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 // -*- mode: C++ -*-

 // Copyright (c) 2010, Google Inc.

 // All rights reserved.

 //

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 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>

 // cfi_assembler.h: Define CFISection, a class for creating properly

 // (and improperly) formatted DWARF CFI data for unit tests.

 #ifndef PROCESSOR_CFI_ASSEMBLER_H_

 #define PROCESSOR_CFI_ASSEMBLER_H_

 #include <string>

 #include "common/dwarf/dwarf2enums.h"

 #include "common/test_assembler.h"

 #include "common/using_std_string.h"

 #include "google_breakpad/common/breakpad_types.h"

 namespace google_breakpad {

 using dwarf2reader::DwarfPointerEncoding;

 using google_breakpad::test_assembler::Endianness;

 using google_breakpad::test_assembler::Label;

 using google_breakpad::test_assembler::Section;

 class CFISection: public Section {

  public:

   // CFI augmentation strings beginning with 'z', defined by the

   // Linux/IA-64 C++ ABI, can specify interesting encodings for

   // addresses appearing in FDE headers and call frame instructions (and

   // for additional fields whose presence the augmentation string

   // specifies). In particular, pointers can be specified to be relative

   // to various base address: the start of the .text section, the

   // location holding the address itself, and so on. These allow the

   // frame data to be position-independent even when they live in

   // write-protected pages. These variants are specified at the

   // following two URLs:

   //

   // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/dwarfext.html

   // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html

   //

   // CFISection leaves the production of well-formed 'z'-augmented CIEs and

   // FDEs to the user, but does provide EncodedPointer, to emit

   // properly-encoded addresses for a given pointer encoding.

   // EncodedPointer uses an instance of this structure to find the base

   // addresses it should use; you can establish a default for all encoded

   // pointers appended to this section with SetEncodedPointerBases.

   struct EncodedPointerBases {

     EncodedPointerBases() : cfi(), text(), data() { }

     // The starting address of this CFI section in memory, for

     // DW_EH_PE_pcrel. DW_EH_PE_pcrel pointers may only be used in data

     // that has is loaded into the program's address space.

     uint64_t cfi;

     // The starting address of this file's .text section, for DW_EH_PE_textrel.

     uint64_t text;

     // The starting address of this file's .got or .eh_frame_hdr section,

     // for DW_EH_PE_datarel.

     uint64_t data;

   };

   // Create a CFISection whose endianness is ENDIANNESS, and where

   // machine addresses are ADDRESS_SIZE bytes long. If EH_FRAME is

   // true, use the .eh_frame format, as described by the Linux

   // Standards Base Core Specification, instead of the DWARF CFI

   // format.

   CFISection(Endianness endianness, size_t address_size,

              bool eh_frame = false)

       : Section(endianness), address_size_(address_size), eh_frame_(eh_frame),

         pointer_encoding_(dwarf2reader::DW_EH_PE_absptr),

         encoded_pointer_bases_(), entry_length_(NULL), in_fde_(false) {

     // The 'start', 'Here', and 'Mark' members of a CFISection all refer

     // to section offsets.

     start() = 0;

   }

   // Return this CFISection's address size.

   size_t AddressSize() const { return address_size_; }

   // Return true if this CFISection uses the .eh_frame format, or

   // false if it contains ordinary DWARF CFI data.

   bool ContainsEHFrame() const { return eh_frame_; }

   // Use ENCODING for pointers in calls to FDEHeader and EncodedPointer.

   void SetPointerEncoding(DwarfPointerEncoding encoding) {

     pointer_encoding_ = encoding;

   }

   // Use the addresses in BASES as the base addresses for encoded

   // pointers in subsequent calls to FDEHeader or EncodedPointer.

   // This function makes a copy of BASES.

   void SetEncodedPointerBases(const EncodedPointerBases &bases) {

     encoded_pointer_bases_ = bases;

   }

   // Append a Common Information Entry header to this section with the

   // given values. If dwarf64 is true, use the 64-bit DWARF initial

   // length format for the CIE's initial length. Return a reference to

   // this section. You should call FinishEntry after writing the last

   // instruction for the CIE.

   //

   // Before calling this function, you will typically want to use Mark

   // or Here to make a label to pass to FDEHeader that refers to this

   // CIE's position in the section.

   CFISection &CIEHeader(uint64_t code_alignment_factor,

                         int data_alignment_factor,

                         unsigned return_address_register,

                         uint8_t version = 3,

                         const string &augmentation = "",

                         bool dwarf64 = false);

   // Append a Frame Description Entry header to this section with the

   // given values. If dwarf64 is true, use the 64-bit DWARF initial

   // length format for the CIE's initial length. Return a reference to

   // this section. You should call FinishEntry after writing the last

   // instruction for the CIE.

   //

   // This function doesn't support entries that are longer than

   // 0xffffff00 bytes. (The "initial length" is always a 32-bit

   // value.) Nor does it support .debug_frame sections longer than

   // 0xffffff00 bytes.

