ARM: 9273/1: Add hwcap for Speculation Barrier(SB)

Speculation Barrier(FEAT_SB) is a feature present in AArch32 state for
Armv8 and is represented by ISAR6.SB identification register.

This feature denotes the presence of SB instruction and hence adding a
hwcap will enable the userspace to check it before trying to use this
instruction.

This commit adds the ID feature bit detection, and uses elf_hwcap2
accordingly.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/include/uapi/asm/hwcap.h b/arch/arm/include/uapi/asm/hwcap.h
index 46833c668ec2f83b9c5cbb50fcda2f967392e0c7..bc9e7d318e25bb811eb9a743497584d37ef11f13 100644 (file)
--- a/arch/arm/include/uapi/asm/hwcap.h
+++ b/arch/arm/include/uapi/asm/hwcap.h
@@ -43,5 +43,6 @@
 #define HWCAP2_SHA1    (1 << 2)
 #define HWCAP2_SHA2    (1 << 3)
 #define HWCAP2_CRC32   (1 << 4)
+#define HWCAP2_SB      (1 << 5)
 
 #endif /* _UAPI__ASMARM_HWCAP_H */

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 5807fa0217853e0f4d2bb14a9e68e25936286212..979612add87ac59720cc786c413ee3081cb51c82 100644 (file)
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -450,6 +450,7 @@ static void __init cpuid_init_hwcaps(void)
 {
        int block;
        u32 isar5;
+       u32 isar6;
 
        if (cpu_architecture() < CPU_ARCH_ARMv7)
                return;
@@ -485,6 +486,12 @@ static void __init cpuid_init_hwcaps(void)
        block = cpuid_feature_extract_field(isar5, 16);
        if (block >= 1)
                elf_hwcap2 |= HWCAP2_CRC32;
+
+       /* Check for Speculation barrier instruction */
+       isar6 = read_cpuid_ext(CPUID_EXT_ISAR6);
+       block = cpuid_feature_extract_field(isar6, 12);
+       if (block >= 1)
+               elf_hwcap2 |= HWCAP2_SB;
 }
 
 static void __init elf_hwcap_fixup(void)
@@ -1264,6 +1271,7 @@ static const char *hwcap2_str[] = {
        "sha1",
        "sha2",
        "crc32",
+       "sb",
        NULL
 };