cmXCOFF: Add helper to parse and edit the XCOFF binary format

4 files changed, 432 insertions, 0 deletions

diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index 26aaa79..6adc9cf 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -57,6 +57,10 @@ if(APPLE)
   set(CMake_USE_MACH_PARSER 1)
 endif()
 
+if(CMAKE_SYSTEM_NAME STREQUAL "AIX")
+  set(CMake_USE_XCOFF_PARSER 1)
+endif()
+
 set(EXECUTABLE_OUTPUT_PATH ${CMake_BIN_DIR})
 
 if(WIN32)
@@ -117,6 +121,11 @@ if(CMake_USE_MACH_PARSER)
   set(MACH_SRCS cmMachO.h cmMachO.cxx)
 endif()
 
+# Check if we can build the XCOFF parser.
+if(CMake_USE_XCOFF_PARSER)
+  set(XCOFF_SRCS cmXCOFF.h cmXCOFF.cxx)
+endif()
+
 #
 # Sources for CMakeLib
 #
@@ -465,6 +474,7 @@ set(SRCS
   cmWorkerPool.h
   cmWorkingDirectory.cxx
   cmWorkingDirectory.h
+  ${XCOFF_SRCS}
   cmXMLParser.cxx
   cmXMLParser.h
   cmXMLSafe.cxx
diff --git a/Source/cmConfigure.cmake.h.in b/Source/cmConfigure.cmake.h.in
index 2fef246..aeca6b4 100644
--- a/Source/cmConfigure.cmake.h.in
+++ b/Source/cmConfigure.cmake.h.in
@@ -18,6 +18,7 @@
 #cmakedefine HAVE_UNSETENV
 #cmakedefine CMake_USE_ELF_PARSER
 #cmakedefine CMake_USE_MACH_PARSER
+#cmakedefine CMake_USE_XCOFF_PARSER
 #define CMake_DEFAULT_RECURSION_LIMIT @CMake_DEFAULT_RECURSION_LIMIT@
 #define CMAKE_BIN_DIR "/@CMAKE_BIN_DIR@"
 #define CMAKE_DATA_DIR "/@CMAKE_DATA_DIR@"
diff --git a/Source/cmXCOFF.cxx b/Source/cmXCOFF.cxx
new file mode 100644
index 0000000..890636e
--- /dev/null
+++ b/Source/cmXCOFF.cxx
@@ -0,0 +1,356 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmXCOFF.h"
+
+#include <algorithm>
+#include <cstddef>
+
+#include <cm/memory>
+
+#include "cmsys/FStream.hxx"
+
+#include "cmStringAlgorithms.h"
+
+// Include the XCOFF format information system header.
+#ifdef _AIX
+#  define __XCOFF32__
+#  define __XCOFF64__
+#  include <xcoff.h>
+#else
+#  error "This source may be compiled only on AIX."
+#endif
+
+class cmXCOFFInternal
+{
+public:
+  // Construct and take ownership of the file stream object.
+  cmXCOFFInternal(cmXCOFF* external, std::unique_ptr<std::iostream> fin,
+                  cmXCOFF::Mode mode)
+    : External(external)
+    , Stream(std::move(fin))
+    , Mode(mode)
+  {
+  }
+
+  // Destruct and delete the file stream object.
+  virtual ~cmXCOFFInternal() = default;
+
+  cmXCOFF::Mode GetMode() const { return this->Mode; }
+
+  virtual cm::optional<cm::string_view> GetLibPath() = 0;
+
+  virtual bool SetLibPath(cm::string_view libPath) = 0;
+  virtual bool RemoveLibPath() = 0;
+
+protected:
+  // Data common to all ELF class implementations.
+
+  // The external cmXCOFF object.
+  cmXCOFF* External;
+
+  // The stream from which to read.
+  std::unique_ptr<std::iostream> Stream;
+
+  cmXCOFF::Mode Mode;
+
+  // Helper methods for subclasses.
