[ELF] - Fix for: bug 30237 - lld does not implement -f option

FreeBSD's libstdc++ build (used on tier-2 architectures) uses GNU ld's 
-f <name> option, which sets the DT_AUXILIARY field to the specified name.
Multiple -f options may be specified and the DT_AUXILIARY entries 
will be added in the order in which they appear.

Patch implements that option.

Differential revision: https://reviews.llvm.org/D24139

llvm-svn: 280475

lld/ELF/Config.h

@@ -76,6 +76,7 @@ struct Configuration {
   llvm::StringRef Sysroot;
   std::string RPath;
   std::vector<VersionDefinition> VersionDefinitions;
+  std::vector<llvm::StringRef> AuxiliaryList;
   std::vector<llvm::StringRef> DynamicList;
   std::vector<llvm::StringRef> SearchPaths;
   std::vector<llvm::StringRef> Undefined;

lld/ELF/Driver.cpp

@@ -490,6 +490,11 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
 
   Config->OFormatBinary = isOutputFormatBinary(Args);
 
+  for (auto *Arg : Args.filtered(OPT_auxiliary))
+    Config->AuxiliaryList.push_back(Arg->getValue());
+  if (!Config->Shared && !Config->AuxiliaryList.empty())
+    error("-f may not be used without -shared");
+
   for (auto *Arg : Args.filtered(OPT_undefined))
     Config->Undefined.push_back(Arg->getValue());
 

lld/ELF/Options.td

@@ -7,6 +7,8 @@ class J<string name>: Joined<["--", "-"], name>;
 class S<string name>: Separate<["--", "-"], name>;
 class JS<string name>: JoinedOrSeparate<["--", "-"], name>;
 
+def auxiliary: S<"auxiliary">, HelpText<"Set DT_AUXILIARY field to the specified name">;
+
 def Bsymbolic: F<"Bsymbolic">, HelpText<"Bind defined symbols locally">;
 
 def Bsymbolic_functions: F<"Bsymbolic-functions">,
@@ -188,6 +190,7 @@ def z: JoinedOrSeparate<["-"], "z">, MetaVarName<"<option>">,
   HelpText<"Linker option extensions">;
 
 // Aliases
+def alias_auxiliary: Separate<["-"], "f">, Alias<auxiliary>;
 def alias_Bdynamic_call_shared: F<"call_shared">, Alias<Bdynamic>;
 def alias_Bdynamic_dy: F<"dy">, Alias<Bdynamic>;
 def alias_Bstatic_dn: F<"dn">, Alias<Bstatic>;

lld/ELF/OutputSections.cpp

@@ -650,6 +650,8 @@ template <class ELFT> void DynamicSection<ELFT>::finalize() {
 
   // Add strings. We know that these are the last strings to be added to
   // DynStrTab and doing this here allows this function to set DT_STRSZ.
+  for (StringRef S : Config->AuxiliaryList)
+    Add({DT_AUXILIARY, Out<ELFT>::DynStrTab->addString(S)});
   if (!Config->RPath.empty())
     Add({Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
          Out<ELFT>::DynStrTab->addString(Config->RPath)});

lld/test/ELF/auxiliary.s

@@ -0,0 +1,12 @@
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld %t.o -shared -f aaa --auxiliary bbb -o %t
+# RUN: llvm-readobj --dynamic-table %t | FileCheck %s
+
+# CHECK:      DynamicSection [
+# CHECK-NEXT: Tag                Type          Name/Value
+# CHECK-NEXT: 0x000000007FFFFFFD AUXILIARY     Auxiliary library: [aaa]
+# CHECK-NEXT: 0x000000007FFFFFFD AUXILIARY     Auxiliary library: [bbb]
+
+# RUN: not ld.lld %t.o -f aaa --auxiliary bbb -o %t 2>&1 \
+# RUN:    | FileCheck -check-prefix=ERR %s
+# ERR: -f may not be used without -shared