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, 9 insertions, 0 deletions

diff --git a/sysdeps/s390/s390-32/dl-machine.h b/sysdeps/s390/s390-32/dl-machine.h
index d09ab68..100a3e0 100644
--- a/sysdeps/s390/s390-32/dl-machine.h
+++ b/sysdeps/s390/s390-32/dl-machine.h
@@ -28,6 +28,9 @@
 #include <dl-irel.h>
 #include <dl-static-tls.h>
 #include <dl-machine-rel.h>
+#include <cpu-features.c>
+
+#define ELF_MACHINE_IRELATIVE       R_390_IRELATIVE
 
 /* This is an older, now obsolete value.  */
 #define EM_S390_OLD	0xA390
@@ -242,6 +245,12 @@ dl_platform_init (void)
   if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
     /* Avoid an empty string which would disturb us.  */
     GLRO(dl_platform) = NULL;
+
+#ifdef SHARED
+  /* init_cpu_features has been called early from __libc_start_main in
+     static executable.  */
+  init_cpu_features (&GLRO(dl_s390_cpu_features));
+#endif
 }
 
 static inline Elf32_Addr