arm64: Reserve HWCAP2_MTE as (1 << 18)

While MTE is not supported in the upstream kernel yet, add a comment
that HWCAP2_MTE as (1 << 18) is reserved. Glibc makes use of it for the
resolving (ifunc) of the MTE-safe string routines.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index d683bcb..22f73fe 100644 (file)
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -95,6 +95,7 @@
 #define KERNEL_HWCAP_DGH               __khwcap2_feature(DGH)
 #define KERNEL_HWCAP_RNG               __khwcap2_feature(RNG)
 #define KERNEL_HWCAP_BTI               __khwcap2_feature(BTI)
+/* reserved for KERNEL_HWCAP_MTE       __khwcap2_feature(MTE) */
 
 /*
  * This yields a mask that user programs can use to figure out what

diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index 2d6ba1c..912162f 100644 (file)
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -74,5 +74,6 @@
 #define HWCAP2_DGH             (1 << 15)
 #define HWCAP2_RNG             (1 << 16)
 #define HWCAP2_BTI             (1 << 17)
+/* reserved for HWCAP2_MTE     (1 << 18) */
 
 #endif /* _UAPI__ASM_HWCAP_H */

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 8663746..393c6fb 100644 (file)
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -93,6 +93,7 @@ static const char *const hwcap_str[] = {
        "dgh",
        "rng",
        "bti",
+       /* reserved for "mte" */
        NULL
 };