[ELF] Update addends in non-allocatable sections for REL targets when creating a relocatable output.

This fixes PR37735.

Differential Revision: https://reviews.llvm.org/D48929

1 files changed, 20 insertions, 1 deletions

diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 89b29294765..1f963e6ec5e 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -729,6 +729,23 @@ void InputSection::relocateNonAlloc(uint8_t *Buf, ArrayRef<RelTy> Rels) {
   }
 }
 
+// This is used when '-r' is given.
+// For REL targets, InputSection::copyRelocations() may store artificial
+// relocations aimed to update addends. They are handled in relocateAlloc()
+// for allocatable sections, and this function does the same for
+// non-allocatable sections, such as sections with debug information.
+static void relocateNonAllocForRelocatable(InputSection *Sec, uint8_t *Buf) {
+  const unsigned Bits = Config->Is64 ? 64 : 32;
+
+  for (const Relocation &Rel : Sec->Relocations) {
+    // InputSection::copyRelocations() adds only R_ABS relocations.
+    assert(Rel.Expr == R_ABS);
+    uint8_t *BufLoc = Buf + Rel.Offset + Sec->OutSecOff;
+    uint64_t TargetVA = SignExtend64(Rel.Sym->getVA(Rel.Addend), Bits);
+    Target->relocateOne(BufLoc, Rel.Type, TargetVA);
+  }
+}
+
 template <class ELFT>
 void InputSectionBase::relocate(uint8_t *Buf, uint8_t *BufEnd) {
   if (Flags & SHF_ALLOC) {
@@ -737,7 +754,9 @@ void InputSectionBase::relocate(uint8_t *Buf, uint8_t *BufEnd) {
   }
 
   auto *Sec = cast<InputSection>(this);
-  if (Sec->AreRelocsRela)
+  if (Config->Relocatable)
+    relocateNonAllocForRelocatable(Sec, Buf);
+  else if (Sec->AreRelocsRela)
     Sec->relocateNonAlloc<ELFT>(Buf, Sec->template relas<ELFT>());
   else
     Sec->relocateNonAlloc<ELFT>(Buf, Sec->template rels<ELFT>());