PowerPC: Influence cpu/arch hwcap features via GLIBC_TUNABLES

This patch enables the option to influence hwcaps used by PowerPC.
The environment variable, GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,-zzz....,
can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature xxx
and zzz, where the feature name is case-sensitive and has to match the ones
mentioned in the file{sysdeps/powerpc/dl-procinfo.c}.

Note that the hwcap tunables only used in the IFUNC selection.
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

4 files changed, 390 insertions, 3 deletions

diff --git a/sysdeps/unix/sysv/linux/powerpc/Makefile b/sysdeps/unix/sysv/linux/powerpc/Makefile
index 93783cae00..24827efe79 100644
--- a/sysdeps/unix/sysv/linux/powerpc/Makefile
+++ b/sysdeps/unix/sysv/linux/powerpc/Makefile
@@ -23,9 +23,14 @@ ifeq ($(subdir),misc)
 sysdep_headers += bits/ppc.h
 sysdep_routines += get_timebase_freq
 tests-static += test-gettimebasefreq-static
-tests += $(tests-static)
-tests += test-gettimebasefreq
-tests += test-powerpc-linux-sysconf
+tests += \
+  $(tests-static) \
+  test-gettimebasefreq \
+  test-powerpc-linux-sysconf \
+  tst-hwcap-tunables \
+  # tests
+
+tst-hwcap-tunables-ARGS = -- $(host-test-program-cmd)
 endif
 
