Revert "Revert "Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded""

This reverts commit 729111cf1824159bb4dd331cab8a829eab30313f.

Reverting the previous commit breaks other LLD buildbots.

llvm-svn: 362743

10 files changed, 100 insertions, 12 deletions

diff --git a/lld/ELF/DWARF.cpp b/lld/ELF/DWARF.cpp
index 6b90a038e87..6ebe7247e90 100644
--- a/lld/ELF/DWARF.cpp
+++ b/lld/ELF/DWARF.cpp
@@ -93,8 +93,11 @@ LLDDwarfObj<ELFT>::findAux(const InputSectionBase &Sec, uint64_t Pos,
   uint32_t SecIndex = File->getSectionIndex(Sym);
 
   // Broken debug info can point to a non-Defined symbol.
-  auto *DR = dyn_cast<Defined>(&File->getRelocTargetSym(Rel));
+  Symbol &S = File->getRelocTargetSym(Rel);
+  auto *DR = dyn_cast<Defined>(&S);
   if (!DR) {
+    if (S.isSection())
+      return None;
     RelType Type = Rel.getType(Config->IsMips64EL);
     if (Type != Target->NoneRel)
       error(toString(File) + ": relocation " + lld::toString(Type) + " at 0x" +
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 815a4ad4c2a..dd384788e34 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -1075,6 +1075,9 @@ template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
 
       if (ESym.st_shndx == SHN_UNDEF)
         this->Symbols[I] = make<Undefined>(this, Name, Binding, StOther, Type);
+      else if (Sec == &InputSection::Discarded)
+        this->Symbols[I] = make<Undefined>(this, Name, Binding, StOther, Type,
+                                           /*DiscardedSecIdx=*/SecIdx);
       else
         this->Symbols[I] =
             make<Defined>(this, Name, Binding, StOther, Type, Value, Size, Sec);
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index de9751722a3..832e02cb2a8 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -438,7 +438,8 @@ void InputSection::copyRelocations(uint8_t *Buf, ArrayRef<RelTy> Rels) {
       // hopefully creates a frame that is ignored at runtime.
       auto *D = dyn_cast<Defined>(&Sym);
       if (!D) {
-        error("STT_SECTION symbol should be defined");
+        warn("STT_SECTION symbol should be defined");
+        P->setSymbolAndType(0, 0, false);
         continue;
       }
       SectionBase *Section = D->Section->Repl;
diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 9eb10f940eb..d3cc608c1e2 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -679,9 +679,17 @@ static std::string maybeReportDiscarded(Undefined &Sym, InputSectionBase &Sec,
     return "";
   ArrayRef<Elf_Shdr_Impl<ELFT>> ObjSections =
       CHECK(File->getObj().sections(), File);
-  std::string Msg =
-      "relocation refers to a symbol in a discarded section: " + toString(Sym) +
-      "\n>>> defined in " + toString(File);
+
+  std::string Msg;
+  if (Sym.Type == ELF::STT_SECTION) {
+    Msg = "relocation refers to a discarded section: ";
+    Msg += CHECK(
+        File->getObj().getSectionName(&ObjSections[Sym.DiscardedSecIdx]), File);
+  } else {
+    Msg = "relocation refers to a symbol in a discarded section: " +
+          toString(Sym);
+  }
+  Msg += "\n>>> defined in " + toString(File);
 
   Elf_Shdr_Impl<ELFT> ELFSec = ObjSections[Sym.DiscardedSecIdx - 1];
   if (ELFSec.sh_type != SHT_GROUP)
diff --git a/lld/test/ELF/comdat-discarded-error.s b/lld/test/ELF/comdat-discarded-error.s
index 3584783cde0..0f6b417b0fa 100644
--- a/lld/test/ELF/comdat-discarded-error.s
+++ b/lld/test/ELF/comdat-discarded-error.s
@@ -5,7 +5,7 @@
 # RUN: echo '.section .text.foo,"axG",@progbits,foo,comdat; .globl bar; bar:' | \
 # RUN:   llvm-mc -filetype=obj -triple=x86_64 - -o %t3.o
 