+  void SetErrorMessage(const char* msg) { this->External->ErrorMessage = msg; }
+};
+
+namespace {
+
+struct XCOFF32
+{
+  typedef struct filehdr filehdr;
+  typedef struct aouthdr aouthdr;
+  typedef struct scnhdr scnhdr;
+  typedef struct ldhdr ldhdr;
+  static const std::size_t aouthdr_size = _AOUTHSZ_EXEC;
+};
+const unsigned char xcoff32_magic[] = { 0x01, 0xDF };
+
+struct XCOFF64
+{
+  typedef struct filehdr_64 filehdr;
+  typedef struct aouthdr_64 aouthdr;
+  typedef struct scnhdr_64 scnhdr;
+  typedef struct ldhdr_64 ldhdr;
+  static const std::size_t aouthdr_size = _AOUTHSZ_EXEC_64;
+};
+const unsigned char xcoff64_magic[] = { 0x01, 0xF7 };
+
+template <typename XCOFF>
+class Impl : public cmXCOFFInternal
+{
+  static_assert(sizeof(typename XCOFF::aouthdr) == XCOFF::aouthdr_size,
+                "aouthdr structure size matches _AOUTHSZ_EXEC macro");
+
+  typename XCOFF::filehdr FileHeader;
+  typename XCOFF::aouthdr AuxHeader;
+  typename XCOFF::scnhdr LoaderSectionHeader;
+  typename XCOFF::ldhdr LoaderHeader;
+
+  std::streamoff LoaderImportFileTablePos = 0;
+  std::vector<char> LoaderImportFileTable;
+
+  bool Read(typename XCOFF::filehdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool Read(typename XCOFF::aouthdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool Read(typename XCOFF::scnhdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool Read(typename XCOFF::ldhdr& x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->read(reinterpret_cast<char*>(&x), sizeof(x)));
+  }
+
+  bool WriteLoaderImportFileTableLength(decltype(XCOFF::ldhdr::l_istlen) x)
+  {
+    // FIXME: Add byte swapping if needed.
+    return static_cast<bool>(
+      this->Stream->write(reinterpret_cast<char const*>(&x), sizeof(x)));
+  }
+
+public:
+  Impl(cmXCOFF* external, std::unique_ptr<std::iostream> fin,
+       cmXCOFF::Mode mode);
+
+  cm::optional<cm::string_view> GetLibPath() override;
+  bool SetLibPath(cm::string_view libPath) override;
+  bool RemoveLibPath() override;
+};
+
+template <typename XCOFF>
+Impl<XCOFF>::Impl(cmXCOFF* external, std::unique_ptr<std::iostream> fin,
+                  cmXCOFF::Mode mode)
+  : cmXCOFFInternal(external, std::move(fin), mode)
+{
+  if (!this->Read(this->FileHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF file header.");
+    return;
+  }
+  if (this->FileHeader.f_opthdr != XCOFF::aouthdr_size) {
+    this->SetErrorMessage("XCOFF auxiliary header missing.");
+    return;
+  }
+  if (!this->Read(this->AuxHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF auxiliary header.");
+    return;
+  }
+  if (this->AuxHeader.o_snloader == 0) {
+    this->SetErrorMessage("XCOFF loader section missing.");
+    return;
+  }
+  if (!this->Stream->seekg((this->AuxHeader.o_snloader - 1) *
+                             sizeof(typename XCOFF::scnhdr),
+                           std::ios::cur)) {
+    this->SetErrorMessage("Failed to seek to XCOFF loader section header.");
+    return;
+  }
+  if (!this->Read(this->LoaderSectionHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF loader section header.");
+    return;
+  }
+  if ((this->LoaderSectionHeader.s_flags & STYP_LOADER) == 0) {
+    this->SetErrorMessage("XCOFF loader section header missing STYP_LOADER.");
+    return;
+  }
+  if (!this->Stream->seekg(this->LoaderSectionHeader.s_scnptr,
+                           std::ios::beg)) {
+    this->SetErrorMessage("Failed to seek to XCOFF loader header.");
+    return;
+  }
+  if (!this->Read(this->LoaderHeader)) {
+    this->SetErrorMessage("Failed to read XCOFF loader header.");
+    return;
+  }
+  this->LoaderImportFileTablePos =
+    this->LoaderSectionHeader.s_scnptr + this->LoaderHeader.l_impoff;
+  if (!this->Stream->seekg(this->LoaderImportFileTablePos)) {
+    this->SetErrorMessage(
+      "Failed to seek to XCOFF loader import file id table.");
+    return;
+  }
+  this->LoaderImportFileTable.resize(this->LoaderHeader.l_istlen);
+  if (!this->Stream->read(this->LoaderImportFileTable.data(),
+                          this->LoaderImportFileTable.size())) {
+    this->SetErrorMessage("Failed to read XCOFF loader import file id table.");
+    return;
+  }
+}
+
+template <typename XCOFF>
+cm::optional<cm::string_view> Impl<XCOFF>::GetLibPath()
+{
+  cm::optional<cm::string_view> result;
+  auto end = std::find(this->LoaderImportFileTable.begin(),
+                       this->LoaderImportFileTable.end(), '\0');
+  if (end != this->LoaderImportFileTable.end()) {
+    result = cm::string_view(this->LoaderImportFileTable.data(),
+                             end - this->LoaderImportFileTable.begin());
+  }
+  return result;
+}
+
+template <typename XCOFF>
+bool Impl<XCOFF>::SetLibPath(cm::string_view libPath)
+{
+  // The new LIBPATH must end in the standard AIX LIBPATH.
