[PATCH v2 1/8] newlib: libc: define M-profile PACBTI-enablement macros

Create an assembly header file that conditionally defines fuction
prologues/epilogues depending on the compile-time mbranch-protection
argument values.

* newlib/libc/machine/arm/pacbti.h: New.
---
 newlib/libc/machine/arm/pacbti.h | 64 ++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 newlib/libc/machine/arm/pacbti.h

diff --git a/newlib/libc/machine/arm/pacbti.h b/newlib/libc/machine/arm/pacbti.h
new file mode 100644
index 000000000..4c31d00bc
--- /dev/null
+++ b/newlib/libc/machine/arm/pacbti.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2022 Arm Ltd
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the company may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* Checki whether leaf function PAC signing has been requested
+   in the -mbranch-protect compile-time option.  */
+#define LEAF_PROTECT_BIT 2
+#define __HAVE_PAC_LEAF \
+	__ARM_FEATURE_PAC_DEFAULT & (1 << LEAF_PROTECT_BIT)
+
+/* Macro to handle function entry depending on branch-protection
+   schemes.  */
+	.macro pacbti_prologue
+#if __HAVE_PAC_LEAF
+#if __ARM_FEATURE_BTI_DEFAULT
+	pacbti ip, lr, sp
+#else
+	pac ip, lr, sp
+#endif /* __ARM_FEATURE_BTI_DEFAULT */
+	.cfi_register 143, 12
+	str ip, [sp, #-4]!
+	.save {ra_auth_code}
+	.cfi_def_cfa_offset 4
+	.cfi_offset 143, -4
+#elif __ARM_FEATURE_BTI_DEFAULT
+	bti
+#endif /* __HAVE_PAC_LEAF */
+	.endm
+
+/* Macro to handle different branch exchange cases depending on
+   branch-protection schemes.  */
+	.macro pacbti_epilogue
+#if __HAVE_PAC_LEAF
+	ldr ip, [sp], #4
+	.cfi_restore 143
+	.cfi_def_cfa_offset 0
+	aut ip, lr, sp
+#endif /* __HAVE_PAC_LEAF */
+	bx lr
+	.endm
-- 
2.36.1