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>

1 files changed, 128 insertions, 0 deletions

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>