[PATCH v4 2/2] arm64: Introduce HWCAPS2_EXECONLY

[Vladimir Murzin]

With EPAN supported it might be handy to user know that PROT_EXEC
gives execute-only permission, so advertise it via HWCAPS2_EXECONLY

Cc: Kees Cook <keescook at chromium.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
 arch/arm64/include/asm/hwcap.h      | 1 +
 arch/arm64/include/asm/sysreg.h     | 1 +
 arch/arm64/include/uapi/asm/hwcap.h | 1 +
 arch/arm64/kernel/cpufeature.c      | 3 +++
 arch/arm64/kernel/cpuinfo.c         | 1 +
 5 files changed, 7 insertions(+)

diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index 9a5498c2c8ee..5ee5bce79233 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -105,6 +105,7 @@
 #define KERNEL_HWCAP_RNG		__khwcap2_feature(RNG)
 #define KERNEL_HWCAP_BTI		__khwcap2_feature(BTI)
 #define KERNEL_HWCAP_MTE		__khwcap2_feature(MTE)
+#define KERNEL_HWCAP_EXECONLY		__khwcap2_feature(EXECONLY)
 
 /*
  * This yields a mask that user programs can use to figure out what
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 817cb3dbcb79..7421139dc44f 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -817,6 +817,7 @@
 
 #define ID_AA64MMFR1_VMIDBITS_8		0
 #define ID_AA64MMFR1_VMIDBITS_16	2
+#define ID_AA64MMFR1_EPAN		3
 
 /* id_aa64mmfr2 */
 #define ID_AA64MMFR2_E0PD_SHIFT		60
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index b8f41aa234ee..61471f47db32 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -75,5 +75,6 @@
 #define HWCAP2_RNG		(1 << 16)
 #define HWCAP2_BTI		(1 << 17)
 #define HWCAP2_MTE		(1 << 18)
+#define HWCAP2_EXECONLY		(1 << 19)
 
 #endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 2ab04967dca7..a49bccb80873 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2332,6 +2332,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 #ifdef CONFIG_ARM64_MTE
 	HWCAP_CAP(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_MTE_SHIFT, FTR_UNSIGNED, ID_AA64PFR1_MTE, CAP_HWCAP, KERNEL_HWCAP_MTE),
 #endif /* CONFIG_ARM64_MTE */
+#ifdef CONFIG_ARM64_EPAN
+	HWCAP_CAP(SYS_ID_AA64MMFR1_EL1, ID_AA64MMFR1_PAN_SHIFT, FTR_UNSIGNED, ID_AA64MMFR1_EPAN, CAP_HWCAP, KERNEL_HWCAP_EXECONLY),
+#endif
 	{},
 };
 
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 77605aec25fe..34c98d984fe3 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -94,6 +94,7 @@ static const char *const hwcap_str[] = {
 	[KERNEL_HWCAP_RNG]		= "rng",
 	[KERNEL_HWCAP_BTI]		= "bti",
 	[KERNEL_HWCAP_MTE]		= "mte",
+	[KERNEL_HWCAP_EXECONLY]		= "xo",
 };
 
 #ifdef CONFIG_COMPAT
-- 
2.24.0