[libunwind][AArch64] Add support for DWARF expression for RA_SIGN_STATE.

Program may set the RA_SIGN_STATE pseudo register by expressions.
Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value
of the register which leads to runtime errors on PAC enabled systems.
In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the
DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions.

[1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1
[2] https://github.com/ARM-software/abi-aa/pull/129

Reviewed By: #libunwind, MaskRay

Differential Revision: https://reviews.llvm.org/D123692

1 files changed, 63 insertions, 0 deletions

diff --git a/libunwind/test/aarch64.ra_sign_state.pass.cpp b/libunwind/test/aarch64.ra_sign_state.pass.cpp
new file mode 100644
index 000000000000..1e09c936d664
--- /dev/null
+++ b/libunwind/test/aarch64.ra_sign_state.pass.cpp
@@ -0,0 +1,63 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: linux && target={{aarch64-.+}}
+
+// This test ensures the .cfi_negate_ra_state the RA_SIGN_STATE pseudo register
+// could be set directly set by a DWARF expression and the unwinder handles it
+// correctly. The two directives can't be mixed in one CIE/FDE sqeuence.
+
+#include <stdlib.h>
+
+__attribute__((noinline, target("branch-protection=pac-ret+leaf")))
+void bar() {
+  // ".cfi_negate_ra_state" is emitted by the compiler.
+  throw 1;
+}
+
+__attribute__((noinline, target("branch-protection=none")))
+void foo() {
+  // Here a DWARF expression sets RA_SIGN_STATE.
+  // The LR is signed manually and stored on the stack.
+  asm volatile(
+      ".cfi_escape 0x16,"    // DW_CFA_val_expression
+                    "34,"    // REG_34(RA_SIGN_STATE)
+                     "1,"    // expression_length(1)
+                    "0x31\n" // DW_OP_lit1
+      "add sp, sp, 16\n"     // Restore SP's value before the stack frame is
+                             // created.
+      "paciasp\n"            // Sign the LR.
+      "str lr, [sp, -0x8]\n" // Overwrite LR on the stack.
+      "sub sp, sp, 16\n"     // Restore SP's value.
+  );
+  bar();
+  _Exit(-1);
+}
+
+__attribute__((noinline, target("branch-protection=pac-ret")))
+void bazz() {
+  // ".cfi_negate_ra_state" is emitted by the compiler.
+  try {
+    foo();
+  } catch (int i) {
+    if (i == 1)
+      throw i;
+    throw 2;
+  }
+}
+
+int main() {
+  try {
+    bazz();
+  } catch (int i) {
+    if (i == 1)
+      _Exit(0);
+  }
+  return -1;
+}