x86/cet: Check legacy shadow stack applications

Add tests to verify that legacy shadow stack applications run properly
when shadow stack is enabled in Linux kernel.

sysdeps/x86/Makefile

@@ -162,6 +162,21 @@ tests-static += \
   tst-cet-legacy-10-static \
 # tests-static
 tst-cet-legacy-1a-ARGS = -- $(host-test-program-cmd)
+
+tests += \
+  tst-shstk-legacy-1a \
+  tst-shstk-legacy-1a-static \
+  tst-shstk-legacy-1b \
+  tst-shstk-legacy-1b-static \
+# tests
+tests-static += \
+  tst-shstk-legacy-1a-static \
+  tst-shstk-legacy-1b-static \
+# tests-static
+extra-objs += \
+  tst-shstk-legacy-1-extra.o \
+# extra-objs
+
 tests += \
   tst-cet-legacy-4a \
   tst-cet-legacy-4b \
@@ -212,6 +227,9 @@ CFLAGS-tst-cet-legacy-7.c += -fcf-protection=none
 CFLAGS-tst-cet-legacy-10.c += -mshstk
 CFLAGS-tst-cet-legacy-10-static.c += -mshstk
 
+CFLAGS-tst-shstk-legacy-1a.c += -fcf-protection=none
+CFLAGS-tst-shstk-legacy-1a-static.c += -fcf-protection=none
+
 $(objpfx)tst-cet-legacy-1: $(objpfx)tst-cet-legacy-mod-1.so \
 		       $(objpfx)tst-cet-legacy-mod-2.so
 $(objpfx)tst-cet-legacy-1a: $(objpfx)tst-cet-legacy-mod-1.so \
@@ -244,6 +262,11 @@ $(objpfx)tst-cet-legacy-6b.out: $(objpfx)tst-cet-legacy-mod-6a.so \
 tst-cet-legacy-6b-ENV = GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
 tst-cet-legacy-9-ENV = GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
 tst-cet-legacy-9-static-ENV = GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
+
+$(objpfx)tst-shstk-legacy-1a: $(objpfx)tst-shstk-legacy-1-extra.o
+$(objpfx)tst-shstk-legacy-1a-static: $(objpfx)tst-shstk-legacy-1-extra.o
+$(objpfx)tst-shstk-legacy-1b: $(objpfx)tst-shstk-legacy-1-extra.o
+$(objpfx)tst-shstk-legacy-1b-static: $(objpfx)tst-shstk-legacy-1-extra.o
 endif
 
 # Add -fcf-protection to CFLAGS when CET is enabled.

sysdeps/x86/tst-shstk-legacy-1-extra.S

@@ -0,0 +1,35 @@
+/* Legacy shadow stack code.
+   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/>.  */
+
+	.text
+	.globl	legacy
+	.type	legacy, @function
+legacy:
+	.cfi_startproc
+#ifdef __x86_64__
+	movq	(%rsp), %rax
+	addq	$8, %rsp
+	jmp	*%rax
+#else
+	movl	(%esp), %eax
+	addl	$4, %esp
+	jmp	*%eax
+#endif
+	.cfi_endproc
+	.size	legacy, .-legacy
+	.section	.note.GNU-stack,"",@progbits

sysdeps/x86/tst-shstk-legacy-1a-static.c

@@ -0,0 +1 @@
+#include "tst-shstk-legacy-1a.c"

sysdeps/x86/tst-shstk-legacy-1a.c

@@ -0,0 +1,32 @@
+/* Check that legacy shadow stack code won't trigger segfault.
+   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 <stdlib.h>
+#include <support/test-driver.h>
+
+/* Check that legacy shadow stack code won't trigger segfault.  */
+extern void legacy (void);
+
+static int
+do_test (void)
+{
+  legacy ();
+  return EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>

sysdeps/x86/tst-shstk-legacy-1b-static.c

@@ -0,0 +1 @@
+#include "tst-shstk-legacy-1b.c"

sysdeps/x86/tst-shstk-legacy-1b.c

@@ -0,0 +1,38 @@
+/* Check that legacy shadow stack code will trigger segfault.
+   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 <stdlib.h>
+#include <sys/platform/x86.h>
+#include <support/test-driver.h>
+#include <support/xsignal.h>
+
+/* Check that legacy shadow stack code will trigger segfault.  */
+extern void legacy (void);
+
+static int
+do_test (void)
+{
+  if (!CPU_FEATURE_ACTIVE (SHSTK))
+    return EXIT_UNSUPPORTED;
+
+  legacy ();
+  return EXIT_FAILURE;
+}
+
+#define EXPECTED_SIGNAL (CPU_FEATURE_ACTIVE (SHSTK) ? SIGSEGV : 0)
+#include <support/test-driver.c>