[LinkerScript] Add matching of output sections to segments

Add method to query segments for specified output section name.
Return error if the section is assigned to unknown segment.
Check matching of sections to segments during layout on the subject of correctness.
NOTE: no actual functionality of using custom segments is implemented.

Differential Revision: http://reviews.llvm.org/D10359

llvm-svn: 239719

4 files changed, 91 insertions, 4 deletions

diff --git a/lld/lib/Core/Error.cpp b/lld/lib/Core/Error.cpp
index 8b7a7e2b528..5d612f66401 100644
--- a/lld/lib/Core/Error.cpp
+++ b/lld/lib/Core/Error.cpp
@@ -56,6 +56,8 @@ public:
     case LinkerScriptReaderError::unrecognized_function_in_expr:
       return "Unrecognized function call when evaluating linker script "
              "expression";
+    case LinkerScriptReaderError::unknown_phdr_ids:
+      return "Unknown header identifiers (missing in PHDRS command) are used";
     }
     llvm_unreachable("An enumerator of LinkerScriptReaderError does not have a "
                      "message defined.");
diff --git a/lld/lib/ReaderWriter/ELF/TargetLayout.cpp b/lld/lib/ReaderWriter/ELF/TargetLayout.cpp
index 87cbcd5cab5..c0dae207bd6 100644
--- a/lld/lib/ReaderWriter/ELF/TargetLayout.cpp
+++ b/lld/lib/ReaderWriter/ELF/TargetLayout.cpp
@@ -320,6 +320,7 @@ template <class ELFT> void TargetLayout<ELFT>::createOutputSections() {
     } else {
       outputSection = new (_allocator.Allocate<OutputSection<ELFT>>())
           OutputSection<ELFT>(section->outputSectionName());
+      checkOutputSectionSegment(outputSection);
       _outputSections.push_back(outputSection);
       outputSectionInsert.first->second = outputSection;
     }
@@ -327,6 +328,17 @@ template <class ELFT> void TargetLayout<ELFT>::createOutputSections() {
   }
 }
 
+// Check that output section has proper segment set
+template <class ELFT>
+void TargetLayout<ELFT>::checkOutputSectionSegment(
+    const OutputSection<ELFT> *sec) {
+  std::vector<const script::PHDR *> phdrs;
+  if (_linkerScriptSema.getPHDRsForOutputSection(sec->name(), phdrs)) {
+    llvm::report_fatal_error(
+        "Linker script has wrong segments set for output sections");
+  }
+}
+
 template <class ELFT>
 uint64_t
 TargetLayout<ELFT>::getLookupSectionFlags(const OutputSection<ELFT> *os) const {
diff --git a/lld/lib/ReaderWriter/ELF/TargetLayout.h b/lld/lib/ReaderWriter/ELF/TargetLayout.h
index 7162cd5fe08..f35bf031146 100644
--- a/lld/lib/ReaderWriter/ELF/TargetLayout.h
+++ b/lld/lib/ReaderWriter/ELF/TargetLayout.h
@@ -209,6 +209,9 @@ public:
   // Output sections with the same name into a OutputSection
   void createOutputSections();
 
+  // Check that output section has proper segment set
+  void checkOutputSectionSegment(const OutputSection<ELFT> *sec);
+
   /// \brief Sort the sections by their order as defined by the layout,
   /// preparing all sections to be assigned to a segment.
   virtual void sortInputSections();
diff --git a/lld/lib/ReaderWriter/LinkerScript.cpp b/lld/lib/ReaderWriter/LinkerScript.cpp
index 6d82e29d95a..79a367d15bf 100644
--- a/lld/lib/ReaderWriter/LinkerScript.cpp
+++ b/lld/lib/ReaderWriter/LinkerScript.cpp
@@ -953,6 +953,9 @@ void PHDR::dump(raw_ostream &os) const {
   os << ";\n";
 }
 
