[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
llvm-svn: 308871
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 81806c5d4d554a94b4e3db10a616ec51b1841d49
diff --git a/src/UnwindCursor.hpp b/src/UnwindCursor.hpp
index 5f9cba9..6892f96 100644
--- a/src/UnwindCursor.hpp
+++ b/src/UnwindCursor.hpp
@@ -744,14 +744,21 @@
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)