base: Add byte order attribute for object files

This adds byte order as an attribute for object files by
introducing new members to the ObjectFile class. This is
populated by the looking at the ELF headers.

Change-Id: Ibe55699175cc0295e0c9d49bdbe02e580988bc4f
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>

diff --git a/src/base/loader/elf_object.cc b/src/base/loader/elf_object.cc
index bdcc92b2c0651a431b20df90038e75966b80d332..4198875361a6b900c9ff76add03af1e81f69ac37 100644 (file)
--- a/src/base/loader/elf_object.cc
+++ b/src/base/loader/elf_object.cc
@@ -112,6 +112,7 @@ ElfObject::ElfObject(ImageFileDataPtr ifd) : ObjectFile(ifd)
 
     determineArch();
     determineOpSys();
+    determineByteOrder();
 
     entry = ehdr.e_entry;
     _programHeaderCount = ehdr.e_phnum;
@@ -323,6 +324,15 @@ ElfObject::determineOpSys()
     }
 }
 
+void
+ElfObject::determineByteOrder()
+{
+    auto edata = ehdr.e_ident[EI_DATA];
+    if (edata == ELFDATANONE)
+        panic("invalid ELF data encoding");
+    byteOrder = (edata == ELFDATA2MSB) ? ByteOrder::big : ByteOrder::little;
+}
+
 void
 ElfObject::handleLoadableSegment(GElf_Phdr phdr, int seg_num)
 {

diff --git a/src/base/loader/elf_object.hh b/src/base/loader/elf_object.hh
index c262912af598d74c2d2eb4754af86a8d152d3b4f..24d0c0c6cb4634e943001d969ee48504e5ee3907 100644 (file)
--- a/src/base/loader/elf_object.hh
+++ b/src/base/loader/elf_object.hh
@@ -64,6 +64,7 @@ class ElfObject : public ObjectFile
 
     void determineArch();
     void determineOpSys();
+    void determineByteOrder();
     void handleLoadableSegment(GElf_Phdr phdr, int seg_num);
 
     // These values are provided to a linux process by the kernel, so we

diff --git a/src/base/loader/object_file.hh b/src/base/loader/object_file.hh
index 0bfd918e8191391161e4d03ac27d61e9833ca926..7d542a98e3c6413510c5161d39cdcb9c4a2afe59 100644 (file)
--- a/src/base/loader/object_file.hh
+++ b/src/base/loader/object_file.hh
@@ -37,6 +37,7 @@
 #include "base/loader/symtab.hh"
 #include "base/logging.hh"
 #include "base/types.hh"
+#include "enums/ByteOrder.hh"
 
 namespace Loader
 {
@@ -76,6 +77,7 @@ class ObjectFile : public ImageFile
   protected:
     Arch arch = UnknownArch;
     OpSys opSys = UnknownOpSys;
+    ByteOrder byteOrder = ByteOrder::little;
 
     SymbolTable _symtab;
 
@@ -102,6 +104,7 @@ class ObjectFile : public ImageFile
 
     Arch  getArch()  const { return arch; }
     OpSys getOpSys() const { return opSys; }
+    ByteOrder getByteOrder() const { return byteOrder; }
 
     const SymbolTable &symtab() const { return _symtab; }