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gecko-dev/tools/profiler/LulDwarfExt.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright 2006, 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>
// This file is derived from the following files in
// toolkit/crashreporter/google-breakpad:
// src/common/dwarf/types.h
// src/common/dwarf/dwarf2enums.h
// src/common/dwarf/bytereader.h
// src/common/dwarf_cfi_to_module.h
// src/common/dwarf/dwarf2reader.h
#ifndef LulDwarfExt_h
#define LulDwarfExt_h
#include <stdint.h>
#include "mozilla/Assertions.h"
#include "LulDwarfSummariser.h"
typedef signed char int8;
typedef short int16;
typedef int int32;
typedef long long int64;
typedef unsigned char uint8;
typedef unsigned short uint16;
typedef unsigned int uint32;
typedef unsigned long long uint64;
#ifdef __PTRDIFF_TYPE__
typedef __PTRDIFF_TYPE__ intptr;
typedef unsigned __PTRDIFF_TYPE__ uintptr;
#else
#error "Can't find pointer-sized integral types."
#endif
namespace lul {
// Exception handling frame description pointer formats, as described
// by the Linux Standard Base Core Specification 4.0, section 11.5,
// DWARF Extensions.
enum DwarfPointerEncoding
{
DW_EH_PE_absptr = 0x00,
DW_EH_PE_omit = 0xff,
DW_EH_PE_uleb128 = 0x01,
DW_EH_PE_udata2 = 0x02,
DW_EH_PE_udata4 = 0x03,
DW_EH_PE_udata8 = 0x04,
DW_EH_PE_sleb128 = 0x09,
DW_EH_PE_sdata2 = 0x0A,
DW_EH_PE_sdata4 = 0x0B,
DW_EH_PE_sdata8 = 0x0C,
DW_EH_PE_pcrel = 0x10,
DW_EH_PE_textrel = 0x20,
DW_EH_PE_datarel = 0x30,
DW_EH_PE_funcrel = 0x40,
DW_EH_PE_aligned = 0x50,
// The GNU toolchain sources define this enum value as well,
// simply to help classify the lower nybble values into signed and
// unsigned groups.
DW_EH_PE_signed = 0x08,
// This is not documented in LSB 4.0, but it is used in both the
// Linux and OS X toolchains. It can be added to any other
// encoding (except DW_EH_PE_aligned), and indicates that the
// encoded value represents the address at which the true address
// is stored, not the true address itself.
DW_EH_PE_indirect = 0x80
};
// We can't use the obvious name of LITTLE_ENDIAN and BIG_ENDIAN
// because it conflicts with a macro
enum Endianness {
ENDIANNESS_BIG,
ENDIANNESS_LITTLE
};
// A ByteReader knows how to read single- and multi-byte values of
// various endiannesses, sizes, and encodings, as used in DWARF
// debugging information and Linux C++ exception handling data.
class ByteReader {
public:
// Construct a ByteReader capable of reading one-, two-, four-, and
// eight-byte values according to ENDIANNESS, absolute machine-sized
// addresses, DWARF-style "initial length" values, signed and
// unsigned LEB128 numbers, and Linux C++ exception handling data's
// encoded pointers.
explicit ByteReader(enum Endianness endianness);
virtual ~ByteReader();
// Read a single byte from BUFFER and return it as an unsigned 8 bit
// number.
uint8 ReadOneByte(const char* buffer) const;
// Read two bytes from BUFFER and return them as an unsigned 16 bit
// number, using this ByteReader's endianness.
uint16 ReadTwoBytes(const char* buffer) const;
// Read four bytes from BUFFER and return them as an unsigned 32 bit
// number, using this ByteReader's endianness. This function returns
// a uint64 so that it is compatible with ReadAddress and
// ReadOffset. The number it returns will never be outside the range
// of an unsigned 32 bit integer.
uint64 ReadFourBytes(const char* buffer) const;
// Read eight bytes from BUFFER and return them as an unsigned 64
// bit number, using this ByteReader's endianness.
uint64 ReadEightBytes(const char* buffer) const;
// Read an unsigned LEB128 (Little Endian Base 128) number from
// BUFFER and return it as an unsigned 64 bit integer. Set LEN to
// the number of bytes read.
