powerpc: Add space for HWCAP3/HWCAP4 in the TCB for future Power.

This patch reserves space for HWCAP3/HWCAP4 in the TCB of powerpc.
These hardware capabilities bits will be used by future Power
architectures.

Versioned symbol '__parse_hwcap_3_4_and_convert_at_platform' advertises
the availability of the new HWCAP3/HWCAP4 data in the TCB.

This is an ABI change for GLIBC 2.39.

Suggested-by: Peter Bergner <bergner@linux.ibm.com>
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>

sysdeps/powerpc/Versions

@@ -24,4 +24,9 @@ ld {
     # and AT_PLATFORM data should be stored into the TCB.
     __parse_hwcap_and_convert_at_platform;
   }
+  GLIBC_2.39 {
+    # Symbol used to version control when the ABI started to specify that
+    # HWCAP3 and HWCAP4 are stored in the TCB.
+    __parse_hwcap_3_4_and_convert_at_platform;
+  }
 }

sysdeps/powerpc/hwcapinfo.c

@@ -70,11 +70,14 @@ __tcb_parse_hwcap_and_convert_at_platform (void)
   /* Consolidate both HWCAP and HWCAP2 into a single doubleword so that
      we can read both in a single load later.  */
   __tcb.hwcap = (h1 << 32) | (h2 & 0xffffffff);
+  __tcb.hwcap_extn = 0x0;
 
 }
 #if IS_IN (rtld)
 versioned_symbol (ld, __tcb_parse_hwcap_and_convert_at_platform, \
 		  __parse_hwcap_and_convert_at_platform, GLIBC_2_23);
+versioned_symbol (ld, __tcb_parse_hwcap_and_convert_at_platform, \
+		  __parse_hwcap_3_4_and_convert_at_platform, GLIBC_2_39);
 #endif
 
 /* Export __parse_hwcap_and_convert_at_platform in libc.a.  This is used by
@@ -83,4 +86,6 @@ versioned_symbol (ld, __tcb_parse_hwcap_and_convert_at_platform, \
 #ifndef SHARED
 weak_alias (__tcb_parse_hwcap_and_convert_at_platform, \
 	    __parse_hwcap_and_convert_at_platform);
+weak_alias (__tcb_parse_hwcap_and_convert_at_platform, \
+	    __parse_hwcap_3_4_and_convert_at_platform);
 #endif

sysdeps/powerpc/nptl/tcb-offsets.sym

@@ -26,3 +26,4 @@ TCB_AT_PLATFORM			(offsetof (tcbhead_t, at_platform) - TLS_TCB_OFFSET - sizeof(t
 PADDING				(offsetof (tcbhead_t, padding) - TLS_TCB_OFFSET - sizeof(tcbhead_t))
 #endif
 TCB_HWCAP			(offsetof (tcbhead_t, hwcap) - TLS_TCB_OFFSET - sizeof (tcbhead_t))
+TCB_HWCAP_EXTN			(offsetof (tcbhead_t, hwcap_extn) - TLS_TCB_OFFSET - sizeof (tcbhead_t))

sysdeps/powerpc/nptl/tls.h

@@ -64,6 +64,9 @@
    are private.  */
 typedef struct
 {
+  /* Reservation for HWCAP3 and HWCAP4 data.  To be accessed by GCC in
+     __builtin_cpu_supports(), so it is a part of the public ABI.  */
+  uint64_t hwcap_extn;
   /* Reservation for HWCAP data.  To be accessed by GCC in
      __builtin_cpu_supports(), so it is a part of public ABI.  */
   uint64_t hwcap;
@@ -138,6 +141,7 @@ typedef struct
   ({ 									      \
     __thread_register = (void *) (tcbp) + TLS_TCB_OFFSET;		      \
     THREAD_SET_HWCAP (__tcb.hwcap);					      \
+    THREAD_SET_HWCAP_EXTN (__tcb.hwcap_extn);				      \
     THREAD_SET_AT_PLATFORM (__tcb.at_platform);				      \
     true;								      \
   })
@@ -147,6 +151,8 @@ typedef struct
     void *tp = (void *) (pd) + TLS_TCB_OFFSET + TLS_PRE_TCB_SIZE;	      \
     (((tcbhead_t *) ((char *) tp - TLS_TCB_OFFSET))[-1].hwcap) =	      \
       THREAD_GET_HWCAP ();						      \
+    (((tcbhead_t *) ((char *) tp - TLS_TCB_OFFSET))[-1].hwcap_extn) =	      \
+      THREAD_GET_HWCAP_EXTN ();						      \
     (((tcbhead_t *) ((char *) tp - TLS_TCB_OFFSET))[-1].at_platform) =	      \
       THREAD_GET_AT_PLATFORM ();
 
@@ -189,12 +195,17 @@ typedef struct
 		     + TLS_PRE_TCB_SIZE))[-1].pointer_guard		      \
      = THREAD_GET_POINTER_GUARD())
 
-/* hwcap field in TCB head.  */
+/* hwcap & hwcap_extn fields in TCB head.  */
 # define THREAD_GET_HWCAP() \
     (((tcbhead_t *) ((char *) __thread_register				      \
 		     - TLS_TCB_OFFSET))[-1].hwcap)
+# define THREAD_GET_HWCAP_EXTN() \
+    (((tcbhead_t *) ((char *) __thread_register				      \
+		     - TLS_TCB_OFFSET))[-1].hwcap_extn)
 # define THREAD_SET_HWCAP(value) \
     (THREAD_GET_HWCAP () = (value))
+# define THREAD_SET_HWCAP_EXTN(value) \
+    (THREAD_GET_HWCAP_EXTN () = (value))
 
 /* at_platform field in TCB head.  */
 # define THREAD_GET_AT_PLATFORM() \

sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist

@@ -8,3 +8,4 @@ GLIBC_2.34 __rtld_version_placeholder F
 GLIBC_2.35 __rseq_flags D 0x4
 GLIBC_2.35 __rseq_offset D 0x4
 GLIBC_2.35 __rseq_size D 0x4
+GLIBC_2.39 __parse_hwcap_3_4_and_convert_at_platform F

sysdeps/unix/sysv/linux/powerpc/powerpc64/be/ld.abilist

@@ -8,3 +8,4 @@ GLIBC_2.34 __rtld_version_placeholder F
 GLIBC_2.35 __rseq_flags D 0x4
 GLIBC_2.35 __rseq_offset D 0x8
 GLIBC_2.35 __rseq_size D 0x4
+GLIBC_2.39 __parse_hwcap_3_4_and_convert_at_platform F

sysdeps/unix/sysv/linux/powerpc/powerpc64/le/ld.abilist

@@ -8,3 +8,4 @@ GLIBC_2.34 __rtld_version_placeholder F
 GLIBC_2.35 __rseq_flags D 0x4
 GLIBC_2.35 __rseq_offset D 0x8
 GLIBC_2.35 __rseq_size D 0x4
+GLIBC_2.39 __parse_hwcap_3_4_and_convert_at_platform F