[LLD][ELF] - Support discarding .dynstr section.

This is a part of https://bugs.llvm.org/show_bug.cgi?id=39810.
The patch allows discarding the .dynstr section using linker script.

Differential revision: https://reviews.llvm.org/D55215

llvm-svn: 348746

3 files changed, 12 insertions, 8 deletions

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 66ce07a2119..dad43d5b537 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -416,7 +416,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
 void LinkerScript::discard(ArrayRef<InputSection *> V) {
   for (InputSection *S : V) {
     if (S == In.ShStrTab || S == In.Dynamic || S == In.DynSymTab ||
-        S == In.DynStrTab || S == In.RelaDyn || S == In.RelrDyn)
+        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/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index a0dab238b4b..d3a7a273bef 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -1313,7 +1313,9 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
   if (!Config->Shared && !Config->Relocatable && !Config->ZRodynamic)
     addInt(DT_DEBUG, 0);
 
-  this->Link = In.DynStrTab->getParent()->SectionIndex;
+  if (OutputSection *Sec = In.DynStrTab->getParent())
+    this->Link = Sec->SectionIndex;
+
   if (!In.RelaDyn->empty()) {
     addInSec(In.RelaDyn->DynamicTag, In.RelaDyn);
     addSize(In.RelaDyn->SizeDynamicTag, In.RelaDyn->getParent());
@@ -1863,7 +1865,8 @@ static bool sortMipsSymbols(const SymbolTableEntry &L,
 }
 
 void SymbolTableBaseSection::finalizeContents() {
-  getParent()->Link = StrTabSec.getParent()->SectionIndex;
+  if (OutputSection *Sec = StrTabSec.getParent())
+    getParent()->Link = Sec->SectionIndex;
 
   if (this->Type != SHT_DYNSYM) {
     sortSymTabSymbols();
@@ -2685,7 +2688,8 @@ void VersionDefinitionSection::finalizeContents() {
   for (VersionDefinition &V : Config->VersionDefinitions)
     V.NameOff = In.DynStrTab->addString(V.Name);
 
-  getParent()->Link = In.DynStrTab->getParent()->SectionIndex;
+  if (OutputSection *Sec = In.DynStrTab->getParent())
+    getParent()->Link = Sec->SectionIndex;
 
   // sh_info should be set to the number of definitions. This fact is missed in
   // documentation, but confirmed by binutils community:
@@ -2829,7 +2833,8 @@ template <class ELFT> void VersionNeedSection<ELFT>::writeTo(uint8_t *Buf) {
 }
 
 template <class ELFT> void VersionNeedSection<ELFT>::finalizeContents() {
-  getParent()->Link = In.DynStrTab->getParent()->SectionIndex;
+  if (OutputSection *Sec = In.DynStrTab->getParent())
+    getParent()->Link = Sec->SectionIndex;
   getParent()->Info = Needed.size();
 }
 
diff --git a/lld/test/ELF/linkerscript/discard-section-err.s b/lld/test/ELF/linkerscript/discard-section-err.s
index 4238b0982f2..13dd688cf16 100644
--- a/lld/test/ELF/linkerscript/discard-section-err.s
+++ b/lld/test/ELF/linkerscript/discard-section-err.s
@@ -17,10 +17,9 @@
 # RUN:   FileCheck -check-prefix=DYNSYM %s
 # DYNSYM: discarding .dynsym section is not allowed
 
+## We allow discarding .dynstr, check we don't crash.
 # RUN: echo "SECTIONS { /DISCARD/ : { *(.dynstr) } }" > %t.script
-# RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
-# RUN:   FileCheck -check-prefix=DYNSTR %s
-# DYNSTR: discarding .dynstr section is not allowed
+# RUN: ld.lld -pie -o %t --script %t.script %t.o
 
 # RUN: echo "SECTIONS { /DISCARD/ : { *(.rela.dyn) } }" > %t.script
 # RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \