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S390: Influence hwcaps/stfle via GLIBC_TUNABLES.

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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.
This commit is contained in:
Stefan Liebler
2023-02-02 14:57:50 +01:00
parent 0b9d2d4a76
commit 41f67ccbe9
12 changed files with 423 additions and 64 deletions
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239
sysdeps/s390/cpu-features.c Normal file
View File

@@ -0,0 +1,239 @@
/* Initialize cpu feature data. s390x version.
Copyright (C) 2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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/>. */
#include <cpu-features.h>
#if HAVE_TUNABLES
# include <elf/dl-tunables.h>
# include <ifunc-memcmp.h>
# include <string.h>
extern __typeof (memcmp) MEMCMP_DEFAULT;
#endif
#if HAVE_TUNABLES
# define S390_COPY_CPU_FEATURES(SRC_PTR, DEST_PTR) \
(DEST_PTR)->hwcap = (SRC_PTR)->hwcap; \
(DEST_PTR)->stfle_bits[0] = (SRC_PTR)->stfle_bits[0];
static void
TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
{
/* The current IFUNC selection is always using the most recent
features which are available via AT_HWCAP or STFLE-bits. But in
some scenarios it is useful to adjust this selection.
The environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....
can be used to enable HWCAP/STFLE feature yyy, disable HWCAP/STFLE feature
xxx, where the feature name is case-sensitive and has to match the ones
used below. Furthermore, the ARCH-level zzz can be used to set various
HWCAP/STFLE features at once. */
/* Copy the features from dl_s390_cpu_features, which contains the features
provided by AT_HWCAP and stfle-instruction. */
struct cpu_features *cpu_features = &GLRO(dl_s390_cpu_features);
struct cpu_features cpu_features_orig;
S390_COPY_CPU_FEATURES (cpu_features, &cpu_features_orig);
struct cpu_features cpu_features_curr;
S390_COPY_CPU_FEATURES (cpu_features, &cpu_features_curr);
const char *token = valp->strval;
do
{
const char *token_end, *feature;
bool disable;
size_t token_len;
size_t feature_len;
/* Find token separator or end of string. */
for (token_end = token; *token_end != ','; token_end++)
if (*token_end == '\0')
break;
/* Determine feature. */
token_len = token_end - token;
if (*token == '-')
{
disable = true;
feature = token + 1;
feature_len = token_len - 1;
}
else
{
disable = false;
feature = token;
feature_len = token_len;
}
/* Handle only the features here which are really used in the
IFUNC-resolvers. All others are ignored as the values are only used
inside glibc. */
bool reset_features = false;
unsigned long int hwcap_mask = 0UL;
unsigned long long stfle_bits0_mask = 0ULL;
if ((*feature == 'z' || *feature == 'a'))
{
if ((feature_len == 5 && *feature == 'z'
&& MEMCMP_DEFAULT (feature, "zEC12", 5) == 0)
|| (feature_len == 6 && *feature == 'a'
&& MEMCMP_DEFAULT (feature, "arch10", 6) == 0))
{
reset_features = true;
disable = true;
hwcap_mask = HWCAP_S390_VXRS | HWCAP_S390_VXRS_EXT
| HWCAP_S390_VXRS_EXT2;
stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
}
else if ((feature_len == 3 && *feature == 'z'
&& MEMCMP_DEFAULT (feature, "z13", 3) == 0)