//
// The unsigned LEB128 representation of an integer N is a variable
// number of bytes:
//
// - If N is between 0 and 0x7f, then its unsigned LEB128
// representation is a single byte whose value is N.
//
// - Otherwise, its unsigned LEB128 representation is (N & 0x7f) |
// 0x80, followed by the unsigned LEB128 representation of N /
// 128, rounded towards negative infinity.
//
// In other words, we break VALUE into groups of seven bits, put
// them in little-endian order, and then write them as eight-bit
// bytes with the high bit on all but the last.
uint64 ReadUnsignedLEB128(const char* buffer, size_t* len) const;
// Read a signed LEB128 number from BUFFER and return it as an
// signed 64 bit integer. Set LEN to the number of bytes read.
//
// The signed LEB128 representation of an integer N is a variable
// number of bytes:
//
// - If N is between -0x40 and 0x3f, then its signed LEB128
// representation is a single byte whose value is N in two's
// complement.
//
// - Otherwise, its signed LEB128 representation is (N & 0x7f) |
// 0x80, followed by the signed LEB128 representation of N / 128,
// rounded towards negative infinity.
//
// In other words, we break VALUE into groups of seven bits, put
// them in little-endian order, and then write them as eight-bit
// bytes with the high bit on all but the last.
int64 ReadSignedLEB128(const char* buffer, size_t* len) const;
// Indicate that addresses on this architecture are SIZE bytes long. SIZE
// must be either 4 or 8. (DWARF allows addresses to be any number of
// bytes in length from 1 to 255, but we only support 32- and 64-bit
// addresses at the moment.) You must call this before using the
// ReadAddress member function.
//
// For data in a .debug_info section, or something that .debug_info
// refers to like line number or macro data, the compilation unit
// header's address_size field indicates the address size to use. Call
// frame information doesn't indicate its address size (a shortcoming of
// the spec); you must supply the appropriate size based on the
// architecture of the target machine.
void SetAddressSize(uint8 size);
// Return the current address size, in bytes. This is either 4,
// indicating 32-bit addresses, or 8, indicating 64-bit addresses.
uint8 AddressSize() const { return address_size_; }
// Read an address from BUFFER and return it as an unsigned 64 bit
// integer, respecting this ByteReader's endianness and address size. You
// must call SetAddressSize before calling this function.
uint64 ReadAddress(const char* buffer) const;
// DWARF actually defines two slightly different formats: 32-bit DWARF
// and 64-bit DWARF. This is *not* related to the size of registers or
// addresses on the target machine; it refers only to the size of section
// offsets and data lengths appearing in the DWARF data. One only needs
// 64-bit DWARF when the debugging data itself is larger than 4GiB.
// 32-bit DWARF can handle x86_64 or PPC64 code just fine, unless the
// debugging data itself is very large.
//
// DWARF information identifies itself as 32-bit or 64-bit DWARF: each
// compilation unit and call frame information entry begins with an
// "initial length" field, which, in addition to giving the length of the
// data, also indicates the size of section offsets and lengths appearing
// in that data. The ReadInitialLength member function, below, reads an
// initial length and sets the ByteReader's offset size as a side effect.
// Thus, in the normal process of reading DWARF data, the appropriate
// offset size is set automatically. So, you should only need to call
// SetOffsetSize if you are using the same ByteReader to jump from the
// midst of one block of DWARF data into another.
// Read a DWARF "initial length" field from START, and return it as
// an unsigned 64 bit integer, respecting this ByteReader's
// endianness. Set *LEN to the length of the initial length in
// bytes, either four or twelve. As a side effect, set this
// ByteReader's offset size to either 4 (if we see a 32-bit DWARF
// initial length) or 8 (if we see a 64-bit DWARF initial length).
