arm64: advertise ARMv8 extensions to 32-bit compat ELF binaries

This adds support for advertising the presence of ARMv8 Crypto
Extensions in the Aarch32 execution state to 32-bit ELF binaries
running in 32-bit compat mode under the arm64 kernel.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

2 files changed, 38 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index 9a4cbd60c88e..024c46183c3c 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -32,6 +32,12 @@
 #define COMPAT_HWCAP_IDIV       (COMPAT_HWCAP_IDIVA|COMPAT_HWCAP_IDIVT)
 #define COMPAT_HWCAP_EVTSTRM    (1 << 21)
 
+#define COMPAT_HWCAP2_AES       (1 << 0)
+#define COMPAT_HWCAP2_PMULL     (1 << 1)
+#define COMPAT_HWCAP2_SHA1      (1 << 2)
+#define COMPAT_HWCAP2_SHA2      (1 << 3)
+#define COMPAT_HWCAP2_CRC32     (1 << 4)
+
 #ifndef __ASSEMBLY__
 /*
  * This yields a mask that user programs can use to figure out what
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 349c49260f09..67da30741a1b 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -243,6 +243,38 @@ static void __init setup_processor(void)
         block = (features >> 16) & 0xf;
         if (block && !(block & 0x8))
                 elf_hwcap |= HWCAP_CRC32;
+
+#ifdef CONFIG_COMPAT
+        /*
+         * ID_ISAR5_EL1 carries similar information as above, but pertaining to
+         * the Aarch32 32-bit execution state.
+         */
+        features = read_cpuid(ID_ISAR5_EL1);
+        block = (features >> 4) & 0xf;
+        if (!(block & 0x8)) {
+                switch (block) {
+                default:
+                case 2:
+                        compat_elf_hwcap2 |= COMPAT_HWCAP2_PMULL;
+                case 1:
+                        compat_elf_hwcap2 |= COMPAT_HWCAP2_AES;
+                case 0:
+                        break;
+                }
+        }
+
+        block = (features >> 8) & 0xf;
+        if (block && !(block & 0x8))
+                compat_elf_hwcap2 |= COMPAT_HWCAP2_SHA1;
+
+        block = (features >> 12) & 0xf;
+        if (block && !(block & 0x8))
+                compat_elf_hwcap2 |= COMPAT_HWCAP2_SHA2;
+
+        block = (features >> 16) & 0xf;
+        if (block && !(block & 0x8))
+                compat_elf_hwcap2 |= COMPAT_HWCAP2_CRC32;
+#endif
 }
 
 static void __init setup_machine_fdt(phys_addr_t dt_phys)