[RFC PATCH 2/2] x86: Alternative <sys/platform/x86.h> implementation

[Florian Weimer]

* H. J. Lu via Libc-alpha:

> You mentioned that the current <sys/platform.h> couldn't be used in
> IFUNC resolver with BIND_NOW.  Do you have a testcase?

This should do it.

From: Florian Weimer <fweimer@redhat.com>
Subject: x86: Add tst-ifunc-free

---
 sysdeps/x86/Makefile         |  2 +-
 sysdeps/x86/tst-ifunc-free.c | 49 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index 081cc72e93..ee2ae5f4a8 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -7,7 +7,7 @@ sysdep-dl-routines += dl-get-cpu-features
 sysdep_headers += sys/platform/x86.h
 
 tests += tst-get-cpu-features tst-get-cpu-features-static \
-	 tst-cpu-features-cpuinfo tst-cpu-features-supports
+	 tst-cpu-features-cpuinfo tst-cpu-features-supports tst-ifunc-free
 tests-static += tst-get-cpu-features-static
 endif
 
diff --git a/sysdeps/x86/tst-ifunc-free.c b/sysdeps/x86/tst-ifunc-free.c
new file mode 100644
index 0000000000..4a140ace0d
--- /dev/null
+++ b/sysdeps/x86/tst-ifunc-free.c
@@ -0,0 +1,49 @@
+/* IFUNC resolver using CPU_FEATURE_USABLE.
+   Copyright (C) 2020 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 <stdlib.h>
+#include <sys/platform/x86.h>
+
+static void
+free_fallback (void *ignored)
+{
+}
+
+static void
+free_rtm (void *ignored)
+{
+}
+
+static void
+(*ifunc_free (void))(void *)
+{
+  if (CPU_FEATURE_USABLE (RTM))
+    return free_rtm;
+  else
+    return free_fallback;
+}
+
+void free (void *) __attribute__ ((ifunc ("ifunc_free")));
+
+static int
+do_test (void)
+{
+  return 0;
+}
+
+#include <support/test-driver.c>