[PATCH] D55211: [LLD][ELF] - Support discarding the .dynamic section.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: ruiu, psmith.
Herald added subscribers: arichardson, emaste.
Herald added a reviewer: espindola.

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.


https://reviews.llvm.org/D55211

Files:
  ELF/LinkerScript.cpp
  ELF/Writer.cpp
  test/ELF/linkerscript/discard-section-err.s


Index: test/ELF/linkerscript/discard-section-err.s
===================================================================
--- test/ELF/linkerscript/discard-section-err.s
+++ test/ELF/linkerscript/discard-section-err.s
@@ -7,11 +7,6 @@
 # RUN:   FileCheck -check-prefix=SHSTRTAB %s
 # SHSTRTAB: discarding .shstrtab section is not allowed
 
-# 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: echo "SECTIONS { /DISCARD/ : { *(.dynsym) } }" > %t.script
 # RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
 # RUN:   FileCheck -check-prefix=DYNSYM %s
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -1621,7 +1621,7 @@
   // 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 @@
     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.
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -415,9 +415,8 @@
 
 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.RelaPlt || S == In.RelaDyn ||
-        S == In.RelrDyn)
+    if (S == In.ShStrTab || S == In.DynSymTab || S == In.DynStrTab ||
+        S == In.RelaPlt || 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


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