[PATCH] ARM: advertise availability of v8 Crypto instructions

[ard.biesheuvel@linaro.org (Ard Biesheuvel)]

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>
---
 arch/arm/kernel/setup.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index e55408e96559..8d4cb1c1c9ac 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -393,6 +393,22 @@ static void __init cpuid_init_hwcaps(void)
 	vmsa = (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xf) >> 0;
 	if (vmsa >= 5)
 		elf_hwcap |= HWCAP_LPAE;
+
+	/* check for supported v8 Crypto instructions on non v7-M CPUs */
+	if (cpu_architecture() == CPU_ARCH_ARMv7) {
+		unsigned int id = read_cpuid_ext(CPUID_EXT_ISAR5);
+
+		switch ((id >> 4) & 0xf) {
+		case 2:	elf_hwcap2 |= HWCAP2_PMULL;
+		case 1:	elf_hwcap2 |= HWCAP2_AES;
+		}
+		if (((id >> 8) & 0xf) == 1)
+			elf_hwcap2 |= HWCAP2_SHA1;
+		if (((id >> 12) & 0xf) == 1)
+			elf_hwcap2 |= HWCAP2_SHA2;
+		if (((id >> 16) & 0xf) == 1)
+			elf_hwcap2 |= HWCAP2_CRC32;
+	}
 }
 
 static void __init elf_hwcap_fixup(void)
-- 
1.8.3.2