commit a54f096265de8495917301d66702863aca4ff6dd
author Logan Chien <tzuhsiang.chien@gmail.com> Fri May 29 15:33:38 2015 +0000
committer Logan Chien <tzuhsiang.chien@gmail.com> Fri May 29 15:33:38 2015 +0000
tree d3bb2f04dbb3bcd420cb71c7a8a60e1cf695809d
parent 0c999a5b9accd00370c89341dc21a056989bb51e

libunwind: Fix unw_step() for ARM EHABI.

This commit fixes the unw_step() for ARM EHABI.  However, this commit
also changes the implementation details for ARM EHABI.

The first change is that the personality function should call
__gnu_unwind_frame() for default (or de facto) frame unwinding based on
the ARM-defined unwind opcode.  The function __gnu_unwind_frame() will
in turn calls unw_step() which actually unwinds the frame.

The second change is that the implementation _Unwind_Backtrace() should
no longer calls unw_step() to unwind the frame; since according to ARM
EHABI, the personality function should unwind the frame for us.

Special thanks to Anton for helpful suggestion on the initial version of
this patch.

llvm-svn: 238560
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 7fab97f364d2e2f0beb7fffa3e42885db72982d5

src/UnwindCursor.hpp

diff --git a/src/UnwindCursor.hpp b/src/UnwindCursor.hpp
index b4d413f..7703af9 100644
--- a/src/UnwindCursor.hpp
+++ b/src/UnwindCursor.hpp
@@ -440,6 +440,20 @@
 
 #if LIBCXXABI_ARM_EHABI
   bool getInfoFromEHABISection(pint_t pc, const UnwindInfoSections &sects);
+
+  int stepWithEHABI() {
+    size_t len = 0;
+    size_t off = 0;
+    // FIXME: Calling decode_eht_entry() here is violating the libunwind
+    // abstraction layer.
+    const uint32_t *ehtp =
+        decode_eht_entry(reinterpret_cast<const uint32_t *>(_info.unwind_info),
+                         &off, &len);
+    if (_Unwind_VRS_Interpret((_Unwind_Context *)this, ehtp, off, len) !=
+            _URC_CONTINUE_UNWIND)
+      return UNW_STEP_END;
+    return UNW_STEP_SUCCESS;
+  }
 #endif
 
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND
@@ -731,7 +745,7 @@
   //   isSingleWordEHT -- whether the entry is in the index.
   unw_word_t personalityRoutine = 0xbadf00d;
   bool scope32 = false;
-  uintptr_t lsda = 0xbadf00d;
+  uintptr_t lsda;
 
   // If the high bit in the exception handling table entry is set, the entry is
   // in compact form (section 6.3 EHABI).
@@ -744,16 +758,19 @@
         personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr0;
         extraWords = 0;
         scope32 = false;
+        lsda = isSingleWordEHT ? 0 : (exceptionTableAddr + 4);
         break;
       case 1:
         personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr1;
         extraWords = (exceptionTableData & 0x00ff0000) >> 16;
         scope32 = false;
+        lsda = exceptionTableAddr + (extraWords + 1) * 4;
         break;
       case 2:
         personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr2;
         extraWords = (exceptionTableData & 0x00ff0000) >> 16;
         scope32 = true;
+        lsda = exceptionTableAddr + (extraWords + 1) * 4;
         break;
       default:
         _LIBUNWIND_ABORT("unknown personality routine");
@@ -1281,7 +1298,7 @@
 #elif _LIBUNWIND_SUPPORT_DWARF_UNWIND
   result = this->stepWithDwarfFDE();
 #elif LIBCXXABI_ARM_EHABI
-  result = UNW_STEP_SUCCESS;
+  result = this->stepWithEHABI();
 #else
   #error Need _LIBUNWIND_SUPPORT_COMPACT_UNWIND or \
               _LIBUNWIND_SUPPORT_DWARF_UNWIND or \