-# RUN: not ld.lld %t1.o %t2.o %t3.o -o /dev/null 2>&1 | FileCheck %s
+# RUN: not ld.lld %t2.o %t3.o %t1.o -o /dev/null 2>&1 | FileCheck %s
 
 # CHECK:      error: relocation refers to a symbol in a discarded section: bar
 # CHECK-NEXT: >>> defined in {{.*}}3.o
@@ -13,6 +13,16 @@
 # CHECK-NEXT: >>> prevailing definition is in {{.*}}2.o
 # CHECK-NEXT: >>> referenced by {{.*}}1.o:(.text+0x1)
 
+# CHECK:      error: relocation refers to a discarded section: .text.foo
+# CHECK-NEXT: >>> defined in {{.*}}1.o
+# CHECK-NEXT: >>> section group signature: foo
+# CHECK-NEXT: >>> prevailing definition is in {{.*}}2.o
+# CHECK-NEXT: >>> referenced by {{.*}}1.o:(.data+0x0)
+
 .globl _start
 _start:
   jmp bar
+
+.section .text.foo,"axG",@progbits,foo,comdat
+.data
+  .quad .text.foo
diff --git a/lld/test/ELF/comdat-discarded-gdb-index.s b/lld/test/ELF/comdat-discarded-gdb-index.s
new file mode 100644
index 00000000000..43505960498
--- /dev/null
+++ b/lld/test/ELF/comdat-discarded-gdb-index.s
@@ -0,0 +1,63 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+# RUN: ld.lld --gdb-index %t.o %t.o -o %t
+
+## .debug_info has a relocation to .text.foo . The second %t.o is discarded.
+## Check we don't error on the relocation.
+# CHECK: .rela.debug_info {
+# CHECK-NEXT: 0xC R_X86_64_64 .text.foo 0x0
+
+.section .text.foo,"axG",@progbits,foo,comdat
+.globl foo
+.Lfunc_begin0:
+foo:
+  ret
+.Lfunc_end0:
+
+.section .debug_abbrev,"",@progbits
+  .byte   1       # Abbreviation Code
+  .byte   17      # DW_TAG_compile_unit
+  .byte   1       # DW_CHILDREN_yes
+  .byte   17      # DW_AT_low_pc
+  .byte   1       # DW_FORM_addr
+  .byte   18      # DW_AT_high_pc
+  .byte   6       # DW_FORM_data4
+  .ascii  "\264B" # DW_AT_GNU_pubnames
+  .byte   25      # DW_FORM_flag_present
+  .byte   0       # EOM(1)
+  .byte   0       # EOM(2)
+  .byte   2       # Abbreviation Code
+  .byte   46      # DW_TAG_subprogram
+  .byte   0       # DW_CHILDREN_no
+  .byte   3       # DW_AT_name
+  .byte   8       # DW_FORM_string
+  .byte   0       # EOM(1)
+  .byte   0       # EOM(2)
+  .byte   0
+
+.section .debug_info,"",@progbits
+.Lcu_begin0:
+  .long   .Lcu_end0 - .Lcu_begin0 - 4
+  .short  4              # DWARF version number
+  .long   0              # Offset Into Abbrev. Section
+  .byte   4              # Address Size
+.Ldie0:
+  .byte   1              # Abbrev [1] DW_TAG_compile_unit
+  .quad   .Lfunc_begin0  # DW_AT_low_pc
+  .long   .Lfunc_end0 - .Lfunc_begin0 # DW_AT_high_pc
+  .byte   2              # Abbrev [2] DW_TAG_subprogram
+  .asciz  "foo"          # DW_AT_name
+  .byte   0
+.Lcu_end0:
+
+.section .debug_gnu_pubnames,"",@progbits
+  .long   .LpubNames_end0 - .LpubNames_begin0
+.LpubNames_begin0:
+  .short  2              # Version
+  .long   .Lcu_begin0    # CU Offset
+  .long   .Lcu_end0 - .Lcu_begin0
+  .long   .Ldie0 - .Lcu_begin0
+  .byte   48             # Attributes: FUNCTION, EXTERNAL
+  .asciz  "foo"          # External Name
+  .long   0
+.LpubNames_end0:
diff --git a/lld/test/ELF/comdat-discarded-reloc.s b/lld/test/ELF/comdat-discarded-reloc.s
index d23baf386e9..d12732cd356 100644
--- a/lld/test/ELF/comdat-discarded-reloc.s
+++ b/lld/test/ELF/comdat-discarded-reloc.s
@@ -1,7 +1,7 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/comdat-discarded-reloc.s -o %t2.o
-# RUN: ld.lld -gc-sections %t.o %t2.o -o %t
+# RUN: ld.lld -gc-sections --noinhibit-exec %t.o %t2.o -o /dev/null
 
