Make PNaCl bitcode files have a different format from LLVM bitcode files.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3405
R=dschuff@chromium.org

Review URL: https://codereview.chromium.org/15907008

1 files changed, 219 insertions, 0 deletions

diff --git a/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h b/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
new file mode 100644
index 0000000000..6e35f62067
--- /dev/null
+++ b/include/llvm/Bitcode/NaCl/NaClBitcodeHeader.h
@@ -0,0 +1,219 @@
+//===-- llvm/Bitcode/NaCl/NaClBitcodeHeader.h - ----------------*- C++ -*-===//
+//      NaCl Bitcode header reader.
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header defines interfaces to read and write NaCl bitcode wire format
+// file headers.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_BITCODE_NACL_NACLBITCODEHEADER_H
+#define LLVM_BITCODE_NACL_NACLBITCODEHEADER_H
+
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/DataTypes.h"
+#include <string>
+#include <vector>
+
+namespace llvm {
+class StreamingMemoryObject;
+
+// Class representing a variable-size metadata field in the bitcode header.
+// Also contains the list of known (typed) Tag IDs.
+//
+// The serialized format has 2 fixed subfields (ID:type and data length) and the
+// variable-length data subfield
+class NaClBitcodeHeaderField {
+  NaClBitcodeHeaderField(const NaClBitcodeHeaderField &) LLVM_DELETED_FUNCTION;
+  void operator=(const NaClBitcodeHeaderField &)LLVM_DELETED_FUNCTION;
+
+public:
+  // Defines the ID associated with the value. Valid values are in
+  // {0x0, ..., 0xFFF}
+  typedef enum {
+    kInvalid = 0,     // KUnknownType.
+    kPNaClVersion = 1 // kUint32.
+  } Tag;
+  // Defines the type of value.
+  typedef enum {
+    kBufferType, // Buffer of form uint8_t[len].
+    kUInt32Type
+  } FieldType;
+  // Defines the number of bytes in a (32-bit) word.
+  static const int WordSize = 4;
+
+  // Defines the encoding of the fixed fields {i.e. ID:type and data length).
+  typedef uint16_t FixedSubfield;
+
+  // Create an invalid header field.
+  NaClBitcodeHeaderField();
+
+  // Create a header field with an uint32_t value.
+  NaClBitcodeHeaderField(Tag MyID, uint32_t value);
+
+  // Create a header field for the given data.
+  NaClBitcodeHeaderField(Tag MyID, size_t MyLen, uint8_t *MyData);
+
+  virtual ~NaClBitcodeHeaderField() {
+    if (Data)
+      delete[] Data;
+  }
+
+  /// \brief Number of bytes used to represent header field.
+  size_t GetTotalSize() const {
+    // Round up to 4 byte alignment
+    return (kTagLenSize + Len + (WordSize - 1)) & ~(WordSize - 1);
+  }
+
+  /// \brief Write field into Buf[BufLen].
+  bool Write(uint8_t *Buf, size_t BufLen) const;
+
+  /// \brief Read field form Buf[BufLen].
+  bool Read(const uint8_t *Buf, size_t BufLen);
+
+  /// \brief Returns string describing field.
+  std::string Contents() const;
+
+  /// \brief Get the data size from a serialized field to allow allocation.
+  static size_t GetDataSizeFromSerialized(const uint8_t *Buf) {
+    FixedSubfield Length;
+    ReadFixedSubfield(&Length, Buf + sizeof(FixedSubfield));
+    return Length;
+  }
+
+  /// \brief Return the ID of the field.
+  Tag GetID() const { return ID; }
+
+  FieldType GetType() const { return FType; }
+
+  /// \brief Return the length of the data (in bytes).
+  size_t GetLen() const { return Len; }
+
+  /// \brief Return the data. Data is array getData()[getLen()].
+  const uint8_t *GetData() const { return Data; }
+
+  /// \brief Returns the uint32_t value stored. Requires that
+  /// getType() == kUint32Type
+  uint32_t GetUInt32Value() const;
+
+private:
+  // Convert ID:Type into a fixed subfield
+  FixedSubfield EncodeTypedID() const { return (ID << 4) | FType; }
+  // Extract out ID and Type from a fixed subfield.
+  void DecodeTypedID(FixedSubfield Subfield, Tag &ID, FieldType &FType) {
+    ID = static_cast<Tag>(Subfield >> 4);
+    FType = static_cast<FieldType>(Subfield & 0xF);
+  }
+  // Combined size of the fixed subfields
