[lld] r348749 - [LLD][ELF] - Support discarding the .dynamic section.

[George Rimar via llvm-commits]

Author: grimar
Date: Mon Dec 10 01:24:49 2018
New Revision: 348749

URL: http://llvm.org/viewvc/llvm-project?rev=348749&view=rev
Log:
[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

Modified:
    lld/trunk/ELF/LinkerScript.cpp
    lld/trunk/ELF/Writer.cpp
    lld/trunk/test/ELF/linkerscript/discard-section-err.s

Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=348749&r1=348748&r2=348749&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Mon Dec 10 01:24:49 2018
@@ -415,8 +415,7 @@ LinkerScript::computeInputSections(const
 
 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

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=348749&r1=348748&r2=348749&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Mon Dec 10 01:24:49 2018
@@ -1621,7 +1621,7 @@ template <class ELFT> void Writer<ELFT>:
   // 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<PhdrEn
     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.

Modified: lld/trunk/test/ELF/linkerscript/discard-section-err.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/discard-section-err.s?rev=348749&r1=348748&r2=348749&view=diff
==============================================================================
--- lld/trunk/test/ELF/linkerscript/discard-section-err.s (original)
+++ lld/trunk/test/ELF/linkerscript/discard-section-err.s Mon Dec 10 01:24:49 2018
@@ -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