 ## ELF spec doesn't allow a relocation to point to a deduplicated
 ## COMDAT section. Unfortunately this happens in practice (e.g. .eh_frame)
diff --git a/lld/test/ELF/comdat.s b/lld/test/ELF/comdat.s
index 86103e5d9eb..9e3f5a81d30 100644
--- a/lld/test/ELF/comdat.s
+++ b/lld/test/ELF/comdat.s
@@ -1,7 +1,7 @@
 // REQUIRES: x86
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/comdat.s -o %t2.o
-// RUN: ld.lld -shared %t.o %t.o %t2.o -o %t
+// RUN: ld.lld -shared %t.o %t2.o -o %t
 // RUN: llvm-objdump -d %t | FileCheck %s
 // RUN: llvm-readobj -S --symbols %t | FileCheck --check-prefix=READ %s
 
@@ -31,9 +31,7 @@ foo:
 // CHECK-EMPTY:
 // CHECK-NEXT: bar:
 // 0x1000 - 0x1001 - 5 = -6
-// 0      - 0x1006 - 5 = -4107
 // CHECK-NEXT:   1001:	{{.*}}  callq  -6
-// CHECK-NEXT:   1006:	{{.*}}  callq  -4107
 
         .section .text3,"axG",@progbits,zed,comdat,unique,0
 
diff --git a/lld/test/ELF/invalid-undef-section-symbol.test b/lld/test/ELF/invalid-undef-section-symbol.test
index 1d66885eadf..80e5a1464d7 100644
--- a/lld/test/ELF/invalid-undef-section-symbol.test
+++ b/lld/test/ELF/invalid-undef-section-symbol.test
@@ -1,5 +1,5 @@
 # RUN: yaml2obj %s -o %t.o
-# RUN: not ld.lld -r %t.o -o /dev/null 2>&1 | FileCheck %s
+# RUN: not ld.lld -r --fatal-warnings %t.o -o /dev/null 2>&1 | FileCheck %s
 
 # We used to crash at this.
 # CHECK: STT_SECTION symbol should be defined
diff --git a/lld/test/ELF/relocatable-eh-frame.s b/lld/test/ELF/relocatable-eh-frame.s
index dee906acb87..6172dd355db 100644
--- a/lld/test/ELF/relocatable-eh-frame.s
+++ b/lld/test/ELF/relocatable-eh-frame.s
@@ -1,10 +1,12 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
-# RUN: ld.lld -r %t.o %t.o -o %t
+# RUN: ld.lld -r %t.o %t.o -o %t 2>&1 | FileCheck --check-prefix=WARN %s
 # RUN: llvm-readobj -r %t | FileCheck %s
 # RUN: ld.lld %t -o %t.so -shared
 # RUN: llvm-objdump -h %t.so | FileCheck --check-prefix=DSO %s
 
+# WARN: STT_SECTION symbol should be defined
+
 # DSO: .eh_frame     00000034
 
 # CHECK:      Relocations [