[ELF] - Do not ignore discarding of .rela.plt/.rela.dyn, allow doing custom layout for them.

Currently when we build input sections list in linker script
we ignore all rel[a] sections. That was done to support
scripts like .rela.dyn : { *(.rela.data) } for emit relocs.

Though as a result following scripts were also silently ignored:

/DISCARD/ : { *(.rela.plt)
/DISCARD/ : { *(.rela.dyn)

and we produced output with this sections. That is not ideal.
The solution this patch suggests is simple: do not ignore synthetic
rel[a] sections. That way we can enable common discarding logic
for them and report a proper error.

Differential revision: https://reviews.llvm.org/D41640

llvm-svn: 328419

1 files changed, 5 insertions, 2 deletions

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index e16b49e785b..2240f7a0887 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -380,7 +380,10 @@ LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
       // For -emit-relocs we have to ignore entries like
       //   .rela.dyn : { *(.rela.data) }
       // which are common because they are in the default bfd script.
-      if (Sec->Type == SHT_REL || Sec->Type == SHT_RELA)
+      // We do not ignore SHT_REL[A] linker-synthesized sections here because
+      // want to support scripts that do custom layout for them.
+      if (!isa<SyntheticSection>(Sec) &&
+          (Sec->Type == SHT_REL || Sec->Type == SHT_RELA))
         continue;
 
       std::string Filename = getFilename(Sec->File);
@@ -405,7 +408,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
 void LinkerScript::discard(ArrayRef<InputSection *> V) {
   for (InputSection *S : V) {
     if (S == InX::ShStrTab || S == InX::Dynamic || S == InX::DynSymTab ||
-        S == InX::DynStrTab)
+        S == InX::DynStrTab || S == InX::RelaPlt || S == InX::RelaDyn)
       error("discarding " + S->Name + " section is not allowed");
 
     // You can discard .hash and .gnu.hash sections by linker scripts. Since