[LLF][ELF] - Support -z global

[grimar]

Summary

-z global is a flag used on Android (see D49198).

Since it is trivial and helps to make LLD a drop-in replacement for bfd,
I think we can add a support.

[grimar]

Ping.

[ruiu]

Please add this option to the manual.

[grimar]

• Documented the new option.

[grimar]

Ping.

[grimar]

Ping.

[ruiu]

LGTM

ELF/Config.h

struct Configuration {
   bool WarnBackrefs;
   bool WarnCommon;
   bool WarnMissingEntry;
   bool WarnSymbolOrdering;
   bool WriteAddends;
   bool ZCombreloc;
   bool ZCopyreloc;
   bool ZExecstack;
+  bool ZGlobal;
   bool ZHazardplt;
   bool ZInitfirst;
   bool ZKeepTextSectionPrefix;
   bool ZNodelete;
   bool ZNodlopen;
   bool ZNow;
   bool ZOrigin;
   bool ZRelro;

ELF/Driver.cpp

for (auto *Arg : Args.filtered_reverse(OPT_z)) {
     if (K2 == Arg->getValue())
       return false;
   }
   return Default;
 }
 
 static bool isKnown(StringRef S) {
   return S == "combreloc" || S == "copyreloc" || S == "defs" ||
-         S == "execstack" || S == "hazardplt" || S == "initfirst" ||
-         S == "keep-text-section-prefix" || S == "lazy" || S == "muldefs" ||
-         S == "nocombreloc" || S == "nocopyreloc" || S == "nodelete" ||
-         S == "nodlopen" || S == "noexecstack" ||
+         S == "execstack" || S == "global" || S == "hazardplt" ||
+         S == "initfirst" || S == "keep-text-section-prefix" || S == "lazy" ||
+         S == "muldefs" || S == "nocombreloc" || S == "nocopyreloc" ||
+         S == "nodelete" || S == "nodlopen" || S == "noexecstack" ||
          S == "nokeep-text-section-prefix" || S == "norelro" || S == "notext" ||
          S == "now" || S == "origin" || S == "relro" || S == "retpolineplt" ||
          S == "rodynamic" || S == "text" || S == "wxneeded" ||
          S.startswith("max-page-size=") || S.startswith("stack-size=");
 }
 
 // Report an error for an unknown -z option.
 static void checkZOptions(opt::InputArgList &Args) {
void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->WarnBackrefs =
       Args.hasFlag(OPT_warn_backrefs, OPT_no_warn_backrefs, false);
   Config->WarnCommon = Args.hasFlag(OPT_warn_common, OPT_no_warn_common, false);
   Config->WarnSymbolOrdering =
       Args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true);
   Config->ZCombreloc = getZFlag(Args, "combreloc", "nocombreloc", true);
   Config->ZCopyreloc = getZFlag(Args, "copyreloc", "nocopyreloc", true);
   Config->ZExecstack = getZFlag(Args, "execstack", "noexecstack", false);
+  Config->ZGlobal = hasZOption(Args, "global");
   Config->ZHazardplt = hasZOption(Args, "hazardplt");
   Config->ZInitfirst = hasZOption(Args, "initfirst");
   Config->ZKeepTextSectionPrefix = getZFlag(
       Args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
   Config->ZNodelete = hasZOption(Args, "nodelete");
   Config->ZNodlopen = hasZOption(Args, "nodlopen");
   Config->ZNow = getZFlag(Args, "now", "lazy", false);
   Config->ZOrigin = hasZOption(Args, "origin");

ELF/SyntheticSections.cpp

template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
   if (this->Size)
     return; // Already finalized.
 
   // Set DT_FLAGS and DT_FLAGS_1.
   uint32_t DtFlags = 0;
   uint32_t DtFlags1 = 0;
   if (Config->Bsymbolic)
     DtFlags |= DF_SYMBOLIC;
+  if (Config->ZGlobal)
+    DtFlags1 |= DF_1_GLOBAL;
   if (Config->ZInitfirst)
     DtFlags1 |= DF_1_INITFIRST;
   if (Config->ZNodelete)
     DtFlags1 |= DF_1_NODELETE;
   if (Config->ZNodlopen)
     DtFlags1 |= DF_1_NOOPEN;
   if (Config->ZNow) {
     DtFlags |= DF_BIND_NOW;

docs/ld.lld.1

 .It Fl z Ar option
 Linker option extensions.
 .Bl -tag -width indent
 .It Cm execstack
 Make the main stack executable.
 Stack permissions are recorded in the
 .Dv PT_GNU_STACK
 segment.
+.It Cm global
+Sets the
+.Dv DF_1_GLOBAL flag in the
+.Dv DYNAMIC
+section.
+Different loaders can decide how to handle this flag on their own.
 .It Cm initfirst
 Sets the
 .Dv DF_1_INITFIRST
 flag to indicate the module should be initialized first.
 .It Cm muldefs
 Do not error if a symbol is defined multiple times.
 The first definition will be used.
 This is a synonym for

test/ELF/dt_flags.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld -shared %t -o %t.so
 
-# RUN: ld.lld -z initfirst -z now -z nodelete -z nodlopen -z origin -Bsymbolic %t %t.so -o %t1
+# RUN: ld.lld -z global -z initfirst -z now -z nodelete -z nodlopen -z origin \
+# RUN:   -Bsymbolic %t %t.so -o %t1
 # RUN: llvm-readobj -dynamic-table %t1 | FileCheck -check-prefix=FLAGS %s
 
 # RUN: ld.lld %t %t.so -o %t2
 # RUN: llvm-readobj -dynamic-table %t2 | FileCheck %s
 
 # RUN: ld.lld -z lazy %t %t.so -o %t2
 # RUN: llvm-readobj -dynamic-table %t2 | FileCheck %s
 
 # FLAGS: DynamicSection [
 # FLAGS:   0x000000000000001E FLAGS ORIGIN SYMBOLIC BIND_NOW
-# FLAGS:   0x000000006FFFFFFB FLAGS_1 NOW NODELETE INITFIRST NOOPEN ORIGIN
+# FLAGS:   0x000000006FFFFFFB FLAGS_1 NOW GLOBAL NODELETE INITFIRST NOOPEN ORIGIN
 # FLAGS: ]
 
 # CHECK: DynamicSection [
 # CHECK-NOT:   FLAGS
 # CHECK-NOT:   FLAGS_1
 # CHECK: ]
 
 .globl _start
 _start: