ELF: Export preempted symbols even if there is a dynamic list.

[pcc]

Summary

Dynamic lists in an executable are additive, not restrictive, so we
must continue to export preempted symbols even with a dynamic list.

This fixes sanitizer interception of libc symbols (and should also fix
symbol preemption by users of sanitizers).

[ruiu]

lld/ELF/Driver.cpp

787–789 ↗

(On Diff #118078)

So, was this just wrong?

[pcc]

lld/ELF/Driver.cpp

787–789 ↗

(On Diff #118078)

I think so, yes. Dynamic lists in executables are additive, while version scripts in DSOs are restrictive, so there's no direct conversion between them.

[ruiu]

LGTM

lld/trunk/ELF/Driver.cpp

void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   // 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))
       if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
         readDynamicList(*Buffer);
 
     for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
-      Config->VersionScriptGlobals.push_back(
+      Config->DynamicList.push_back(
           {Arg->getValue(), /*IsExternCpp*/ false, /*HasWildcard*/ false});
-
-    // Dynamic lists are a simplified linker script that doesn't need the
-    // "global:" and implicitly ends with a "local:*". Set the variables
-    // needed to simulate that.
-    if (Args.hasArg(OPT_dynamic_list) ||
-        Args.hasArg(OPT_export_dynamic_symbol)) {
-      Config->ExportDynamic = true;
-      if (!Config->Shared)
-        Config->DefaultSymbolVersion = VER_NDX_LOCAL;
-    }
   }
 
   if (auto *Arg = Args.getLastArg(OPT_version_script))
     if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
       readVersionScript(*Buffer);
 }
 
 // Some Config members do not directly correspond to any particular

lld/trunk/ELF/SymbolTable.cpp

for (SymbolVersion &Ver : Config->DynamicList) {
     std::vector<SymbolBody *> Syms;
     if (Ver.HasWildcard)
       Syms = findByVersion(Ver);
     else
       Syms = findAllByVersion(Ver);
 
     for (SymbolBody *B : Syms) {
       if (!Config->Shared)
-        B->symbol()->VersionId = VER_NDX_GLOBAL;
+        B->symbol()->ExportDynamic = true;
       else if (B->symbol()->includeInDynsym())
         B->IsPreemptible = true;
     }
   }
 }
 
 // Set symbol versions to symbols. This function handles patterns
 // containing no wildcard characters.

lld/trunk/test/ELF/gc-sections-shared.s

 # CHECK-NEXT:     Value:
 # CHECK-NEXT:     Size:
 # CHECK-NEXT:     Binding: Local
 # CHECK-NEXT:     Type:
 # CHECK-NEXT:     Other:
 # CHECK-NEXT:     Section: Undefined (0x0)
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: bar
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Global
+# CHECK-NEXT:     Type:
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: .text
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: bar2
 # CHECK-NEXT:     Value:
 # CHECK-NEXT:     Size:
 # CHECK-NEXT:     Binding: Global
 # CHECK-NEXT:     Type:
 # CHECK-NEXT:     Other:
 # CHECK-NEXT:     Section: Undefined
 # CHECK-NEXT:   }