[PATCH] D33496: [LLD][ELF] Move creation of .ARM.exidx sentinel before LinkerScript creation

[Peter Smith via Phabricator via llvm-commits]

peter.smith updated this revision to Diff 100238.
peter.smith added a comment.

Updated patch to just append the .ARM.exidx sentinel section to an existing LinkerScript InputSectionDescription.

To do the insertion I've moved the LinkerScript::inputSectionRanges() function from https://reviews.llvm.org/D33500 so we can use it do the insertion and updated https://reviews.llvm.org/D33500.


https://reviews.llvm.org/D33496

Files:
  ELF/LinkerScript.cpp
  ELF/LinkerScript.h
  ELF/Writer.cpp


Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -1195,8 +1195,6 @@
   if (ErrorCount)
     return;
 
-  // So far we have added sections from input object files.
-  // This function adds linker-created Out::* sections.
   addPredefinedSections();
   removeUnusedSyntheticSections(OutputSections);
 
@@ -1264,8 +1262,17 @@
   // ARM ABI requires .ARM.exidx to be terminated by some piece of data.
   // We have the terminater synthetic section class. Add that at the end.
   auto *OS = dyn_cast_or_null<OutputSection>(findSection(".ARM.exidx"));
-  if (OS && !OS->Sections.empty() && !Config->Relocatable)
-    OS->addSection(make<ARMExidxSentinelSection>());
+  if (!OS || OS->Sections.empty() || Config->Relocatable)
+    return;
+
+  auto *Sentinel = make<ARMExidxSentinelSection>();
+  OS->addSection(Sentinel);
+  // If there are linker script commands existing at this point then add the
+  // sentinel to these too.
+  std::vector<std::vector<InputSection *> *> Ranges =
+      Script->inputSectionRanges(OS->Name);
+  if (!Ranges.empty())
+    Ranges.back()->push_back(Sentinel);
 }
 
 // The linker is expected to define SECNAME_start and SECNAME_end
Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -258,6 +258,8 @@
 
   std::vector<OutputSection *> *OutputSections;
   void fabricateDefaultCommands();
+  std::vector<std::vector<InputSection *> *>
+  inputSectionRanges(StringRef S);
   void addOrphanSections(OutputSectionFactory &Factory);
   void removeEmptyCommands();
   void adjustSectionsBeforeSorting();
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -510,6 +510,28 @@
   }
 }
 
+// For an OutputSection S, return the InputSectionDescriptions that are
+// associated with S. The intention is that callers can iterate over
+// InputSectionDescription::Sections and insert sections such as Thunks.
+std::vector<std::vector<InputSection *> *>
+LinkerScript::inputSectionRanges(StringRef S) {
+  std::vector<std::vector<InputSection *> *> Ranges;
+  auto OutCmdPos = std::find_if(
+      Opt.Commands.begin(), Opt.Commands.end(), [=](BaseCommand *Cmd) {
+        if (auto *OSCmd = dyn_cast<OutputSectionCommand>(Cmd))
+          return (OSCmd->Name == S);
+        return false;
+      });
+  if (OutCmdPos == Opt.Commands.end())
+    return Ranges;
+  auto *OutCmd = cast<OutputSectionCommand>(*OutCmdPos);
+  for (auto *BaseCmd : OutCmd->Commands) {
+    if (auto *ISD = dyn_cast<InputSectionDescription>(BaseCmd))
+      Ranges.push_back(&ISD->Sections);
+  }
+  return Ranges;
+}
+
 uint64_t LinkerScript::advance(uint64_t Size, unsigned Align) {
   bool IsTbss = (CurOutSec->Flags & SHF_TLS) && CurOutSec->Type == SHT_NOBITS;
   uint64_t Start = IsTbss ? Dot + ThreadBssOffset : Dot;


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