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, 46 insertions, 0 deletions

diff --git a/sysdeps/s390/cpu-features.h b/sysdeps/s390/cpu-features.h
new file mode 100644
index 0000000000..5e6b58f7c5
--- /dev/null
+++ b/sysdeps/s390/cpu-features.h
@@ -0,0 +1,46 @@
+/* Initialize cpu feature data.  s390x version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef __CPU_FEATURES_S390X_H
+# define __CPU_FEATURES_S390X_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_STFLE_MASK_ARCH13_MIE3 (1ULL << (63 - S390_STFLE_BITS_ARCH13_MIE3))
+
+
+#define S390_IS_ARCH13_MIE3(STFLE_BITS_ARRAY)			\
+  (((STFLE_BITS_ARRAY)[0] & S390_STFLE_MASK_ARCH13_MIE3) != 0)
+
+#define S390_IS_Z196(STFLE_BITS_ARRAY)			\
+  (((STFLE_BITS_ARRAY)[0] & (1ULL << (63 - S390_STFLE_BITS_Z196))) != 0)
+
+#define S390_IS_Z10(STFLE_BITS_ARRAY)				\
+  (((STFLE_BITS_ARRAY)[0] & (1ULL << (63 - S390_STFLE_BITS_Z10))) != 0)
+
+struct cpu_features
+{
+  unsigned long int hwcap;
+  unsigned long int __reserved_hwcap2;
+  unsigned long long stfle_bits[3];
+  unsigned long long __reserved[11];
+};
+
+#endif /* __CPU_FEATURES_S390X_H  */