[ELF] - do not create special symbols when creating relocatable output

__start_/__end_ <section-name> symbols and other specials like:
preinit_array_start/end
init_array_start/end
fini_array_start/end

should not be created by linker when creating relocatable files.

Differential revision: http://reviews.llvm.org/D17774

llvm-svn: 262366

lld/ELF/Writer.cpp

@@ -1001,9 +1001,11 @@ template <class ELFT> bool Writer<ELFT>::createSections() {
   // The linker needs to define SECNAME_start, SECNAME_end and SECNAME_stop
   // symbols for sections, so that the runtime can get the start and end
   // addresses of each section by section name. Add such symbols.
-  addStartEndSymbols();
+  if (!Config->Relocatable) {
-  for (OutputSectionBase<ELFT> *Sec : RegularSections)
+    addStartEndSymbols();
-    addStartStopSymbols(Sec);
+    for (OutputSectionBase<ELFT> *Sec : RegularSections)
+      addStartStopSymbols(Sec);
+  }
   if (isOutputDynamic())
     Symtab.addSynthetic("_DYNAMIC", *Out<ELFT>::Dynamic, 0, STV_HIDDEN);
 

lld/test/ELF/relocatable-symbols.s

@@ -0,0 +1,183 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld -r %t -o %tout
+# RUN: llvm-objdump -d %tout | FileCheck -check-prefix=DISASM %s
+# RUN: llvm-readobj -symbols -r %tout | FileCheck -check-prefix=SYMBOL %s
+
+# DISASM:      _start:
+# DISASM-NEXT:   0: {{.*}} callq 0
+# DISASM-NEXT:   5: {{.*}} callq 0
+# DISASM-NEXT:   a: {{.*}} callq 0
+# DISASM-NEXT:   f: {{.*}} callq 0
+# DISASM-NEXT:  14: {{.*}} callq 0
+# DISASM-NEXT:  19: {{.*}} callq 0
+# DISASM-NEXT:  1e: {{.*}} callq 0
+# DISASM-NEXT:  23: {{.*}} callq 0
+# DISASM-NEXT:  28: {{.*}} callq 0
+# DISASM-NEXT:  2d: {{.*}} callq 0
+# DISASM-NEXT:  32: {{.*}} callq 0
+# DISASM-NEXT:  37: {{.*}} callq 0
+# DISASM-NEXT: Disassembly of section foo:
+# DISASM-NEXT: foo:
+# DISASM-NEXT:  0: 90 nop
+# DISASM-NEXT:  1: 90 nop
+# DISASM-NEXT:  2: 90 nop
+# DISASM-NEXT: Disassembly of section bar:
+# DISASM-NEXT: bar:
+# DISASM-NEXT:  0: 90 nop
+# DISASM-NEXT:  1: 90 nop
+# DISASM-NEXT:  2: 90 nop
+
+# SYMBOL:      Relocations [
+# SYMBOL-NEXT:  Section ({{.*}}) .rela.text {
+# SYMBOL-NEXT:     0x1 R_X86_64_PC32 __start_foo 0x0
+# SYMBOL-NEXT:     0x6 R_X86_64_PC32 __stop_foo 0x0
+# SYMBOL-NEXT:     0xB R_X86_64_PC32 __start_bar 0x0
+# SYMBOL-NEXT:     0x10 R_X86_64_PC32 __stop_bar 0x0
+# SYMBOL-NEXT:     0x15 R_X86_64_PC32 __start_doo 0x0
+# SYMBOL-NEXT:     0x1A R_X86_64_PC32 __stop_doo 0x0
+# SYMBOL-NEXT:     0x1F R_X86_64_PC32 __preinit_array_start 0x0
+# SYMBOL-NEXT:     0x24 R_X86_64_PC32 __preinit_array_end 0x0
+# SYMBOL-NEXT:     0x29 R_X86_64_PC32 __init_array_start 0x0
+# SYMBOL-NEXT:     0x2E R_X86_64_PC32 __init_array_end 0x0
+# SYMBOL-NEXT:     0x33 R_X86_64_PC32 __fini_array_start 0x0
+# SYMBOL-NEXT:     0x38 R_X86_64_PC32 __fini_array_end 0x0
+# SYMBOL-NEXT:   }
+# SYMBOL-NEXT: ]
+# SYMBOL:      Symbol {
+# SYMBOL:        Name: __fini_array_end
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __fini_array_start
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __init_array_end
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __init_array_start
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __preinit_array_end
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __preinit_array_start
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __start_bar
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __start_doo
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __start_foo
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __stop_bar
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __stop_doo
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+# SYMBOL-NEXT: Symbol {
+# SYMBOL-NEXT:   Name: __stop_foo
+# SYMBOL-NEXT:   Value: 0x0
+# SYMBOL-NEXT:   Size: 0
+# SYMBOL-NEXT:   Binding: Global
+# SYMBOL-NEXT:   Type: None
+# SYMBOL-NEXT:   Other: 0
+# SYMBOL-NEXT:   Section: Undefined
+# SYMBOL-NEXT: }
+
+.global _start
+.text
+_start:
+ call __start_foo
+ call __stop_foo
+
+ call __start_bar
+ call __stop_bar
+
+ call __start_doo
+ call __stop_doo
+
+ call __preinit_array_start
+ call __preinit_array_end
+ call __init_array_start
+ call __init_array_end
+ call __fini_array_start
+ call __fini_array_end
+
+.section foo,"ax"
+ nop
+ nop
+ nop
+
+.section bar,"ax"
+ nop
+ nop
+ nop