From: George Rimar <grimar@accesssoftek.com>
Date: Mon, 10 Dec 2018 09:24:49 +0000 (+0000)
Subject: [LLD][ELF] - Support discarding the .dynamic section.
X-Git-Tag: llvmorg-8.0.0-rc1~2483
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=1f958ed2693e889b6a02c7381578d2d202a1a409;p=platform%2Fupstream%2Fllvm.git

[LLD][ELF] - Support discarding the .dynamic section.

This is a part of https://bugs.llvm.org/show_bug.cgi?id=39810.

Seems it turns out that supporting /DISCARD/ for the .dynamic section with the
linker script is something we can do easily. The patch does this.

Differential revision: https://reviews.llvm.org/D55211

llvm-svn: 348749
---

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index e37b4a3..fbc0254 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -415,8 +415,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
 
 void LinkerScript::discard(ArrayRef<InputSection *> V) {
   for (InputSection *S : V) {
-    if (S == In.ShStrTab || S == In.Dynamic || S == In.RelaDyn ||
-        S == In.RelrDyn)
+    if (S == In.ShStrTab || S == In.RelaDyn || S == In.RelrDyn)
       error("discarding " + S->Name + " section is not allowed");
 
     // You can discard .hash and .gnu.hash sections by linker scripts. Since
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 64f4f65..5eed018 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1621,7 +1621,7 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
   // It should be okay as no one seems to care about the type.
   // Even the author of gold doesn't remember why gold behaves that way.
   // https://sourceware.org/ml/binutils/2002-03/msg00360.html
-  if (In.DynSymTab)
+  if (In.Dynamic->Parent)
     Symtab->addDefined("_DYNAMIC", STV_HIDDEN, STT_NOTYPE, 0 /*Value*/,
                        /*Size=*/0, STB_WEAK, In.Dynamic,
                        /*File=*/nullptr);
@@ -1935,9 +1935,8 @@ template <class ELFT> std::vector<PhdrEntry *> Writer<ELFT>::createPhdrs() {
     Ret.push_back(TlsHdr);
 
   // Add an entry for .dynamic.
-  if (In.DynSymTab)
-    AddHdr(PT_DYNAMIC, In.Dynamic->getParent()->getPhdrFlags())
-        ->add(In.Dynamic->getParent());
+  if (OutputSection *Sec = In.Dynamic->getParent())
+    AddHdr(PT_DYNAMIC, Sec->getPhdrFlags())->add(Sec);
 
   // PT_GNU_RELRO includes all sections that should be marked as
   // read-only by dynamic linker after proccessing relocations.
diff --git a/lld/test/ELF/linkerscript/discard-section-err.s b/lld/test/ELF/linkerscript/discard-section-err.s
index 82105b5..bb77dbb 100644
--- a/lld/test/ELF/linkerscript/discard-section-err.s
+++ b/lld/test/ELF/linkerscript/discard-section-err.s
@@ -7,10 +7,9 @@
 # RUN:   FileCheck -check-prefix=SHSTRTAB %s
 # SHSTRTAB: discarding .shstrtab section is not allowed
 
+## We allow discarding .dynamic, check we don't crash.
 # RUN: echo "SECTIONS { /DISCARD/ : { *(.dynamic) } }" > %t.script
-# RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
-# RUN:   FileCheck -check-prefix=DYNAMIC %s
-# DYNAMIC: discarding .dynamic section is not allowed
+# RUN: ld.lld -pie -o %t --script %t.script %t.o
 
 ## We allow discarding .dynsym, check we don't crash.
 # RUN: echo "SECTIONS { /DISCARD/ : { *(.dynsym) } }" > %t.script