arm64: Expose ARMv8.5 CondM capability to userspace

ARMv8.5 adds new instructions XAFLAG and AXFLAG to translate the
representation of the results of floating point comparisons between the
native ARM format and an alternative format used by some software. Add
a hwcap allowing userspace to determine if they are present, since we
referred to earlier CondM extensions as FLAGM call these extensions
FLAGM2.
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Documentation/arm64/elf_hwcaps.txt

@@ -207,6 +207,10 @@ HWCAP_FLAGM
 
     Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0001.
 
+HWCAP2_FLAGM2
+
+    Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0010.
+
 HWCAP_SSBS
 
     Functionality implied by ID_AA64PFR1_EL1.SSBS == 0b0010.

arch/arm64/include/asm/hwcap.h

@@ -95,6 +95,7 @@
 #define KERNEL_HWCAP_SVEBITPERM		__khwcap2_feature(SVEBITPERM)
 #define KERNEL_HWCAP_SVESHA3		__khwcap2_feature(SVESHA3)
 #define KERNEL_HWCAP_SVESM4		__khwcap2_feature(SVESM4)
+#define KERNEL_HWCAP_FLAGM2		__khwcap2_feature(FLAGM2)
 
 /*
  * This yields a mask that user programs can use to figure out what

arch/arm64/include/uapi/asm/hwcap.h

@@ -63,5 +63,6 @@
 #define HWCAP2_SVEBITPERM	(1 << 4)
 #define HWCAP2_SVESHA3		(1 << 5)
 #define HWCAP2_SVESM4		(1 << 6)
+#define HWCAP2_FLAGM2		(1 << 7)
 
 #endif /* _UAPI__ASM_HWCAP_H */

arch/arm64/kernel/cpufeature.c

@@ -1628,6 +1628,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_DP_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_ASIMDDP),
 	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_FHM_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_ASIMDFHM),
 	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_TS_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_FLAGM),
+	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_TS_SHIFT, FTR_UNSIGNED, 2, CAP_HWCAP, KERNEL_HWCAP_FLAGM2),
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, KERNEL_HWCAP_FP),
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_FPHP),
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, KERNEL_HWCAP_ASIMD),

arch/arm64/kernel/cpuinfo.c

@@ -92,6 +92,7 @@ static const char *const hwcap_str[] = {
 	"svebitperm",
 	"svesha3",
 	"svesm4",
+	"flagm2",
 	NULL
 };