S390: Influence hwcaps/stfle via GLIBC_TUNABLES.

This patch enables the option to influence hwcaps and stfle bits used
by the s390 specific ifunc-resolvers.  The currently x86-specific
tunable glibc.cpu.hwcaps is also used on s390x to achieve the task. In
addition the user can also set a CPU arch-level like z13 instead of
single HWCAP and STFLE features.

Note that the tunable only handles the features which are really used
in the IFUNC-resolvers.  All others are ignored as the values are only
used inside glibc.  Thus we can influence:
- HWCAP_S390_VXRS (z13)
- HWCAP_S390_VXRS_EXT (z14)
- HWCAP_S390_VXRS_EXT2 (z15)
- STFLE_MIE3 (z15)

The influenced hwcap/stfle-bits are stored in the s390-specific
cpu_features struct which also contains reserved fields for future
usage.

The ifunc-resolvers and users of stfle bits are adjusted to use the
information from cpu_features struct.

On 31bit, the ELF_MACHINE_IRELATIVE macro is now also defined.
Otherwise the new ifunc-resolvers segfaults as they depend on
the not yet processed_rtld_global_ro@GLIBC_PRIVATE relocation.

1 files changed, 8 insertions, 33 deletions

diff --git a/sysdeps/s390/multiarch/ifunc-resolve.h b/sysdeps/s390/multiarch/ifunc-resolve.h
index 4e1445d717..12b55da679 100644
--- a/sysdeps/s390/multiarch/ifunc-resolve.h
+++ b/sysdeps/s390/multiarch/ifunc-resolve.h
@@ -19,42 +19,17 @@
 
 #include <unistd.h>
 #include <dl-procinfo.h>
+#include <cpu-features.h>
 
-#define S390_STFLE_BITS_Z10  34 /* General instructions extension */
-#define S390_STFLE_BITS_Z196 45 /* Distinct operands, pop ... */
-#define S390_STFLE_BITS_ARCH13_MIE3 61 /* Miscellaneous-Instruction-Extensions
-					  Facility 3, e.g. mvcrl.  */
-
-#define S390_IS_ARCH13_MIE3(STFLE_BITS)			\
-  ((STFLE_BITS & (1ULL << (63 - S390_STFLE_BITS_ARCH13_MIE3))) != 0)
-
-#define S390_IS_Z196(STFLE_BITS)			\
-  ((STFLE_BITS & (1ULL << (63 - S390_STFLE_BITS_Z196))) != 0)
-
-#define S390_IS_Z10(STFLE_BITS)				\
-  ((STFLE_BITS & (1ULL << (63 - S390_STFLE_BITS_Z10))) != 0)
-
-#define S390_STORE_STFLE(STFLE_BITS)					\
-  /* We want just 1 double word to be returned.  */			\
-  register unsigned long reg0 __asm__("0") = 0;				\
-									\
-  __asm__ __volatile__(".machine push"        "\n\t"			\
-		       ".machine \"z9-109\""  "\n\t"			\
-		       ".machinemode \"zarch_nohighgprs\"\n\t"		\
-		       "stfle %0"             "\n\t"			\
-		       ".machine pop"         "\n"			\
-		       : "=QS" (STFLE_BITS), "+d" (reg0)		\
-		       : : "cc");
 #define s390_libc_ifunc_expr_stfle_init()				\
-  unsigned long long stfle_bits = 0ULL;					\
-  if (__glibc_likely ((hwcap & HWCAP_S390_STFLE)			\
-		      && (hwcap & HWCAP_S390_ZARCH)			\
-		      && (hwcap & HWCAP_S390_HIGH_GPRS)))		\
-    {									\
-      S390_STORE_STFLE (stfle_bits);					\
-    }
+  const unsigned long long *stfle_bits = features->stfle_bits;
+
+#define s390_libc_ifunc_expr_init()					\
+  const struct cpu_features *features = &GLRO(dl_s390_cpu_features);	\
+  /* The hwcap from kernel is passed as argument, but we		\
+     explicitly use the hwcaps from cpu-features struct.   */		\
+  hwcap = features->hwcap;
 
-#define s390_libc_ifunc_expr_init()
 #define s390_libc_ifunc_expr(TYPE_FUNC, FUNC, EXPR)		\
   __ifunc (TYPE_FUNC, FUNC, EXPR, unsigned long int hwcap,	\
 	   s390_libc_ifunc_expr_init);