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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);
// 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_