[libunwind] 77aa9ca - [libunwind] Support cfi_undefined and cfi_register for float registers.

[Daniel Kiss via cfe-commits]

Author: Daniel Kiss
Date: 2021-09-27T12:04:02+02:00
New Revision: 77aa9ca92ae4732f5f92e580e14bb4d757f6b364

URL: https://github.com/llvm/llvm-project/commit/77aa9ca92ae4732f5f92e580e14bb4d757f6b364
DIFF: https://github.com/llvm/llvm-project/commit/77aa9ca92ae4732f5f92e580e14bb4d757f6b364.diff

LOG:  [libunwind] Support cfi_undefined and cfi_register for float registers.

During a backtrace the `.cfi_undefined` for a float register causes an assert in libunwind.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D110144

Added: 
    libunwind/test/floatregister.pass.cpp

Modified: 
    libunwind/src/DwarfInstructions.hpp

Removed: 
    


################################################################################
diff  --git a/libunwind/src/DwarfInstructions.hpp b/libunwind/src/DwarfInstructions.hpp
index 60b242e0c143..53baf6a148f3 100644
--- a/libunwind/src/DwarfInstructions.hpp
+++ b/libunwind/src/DwarfInstructions.hpp
@@ -115,12 +115,13 @@ double DwarfInstructions<A, R>::getSavedFloatRegister(
     return addressSpace.getDouble(
         evaluateExpression((pint_t)savedReg.value, addressSpace,
                             registers, cfa));
-
+  case CFI_Parser<A>::kRegisterInRegister:
+    return registers.getFloatRegister((int)savedReg.value);
+  case CFI_Parser<A>::kRegisterUndefined:
+    return 0.0;
   case CFI_Parser<A>::kRegisterIsExpression:
   case CFI_Parser<A>::kRegisterUnused:
-  case CFI_Parser<A>::kRegisterUndefined:
   case CFI_Parser<A>::kRegisterOffsetFromCFA:
-  case CFI_Parser<A>::kRegisterInRegister:
     // FIX ME
     break;
   }

diff  --git a/libunwind/test/floatregister.pass.cpp b/libunwind/test/floatregister.pass.cpp
new file mode 100644
index 000000000000..64107e6d490b
--- /dev/null
+++ b/libunwind/test/floatregister.pass.cpp
@@ -0,0 +1,51 @@
+// -*- 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-.+}}
+
+// Basic test for float registers number are accepted.
+
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unwind.h>
+
+_Unwind_Reason_Code frame_handler(struct _Unwind_Context *ctx, void *arg) {
+  (void)arg;
+  Dl_info info = {0, 0, 0, 0};
+
+  // Unwind util the main is reached, above frames depend on the platform and
+  // architecture.
+  if (dladdr(reinterpret_cast<void *>(_Unwind_GetIP(ctx)), &info) &&
+      info.dli_sname && !strcmp("main", info.dli_sname))
+    _Exit(0);
+
+  return _URC_NO_REASON;
+}
+
+__attribute__((noinline)) void foo() {
+  // Provide some CFI directives that instructs the unwinder where given
+  // float register is.
+#if defined(__aarch64__)
+  // DWARF register number for V0-V31 registers are 64-95.
+  // Previous value of V0 is saved at offset 0 from CFA.
+  asm volatile(".cfi_offset 64, 0");
+  // From now on the previous value of register can't be restored anymore.
+  asm volatile(".cfi_undefined 65");
+  asm volatile(".cfi_undefined 95");
+  // Previous value of V2 is in V30.
+  asm volatile(".cfi_register  66, 94");
+#endif
+  _Unwind_Backtrace(frame_handler, NULL);
+}
+
+int main() {
+  foo();
+  return -2;
+}