x86/CET: Fix property note parser [BZ #23467]

GNU_PROPERTY_X86_FEATURE_1_AND may not be the first property item.  We
need to check each property item until we reach the end of the property
or find GNU_PROPERTY_X86_FEATURE_1_AND.

This patch adds 2 tests.  The first test checks if IBT is enabled and
the second test reads the output from the first test to check if IBT
is is enabled.  The second second test fails if IBT isn't enabled
properly.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	[BZ #23467]
	* sysdeps/unix/sysv/linux/x86/Makefile (tests): Add
	tst-cet-property-1 and tst-cet-property-2 if CET is enabled.
	(CFLAGS-tst-cet-property-1.o): New.
	(ASFLAGS-tst-cet-property-dep-2.o): Likewise.
	($(objpfx)tst-cet-property-2): Likewise.
	($(objpfx)tst-cet-property-2.out): Likewise.
	* sysdeps/unix/sysv/linux/x86/tst-cet-property-1.c: New file.
	* sysdeps/unix/sysv/linux/x86/tst-cet-property-2.c: Likewise.
	* sysdeps/unix/sysv/linux/x86/tst-cet-property-dep-2.S: Likewise.
	* sysdeps/x86/dl-prop.h (_dl_process_cet_property_note): Parse
	each property item until GNU_PROPERTY_X86_FEATURE_1_AND is found.

1 files changed, 44 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/x86/tst-cet-property-1.c b/sysdeps/unix/sysv/linux/x86/tst-cet-property-1.c
new file mode 100644
index 0000000000..21130faefc
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/tst-cet-property-1.c
@@ -0,0 +1,44 @@
+/* Test CET property note parser.
+   Copyright (C) 2018 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 <stdio.h>
+#include <elf.h>
+#include <tcb-offsets.h>
+
+/* This test prints out "IBT" if Intel indirect branch tracking (IBT)
+   is enabled at run-time, which is checked by tst-cet-property-2 to
+   verify that the IBT violation is caught on IBT machines.  */
+
+static int
+do_test (void)
+{
+  unsigned int feature_1;
+#ifdef __x86_64__
+# define SEG_REG "fs"
+#else
+# define SEG_REG "gs"
+#endif
+  asm ("movl %%" SEG_REG ":%P1, %0"
+       : "=r" (feature_1) : "i" (FEATURE_1_OFFSET));
+  if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
+    printf ("IBT\n");
+
+  return 0;
+}
+
+#include <support/test-driver.c>