Add a function to get the segment name of a section.

On MachO, sections also have segment names. When a tool looking at a .o file
prints a segment name, this is what they mean. In reality, a .o has only one
anonymous, segment.

This patch adds a MachO only function to fetch that segment name. I named it
getSectionFinalSegmentName since the main use for the name seems to be inform
the linker with segment this section should go to.

The patch also changes MachOObjectFile::getSectionName to return just the
section name instead of computing SegmentName,SectionName.

The main difference from the previous patch is that it doesn't use
InMemoryStruct. It is extremely dangerous: if the endians match it returns
a pointer to the file buffer, if not, it returns a pointer to an internal buffer
that is overwritten in the next API call.

We should change all of this code to use
support::detail::packed_endian_specific_integral like ELF, but since these
functions only handle strings, they work with big and little endian machines
as is.

I have tested this by installing ubuntu 12.10 ppc on qemu, that is why it took
so long :-)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170838 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 41 insertions, 14 deletions

diff --git a/lib/Object/MachOObjectFile.cpp b/lib/Object/MachOObjectFile.cpp
index 40f5390a96..0ad8893400 100644
--- a/lib/Object/MachOObjectFile.cpp
+++ b/lib/Object/MachOObjectFile.cpp
@@ -473,28 +473,55 @@ static bool is64BitLoadCommand(const MachOObject *MachOObj, DataRefImpl DRI) {
   return false;
 }
 
+static StringRef parseSegmentOrSectionName(const char *P) {
+  if (P[15] == 0)
+    // Null terminated.
+    return P;
+  // Not null terminated, so this is a 16 char string.
+  return StringRef(P, 16);
+}
+
 error_code MachOObjectFile::getSectionName(DataRefImpl DRI,
                                            StringRef &Result) const {
-  // FIXME: thread safety.
-  static char result[34];
   if (is64BitLoadCommand(MachOObj.get(), DRI)) {
     LoadCommandInfo LCI = MachOObj->getLoadCommandInfo(DRI.d.a);
-    InMemoryStruct<macho::Section64> Sect;
-    MachOObj->ReadSection64(LCI, DRI.d.b, Sect);
-
-    strcpy(result, Sect->SegmentName);
-    strcat(result, ",");
-    strcat(result, Sect->Name);
+    unsigned SectionOffset = LCI.Offset + sizeof(macho::Segment64LoadCommand) +
+      DRI.d.b * sizeof(macho::Section64);
+    StringRef Data = MachOObj->getData(SectionOffset, sizeof(macho::Section64));
+    const macho::Section64 *sec =
+      reinterpret_cast<const macho::Section64*>(Data.data());
+    Result = parseSegmentOrSectionName(sec->Name);
   } else {
     LoadCommandInfo LCI = MachOObj->getLoadCommandInfo(DRI.d.a);
-    InMemoryStruct<macho::Section> Sect;
-    MachOObj->ReadSection(LCI, DRI.d.b, Sect);
+    unsigned SectionOffset = LCI.Offset + sizeof(macho::SegmentLoadCommand) +
+      DRI.d.b * sizeof(macho::Section);
+    StringRef Data = MachOObj->getData(SectionOffset, sizeof(macho::Section));
+    const macho::Section *sec =
+      reinterpret_cast<const macho::Section*>(Data.data());
+    Result = parseSegmentOrSectionName(sec->Name);
+  }
+  return object_error::success;
+}
 
-    strcpy(result, Sect->SegmentName);
-    strcat(result, ",");
-    strcat(result, Sect->Name);
+error_code MachOObjectFile::getSectionFinalSegmentName(DataRefImpl Sec,
+                                                       StringRef &Res) const {
+  if (is64BitLoadCommand(MachOObj.get(), Sec)) {
+    LoadCommandInfo LCI = MachOObj->getLoadCommandInfo(Sec.d.a);
+    unsigned SectionOffset = LCI.Offset + sizeof(macho::Segment64LoadCommand) +
+      Sec.d.b * sizeof(macho::Section64);
+    StringRef Data = MachOObj->getData(SectionOffset, sizeof(macho::Section64));
+    const macho::Section64 *sec =
+      reinterpret_cast<const macho::Section64*>(Data.data());
+    Res = parseSegmentOrSectionName(sec->SegmentName);
+  } else {
+    LoadCommandInfo LCI = MachOObj->getLoadCommandInfo(Sec.d.a);
+    unsigned SectionOffset = LCI.Offset + sizeof(macho::SegmentLoadCommand) +
+      Sec.d.b * sizeof(macho::Section);
+    StringRef Data = MachOObj->getData(SectionOffset, sizeof(macho::Section));
+    const macho::Section *sec =
+      reinterpret_cast<const macho::Section*>(Data.data());
+    Res = parseSegmentOrSectionName(sec->SegmentName);
   }
-  Result = StringRef(result);
   return object_error::success;
 }