//
// A DWARF initial length is either:
//
// - a byte count stored as an unsigned 32-bit value less than
// 0xffffff00, indicating that the data whose length is being
// measured uses the 32-bit DWARF format, or
//
// - The 32-bit value 0xffffffff, followed by a 64-bit byte count,
// indicating that the data whose length is being measured uses
// the 64-bit DWARF format.
uint64 ReadInitialLength(const char* start, size_t* len);
// Read an offset from BUFFER and return it as an unsigned 64 bit
// integer, respecting the ByteReader's endianness. In 32-bit DWARF, the
// offset is 4 bytes long; in 64-bit DWARF, the offset is eight bytes
// long. You must call ReadInitialLength or SetOffsetSize before calling
// this function; see the comments above for details.
uint64 ReadOffset(const char* buffer) const;
// Return the current offset size, in bytes.
// A return value of 4 indicates that we are reading 32-bit DWARF.
// A return value of 8 indicates that we are reading 64-bit DWARF.
uint8 OffsetSize() const { return offset_size_; }
// Indicate that section offsets and lengths are SIZE bytes long. SIZE
// must be either 4 (meaning 32-bit DWARF) or 8 (meaning 64-bit DWARF).
// Usually, you should not call this function yourself; instead, let a
// call to ReadInitialLength establish the data's offset size
// automatically.
void SetOffsetSize(uint8 size);
// The Linux C++ ABI uses a variant of DWARF call frame information
// for exception handling. This data is included in the program's
// address space as the ".eh_frame" section, and intepreted at
// runtime to walk the stack, find exception handlers, and run
// cleanup code. The format is mostly the same as DWARF CFI, with
// some adjustments made to provide the additional
// exception-handling data, and to make the data easier to work with
// in memory --- for example, to allow it to be placed in read-only
// memory even when describing position-independent code.
//
// In particular, exception handling data can select a number of
// different encodings for pointers that appear in the data, as
// described by the DwarfPointerEncoding enum. There are actually
// four axes(!) to the encoding:
//
// - The pointer size: pointers can be 2, 4, or 8 bytes long, or use
// the DWARF LEB128 encoding.
//
// - The pointer's signedness: pointers can be signed or unsigned.
//
// - The pointer's base address: the data stored in the exception
// handling data can be the actual address (that is, an absolute
// pointer), or relative to one of a number of different base
// addreses --- including that of the encoded pointer itself, for
// a form of "pc-relative" addressing.
//
// - The pointer may be indirect: it may be the address where the
// true pointer is stored. (This is used to refer to things via
// global offset table entries, program linkage table entries, or
// other tricks used in position-independent code.)
//
// There are also two options that fall outside that matrix
// altogether: the pointer may be omitted, or it may have padding to
// align it on an appropriate address boundary. (That last option
// may seem like it should be just another axis, but it is not.)
// Indicate that the exception handling data is loaded starting at
// SECTION_BASE, and that the start of its buffer in our own memory
// is BUFFER_BASE. This allows us to find the address that a given
// byte in our buffer would have when loaded into the program the
// data describes. We need this to resolve DW_EH_PE_pcrel pointers.
void SetCFIDataBase(uint64 section_base, const char *buffer_base);
// Indicate that the base address of the program's ".text" section
// is TEXT_BASE. We need this to resolve DW_EH_PE_textrel pointers.
void SetTextBase(uint64 text_base);
// Indicate that the base address for DW_EH_PE_datarel pointers is
// DATA_BASE. The proper value depends on the ABI; it is usually the
// address of the global offset table, held in a designated register in
// position-independent code. You will need to look at the startup code
// for the target system to be sure. I tried; my eyes bled.
void SetDataBase(uint64 data_base);
// Indicate that the base address for the FDE we are processing is
// FUNCTION_BASE. This is the start address of DW_EH_PE_funcrel
// pointers. (This encoding does not seem to be used by the GNU
// toolchain.)
void SetFunctionBase(uint64 function_base);
// Indicate that we are no longer processing any FDE, so any use of
// a DW_EH_PE_funcrel encoding is an error.
void ClearFunctionBase();
// Return true if ENCODING is a valid pointer encoding.
bool ValidEncoding(DwarfPointerEncoding encoding) const;
// Return true if we have all the information we need to read a
// pointer that uses ENCODING. This checks that the appropriate
// SetFooBase function for ENCODING has been called.
bool UsableEncoding(DwarfPointerEncoding encoding) const;
// Read an encoded pointer from BUFFER using ENCODING; return the
// absolute address it represents, and set *LEN to the pointer's
// length in bytes, including any padding for aligned pointers.