 ifeq ($(subdir),csu)
diff --git a/sysdeps/unix/sysv/linux/powerpc/cpu-features.c b/sysdeps/unix/sysv/linux/powerpc/cpu-features.c
new file mode 100644
index 0000000000..7c6e20e702
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/cpu-features.c
@@ -0,0 +1,124 @@
+/* Initialize cpu feature data.  PowerPC version.
+   Copyright (C) 2017-2023 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 <array_length.h>
+#include <stdint.h>
+#include <cpu-features.h>
+#include <elf/dl-tunables.h>
+#include <unistd.h>
+#include <string.h>
+
+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 AT_HWCAP2.  But in
+     some scenarios it is useful to adjust this selection.
+
+     The environment variable:
+
+     GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,....
+
+     Can be used to enable HWCAP/HWCAP2 feature yyy, disable HWCAP/HWCAP2
+     feature xxx, where the feature name is case-sensitive and has to match
+     the ones mentioned in the file{sysdeps/powerpc/dl-procinfo.c}. */
+
+  /* Copy the features from dl_powerpc_cpu_features, which contains the
+     features provided by AT_HWCAP and AT_HWCAP2.  */
+  struct cpu_features *cpu_features = &GLRO(dl_powerpc_cpu_features);
+  unsigned long int tcbv_hwcap = cpu_features->hwcap;
+  unsigned long int tcbv_hwcap2 = cpu_features->hwcap2;
+  const char *token = valp->strval;
+  do
+    {
+      const char *token_end, *feature;
+      bool disable;
+      size_t token_len, i, feature_len, offset = 0;
+      /* 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;
+	}
+      for (i = 0; i < array_length (hwcap_tunables); ++i)
+	{
+	  const char *hwcap_name = hwcap_names + offset;
+	  size_t hwcap_name_len = strlen (hwcap_name);
+	  /* Check the tunable name on the supported list.  */
+	  if (hwcap_name_len == feature_len
+	      && memcmp (feature, hwcap_name, feature_len) == 0)
+	    {
+	      /* Update the hwcap and hwcap2 bits.  */
+	      if (disable)
+		{
+		  /* Id is 1 for hwcap2 tunable.  */
+		  if (hwcap_tunables[i].id)
+		    cpu_features->hwcap2 &= ~(hwcap_tunables[i].mask);
+		  else
+		    cpu_features->hwcap &= ~(hwcap_tunables[i].mask);
+		}
+	      else
+		{
+		  /* Enable the features and also check that no unsupported
+		     features were enabled by user.  */
+		  if (hwcap_tunables[i].id)
+		    cpu_features->hwcap2 |= (tcbv_hwcap2 & hwcap_tunables[i].mask);
+		  else
+		    cpu_features->hwcap |= (tcbv_hwcap & hwcap_tunables[i].mask);
+		}
+	      break;
+	    }
+	  offset += hwcap_name_len + 1;
+	}
+	token += token_len;
+	/* ... and skip token separator for next round.  */
+	if (*token == ',')
+	  token++;
+    }
+  while (*token != '\0');
+}
+
+static inline void
+init_cpu_features (struct cpu_features *cpu_features, uint64_t hwcaps[])
+{
+  /* Fill the cpu_features with the supported hwcaps
+     which are set by __tcb_parse_hwcap_and_convert_at_platform.  */
+  cpu_features->hwcap = hwcaps[0];
+  cpu_features->hwcap2 = hwcaps[1];
+  /* Default is to use aligned memory access on optimized function unless
+     tunables is enable, since for this case user can explicit disable
+     unaligned optimizations.  */
+  int32_t cached_memfunc = TUNABLE_GET (glibc, cpu, cached_memopt, int32_t,
+					NULL);
+  cpu_features->use_cached_memopt = (cached_memfunc > 0);
+  TUNABLE_GET (glibc, cpu, hwcaps, tunable_val_t *,
+	       TUNABLE_CALLBACK (set_hwcaps));
+}
diff --git a/sysdeps/unix/sysv/linux/powerpc/cpu-features.h b/sysdeps/unix/sysv/linux/powerpc/cpu-features.h
new file mode 100644
index 0000000000..e5fce88e5e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/cpu-features.h
@@ -0,0 +1,130 @@
+/* Initialize cpu feature data.  PowerPC version.
+   Copyright (C) 2017-2023 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_POWERPC_H
+# define __CPU_FEATURES_POWERPC_H
+
+#include <stdbool.h>
+#include <sys/auxv.h>
+
+struct cpu_features
+{
+  bool use_cached_memopt;
+  unsigned long int hwcap;
+  unsigned long int hwcap2;
+};
+
+static const char hwcap_names[] = {
+  "4xxmac\0"
+  "altivec\0"
+  "arch_2_05\0"
+  "arch_2_06\0"
+  "archpmu\0"
+  "booke\0"
+  "cellbe\0"
+  "dfp\0"
+  "efpdouble\0"
+  "efpsingle\0"
+  "fpu\0"
+  "ic_snoop\0"
+  "mmu\0"
+  "notb\0"
+  "pa6t\0"
+  "power4\0"
+  "power5\0"
+  "power5+\0"
+  "power6x\0"
+  "ppc32\0"
+  "ppc601\0"
+  "ppc64\0"
+  "ppcle\0"
+  "smt\0"
+  "spe\0"
+  "true_le\0"
+  "ucache\0"
+  "vsx\0"
+  "arch_2_07\0"
+  "dscr\0"
+  "ebb\0"
+  "htm\0"
+  "htm-nosc\0"
+  "htm-no-suspend\0"
+  "isel\0"
+  "tar\0"
+  "vcrypto\0"
+  "arch_3_00\0"
+  "ieee128\0"
+  "darn\0"
+  "scv\0"
+  "arch_3_1\0"
+  "mma\0"
+};
+
+static const struct
+{
+  unsigned int mask;
+  bool id;
+} hwcap_tunables[] = {
+   /* AT_HWCAP tunable masks.  */
+   { PPC_FEATURE_HAS_4xxMAC,                 0 },
+   { PPC_FEATURE_HAS_ALTIVEC,                0 },
+   { PPC_FEATURE_ARCH_2_05,                  0 },
+   { PPC_FEATURE_ARCH_2_06,                  0 },
+   { PPC_FEATURE_PSERIES_PERFMON_COMPAT,     0 },
+   { PPC_FEATURE_BOOKE,                      0 },
+   { PPC_FEATURE_CELL_BE,                    0 },
+   { PPC_FEATURE_HAS_DFP,                    0 },
+   { PPC_FEATURE_HAS_EFP_DOUBLE,             0 },
