[llvm-objcopy] Match GNU behaviour regarding file symbols

GNU objcopy removes STT_FILE symbols for strip-debug operations, and
keeps them for --discard-all operation. Match their behaviour for
llvm-objcopy.

Bug: https://github.com/android/ndk/issues/1212

Differential Revision: https://reviews.llvm.org/D76675

llvm/test/tools/llvm-objcopy/ELF/keep-file-symbols.test

@@ -9,6 +9,16 @@
 # RUN: llvm-strip --keep-file-symbols --strip-symbol foo %t -o %t4
 # RUN: llvm-readobj --symbols %t4 | FileCheck %s --check-prefix=STRIP
 
+# RUN: llvm-objcopy --keep-file-symbols --strip-debug %t %t5
+# RUN: llvm-readobj --symbols %t5 | FileCheck %s --check-prefix=STRIPDEBUG
+# RUN: llvm-objcopy --keep-file-symbols --strip-unneeded %t %t6
+# RUN: llvm-readobj --symbols %t6 | FileCheck %s --check-prefix=STRIPDEBUG
+
+# RUN: llvm-strip --keep-file-symbols --strip-debug %t -o %t7
+# RUN: llvm-readobj --symbols %t7 | FileCheck %s --check-prefix=STRIPDEBUG
+# RUN: llvm-strip --keep-file-symbols --strip-unneeded %t -o %t8
+# RUN: llvm-readobj --symbols %t8 | FileCheck %s --check-prefix=STRIPDEBUG
+
 !ELF
 FileHeader:
   Class:           ELFCLASS64
@@ -16,6 +26,9 @@ FileHeader:
   Type:            ET_REL
   Machine:         EM_X86_64
 Sections:
+  - Name:            .debugfoo
+    Type:            SHT_PROGBITS
+    Content:         "00000000"
   - Name:            .text
     Type:            SHT_PROGBITS
     Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
@@ -30,6 +43,9 @@ Symbols:
     Type:     STT_FUNC
     Section:  .text
     Binding:  STB_GLOBAL
+  - Name:     debugfoo
+    Section:  .debugfoo
+    Binding:  STB_GLOBAL
 
 #STRIPALL: Symbols [
 #STRIPALL-NEXT:  Symbol {
@@ -80,4 +96,43 @@ Symbols:
 #STRIP-NEXT:    Other: 0
 #STRIP-NEXT:    Section: .text
 #STRIP-NEXT:  }
+#STRIP-NEXT:  Symbol {
+#STRIP-NEXT:    Name: debugfoo
+#STRIP-NEXT:    Value: 0x0
+#STRIP-NEXT:    Size: 0
+#STRIP-NEXT:    Binding: Global
+#STRIP-NEXT:    Type: None
+#STRIP-NEXT:    Other: 0
+#STRIP-NEXT:    Section: .debugfoo
+#STRIP-NEXT:  }
 #STRIP-NEXT:]
+
+#STRIPDEBUG: Symbols [
+#STRIPDEBUG-NEXT:  Symbol {
+#STRIPDEBUG-NEXT:    Name:
+#STRIPDEBUG-NEXT:    Value: 0x0
+#STRIPDEBUG-NEXT:    Size: 0
+#STRIPDEBUG-NEXT:    Binding: Local
+#STRIPDEBUG-NEXT:    Type: None
+#STRIPDEBUG-NEXT:    Other: 0
+#STRIPDEBUG-NEXT:    Section: Undefined
+#STRIPDEBUG-NEXT:  }
+#STRIPDEBUG-NEXT:  Symbol {
+#STRIPDEBUG-NEXT:    Name: foo
+#STRIPDEBUG-NEXT:    Value: 0x0
+#STRIPDEBUG-NEXT:    Size: 0
+#STRIPDEBUG-NEXT:    Binding: Local
+#STRIPDEBUG-NEXT:    Type: File
+#STRIPDEBUG-NEXT:    Other: 0
+#STRIPDEBUG-NEXT:    Section: .text
+#STRIPDEBUG-NEXT:  }
+#STRIPDEBUG-NEXT:  Symbol {
+#STRIPDEBUG-NEXT:    Name: bar
+#STRIPDEBUG-NEXT:    Value: 0x0
+#STRIPDEBUG-NEXT:    Size: 0
+#STRIPDEBUG-NEXT:    Binding: Global
+#STRIPDEBUG-NEXT:    Type: Function
+#STRIPDEBUG-NEXT:    Other: 0
+#STRIPDEBUG-NEXT:    Section: .text
+#STRIPDEBUG-NEXT:  }
+#STRIPDEBUG-NEXT:]

llvm/test/tools/llvm-objcopy/ELF/strip-debug.test

@@ -116,6 +116,8 @@ Symbols:
   - Name:    debugfoo
     Section: .debugfoo
     Binding:  STB_GLOBAL
+  - Name:    filesymbol
+    Type:    STT_FILE
 
 # CHECK: SectionHeaderCount: 5
 
@@ -124,7 +126,7 @@ Symbols:
 # CHECK: Name: .strtab
 # CHECK: Name: .shstrtab
 
-# Check that *only* foo is copied and not debugfoo
+# Check that *only* foo is copied and not debugfoo or filesymbol.
 # CHECK:      Symbols [
 # CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name:

llvm/tools/llvm-objcopy/CopyConfig.cpp

@@ -667,8 +667,10 @@ parseObjcopyOptions(ArrayRef<const char *> ArgsArr,
   Config.KeepFileSymbols = InputArgs.hasArg(OBJCOPY_keep_file_symbols);
   Config.DecompressDebugSections =
       InputArgs.hasArg(OBJCOPY_decompress_debug_sections);
-  if (Config.DiscardMode == DiscardType::All)
+  if (Config.DiscardMode == DiscardType::All) {
     Config.StripDebug = true;
+    Config.KeepFileSymbols = true;
+  }
   for (auto Arg : InputArgs.filtered(OBJCOPY_localize_symbol))
     if (Error E = Config.SymbolsToLocalize.addMatcher(NameOrPattern::create(
             Arg->getValue(), SymbolMatchStyle, ErrorCallback)))
@@ -938,8 +940,10 @@ parseStripOptions(ArrayRef<const char *> ArgsArr,
       !Config.StripAllGNU && Config.SymbolsToRemove.empty())
     Config.StripAll = true;
 
-  if (Config.DiscardMode == DiscardType::All)
+  if (Config.DiscardMode == DiscardType::All) {
     Config.StripDebug = true;
+    Config.KeepFileSymbols = true;
+  }
 
   Config.DeterministicArchives =
       InputArgs.hasFlag(STRIP_enable_deterministic_archives,

llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp

@@ -420,6 +420,9 @@ static Error updateAndRemoveSymbols(const CopyConfig &Config, Object &Obj) {
     if (Config.StripAll || Config.StripAllGNU)
       return true;
 
+    if (Config.StripDebug && Sym.Type == STT_FILE)
+      return true;
+
     if (Config.SymbolsToRemove.matches(Sym.Name))
       return true;