+static PHDR none("NONE", 0, false, false, NULL, 0);
+const PHDR *PHDR::NONE = &none;
+
 void PHDRS::dump(raw_ostream &os) const {
   os << "PHDRS\n{\n";
   for (auto &&phdr : _phdrs) {
@@ -2353,10 +2356,7 @@ Extern *Parser::parseExtern() {
 }
 
 // Sema member functions
-Sema::Sema()
-    : _scripts(), _layoutCommands(), _memberToLayoutOrder(),
-      _memberNameWildcards(), _cacheSectionOrder(), _cacheExpressionOrder(),
-      _deliveredExprs(), _symbolTable() {}
+Sema::Sema() : _parsedPHDRS(false) {}
 
 void Sema::perform() {
   for (auto &parser : _scripts)
@@ -2465,6 +2465,18 @@ uint64_t Sema::getLinkerScriptExprValue(StringRef name) const {
   return it->second;
 }
 
+std::error_code
+Sema::getPHDRsForOutputSection(StringRef name,
+                               std::vector<const PHDR *> &phdrs) const {
+  // Cache results if not done yet.
+  if (auto ec = const_cast<Sema *>(this)->buildSectionToPHDR())
+    return ec;
+
+  auto vec = _sectionToPHDR.lookup(name);
+  std::copy(std::begin(vec), std::end(vec), std::back_inserter(phdrs));
+  return std::error_code();
+}
+
 void Sema::dump() const {
   raw_ostream &os = llvm::outs();
   os << "Linker script semantics dump\n";
@@ -2701,6 +2713,64 @@ bool Sema::localCompare(int order, const SectionKey &lhs,
   return false;
 }
 
+std::error_code Sema::buildSectionToPHDR() {
+  if (_parsedPHDRS)
+    return std::error_code();
+  _parsedPHDRS = true;
+
+  // No scripts - nothing to do.
+  if (_scripts.empty() || _layoutCommands.empty())
+    return std::error_code();
+
+  // Collect all header declarations.
+  llvm::StringMap<const PHDR *> phdrs;
+  for (auto &parser : _scripts) {
+    for (auto *cmd : parser->get()->_commands) {
+      if (auto *ph = dyn_cast<PHDRS>(cmd)) {
+        for (auto *p : *ph)
+          phdrs[p->name()] = p;
+      }
+    }
+  }
+  const bool noPhdrs = phdrs.empty();
+
+  // Add NONE header to the map provided there's no user-defined
+  // header with the same name.
+  if (!_sectionToPHDR.count(PHDR::NONE->name()))
+    phdrs[PHDR::NONE->name()] = PHDR::NONE;
+
+  // Match output sections to available headers.
+  llvm::SmallVector<const PHDR *, 2> phdrsCur, phdrsLast { PHDR::NONE };
+  for (const Command *cmd : _layoutCommands) {
+    auto osd = dyn_cast<OutputSectionDescription>(cmd);
+    if (!osd || osd->isDiscarded())
+      continue;
+
+    phdrsCur.clear();
+    for (StringRef name : osd->PHDRs()) {
+      auto it = phdrs.find(name);
+      if (it == phdrs.end()) {
+        return LinkerScriptReaderError::unknown_phdr_ids;
+      }
+      phdrsCur.push_back(it->second);
+    }
+
+    // If no headers and no errors - insert empty headers set.
+    // If the current set of headers is empty, then use the last non-empty
+    // set. Otherwise mark the current set to be the last non-empty set for
+    // successors.
+    if (noPhdrs)
+      phdrsCur.clear();
+    else if (phdrsCur.empty())
+      phdrsCur = phdrsLast;
+    else
+      phdrsLast = phdrsCur;
+
+    _sectionToPHDR[osd->name()] = phdrsCur;
+  }
+  return std::error_code();
+}
+
 static bool hasWildcard(StringRef name) {
   for (auto ch : name)
     if (ch == '*' || ch == '?' || ch == '[' || ch == '\\')