From 09247f8955f3cf868cfee2cc54b2b1b9e8f270b3 Mon Sep 17 00:00:00 2001
From: Sean Silva <chisophugis@gmail.com>
Date: Thu, 4 Feb 2016 21:41:07 +0000
Subject: [PATCH] Don't push relocation sections onto
 InputSection<ELFT>::Discarded.RelocSections

Summary:
LLVM3.3 (and earlier) would fail to include a relocation section in
the group that the section it was relocating is in. Object files
affected by this issue have been encountered in the wild when using LLD.

This would result in a siutation like:

  Section {
    Index: 5
    Name: .text._Z3fooIiEvv (6)
    Type: SHT_PROGBITS (0x1)
    Flags [ (0x206)
      SHF_ALLOC (0x2)
      SHF_EXECINSTR (0x4)
      SHF_GROUP (0x200)
    ]
    Address: 0x0
    Offset: 0x48
    Size: 5
    Link: 0
    Info: 0
    AddressAlignment: 1
    EntrySize: 0
  }
  Section {
    Index: 6
    Name: .rela.text._Z3fooIiEvv (1)
    Type: SHT_RELA (0x4)
    Flags [ (0x0)
    ]
    Address: 0x0
    Offset: 0x3F0
    Size: 24
    Link: 8
    Info: 5
    AddressAlignment: 8
    EntrySize: 24
  }

In LLD, during symbol resolution, we discard the section containing the
weak symbol, but this amounts to replacing it with
InputSection<ELFT>::Discarded.
When we later saw the corresponding relocation section, we would then
end up pusing onto InputSection<ELFT>::Discarded.RelocSections, which is
bogus.

Reviewers: ruiu, rafael

Subscribers: llvm-commits, Bigcheese

Differential Revision: http://reviews.llvm.org/D16898

llvm-svn: 259831
---
 lld/ELF/InputFiles.cpp                          |   5 +++++
 lld/test/ELF/Inputs/llvm33-rela-outside-group.o | Bin 0 -> 1032 bytes
 lld/test/ELF/llvm33-rela-outside-group.s        |  11 +++++++++++
 3 files changed, 16 insertions(+)
 create mode 100644 lld/test/ELF/Inputs/llvm33-rela-outside-group.o
 create mode 100644 lld/test/ELF/llvm33-rela-outside-group.s

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index cee398bd8a9c..21b385a8683d 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -214,6 +214,11 @@ void ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &ComdatGroups) {
         fatal("Invalid relocated section index");
       InputSectionBase<ELFT> *RelocatedSection =
           Sections[RelocatedSectionIndex];
+      // Strictly speaking, a relocation section must be included in the
+      // group of the section it relocates. However, LLVM 3.3 and earlier
+      // would fail to do so, so we gracefully handle that case.
+      if (RelocatedSection == &InputSection<ELFT>::Discarded)
+        continue;
       if (!RelocatedSection)
         fatal("Unsupported relocation reference");
       if (auto *S = dyn_cast<InputSection<ELFT>>(RelocatedSection)) {
diff --git a/lld/test/ELF/Inputs/llvm33-rela-outside-group.o b/lld/test/ELF/Inputs/llvm33-rela-outside-group.o
new file mode 100644
index 0000000000000000000000000000000000000000..2e2f2dc99ea3de3bd0c036976f945c0fc92c32e6
GIT binary patch
literal 1032
zcmbtTJ5B>Z4E1J#02Oqp5E325G*BY61wnw|0yJn=gpUMTv^zvlaSe{cF*pJx2S5Tp
zuP1UwQy{REvHkpc9?#}we0n%2ijq_c+NUBqM!y=n61$>R8cOaW`yYb2c5>%km^=k{
zalUiaG{?8&>68Q^S9cw`>$Z7(AlKb=p$)!fE9&Qa@h^Sw((GTy7FVxlI#h}+8@<H#
zg8EU9*vB3avvOn|W5>D(9k7A=*<v;D+xiX8$Bcii$J{diK#5gFe!Q6#<XVBB-U;zf
z9SHk@U`F(UhD3au?R0j;&v3Au^lEmd{CgZpMwi@?Hht5|71p?G%D>B4j{jZ3^xH`J
zwS88V*~!3{V+5YtB=GbVdb(0xZk`&Mo0)vfy*8iPd$n)L{s%QD-V?hW^6%@rmmk?^
BFwFn}

literal 0
HcmV?d00001

diff --git a/lld/test/ELF/llvm33-rela-outside-group.s b/lld/test/ELF/llvm33-rela-outside-group.s
new file mode 100644
index 000000000000..612753706f8a
--- /dev/null
+++ b/lld/test/ELF/llvm33-rela-outside-group.s
@@ -0,0 +1,11 @@
+// Input file generated with:
+// llvm33/llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %S/Inputs/llvm33-rela-outside-group.o
+//
+// RUN: ld.lld -shared %S/Inputs/llvm33-rela-outside-group.o %S/Inputs/llvm33-rela-outside-group.o
+
+	.global bar
+	.weak	_Z3fooIiEvv
+
+	.section	.text._Z3fooIiEvv,"axG",@progbits,_Z3fooIiEvv,comdat
+_Z3fooIiEvv:
+	callq	bar