|| (feature_len == 6 && *feature == 'a'
&& MEMCMP_DEFAULT (feature, "arch11", 6) == 0))
{
reset_features = true;
disable = true;
hwcap_mask = HWCAP_S390_VXRS_EXT | HWCAP_S390_VXRS_EXT2;
stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
}
else if ((feature_len == 3 && *feature == 'z'
&& MEMCMP_DEFAULT (feature, "z14", 3) == 0)
|| (feature_len == 6 && *feature == 'a'
&& MEMCMP_DEFAULT (feature, "arch12", 6) == 0))
{
reset_features = true;
disable = true;
hwcap_mask = HWCAP_S390_VXRS_EXT2;
stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
}
else if ((feature_len == 3 && *feature == 'z'
&& (MEMCMP_DEFAULT (feature, "z15", 3) == 0
|| MEMCMP_DEFAULT (feature, "z16", 3) == 0))
|| (feature_len == 6
&& (MEMCMP_DEFAULT (feature, "arch13", 6) == 0
|| MEMCMP_DEFAULT (feature, "arch14", 6) == 0)))
{
/* For z15 or newer we don't have to disable something,
but we have to reset to the original values. */
reset_features = true;
}
}
else if (*feature == 'H')
{
if (feature_len == 15
&& MEMCMP_DEFAULT (feature, "HWCAP_S390_VXRS", 15) == 0)
{
hwcap_mask = HWCAP_S390_VXRS;
if (disable)
hwcap_mask |= HWCAP_S390_VXRS_EXT | HWCAP_S390_VXRS_EXT2;
}
else if (feature_len == 19
&& MEMCMP_DEFAULT (feature, "HWCAP_S390_VXRS_EXT", 19) == 0)
{
hwcap_mask = HWCAP_S390_VXRS_EXT;
if (disable)
hwcap_mask |= HWCAP_S390_VXRS_EXT2;
else
hwcap_mask |= HWCAP_S390_VXRS;
}
else if (feature_len == 20
&& MEMCMP_DEFAULT (feature, "HWCAP_S390_VXRS_EXT2", 20) == 0)
{
hwcap_mask = HWCAP_S390_VXRS_EXT2;
if (!disable)
hwcap_mask |= HWCAP_S390_VXRS | HWCAP_S390_VXRS_EXT;
}
}
else if (*feature == 'S')
{
if (feature_len == 10
&& MEMCMP_DEFAULT (feature, "STFLE_MIE3", 10) == 0)
{
stfle_bits0_mask = S390_STFLE_MASK_ARCH13_MIE3;
}
}
/* Perform the actions determined above. */
if (reset_features)
{
S390_COPY_CPU_FEATURES (&cpu_features_orig, &cpu_features_curr);
}
if (hwcap_mask != 0UL)
{
if (disable)
cpu_features_curr.hwcap &= ~hwcap_mask;
else
cpu_features_curr.hwcap |= hwcap_mask;
}
if (stfle_bits0_mask != 0ULL)
{
if (disable)
cpu_features_curr.stfle_bits[0] &= ~stfle_bits0_mask;
else
cpu_features_curr.stfle_bits[0] |= stfle_bits0_mask;
}
/* Jump over current token ... */
token += token_len;
/* ... and skip token separator for next round. */
if (*token == ',') token++;
}
while (*token != '\0');
/* Copy back the features after checking that no unsupported features were
enabled by user. */
cpu_features->hwcap = cpu_features_curr.hwcap & cpu_features_orig.hwcap;
cpu_features->stfle_bits[0] = cpu_features_curr.stfle_bits[0]
& cpu_features_orig.stfle_bits[0];
}
#endif
static inline void
init_cpu_features (struct cpu_features *cpu_features)
{
/* Fill cpu_features as passed by kernel and machine. */
cpu_features->hwcap = GLRO(dl_hwcap);
/* We want just 1 double word to be returned. */
if (__glibc_likely ((cpu_features->hwcap & HWCAP_S390_STFLE)
&& (cpu_features->hwcap & HWCAP_S390_ZARCH)
&& (cpu_features->hwcap & HWCAP_S390_HIGH_GPRS)))
{
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" (cpu_features->stfle_bits[0]),
"+d" (reg0)
: : "cc");
}
else
{
cpu_features->stfle_bits[0] = 0ULL;
}
#if HAVE_TUNABLES
TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));
#endif
}