From: Will Deacon <will.deacon@arm.com>
Date: Mon, 26 Jan 2015 18:46:19 +0000 (+0000)
Subject: arm64: elf: advertise 8.1 atomic instructions as new hwcap
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=40a1db2434a1b62332b1af25cfa14d7b8c0301fe;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

arm64: elf: advertise 8.1 atomic instructions as new hwcap

The ARM v8.1 architecture introduces new atomic instructions to the A64
instruction set for things like cmpxchg, so advertise their availability
to userspace using a hwcap.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---

diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index 73cf0f54d57c..361c8a8ef55f 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -27,5 +27,6 @@
 #define HWCAP_SHA1		(1 << 5)
 #define HWCAP_SHA2		(1 << 6)
 #define HWCAP_CRC32		(1 << 7)
+#define HWCAP_ATOMICS		(1 << 8)
 
 #endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index e7a1e719f127..b2f9895ecf7b 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -278,6 +278,19 @@ static void __init setup_processor(void)
 	if (block && !(block & 0x8))
 		elf_hwcap |= HWCAP_CRC32;
 
+	block = (features >> 20) & 0xf;
+	if (!(block & 0x8)) {
+		switch (block) {
+		default:
+		case 2:
+			elf_hwcap |= HWCAP_ATOMICS;
+		case 1:
+			/* RESERVED */
+		case 0:
+			break;
+		}
+	}
+
 #ifdef CONFIG_COMPAT
 	/*
 	 * ID_ISAR5_EL1 carries similar information as above, but pertaining to
@@ -457,6 +470,7 @@ static const char *hwcap_str[] = {
 	"sha1",
 	"sha2",
 	"crc32",
+	"atomics",
 	NULL
 };