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+// -*- mode: C++ -*-
+
+// Copyright (c) 2010, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// 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,
+ uint8_t address_size = 8,
+ uint8_t segment_size = 0);
+
+ // 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_