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Fangrui Song ba51fd5664 Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded 
This restores r361830 "[ELF] Error on relocations to STT_SECTION symbols if the sections were discarded"
and dependent commits (r362218, r362497) which were reverted by r364321, with a fix of a --gdb-index issue.

.rela.debug_ranges contains relocations of range list entries:

    // start address of a range list entry
    // old: 0; after r361830: 0
    00000000000033a0 R_X86_64_64 .text._ZN2v88internal7Isolate7factoryEv + 0
    // end address of a range list entry
    // old: 0xe; after r361830: 0
    00000000000033a8 R_X86_64_64 .text._ZN2v88internal7Isolate7factoryEv + e

If both start and end addresses of a range list entry resolve to 0,
DWARFDebugRangeList::isEndOfListEntry() will return true, then the
.debug_range decoding loop will terminate prematurely:

    while (true) {
      decode StartAddress
      decode EndAddress
      if (Entry.isEndOfListEntry()) // prematurely
        break;
      Entries.push_back(Entry);
    }

In lld/ELF/SyntheticSections.cpp, readAddressAreas() will read
incomplete address ranges and the resulting .gdb_index will be
incomplete. For files that gdb hasn't loaded their debug info, gdb uses
.gdb_index to map addresses to CUs. The absent entries make gdb fail to
symbolize some addresses.

To address this issue, we simply allow relocations to undefined symbols
in DWARF.cpp:findAux() and let RelocationResolver resolve them.

This patch should fix:

[1] http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190603/659848.html
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=978067

llvm-svn: 364391
 		2019-06-26 08:09:08 +00:00
..
COFF Port r363962 to COFF: Deduplicate undefined symbol diagnostics 2019-06-25 09:55:55 +00:00
Common [lld] Allow args::getInterger to parse args larger than 2^31-1 2019-06-07 06:05:26 +00:00
ELF Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded 2019-06-26 08:09:08 +00:00
MinGW [MinGW] Support the --subsystem=val option in joined form 2019-06-14 17:50:39 +00:00
cmake/modules [CMake] Properly conditionalize installation of lld libraries 2018-03-09 13:09:36 +00:00
docs Add --undefined-glob which is an --undefined with wildcard pattern match 2019-06-14 14:00:59 +00:00
include/lld [lld] Allow args::getInterger to parse args larger than 2^31-1 2019-06-07 06:05:26 +00:00
lib Use llvm::stable_sort 2019-04-23 02:42:06 +00:00
test Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded 2019-06-26 08:09:08 +00:00
tools/lld Fix -DBUILD_SHARED_LIBS=on build after r362977 2019-06-11 01:50:58 +00:00
unittests Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
utils Python 2/3 compatibility 2019-03-20 07:42:13 +00:00
wasm [WebAssembly] Fix accidental omission from rLLD364367 2019-06-26 01:26:53 +00:00
.arcconfig [lld] Set up .arcconfig to point to new Diffusion LLD repository 2017-12-06 20:56:23 +00:00
.clang-format
…
.gitignore
…
CMakeLists.txt
…
CODE_OWNERS.TXT
…
LICENSE.TXT Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
README.md Note that the test .tar.xz has been updated. 2017-12-22 19:37:32 +00:00

README.md

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.