   CFISection &FDEHeader(Label cie_pointer,

                         uint64_t initial_location,

                         uint64_t address_range,

                         bool dwarf64 = false);

   // Note the current position as the end of the last CIE or FDE we

   // started, after padding with DW_CFA_nops for alignment. This

   // defines the label representing the entry's length, cited in the

   // entry's header. Return a reference to this section.

   CFISection &FinishEntry();

   // Append the contents of BLOCK as a DW_FORM_block value: an

   // unsigned LEB128 length, followed by that many bytes of data.

   CFISection &Block(const string &block) {

     ULEB128(block.size());

     Append(block);

     return *this;

   }

   // Append ADDRESS to this section, in the appropriate size and

   // endianness. Return a reference to this section.

   CFISection &Address(uint64_t address) {

     Section::Append(endianness(), address_size_, address);

     return *this;

   }

   CFISection &Address(Label address) {

     Section::Append(endianness(), address_size_, address);

     return *this;

   }

   // Append ADDRESS to this section, using ENCODING and BASES. ENCODING

   // defaults to this section's default encoding, established by

   // SetPointerEncoding. BASES defaults to this section's bases, set by

   // SetEncodedPointerBases. If the DW_EH_PE_indirect bit is set in the

   // encoding, assume that ADDRESS is where the true address is stored.

   // Return a reference to this section.

   // 

   // (C++ doesn't let me use default arguments here, because I want to

   // refer to members of *this in the default argument expression.)

   CFISection &EncodedPointer(uint64_t address) {

     return EncodedPointer(address, pointer_encoding_, encoded_pointer_bases_);

   }

   CFISection &EncodedPointer(uint64_t address, DwarfPointerEncoding encoding) {

     return EncodedPointer(address, encoding, encoded_pointer_bases_);

   }

   CFISection &EncodedPointer(uint64_t address, DwarfPointerEncoding encoding,

                              const EncodedPointerBases &bases);

   // Restate some member functions, to keep chaining working nicely.

   CFISection &Mark(Label *label)   { Section::Mark(label); return *this; }

   CFISection &D8(uint8_t v)       { Section::D8(v);       return *this; }

   CFISection &D16(uint16_t v)     { Section::D16(v);      return *this; }

   CFISection &D16(Label v)         { Section::D16(v);      return *this; }

   CFISection &D32(uint32_t v)     { Section::D32(v);      return *this; }

   CFISection &D32(const Label &v)  { Section::D32(v);      return *this; }

   CFISection &D64(uint64_t v)     { Section::D64(v);      return *this; }

   CFISection &D64(const Label &v)  { Section::D64(v);      return *this; }

   CFISection &LEB128(long long v)  { Section::LEB128(v);   return *this; }

   CFISection &ULEB128(uint64_t v) { Section::ULEB128(v);  return *this; }

  private:

   // A length value that we've appended to the section, but is not yet

   // known. LENGTH is the appended value; START is a label referring

   // to the start of the data whose length was cited.

   struct PendingLength {

     Label length;

     Label start;

   };

   // Constants used in CFI/.eh_frame data:

   // If the first four bytes of an "initial length" are this constant, then

   // the data uses the 64-bit DWARF format, and the length itself is the

   // subsequent eight bytes.

   static const uint32_t kDwarf64InitialLengthMarker = 0xffffffffU;

   // The CIE identifier for 32- and 64-bit DWARF CFI and .eh_frame data.

   static const uint32_t kDwarf32CIEIdentifier = ~(uint32_t)0;

   static const uint64_t kDwarf64CIEIdentifier = ~(uint64_t)0;

   static const uint32_t kEHFrame32CIEIdentifier = 0;

   static const uint64_t kEHFrame64CIEIdentifier = 0;

   // The size of a machine address for the data in this section.

   size_t address_size_;

   // If true, we are generating a Linux .eh_frame section, instead of

   // a standard DWARF .debug_frame section.

   bool eh_frame_;

   // The encoding to use for FDE pointers.

   DwarfPointerEncoding pointer_encoding_;

   // The base addresses to use when emitting encoded pointers.

   EncodedPointerBases encoded_pointer_bases_;

   // The length value for the current entry.

   //

   // Oddly, this must be dynamically allocated. Labels never get new

   // values; they only acquire constraints on the value they already

   // have, or assert if you assign them something incompatible. So

   // each header needs truly fresh Label objects to cite in their

   // headers and track their positions. The alternative is explicit

   // destructor invocation and a placement new. Ick.

   PendingLength *entry_length_;

   // True if we are currently emitting an FDE --- that is, we have

   // called FDEHeader but have not yet called FinishEntry.

   bool in_fde_;

   // If in_fde_ is true, this is its starting address. We use this for

   // emitting DW_EH_PE_funcrel pointers.

   uint64_t fde_start_address_;

 };

 }  // namespace google_breakpad

 #endif  // PROCESSOR_CFI_ASSEMBLER_H_