commit d6c1e4853e21dae4d74a1681325369c35ae89a87
author Daniel Kiss <daniel.kiss@arm.com> Wed Sep 16 23:03:19 2020 +0200
committer Daniel Kiss <daniel.kiss@arm.com> Wed Sep 16 23:53:36 2020 +0200
tree 20747fcf1aa49aafe0d5a13b8ed41e88a1ab80b2
parent dd405c9869e43ffd63ceb9170c9abf679bd67a41

[libunwind] Support for leaf function unwinding.

Unwinding leaf function is useful in cases when the backtrace finds a
leaf function for example when it caused a signal.
This patch also add the support for the DW_CFA_undefined because it marks
the end of the frames.

Ryan Prichard provided code for the tests.

Reviewed By: #libunwind, mstorsjo

Differential Revision: https://reviews.llvm.org/D83573

Cr-Mirrored-From: https://chromium.googlesource.com/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 23bef7ee9923b1262326981960397e8cd95d6923

src/DwarfInstructions.hpp

diff --git a/src/DwarfInstructions.hpp b/src/DwarfInstructions.hpp
index ee98f53..c39cabe 100644
--- a/src/DwarfInstructions.hpp
+++ b/src/DwarfInstructions.hpp
@@ -93,7 +93,8 @@
 
   case CFI_Parser<A>::kRegisterInRegister:
     return registers.getRegister((int)savedReg.value);
-
+  case CFI_Parser<A>::kRegisterUndefined:
+    return 0;
   case CFI_Parser<A>::kRegisterUnused:
   case CFI_Parser<A>::kRegisterOffsetFromCFA:
     // FIX ME
@@ -117,6 +118,7 @@
 
   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
@@ -140,6 +142,7 @@
 
   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
@@ -190,6 +193,10 @@
                                     prolog.savedRegisters[i]));
           else
             return UNW_EBADREG;
+        } else if (i == (int)cieInfo.returnAddressRegister) {
+            // Leaf function keeps the return address in register and there is no
+            // explicit intructions how to restore it.
+            returnAddress = registers.getRegister(cieInfo.returnAddressRegister);
         }
       }
 

src/DwarfParser.hpp

diff --git a/src/DwarfParser.hpp b/src/DwarfParser.hpp
index c98c4f9..1ce2cf2 100644
--- a/src/DwarfParser.hpp
+++ b/src/DwarfParser.hpp
@@ -69,6 +69,7 @@
   };
   enum RegisterSavedWhere {
     kRegisterUnused,
+    kRegisterUndefined,
     kRegisterInCFA,
     kRegisterOffsetFromCFA,
     kRegisterInRegister,
@@ -503,7 +504,7 @@
                 "malformed DW_CFA_undefined DWARF unwind, reg too big");
         return false;
       }
-      results->setRegisterLocation(reg, kRegisterUnused, initialState);
+      results->setRegisterLocation(reg, kRegisterUndefined, initialState);
       _LIBUNWIND_TRACE_DWARF("DW_CFA_undefined(reg=%" PRIu64 ")\n", reg);
       break;
     case DW_CFA_same_value: