This patch adds new functions to the SectionRef and ObjectFile interfaces to determine whether or not a section is meant to be read-only. These functions will be used by the MCJIT RuntimeDyld to give hints to the memory manager during the object loading process in a future patch.

Patch by Ashok Thirumurthi.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165586 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Object/COFF.h

@@ -128,6 +128,7 @@ protected:
   virtual error_code isSectionBSS(DataRefImpl Sec, bool &Res) const;
   virtual error_code isSectionVirtual(DataRefImpl Sec, bool &Res) const;
   virtual error_code isSectionZeroInit(DataRefImpl Sec, bool &Res) const;
+  virtual error_code isSectionReadOnlyData(DataRefImpl Sec, bool &Res) const;
   virtual error_code isSectionRequiredForExecution(DataRefImpl Sec,
                                                    bool &Res) const;
   virtual error_code sectionContainsSymbol(DataRefImpl Sec, DataRefImpl Symb,

include/llvm/Object/ELF.h

@@ -640,6 +640,7 @@ protected:
                                                    bool &Res) const;
   virtual error_code isSectionVirtual(DataRefImpl Sec, bool &Res) const;
   virtual error_code isSectionZeroInit(DataRefImpl Sec, bool &Res) const;
+  virtual error_code isSectionReadOnlyData(DataRefImpl Sec, bool &Res) const;
   virtual error_code sectionContainsSymbol(DataRefImpl Sec, DataRefImpl Symb,
                                            bool &Result) const;
   virtual relocation_iterator getSectionRelBegin(DataRefImpl Sec) const;
@@ -1288,7 +1289,8 @@ error_code ELFObjectFile<target_endianness, is64Bits>
 }
 
 template<support::endianness target_endianness, bool is64Bits>
-error_code ELFObjectFile<target_endianness, is64Bits>::isSectionZeroInit(DataRefImpl Sec,
+error_code ELFObjectFile<target_endianness, is64Bits>
+                        ::isSectionZeroInit(DataRefImpl Sec,
                                             bool &Result) const {
   const Elf_Shdr *sec = reinterpret_cast<const Elf_Shdr *>(Sec.p);
   // For ELF, all zero-init sections are virtual (that is, they occupy no space
@@ -1300,6 +1302,18 @@ error_code ELFObjectFile<target_endianness, is64Bits>::isSectionZeroInit(DataRef
   return object_error::success;
 }
 
+template<support::endianness target_endianness, bool is64Bits>
+error_code ELFObjectFile<target_endianness, is64Bits>
+                       ::isSectionReadOnlyData(DataRefImpl Sec,
+                                               bool &Result) const {
+  const Elf_Shdr *sec = reinterpret_cast<const Elf_Shdr *>(Sec.p);
+  if (sec->sh_flags & ELF::SHF_WRITE || sec->sh_flags & ELF::SHF_EXECINSTR)
+    Result = false;
+  else
+    Result = true;
+  return object_error::success;
+}
+
 template<support::endianness target_endianness, bool is64Bits>
 error_code ELFObjectFile<target_endianness, is64Bits>
                           ::sectionContainsSymbol(DataRefImpl Sec,

include/llvm/Object/MachO.h

@@ -76,6 +76,7 @@ protected:
                                                    bool &Res) const;
   virtual error_code isSectionVirtual(DataRefImpl Sec, bool &Res) const;
   virtual error_code isSectionZeroInit(DataRefImpl Sec, bool &Res) const;
+  virtual error_code isSectionReadOnlyData(DataRefImpl Sec, bool &Res) const;
   virtual error_code sectionContainsSymbol(DataRefImpl DRI, DataRefImpl S,
                                            bool &Result) const;
   virtual relocation_iterator getSectionRelBegin(DataRefImpl Sec) const;

include/llvm/Object/ObjectFile.h

@@ -163,6 +163,7 @@ public:
   error_code isRequiredForExecution(bool &Result) const;
   error_code isVirtual(bool &Result) const;
   error_code isZeroInit(bool &Result) const;
+  error_code isReadOnlyData(bool &Result) const;
 
   error_code containsSymbol(SymbolRef S, bool &Result) const;
 
@@ -316,6 +317,7 @@ protected:
   // A section is 'virtual' if its contents aren't present in the object image.
   virtual error_code isSectionVirtual(DataRefImpl Sec, bool &Res) const = 0;
   virtual error_code isSectionZeroInit(DataRefImpl Sec, bool &Res) const = 0;
+  virtual error_code isSectionReadOnlyData(DataRefImpl Sec, bool &Res) const = 0;
   virtual error_code sectionContainsSymbol(DataRefImpl Sec, DataRefImpl Symb,
                                            bool &Result) const = 0;
   virtual relocation_iterator getSectionRelBegin(DataRefImpl Sec) const = 0;
@@ -510,6 +512,10 @@ inline error_code SectionRef::isZeroInit(bool &Result) const {
   return OwningObject->isSectionZeroInit(SectionPimpl, Result);
 }
 
+inline error_code SectionRef::isReadOnlyData(bool &Result) const {
+  return OwningObject->isSectionReadOnlyData(SectionPimpl, Result);
+}
+
 inline error_code SectionRef::containsSymbol(SymbolRef S, bool &Result) const {
   return OwningObject->sectionContainsSymbol(SectionPimpl, S.SymbolPimpl,
                                              Result);

lib/Object/COFFObjectFile.cpp

@@ -377,6 +377,13 @@ error_code COFFObjectFile::isSectionZeroInit(DataRefImpl Sec,
   return object_error::success;
 }
 
+error_code COFFObjectFile::isSectionReadOnlyData(DataRefImpl Sec,
+                                                bool &Result) const {
+  // FIXME: Unimplemented.
+  Result = false;
+  return object_error::success;
+}
+
 error_code COFFObjectFile::sectionContainsSymbol(DataRefImpl Sec,
                                                  DataRefImpl Symb,
                                                  bool &Result) const {

lib/Object/MachOObjectFile.cpp

@@ -612,6 +612,17 @@ error_code MachOObjectFile::isSectionZeroInit(DataRefImpl DRI,
   return object_error::success;
 }
 
+error_code MachOObjectFile::isSectionReadOnlyData(DataRefImpl Sec,
+                                                  bool &Result) const {
+  // Consider using the code from isSectionText to look for __const sections.
+  // Alternately, emit S_ATTR_PURE_INSTRUCTIONS and/or S_ATTR_SOME_INSTRUCTIONS
+  // to use section attributes to distinguish code from data.
+
+  // FIXME: Unimplemented.
+  Result = false;
+  return object_error::success;
+}
+
 error_code MachOObjectFile::sectionContainsSymbol(DataRefImpl Sec,
                                                   DataRefImpl Symb,
                                                   bool &Result) const {