+#define CM_AIX_LIBPATH "/usr/lib:/lib"
+  std::string libPathBuf;
+  if (libPath != CM_AIX_LIBPATH &&
+      !cmHasLiteralSuffix(libPath, ":" CM_AIX_LIBPATH)) {
+    libPathBuf = std::string(libPath);
+    if (!libPathBuf.empty() && libPathBuf.back() != ':') {
+      libPathBuf.push_back(':');
+    }
+    libPathBuf += CM_AIX_LIBPATH;
+    libPath = libPathBuf;
+  }
+#undef CM_AIX_LIBPATH
+
+  auto oldEnd = std::find(this->LoaderImportFileTable.begin(),
+                          this->LoaderImportFileTable.end(), '\0');
+  if (oldEnd == this->LoaderImportFileTable.end()) {
+    this->SetErrorMessage("XCOFF loader import file id table is invalid.");
+    return false;
+  }
+  if ((this->LoaderImportFileTable.begin() + libPath.size()) > oldEnd) {
+    this->SetErrorMessage("XCOFF loader import file id table is too small.");
+    return false;
+  }
+
+  {
+    std::vector<char> ift;
+    ift.reserve(this->LoaderImportFileTable.size());
+    // Start with the new LIBPATH.
+    ift.insert(ift.end(), libPath.begin(), libPath.end());
+    // Add the rest of the original table.
+    ift.insert(ift.end(), oldEnd, this->LoaderImportFileTable.end());
+    // If the new table is shorter, zero out the leftover space.
+    ift.resize(this->LoaderImportFileTable.size(), 0);
+    this->LoaderHeader.l_istlen =
+      static_cast<decltype(XCOFF::ldhdr::l_istlen)>(ift.size());
+    this->LoaderImportFileTable = std::move(ift);
+  }
+
+  if (!this->Stream->seekp(this->LoaderSectionHeader.s_scnptr +
+                             offsetof(typename XCOFF::ldhdr, l_istlen),
+                           std::ios::beg)) {
+    this->SetErrorMessage(
+      "Failed to seek to XCOFF loader header import file id table length.");
+    return false;
+  }
+  if (!this->WriteLoaderImportFileTableLength(this->LoaderHeader.l_istlen)) {
+    this->SetErrorMessage(
+      "Failed to write XCOFF loader header import file id table length.");
+    return false;
+  }
+  if (!this->Stream->seekp(this->LoaderImportFileTablePos, std::ios::beg)) {
+    this->SetErrorMessage(
+      "Failed to seek to XCOFF loader import file id table.");
+    return false;
+  }
+  if (!this->Stream->write(this->LoaderImportFileTable.data(),
+                           this->LoaderImportFileTable.size())) {
+    this->SetErrorMessage(
+      "Failed to write XCOFF loader import file id table.");
+    return false;
+  }
+
+  return true;
+}
+
+template <typename XCOFF>
+bool Impl<XCOFF>::RemoveLibPath()
+{
+  return this->SetLibPath({});
+}
+}
+
+//============================================================================
+// External class implementation.
+
+cmXCOFF::cmXCOFF(const char* fname, Mode mode)
+{
+  // Try to open the file.
+  std::ios::openmode fmode = std::ios::in | std::ios::binary;
+  if (mode == Mode::ReadWrite) {
+    fmode |= std::ios::out;
+  }
+  auto f = cm::make_unique<cmsys::fstream>(fname, fmode);
+
+  // Quit now if the file could not be opened.
