TODO(drop): aarch64: morello: CPU feature detection for Morello

Initial detection of Arm Morello architecture from the HWCAP2 bit and CPU
identification from MIDR_EL0.

TODO: not needed?
- lp64 does not have to detect
- purecap can assume morello

sysdeps/aarch64/multiarch/init-arch.h

@@ -35,4 +35,6 @@
   bool __attribute__((unused)) mte =					      \
     MTE_ENABLED ();							      \
   bool __attribute__((unused)) sve =					      \
-    GLRO(dl_aarch64_cpu_features).sve;
+    GLRO(dl_aarch64_cpu_features).sve;					      \
+  bool __attribute__((unused)) morello =				      \
+    GLRO(dl_hwcap2) & HWCAP2_MORELLO;

sysdeps/unix/sysv/linux/aarch64/cpu-features.c

@@ -126,4 +126,7 @@ init_cpu_features (struct cpu_features *cpu_features)
 
   /* Check if SVE is supported.  */
   cpu_features->sve = GLRO (dl_hwcap) & HWCAP_SVE;
+
+  /* Check if Morello is supported.  */
+  cpu_features->morello = GLRO (dl_hwcap2) & HWCAP2_MORELLO;
 }

sysdeps/unix/sysv/linux/aarch64/cpu-features.h

@@ -68,6 +68,11 @@
 #define IS_A64FX(midr) (MIDR_IMPLEMENTOR(midr) == 'F'			      \
 			&& MIDR_PARTNUM(midr) == 0x001)
 
+/* TODO: This is based on the Morello Fast Model.
+	 Will MIDR_IMPLEMENTOR change to 'A'?  */
+#define IS_MORELLO(midr) (MIDR_IMPLEMENTOR(midr) == 0x3f       \
+                         && MIDR_PARTNUM(midr) == 0x412)
+
 struct cpu_features
 {
   uint64_t midr_el1;
@@ -76,6 +81,7 @@ struct cpu_features
   /* Currently, the GLIBC memory tagging tunable only defines 8 bits.  */
   uint8_t mte_state;
   bool sve;
+  bool morello;
 };
 
 #endif /* _CPU_FEATURES_AARCH64_H  */