From 81806c5d4d554a94b4e3db10a616ec51b1841d49 Mon Sep 17 00:00:00 2001 From: Momchil Velikov Date: Mon, 24 Jul 2017 09:19:32 +0000 Subject: [PATCH] [libunwind] Handle .ARM.exidx tables without sentinel last entry UnwindCursor::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 --- libunwind/src/UnwindCursor.hpp | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp index 5f9cba9ff764..6892f9639d81 100644 --- a/libunwind/src/UnwindCursor.hpp +++ b/libunwind/src/UnwindCursor.hpp @@ -744,14 +744,21 @@ bool UnwindCursor::getInfoFromEHABISection( EHABISectionIterator::begin(_addressSpace, sects); EHABISectionIterator end = EHABISectionIterator::end(_addressSpace, sects); + if (begin == end) + return false; EHABISectionIterator itNextPC = std::upper_bound(begin, end, pc); - if (itNextPC == begin || itNextPC == end) + if (itNextPC == begin) return false; EHABISectionIterator 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::max() + : itNextPC.functionAddress(); pint_t indexDataAddr = itThisPC.dataAddress(); if (indexDataAddr == 0)