//
// This function calls 'abort' if ENCODING is invalid or refers to a
// base address this reader hasn't been given, so you should check
// with ValidEncoding and UsableEncoding first if you would rather
// die in a more helpful way.
uint64 ReadEncodedPointer(const char *buffer, DwarfPointerEncoding encoding,
size_t *len) const;
private:
// Function pointer type for our address and offset readers.
typedef uint64 (ByteReader::*AddressReader)(const char*) const;
// Read an offset from BUFFER and return it as an unsigned 64 bit
// integer. DWARF2/3 define offsets as either 4 or 8 bytes,
// generally depending on the amount of DWARF2/3 info present.
// This function pointer gets set by SetOffsetSize.
AddressReader offset_reader_;
// Read an address from BUFFER and return it as an unsigned 64 bit
// integer. DWARF2/3 allow addresses to be any size from 0-255
// bytes currently. Internally we support 4 and 8 byte addresses,
// and will CHECK on anything else.
// This function pointer gets set by SetAddressSize.
AddressReader address_reader_;
Endianness endian_;
uint8 address_size_;
uint8 offset_size_;
// Base addresses for Linux C++ exception handling data's encoded pointers.
bool have_section_base_, have_text_base_, have_data_base_;
bool have_function_base_;
uint64 section_base_;
uint64 text_base_, data_base_, function_base_;
const char *buffer_base_;
};
inline uint8 ByteReader::ReadOneByte(const char* buffer) const {
return buffer[0];
}
inline uint16 ByteReader::ReadTwoBytes(const char* signed_buffer) const {
const unsigned char *buffer
= reinterpret_cast<const unsigned char *>(signed_buffer);
const uint16 buffer0 = buffer[0];
const uint16 buffer1 = buffer[1];
if (endian_ == ENDIANNESS_LITTLE) {
return buffer0 | buffer1 << 8;
} else {
return buffer1 | buffer0 << 8;
}
}
inline uint64 ByteReader::ReadFourBytes(const char* signed_buffer) const {
const unsigned char *buffer
= reinterpret_cast<const unsigned char *>(signed_buffer);
const uint32 buffer0 = buffer[0];
const uint32 buffer1 = buffer[1];
const uint32 buffer2 = buffer[2];
const uint32 buffer3 = buffer[3];
if (endian_ == ENDIANNESS_LITTLE) {
return buffer0 | buffer1 << 8 | buffer2 << 16 | buffer3 << 24;
} else {
return buffer3 | buffer2 << 8 | buffer1 << 16 | buffer0 << 24;
}
}
inline uint64 ByteReader::ReadEightBytes(const char* signed_buffer) const {
const unsigned char *buffer
= reinterpret_cast<const unsigned char *>(signed_buffer);
const uint64 buffer0 = buffer[0];
const uint64 buffer1 = buffer[1];
const uint64 buffer2 = buffer[2];
const uint64 buffer3 = buffer[3];
const uint64 buffer4 = buffer[4];
const uint64 buffer5 = buffer[5];
const uint64 buffer6 = buffer[6];
const uint64 buffer7 = buffer[7];
if (endian_ == ENDIANNESS_LITTLE) {
return buffer0 | buffer1 << 8 | buffer2 << 16 | buffer3 << 24 |
buffer4 << 32 | buffer5 << 40 | buffer6 << 48 | buffer7 << 56;
} else {
return buffer7 | buffer6 << 8 | buffer5 << 16 | buffer4 << 24 |
buffer3 << 32 | buffer2 << 40 | buffer1 << 48 | buffer0 << 56;
}
}
// Read an unsigned LEB128 number. Each byte contains 7 bits of
// information, plus one bit saying whether the number continues or
// not.
