[PATCH] D36499: If --dynamic-list is given, only those symbols are preemptible

[Rafael Ávila de Espíndola via Phabricator via llvm-commits]

rafael created this revision.
Herald added subscribers: emaste, rengolin.

This is PR34053.

The implementation is a bit of a hack, given the precise location where IsPreemtible is set, it cannot be used from SymbolTable::handleAnonymousVersion.

I could add another method to SymbolTable if you think that would be better.


https://reviews.llvm.org/D36499

Files:
  ELF/Config.h
  ELF/Driver.cpp
  ELF/SymbolTable.h
  ELF/Writer.cpp
  test/ELF/dynamic-list-preempt.s


Index: test/ELF/dynamic-list-preempt.s
===================================================================
--- /dev/null
+++ test/ELF/dynamic-list-preempt.s
@@ -0,0 +1,23 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: echo "{ foo; };" > %t.list
+# RUN: ld.lld -dynamic-list %t.list -shared %t.o -o %t.so
+# RUN: llvm-readobj -r %t.so | FileCheck %s
+
+# CHECK:      Relocations [
+# CHECK-NEXT:   Section ({{.*}}) .rela.plt {
+# CHECK-NEXT:     R_X86_64_JUMP_SLOT foo 0x0
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+	.globl	foo
+foo:
+	ret
+
+	.globl	bar
+bar:
+	ret
+
+	call	foo at PLT
+	call	bar at PLT
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -1182,8 +1182,18 @@
   applySynthetic({In<ELFT>::EhFrame},
                  [](SyntheticSection *SS) { SS->finalizeContents(); });
 
-  for (Symbol *S : Symtab->getSymbols())
-    S->body()->IsPreemptible = S->body()->computeIsPreemptible();
+  if (Config->HasDynamicList) {
+    for (SymbolVersion V : Config->VersionScriptGlobals) {
+      if (V.HasWildcard)
+        error("foo");
+      std::vector<SymbolBody *> Syms = Symtab->findByVersion(V);
+      for (SymbolBody *B : Syms)
+        B->IsPreemptible = true;
+    }
+  } else {
+    for (Symbol *S : Symtab->getSymbols())
+      S->body()->IsPreemptible = S->body()->computeIsPreemptible();
+  }
 
   // Scan relocations. This must be done after every symbol is declared so that
   // we can correctly decide if a dynamic relocation is needed.
Index: ELF/SymbolTable.h
===================================================================
--- ELF/SymbolTable.h
+++ ELF/SymbolTable.h
@@ -91,8 +91,9 @@
 
   void trace(StringRef Name);
 
-private:
   std::vector<SymbolBody *> findByVersion(SymbolVersion Ver);
+
+private:
   std::vector<SymbolBody *> findAllByVersion(SymbolVersion Ver);
 
   llvm::StringMap<std::vector<SymbolBody *>> &getDemangledSyms();
Index: ELF/Driver.cpp
===================================================================
--- ELF/Driver.cpp
+++ ELF/Driver.cpp
@@ -744,9 +744,11 @@
   // symbols private. Note that -export-dynamic takes precedence over them
   // as it says all symbols should be exported.
   if (!HasExportDynamic) {
-    for (auto *Arg : Args.filtered(OPT_dynamic_list))
+    for (auto *Arg : Args.filtered(OPT_dynamic_list)) {
+      Config->HasDynamicList = true;
       if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
         readDynamicList(*Buffer);
+    }
 
     for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
       Config->VersionScriptGlobals.push_back(
Index: ELF/Config.h
===================================================================
--- ELF/Config.h
+++ ELF/Config.h
@@ -84,6 +84,7 @@
   llvm::StringMap<uint64_t> SectionStartMap;
   llvm::StringRef Chroot;
   llvm::StringRef DynamicLinker;
+  bool HasDynamicList;
   llvm::StringRef Entry;
   llvm::StringRef Emulation;
   llvm::StringRef Fini;


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