Commit c68cac09 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r308871: 

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r308871 | chill | 2017-07-24 02:19:32 -0700 (Mon, 24 Jul 2017) | 17 lines

[libunwind] Handle .ARM.exidx tables without sentinel last entry

UnwindCursor<A, R>::getInfoFromEHABISection assumes the last
entry in the index table never corresponds to a real function.
Indeed, GNU ld always inserts an EXIDX_CANTUNWIND entry,
containing the end of the .text section. However, the EHABI specification
(http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf)
does not seem to contain text that requires the presence of a sentinel entry.
In that sense the libunwind implementation isn't compliant with the specification.

This patch makes getInfoFromEHABISection examine the last entry in the index
table if upper_bound returns the end iterator.

Fixes https://bugs.llvm.org/show_bug.cgi?id=31091

Differential revision: https://reviews.llvm.org/D35265

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llvm-svn: 309143
parent 819eb09f

libunwind/src/UnwindCursor.hpp

+9 −2
Original line number Diff line number Diff line
@@ -744,14 +744,21 @@ bool UnwindCursor<A, R>::getInfoFromEHABISection( 
      EHABISectionIterator<A>::begin(_addressSpace, sects);

  EHABISectionIterator<A> end =

      EHABISectionIterator<A>::end(_addressSpace, sects);

  if (begin == end)

    return false;



  EHABISectionIterator<A> itNextPC = std::upper_bound(begin, end, pc);

  if (itNextPC == begin || itNextPC == end)

  if (itNextPC == begin)

    return false;

  EHABISectionIterator<A> itThisPC = itNextPC - 1;



  pint_t thisPC = itThisPC.functionAddress();

  pint_t nextPC = itNextPC.functionAddress();

  // If an exception is thrown from a function, corresponding to the last entry

  // in the table, we don't really know the function extent and have to choose a

  // value for nextPC. Choosing max() will allow the range check during trace to

  // succeed.

  pint_t nextPC = (itNextPC == end) ? std::numeric_limits<pint_t>::max()

                                    : itNextPC.functionAddress();

  pint_t indexDataAddr = itThisPC.dataAddress();



  if (indexDataAddr == 0)