inline uint64 ByteReader::ReadUnsignedLEB128(const char* buffer,
size_t* len) const {
uint64 result = 0;
size_t num_read = 0;
unsigned int shift = 0;
unsigned char byte;
do {
byte = *buffer++;
num_read++;
result |= (static_cast<uint64>(byte & 0x7f)) << shift;
shift += 7;
} while (byte & 0x80);
*len = num_read;
return result;
}
// Read a signed LEB128 number. These are like regular LEB128
// numbers, except the last byte may have a sign bit set.
inline int64 ByteReader::ReadSignedLEB128(const char* buffer,
size_t* len) const {
int64 result = 0;
unsigned int shift = 0;
size_t num_read = 0;
unsigned char byte;
do {
byte = *buffer++;
num_read++;
result |= (static_cast<uint64>(byte & 0x7f) << shift);
shift += 7;
} while (byte & 0x80);
if ((shift < 8 * sizeof (result)) && (byte & 0x40))
result |= -((static_cast<int64>(1)) << shift);
*len = num_read;
return result;
}
inline uint64 ByteReader::ReadOffset(const char* buffer) const {
MOZ_ASSERT(this->offset_reader_);
return (this->*offset_reader_)(buffer);
}
inline uint64 ByteReader::ReadAddress(const char* buffer) const {
MOZ_ASSERT(this->address_reader_);
return (this->*address_reader_)(buffer);
}
inline void ByteReader::SetCFIDataBase(uint64 section_base,
const char *buffer_base) {
section_base_ = section_base;
buffer_base_ = buffer_base;
have_section_base_ = true;
}
inline void ByteReader::SetTextBase(uint64 text_base) {
text_base_ = text_base;
have_text_base_ = true;
}
inline void ByteReader::SetDataBase(uint64 data_base) {
data_base_ = data_base;
have_data_base_ = true;
}
inline void ByteReader::SetFunctionBase(uint64 function_base) {
function_base_ = function_base;
have_function_base_ = true;
}
inline void ByteReader::ClearFunctionBase() {
have_function_base_ = false;
}
// (derived from)
// dwarf_cfi_to_module.h: Define the DwarfCFIToModule class, which
// accepts parsed DWARF call frame info and adds it to a Summariser object.
// This class is a reader for DWARF's Call Frame Information. CFI
// describes how to unwind stack frames --- even for functions that do
// not follow fixed conventions for saving registers, whose frame size
// varies as they execute, etc.
//
// CFI describes, at each machine instruction, how to compute the
// stack frame's base address, how to find the return address, and
// where to find the saved values of the caller's registers (if the
// callee has stashed them somewhere to free up the registers for its
// own use).
//
// For example, suppose we have a function whose machine code looks
// like this (imagine an assembly language that looks like C, for a
// machine with 32-bit registers, and a stack that grows towards lower
// addresses):
//
// func: ; entry point; return address at sp
// func+0: sp = sp - 16 ; allocate space for stack frame
// func+1: sp[12] = r0 ; save r0 at sp+12
// ... ; other code, not frame-related
// func+10: sp -= 4; *sp = x ; push some x on the stack
// ... ; other code, not frame-related
// func+20: r0 = sp[16] ; restore saved r0
// func+21: sp += 20 ; pop whole stack frame
// func+22: pc = *sp; sp += 4 ; pop return address and jump to it
//
// DWARF CFI is (a very compressed representation of) a table with a
// row for each machine instruction address and a column for each
// register showing how to restore it, if possible.
//
// A special column named "CFA", for "Canonical Frame Address", tells how
// to compute the base address of the frame; registers' entries may
// refer to the CFA in describing where the registers are saved.
//
// Another special column, named "RA", represents the return address.
