* [PATCH v3] ARM: advertise availability of v8 Crypto instructions
@ 2015-03-10 7:54 Ard Biesheuvel
2015-03-18 11:01 ` Russell King - ARM Linux
0 siblings, 1 reply; 2+ messages in thread
From: Ard Biesheuvel @ 2015-03-10 7:54 UTC (permalink / raw)
To: linux-arm-kernel
When running the 32-bit ARM kernel on ARMv8 capable bare metal (e.g.,
32-bit Android userland and kernel on a Cortex-A53), or as a KVM guest
on a 64-bit host, we should advertise the availability of the Crypto
instructions, so that userland libraries such as OpenSSL may use them.
(Support for the v8 Crypto instructions in the 32-bit build was added
to OpenSSL more than six months ago)
This adds the ID feature bit detection, and sets elf_hwcap2 accordingly.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
v3:
- reuse logic from arm64 kernel: the feature blocks are signed quantities
that represent incremental functionality for non-negative values.
v2:
- drop redundant architecture check -> accessing ID_ISAR5 should be safe
even on v7-M, and even if we don't expect to find crypto features there
arch/arm/kernel/setup.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index e55408e96559..fe07efca2f12 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -375,7 +375,7 @@ void __init early_print(const char *str, ...)
static void __init cpuid_init_hwcaps(void)
{
- unsigned int divide_instrs, vmsa;
+ unsigned int divide_instrs, vmsa, features, block;
if (cpu_architecture() < CPU_ARCH_ARMv7)
return;
@@ -393,6 +393,37 @@ static void __init cpuid_init_hwcaps(void)
vmsa = (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xf) >> 0;
if (vmsa >= 5)
elf_hwcap |= HWCAP_LPAE;
+
+ /*
+ * ID_ISAR5 contains 4-bit wide signed feature blocks.
+ * The blocks we test below represent incremental functionality
+ * for non-negative values. Negative values are reserved.
+ */
+ features = read_cpuid_ext(ID_ISAR5);
+ block = (features >> 4) & 0xf;
+ if (!(block & 0x8)) {
+ switch (block) {
+ default:
+ case 2:
+ elf_hwcap2 |= HWCAP2_PMULL;
+ case 1:
+ elf_hwcap2 |= HWCAP2_AES;
+ case 0:
+ break;
+ }
+ }
+
+ block = (features >> 8) & 0xf;
+ if (block && !(block & 0x8))
+ elf_hwcap2 |= HWCAP2_SHA1;
+
+ block = (features >> 12) & 0xf;
+ if (block && !(block & 0x8))
+ elf_hwcap2 |= HWCAP2_SHA2;
+
+ block = (features >> 16) & 0xf;
+ if (block && !(block & 0x8))
+ elf_hwcap2 |= HWCAP2_CRC32;
}
static void __init elf_hwcap_fixup(void)
--
1.8.3.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH v3] ARM: advertise availability of v8 Crypto instructions
2015-03-10 7:54 [PATCH v3] ARM: advertise availability of v8 Crypto instructions Ard Biesheuvel
@ 2015-03-18 11:01 ` Russell King - ARM Linux
0 siblings, 0 replies; 2+ messages in thread
From: Russell King - ARM Linux @ 2015-03-18 11:01 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Mar 10, 2015 at 08:54:48AM +0100, Ard Biesheuvel wrote:
> @@ -393,6 +393,37 @@ static void __init cpuid_init_hwcaps(void)
> vmsa = (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xf) >> 0;
> if (vmsa >= 5)
> elf_hwcap |= HWCAP_LPAE;
> +
> + /*
> + * ID_ISAR5 contains 4-bit wide signed feature blocks.
> + * The blocks we test below represent incremental functionality
> + * for non-negative values. Negative values are reserved.
> + */
> + features = read_cpuid_ext(ID_ISAR5);
> + block = (features >> 4) & 0xf;
Okay, what I'd like to see is something like:
block = cpuid_feature_extract_field(features, 4);
with this in cputype.h:
static inline int cpuid_feature_extract_field(u32 features, unsigned int field)
{
int feature = (features >> field) & 15;
/* feature registers are signed values */
if (feature > 8)
feature -= 16;
return feature;
}
We can then use proper signed tests in the code - and convert all tests
to use this helper.
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
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