+  if (!f || !*f) {
+    this->ErrorMessage = "Error opening input file.";
+    return;
+  }
+
+  // Read the XCOFF magic number.
+  unsigned char magic[2];
+  if (!f->read(reinterpret_cast<char*>(magic), sizeof(magic))) {
+    this->ErrorMessage = "Error reading XCOFF magic number.";
+    return;
+  }
+  if (!f->seekg(0)) {
+    this->ErrorMessage = "Error seeking to beginning of file.";
+    return;
+  }
+
+  // Check the XCOFF type.
+  if (magic[0] == xcoff32_magic[0] && magic[1] == xcoff32_magic[1]) {
+    this->Internal = cm::make_unique<Impl<XCOFF32>>(this, std::move(f), mode);
+  } else if (magic[0] == xcoff64_magic[0] && magic[1] == xcoff64_magic[1]) {
+    this->Internal = cm::make_unique<Impl<XCOFF64>>(this, std::move(f), mode);
+  } else {
+    this->ErrorMessage = "File is not a XCOFF32 or XCOFF64 binary.";
+  }
+}
+
+cmXCOFF::~cmXCOFF() = default;
+
+cmXCOFF::cmXCOFF(cmXCOFF&&) = default;
+cmXCOFF& cmXCOFF::operator=(cmXCOFF&&) = default;
+
+bool cmXCOFF::Valid() const
+{
+  return this->Internal && this->ErrorMessage.empty();
+}
+
+cm::optional<cm::string_view> cmXCOFF::GetLibPath() const
+{
+  cm::optional<cm::string_view> result;
+  if (this->Valid()) {
+    result = this->Internal->GetLibPath();
+  }
+  return result;
+}
+
+bool cmXCOFF::SetLibPath(cm::string_view libPath)
+{
+  return this->Valid() && this->Internal->GetMode() == Mode::ReadWrite &&
+    this->Internal->SetLibPath(libPath);
+}
+
+bool cmXCOFF::RemoveLibPath()
+{
+  return this->Valid() && this->Internal->GetMode() == Mode::ReadWrite &&
+    this->Internal->RemoveLibPath();
+}
diff --git a/Source/cmXCOFF.h b/Source/cmXCOFF.h
new file mode 100644
index 0000000..16cda9d
--- /dev/null
+++ b/Source/cmXCOFF.h
@@ -0,0 +1,65 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#pragma once
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include <iosfwd>
+#include <memory>
+#include <string>
+
+#include <cm/optional>
+#include <cm/string_view>
+
+#if !defined(CMake_USE_XCOFF_PARSER)
+#  error "This file may be included only if CMake_USE_XCOFF_PARSER is enabled."
+#endif
+
+class cmXCOFFInternal;
+
+/** \class cmXCOFF
+ * \brief XCOFF parser.
+ */
+class cmXCOFF
+{
+public:
+  enum class Mode
+  {
+    ReadOnly,
+    ReadWrite
+  };
+
+  /** Construct with the name of the XCOFF input file to parse.  */
+  cmXCOFF(const char* fname, Mode = Mode::ReadOnly);
+
+  /** Destruct.   */
+  ~cmXCOFF();
+
+  cmXCOFF(cmXCOFF&&);
+  cmXCOFF(cmXCOFF const&) = delete;
+  cmXCOFF& operator=(cmXCOFF&&);
+  cmXCOFF& operator=(cmXCOFF const&) = delete;
+
+  /** Get the error message if any.  */
+  std::string const& GetErrorMessage() const { return this->ErrorMessage; }
+
+  /** Boolean conversion.  True if the XCOFF file is valid.  */
+  explicit operator bool() const { return this->Valid(); }
+
+  /** Get the LIBPATH (RPATH) parsed from the file, if any.  */
+  cm::optional<cm::string_view> GetLibPath() const;
+
+  /** Set the LIBPATH (RPATH).
+      Works only if cmXCOFF was constructed with Mode::ReadWrite.  */
+  bool SetLibPath(cm::string_view libPath);
+
+  /** Remove the LIBPATH (RPATH).
+      Works only if cmXCOFF was constructed with Mode::ReadWrite.  */
+  bool RemoveLibPath();
+
+private:
+  friend class cmXCOFFInternal;
+  bool Valid() const;
+  std::unique_ptr<cmXCOFFInternal> Internal;
+  std::string ErrorMessage;
+};