+  const static size_t kTagLenSize = 2 * sizeof(FixedSubfield);
+  static void WriteFixedSubfield(FixedSubfield Value, uint8_t *Buf) {
+    Buf[0] = Value & 0xFF;
+    Buf[1] = (Value >> 8) & 0xFF;
+  }
+  static void ReadFixedSubfield(FixedSubfield *Value, const uint8_t *Buf) {
+    *Value = Buf[0] | Buf[1] << 8;
+  }
+  Tag ID;
+  FieldType FType;
+  size_t Len;
+  uint8_t *Data;
+};
+
+/// \brief Class holding parsed header fields in PNaCl bitcode file.
+class NaClBitcodeHeader {
+  // The set of parsed header fields. The header takes ownership of
+  // all fields in this vector.
+  std::vector<NaClBitcodeHeaderField *> Fields;
+  // The number of bytes in the PNaCl header.
+  size_t HeaderSize;
+  // String defining why it is unsupported (if unsupported).
+  std::string UnsupportedMessage;
+  // Flag defining if header is supported.
+  bool IsSupportedFlag;
+  // Flag defining if the corresponding bitcode file is readable.
+  bool IsReadableFlag;
+  // Defines the PNaCl version defined by the header file.
+  uint32_t PNaClVersion;
+
+public:
+  static const int WordSize = NaClBitcodeHeaderField::WordSize;
+
+  NaClBitcodeHeader();
+  ~NaClBitcodeHeader();
+
+  /// \brief Installs the fields of the header, defining if the header
+  /// is readable and supported.
+  void InstallFields();
+
+  /// \brief Read the PNaCl bitcode header, The format of the header is:
+  ///
+  ///    1) 'PEXE' - The four character sequence defining the magic number.
+  ///    2) uint_16 num_fields - The number of NaClBitcodeHeaderField's.
+  ///    3) uint_16 num_bytes - The number of bytes to hold fields in
+  ///                           the header.
+  ///    4) NaClBitcodeHeaderField f1 - The first bitcode header field.
+  ///    ...
+  ///    2 + num_fields) NaClBitcodeHeaderField fn - The last bitcode header
+  /// field.
+  ///
+  /// Returns false if able to read (all of) the bitcode header.
+  bool Read(const unsigned char *&BufPtr, const unsigned char *&BufEnd);
+
+  // \brief Read the PNaCl bitcode header, recording the fields found
+  // in the header. Returns false if able to read (all of) the bitcode header.
+  bool Read(StreamingMemoryObject *Bytes);
+
+  // \brief Returns the number of bytes read to consume the header.
+  size_t getHeaderSize() { return HeaderSize; }
+
+  /// \brief Returns C string describing why the header describes
+  /// an unsupported PNaCl Bitcode file. Returns 0 if supported.
+  const std::string Unsupported() const { return UnsupportedMessage; }
+
+  /// \brief Returns true if supported. That is, it can be run in the
+  /// browser.
+  bool IsSupported() const { return IsSupportedFlag; }
+
+  /// \brief Returns true if the bitcode file should be readable. Note
+  /// that just because it is readable, it doesn't necessarily mean that
+  /// it is supported.
+  bool IsReadable() const { return IsReadableFlag; }
+
+  /// \brief Returns number of fields defined.
+  size_t NumberFields() const { return Fields.size(); }
+
+  /// \brief Returns a pointer to the field with the given ID
+  /// (0 if no such field).
+  NaClBitcodeHeaderField *GetTaggedField(NaClBitcodeHeaderField::Tag ID) const;
+
+  /// \brief Returns a pointer to the Nth field in the header
+  /// (0 if no such field).
+  NaClBitcodeHeaderField *GetField(size_t index) const;
+
+  /// \brief Returns the PNaClVersion, as defined by the header.
+  uint32_t GetPNaClVersion() const { return PNaClVersion; }
+
+private:
+  // Reads and verifies the first 8 bytes of the header, consisting
+  // of the magic number 'PEXE', and the value defining the number
+  // of fields and number of bytes used to hold fields.
+  // Returns false if successful.
+  bool ReadPrefix(const unsigned char *BufPtr, const unsigned char *BufEnd,
+                  unsigned &NumFields, unsigned &NumBytes);
+
+  // Reads and verifies the fields in the header.
+  // Returns false if successful.
+  bool ReadFields(const unsigned char *BufPtr, const unsigned char *BufEnd,
+                  unsigned NumFields, unsigned NumBytes);
+
+};
+
+} // namespace llvm
+
+#endif