+   { PPC_FEATURE_HAS_EFP_SINGLE,             0 },
+   { PPC_FEATURE_HAS_FPU,                    0 },
+   { PPC_FEATURE_ICACHE_SNOOP,               0 },
+   { PPC_FEATURE_HAS_MMU,                    0 },
+   { PPC_FEATURE_NO_TB,                      0 },
+   { PPC_FEATURE_PA6T,                       0 },
+   { PPC_FEATURE_POWER4,                     0 },
+   { PPC_FEATURE_POWER5,                     0 },
+   { PPC_FEATURE_POWER5_PLUS,                0 },
+   { PPC_FEATURE_POWER6_EXT,                 0 },
+   { PPC_FEATURE_32,                         0 },
+   { PPC_FEATURE_601_INSTR,                  0 },
+   { PPC_FEATURE_64,                         0 },
+   { PPC_FEATURE_PPC_LE,                     0 },
+   { PPC_FEATURE_SMT,                        0 },
+   { PPC_FEATURE_HAS_SPE,                    0 },
+   { PPC_FEATURE_TRUE_LE,                    0 },
+   { PPC_FEATURE_UNIFIED_CACHE,              0 },
+   { PPC_FEATURE_HAS_VSX,                    0 },
+
+   /* AT_HWCAP2 tunable masks.  */
+   { PPC_FEATURE2_ARCH_2_07,                 1 },
+   { PPC_FEATURE2_HAS_DSCR,                  1 },
+   { PPC_FEATURE2_HAS_EBB,                   1 },
+   { PPC_FEATURE2_HAS_HTM,                   1 },
+   { PPC_FEATURE2_HTM_NOSC,                  1 },
+   { PPC_FEATURE2_HTM_NO_SUSPEND,            1 },
+   { PPC_FEATURE2_HAS_ISEL,                  1 },
+   { PPC_FEATURE2_HAS_TAR,                   1 },
+   { PPC_FEATURE2_HAS_VEC_CRYPTO,            1 },
+   { PPC_FEATURE2_ARCH_3_00,                 1 },
+   { PPC_FEATURE2_HAS_IEEE128,               1 },
+   { PPC_FEATURE2_DARN,                      1 },
+   { PPC_FEATURE2_SCV,                       1 },
+   { PPC_FEATURE2_ARCH_3_1,                  1 },
+   { PPC_FEATURE2_MMA,                       1 },
+};
+
+#endif /* __CPU_FEATURES_H  */
diff --git a/sysdeps/unix/sysv/linux/powerpc/tst-hwcap-tunables.c b/sysdeps/unix/sysv/linux/powerpc/tst-hwcap-tunables.c
new file mode 100644
index 0000000000..2631016a3a
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/tst-hwcap-tunables.c
@@ -0,0 +1,128 @@
+/* Tests for powerpc GLIBC_TUNABLES=glibc.cpu.hwcaps filter.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <array_length.h>
+#include <getopt.h>
+#include <ifunc-impl-list.h>
+#include <spawn.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xunistd.h>
+#include <sys/auxv.h>
+#include <sys/wait.h>
+
+/* Nonzero if the program gets called via `exec'.  */
+#define CMDLINE_OPTIONS \
+  { "restart", no_argument, &restart, 1 },
+static int restart;
+
+/* Hold the four initial argument used to respawn the process, plus the extra
+   '--direct', '--restart', and the function to check  */
+static char *spargs[8];
+static int fc;
+
+/* Called on process re-execution.  */
+_Noreturn static void
+handle_restart (int argc, char *argv[])
+{
+  TEST_VERIFY_EXIT (argc == 1);
+  const char *funcname = argv[0];
+
+  struct libc_ifunc_impl impls[32];
+  int cnt = __libc_ifunc_impl_list ("memcpy", impls, array_length (impls));
+  if (cnt == 0)
+    _exit (EXIT_SUCCESS);
+  TEST_VERIFY_EXIT (cnt >= 1);
+  for (int i = 0; i < cnt; i++) {
+    if (strcmp (impls[i].name, funcname) == 0)
+      {
+	TEST_COMPARE (impls[i].usable, false);
+	break;
+      }
+  }
+
+  _exit (EXIT_SUCCESS);
+}
+
+static void
+run_test (const char *filter, const char *funcname)
+{
+  printf ("info: checking filter %s (expect %s ifunc selection to be removed)\n",
+	  filter, funcname);
+  char *tunable = xasprintf ("GLIBC_TUNABLES=glibc.cpu.hwcaps=%s", filter);
+  char *const newenvs[] = { (char*) tunable, NULL };
+  spargs[fc] = (char *) funcname;
+
+  pid_t pid;
+  TEST_COMPARE (posix_spawn (&pid, spargs[0], NULL, NULL, spargs, newenvs), 0);
+  int status;
+  TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
+  TEST_VERIFY (WIFEXITED (status));
+  TEST_VERIFY (!WIFSIGNALED (status));
+  TEST_COMPARE (WEXITSTATUS (status), 0);
+
+  free (tunable);
+}
+
+static int
+do_test (int argc, char *argv[])
+{
+  if (restart)
+    handle_restart (argc - 1, &argv[1]);
+
+  TEST_VERIFY_EXIT (argc == 2 || argc == 5);
+
+  int i;
+  for (i = 0; i < argc - 1; i++)
+    spargs[i] = argv[i + 1];
+  spargs[i++] = (char *) "--direct";
+  spargs[i++] = (char *) "--restart";
+  fc = i++;
+  spargs[i] = NULL;
+
+  unsigned long int hwcap = getauxval (AT_HWCAP);
+  unsigned long int hwcap2 = getauxval (AT_HWCAP2);
+  if (__WORDSIZE == 64)
+    {
+      if (hwcap2 & PPC_FEATURE2_ARCH_3_1)
+	run_test ("-arch_3_1", "__memcpy_power10");
+      if (hwcap2 & PPC_FEATURE2_ARCH_2_07)
+	run_test ("-arch_2_07", "__memcpy_power8_cached");
+      if (hwcap & PPC_FEATURE_ARCH_2_06)
+	run_test ("-arch_2_06", "__memcpy_power7");
+      if (hwcap & PPC_FEATURE_ARCH_2_05)
+	run_test ("-arch_2_06,-arch_2_05","__memcpy_power6");
+      run_test ("-arch_2_06,-arch_2_05,-power5+,-power5,-power4", "__memcpy_power4");
+    }
+  else
+    {
+      if (hwcap & PPC_FEATURE_HAS_VSX)
+	run_test ("-vsx", "__memcpy_power7");
+      if (hwcap & PPC_FEATURE_ARCH_2_06)
+	run_test ("-arch_2_06", "__memcpy_a2");
+      if (hwcap & PPC_FEATURE_ARCH_2_05)
+	run_test ("-arch_2_05", "__memcpy_power6");
+    }
+  return 0;
+}
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>