//
// For example, here is a complete (uncompressed) table describing the
// function above:
//
// insn cfa r0 r1 ... ra
// =======================================
// func+0: sp cfa[0]
// func+1: sp+16 cfa[0]
// func+2: sp+16 cfa[-4] cfa[0]
// func+11: sp+20 cfa[-4] cfa[0]
// func+21: sp+20 cfa[0]
// func+22: sp cfa[0]
//
// Some things to note here:
//
// - Each row describes the state of affairs *before* executing the
// instruction at the given address. Thus, the row for func+0
// describes the state before we allocate the stack frame. In the
// next row, the formula for computing the CFA has changed,
// reflecting that allocation.
//
// - The other entries are written in terms of the CFA; this allows
// them to remain unchanged as the stack pointer gets bumped around.
// For example, the rule for recovering the return address (the "ra"
// column) remains unchanged throughout the function, even as the
// stack pointer takes on three different offsets from the return
// address.
//
// - Although we haven't shown it, most calling conventions designate
// "callee-saves" and "caller-saves" registers. The callee must
// preserve the values of callee-saves registers; if it uses them,
// it must save their original values somewhere, and restore them
// before it returns. In contrast, the callee is free to trash
// caller-saves registers; if the callee uses these, it will
// probably not bother to save them anywhere, and the CFI will
// probably mark their values as "unrecoverable".
//
// (However, since the caller cannot assume the callee was going to
// save them, caller-saves registers are probably dead in the caller
// anyway, so compilers usually don't generate CFA for caller-saves
// registers.)
//
// - Exactly where the CFA points is a matter of convention that
// depends on the architecture and ABI in use. In the example, the
// CFA is the value the stack pointer had upon entry to the
// function, pointing at the saved return address. But on the x86,
// the call frame information generated by GCC follows the
// convention that the CFA is the address *after* the saved return
// address.
//
// But by definition, the CFA remains constant throughout the
// lifetime of the frame. This makes it a useful value for other
// columns to refer to. It is also gives debuggers a useful handle
// for identifying a frame.
//
// If you look at the table above, you'll notice that a given entry is
// often the same as the one immediately above it: most instructions
// change only one or two aspects of the stack frame, if they affect
// it at all. The DWARF format takes advantage of this fact, and
// reduces the size of the data by mentioning only the addresses and
// columns at which changes take place. So for the above, DWARF CFI
// data would only actually mention the following:
//
// insn cfa r0 r1 ... ra
// =======================================
// func+0: sp cfa[0]
// func+1: sp+16
// func+2: cfa[-4]
// func+11: sp+20
// func+21: r0
// func+22: sp
//
// In fact, this is the way the parser reports CFI to the consumer: as
// a series of statements of the form, "At address X, column Y changed
// to Z," and related conventions for describing the initial state.
//
// Naturally, it would be impractical to have to scan the entire
// program's CFI, noting changes as we go, just to recover the
// unwinding rules in effect at one particular instruction. To avoid
// this, CFI data is grouped into "entries", each of which covers a
// specified range of addresses and begins with a complete statement
// of the rules for all recoverable registers at that starting
// address. Each entry typically covers a single function.
//
// Thus, to compute the contents of a given row of the table --- that
// is, rules for recovering the CFA, RA, and registers at a given
// instruction --- the consumer should find the entry that covers that
// instruction's address, start with the initial state supplied at the
// beginning of the entry, and work forward until it has processed all
// the changes up to and including those for the present instruction.
//
// There are seven kinds of rules that can appear in an entry of the
// table:
//
// - "undefined": The given register is not preserved by the callee;
// its value cannot be recovered.
//
// - "same value": This register has the same value it did in the callee.
//
// - offset(N): The register is saved at offset N from the CFA.
//
// - val_offset(N): The value the register had in the caller is the
// CFA plus offset N. (This is usually only useful for describing
// the stack pointer.)
//
// - register(R): The register's value was saved in another register R.
//
// - expression(E): Evaluating the DWARF expression E using the
// current frame's registers' values yields the address at which the
// register was saved.
