64_HW_DBM				29

> +#define ARM64_HAS_ADDRESS_AUTH_ARCH		30

> +#define ARM64_HAS_ADDRESS_AUTH_IMP_DEF		31


Where are these caps used ? I couldn't find anything in the series
that uses them. Otherwise looks good to me.

Cheers

Suzuki
Mark Rutland May 25, 2018, 10:01 a.m. | #2
On Wed, May 23, 2018 at 09:48:28AM +0100, Suzuki K Poulose wrote:
> 

> Mark,

> 

> On 03/05/18 14:20, Mark Rutland wrote:

> > So that we can dynamically handle the presence of pointer authentication

> > functionality, wire up probing code in cpufeature.c.

> > 

> >  From ARMv8.3 onwards, ID_AA64ISAR1 is no longer entirely RES0, and now

> > has four fields describing the presence of pointer authentication

> > functionality:

> > 

> > * APA - address authentication present, using an architected algorithm

> > * API - address authentication present, using an IMP DEF algorithm

> > * GPA - generic authentication present, using an architected algorithm

> > * GPI - generic authentication present, using an IMP DEF algorithm

> > 

> > For the moment we only care about address authentication, so we only

> > need to check APA and API. It is assumed that if all CPUs support an IMP

> > DEF algorithm, the same algorithm is used across all CPUs.

> > 

> > Note that when we implement KVM support, we will also need to ensure

> > that CPUs have uniform support for GPA and GPI.

> > 

> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>

> > Cc: Catalin Marinas <catalin.marinas@arm.com>

> > Cc: Suzuki K Poulose <suzuki.poulose@arm.com>

> > Cc: Will Deacon <will.deacon@arm.com>

> > ---

> >   arch/arm64/include/asm/cpucaps.h |  5 ++++-

> >   arch/arm64/kernel/cpufeature.c   | 47 ++++++++++++++++++++++++++++++++++++++++

> >   2 files changed, 51 insertions(+), 1 deletion(-)

> > 

> > diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h

> > index bc51b72fafd4..9dcb4d1b14f5 100644

> > --- a/arch/arm64/include/asm/cpucaps.h

> > +++ b/arch/arm64/include/asm/cpucaps.h

> > @@ -48,7 +48,10 @@

> >   #define ARM64_HAS_CACHE_IDC			27

> >   #define ARM64_HAS_CACHE_DIC			28

> >   #define ARM64_HW_DBM				29

> > +#define ARM64_HAS_ADDRESS_AUTH_ARCH		30

> > +#define ARM64_HAS_ADDRESS_AUTH_IMP_DEF		31

> 

> Where are these caps used ? I couldn't find anything in the series

> that uses them. Otherwise looks good to me.


Those were consumed by KVM support, which needed to detect if CPUs had
mismatched support. Currently they're just placeholders as I need a
cpucap value for the separate IMP-DEF / architected probing cases.

I *could* get rid of those and just have the ARM64_HAS_ADDRESS_AUTH case
log "Address authentication", but I wanted to have separate messages for
IMP-DEF vs architected.

Thanks,
Mark.
Will Deacon July 4, 2018, 4:09 p.m. | #3
On Fri, May 25, 2018 at 11:01:37AM +0100, Mark Rutland wrote:
> On Wed, May 23, 2018 at 09:48:28AM +0100, Suzuki K Poulose wrote:

> > On 03/05/18 14:20, Mark Rutland wrote:

> > > diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h

> > > index bc51b72fafd4..9dcb4d1b14f5 100644

> > > --- a/arch/arm64/include/asm/cpucaps.h

> > > +++ b/arch/arm64/include/asm/cpucaps.h

> > > @@ -48,7 +48,10 @@

> > >   #define ARM64_HAS_CACHE_IDC			27

> > >   #define ARM64_HAS_CACHE_DIC			28

> > >   #define ARM64_HW_DBM				29

> > > +#define ARM64_HAS_ADDRESS_AUTH_ARCH		30

> > > +#define ARM64_HAS_ADDRESS_AUTH_IMP_DEF		31

> > 

> > Where are these caps used ? I couldn't find anything in the series

> > that uses them. Otherwise looks good to me.

> 

> Those were consumed by KVM support, which needed to detect if CPUs had

> mismatched support. Currently they're just placeholders as I need a

> cpucap value for the separate IMP-DEF / architected probing cases.

> 

> I *could* get rid of those and just have the ARM64_HAS_ADDRESS_AUTH case

> log "Address authentication", but I wanted to have separate messages for

> IMP-DEF vs architected.


Why? Surely it only matters if we find a mixture, and then you'll shout
loudly. I'd certainly be in favour of reducing the number of caps you're
adding here, particularly if they're just there for a line in dmesg.

Will

Patch

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index bc51b72fafd4..9dcb4d1b14f5 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -48,7 +48,10 @@ 
 #define ARM64_HAS_CACHE_IDC			27
 #define ARM64_HAS_CACHE_DIC			28
 #define ARM64_HW_DBM				29
+#define ARM64_HAS_ADDRESS_AUTH_ARCH		30
+#define ARM64_HAS_ADDRESS_AUTH_IMP_DEF		31
+#define ARM64_HAS_ADDRESS_AUTH			32
 
-#define ARM64_NCAPS				30
+#define ARM64_NCAPS				33
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 536d572e5596..01b1a7e7d70f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -142,6 +142,10 @@  static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_LRCPC_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_FCMA_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_JSCVT_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_API_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_APA_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_DPB_SHIFT, 4, 0),
 	ARM64_FTR_END,
 };
@@ -1025,6 +1029,22 @@  static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
 }
 #endif
 
+#ifdef CONFIG_ARM64_PTR_AUTH
+static bool has_address_auth(const struct arm64_cpu_capabilities *entry,
+			     int __unused)
+{
+	u64 isar1 = read_sanitised_ftr_reg(SYS_ID_AA64ISAR1_EL1);
+	bool api, apa;
+
+	apa = cpuid_feature_extract_unsigned_field(isar1,
+					ID_AA64ISAR1_APA_SHIFT) > 0;
+	api = cpuid_feature_extract_unsigned_field(isar1,
+					ID_AA64ISAR1_API_SHIFT) > 0;
+
+	return apa || api;
+}
+#endif /* CONFIG_ARM64_PTR_AUTH */
+
 static const struct arm64_cpu_capabilities arm64_features[] = {
 	{
 		.desc = "GIC system register CPU interface",
@@ -1201,6 +1221,33 @@  static const struct arm64_cpu_capabilities arm64_features[] = {
 		.cpu_enable = cpu_enable_hw_dbm,
 	},
 #endif
+#ifdef CONFIG_ARM64_PTR_AUTH
+	{
+		.desc = "Address authentication (architected algorithm)",
+		.capability = ARM64_HAS_ADDRESS_AUTH_ARCH,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.sys_reg = SYS_ID_AA64ISAR1_EL1,
+		.sign = FTR_UNSIGNED,
+		.field_pos = ID_AA64ISAR1_APA_SHIFT,
+		.min_field_value = ID_AA64ISAR1_APA_ARCHITECTED,
+		.matches = has_cpuid_feature,
+	},
+	{
+		.desc = "Address authentication (IMP DEF algorithm)",
+		.capability = ARM64_HAS_ADDRESS_AUTH_IMP_DEF,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.sys_reg = SYS_ID_AA64ISAR1_EL1,
+		.sign = FTR_UNSIGNED,
+		.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,
+	},
+#endif /* CONFIG_ARM64_PTR_AUTH */
 	{},
 };