//
// - val_expression(E): Evaluating the DWARF expression E using the
// current frame's registers' values yields the value the register
// had in the caller.
class CallFrameInfo {
public:
// The different kinds of entries one finds in CFI. Used internally,
// and for error reporting.
enum EntryKind { kUnknown, kCIE, kFDE, kTerminator };
// The handler class to which the parser hands the parsed call frame
// information. Defined below.
class Handler;
// A reporter class, which CallFrameInfo uses to report errors
// encountered while parsing call frame information. Defined below.
class Reporter;
// Create a DWARF CFI parser. BUFFER points to the contents of the
// .debug_frame section to parse; BUFFER_LENGTH is its length in bytes.
// REPORTER is an error reporter the parser should use to report
// problems. READER is a ByteReader instance that has the endianness and
// address size set properly. Report the data we find to HANDLER.
//
// This class can also parse Linux C++ exception handling data, as found
// in '.eh_frame' sections. This data is a variant of DWARF CFI that is
// placed in loadable segments so that it is present in the program's
// address space, and is interpreted by the C++ runtime to search the
// call stack for a handler interested in the exception being thrown,
// actually pop the frames, and find cleanup code to run.
//
// There are two differences between the call frame information described
// in the DWARF standard and the exception handling data Linux places in
// the .eh_frame section:
//
// - Exception handling data uses uses a different format for call frame
// information entry headers. The distinguished CIE id, the way FDEs
// refer to their CIEs, and the way the end of the series of entries is
// determined are all slightly different.
//
// If the constructor's EH_FRAME argument is true, then the
// CallFrameInfo parses the entry headers as Linux C++ exception
// handling data. If EH_FRAME is false or omitted, the CallFrameInfo
// parses standard DWARF call frame information.
//
// - Linux C++ exception handling data uses CIE augmentation strings
// beginning with 'z' to specify the presence of additional data after
// the CIE and FDE headers and special encodings used for addresses in
// frame description entries.
//
// CallFrameInfo can handle 'z' augmentations in either DWARF CFI or
// exception handling data if you have supplied READER with the base
// addresses needed to interpret the pointer encodings that 'z'
// augmentations can specify. See the ByteReader interface for details
// about the base addresses. See the CallFrameInfo::Handler interface
// for details about the additional information one might find in
// 'z'-augmented data.
//
// Thus:
//
// - If you are parsing standard DWARF CFI, as found in a .debug_frame
// section, you should pass false for the EH_FRAME argument, or omit
// it, and you need not worry about providing READER with the
// additional base addresses.
//
// - If you want to parse Linux C++ exception handling data from a
// .eh_frame section, you should pass EH_FRAME as true, and call
// READER's Set*Base member functions before calling our Start method.
//
// - If you want to parse DWARF CFI that uses the 'z' augmentations
// (although I don't think any toolchain ever emits such data), you
// could pass false for EH_FRAME, but call READER's Set*Base members.
//
// The extensions the Linux C++ ABI makes to DWARF for exception
// handling are described here, rather poorly:
// 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
//
// The mechanics of C++ exception handling, personality routines,
// and language-specific data areas are described here, rather nicely:
// http://www.codesourcery.com/public/cxx-abi/abi-eh.html
CallFrameInfo(const char *buffer, size_t buffer_length,
ByteReader *reader, Handler *handler, Reporter *reporter,
bool eh_frame = false)
: buffer_(buffer), buffer_length_(buffer_length),
reader_(reader), handler_(handler), reporter_(reporter),
eh_frame_(eh_frame) { }
~CallFrameInfo() { }
// Parse the entries in BUFFER, reporting what we find to HANDLER.
// Return true if we reach the end of the section successfully, or
// false if we encounter an error.
bool Start();
// Return the textual name of KIND. For error reporting.
static const char *KindName(EntryKind kind);
private:
struct CIE;
// A CFI entry, either an FDE or a CIE.
struct Entry {
// The starting offset of the entry in the section, for error
// reporting.
size_t offset;
// The start of this entry in the buffer.
const char *start;
// Which kind of entry this is.
//
// We want to be able to use this for error reporting even while we're
// in the midst of parsing. Error reporting code may assume that kind,
// offset, and start fields are valid, although kind may be kUnknown.
EntryKind kind;
// The end of this entry's common prologue (initial length and id), and
// the start of this entry's kind-specific fields.
const char *fields;
// The start of this entry's instructions.
const char *instructions;
// The address past the entry's last byte in the buffer. (Note that
// since offset points to the entry's initial length field, and the
// length field is the number of bytes after that field, this is not
// simply buffer_ + offset + length.)
const char *end;
// For both DWARF CFI and .eh_frame sections, this is the CIE id in a
// CIE, and the offset of the associated CIE in an FDE.
uint64 id;
// The CIE that applies to this entry, if we've parsed it. If this is a
// CIE, then this field points to this structure.
CIE *cie;
};
// A common information entry (CIE).
struct CIE: public Entry {
uint8 version; // CFI data version number
std::string augmentation; // vendor format extension markers
uint64 code_alignment_factor; // scale for code address adjustments
int data_alignment_factor; // scale for stack pointer adjustments
unsigned return_address_register; // which register holds the return addr
// True if this CIE includes Linux C++ ABI 'z' augmentation data.
bool has_z_augmentation;
// Parsed 'z' augmentation data. These are meaningful only if
// has_z_augmentation is true.
bool has_z_lsda; // The 'z' augmentation included 'L'.
bool has_z_personality; // The 'z' augmentation included 'P'.
bool has_z_signal_frame; // The 'z' augmentation included 'S'.
// If has_z_lsda is true, this is the encoding to be used for language-
// specific data area pointers in FDEs.
DwarfPointerEncoding lsda_encoding;
// If has_z_personality is true, this is the encoding used for the
// personality routine pointer in the augmentation data.
DwarfPointerEncoding personality_encoding;
// If has_z_personality is true, this is the address of the personality
// routine --- or, if personality_encoding & DW_EH_PE_indirect, the
// address where the personality routine's address is stored.
uint64 personality_address;
// This is the encoding used for addresses in the FDE header and
// in DW_CFA_set_loc instructions. This is always valid, whether
// or not we saw a 'z' augmentation string; its default value is
// DW_EH_PE_absptr, which is what normal DWARF CFI uses.
DwarfPointerEncoding pointer_encoding;
};
// A frame description entry (FDE).
struct FDE: public Entry {
uint64 address; // start address of described code
uint64 size; // size of described code, in bytes
// If cie->has_z_lsda is true, then this is the language-specific data
// area's address --- or its address's address, if cie->lsda_encoding
// has the DW_EH_PE_indirect bit set.
uint64 lsda_address;
};
// Internal use.
class Rule;
class UndefinedRule;
class SameValueRule;
class OffsetRule;
class ValOffsetRule;
class RegisterRule;
class ExpressionRule;
class ValExpressionRule;
class RuleMap;
class State;
// Parse the initial length and id of a CFI entry, either a CIE, an FDE,
// or a .eh_frame end-of-data mark. CURSOR points to the beginning of the
// data to parse. On success, populate ENTRY as appropriate, and return
// true. On failure, report the problem, and return false. Even if we
// return false, set ENTRY->end to the first byte after the entry if we
// were able to figure that out, or NULL if we weren't.
bool ReadEntryPrologue(const char *cursor, Entry *entry);
// Parse the fields of a CIE after the entry prologue, including any 'z'
// augmentation data. Assume that the 'Entry' fields of CIE are
// populated; use CIE->fields and CIE->end as the start and limit for
// parsing. On success, populate the rest of *CIE, and return true; on
// failure, report the problem and return false.
bool ReadCIEFields(CIE *cie);
// Parse the fields of an FDE after the entry prologue, including any 'z'
// augmentation data. Assume that the 'Entry' fields of *FDE are
// initialized; use FDE->fields and FDE->end as the start and limit for
// parsing. Assume that FDE->cie is fully initialized. On success,
// populate the rest of *FDE, and return true; on failure, report the
// problem and return false.
bool ReadFDEFields(FDE *fde);
// Report that ENTRY is incomplete, and return false. This is just a
// trivial wrapper for invoking reporter_->Incomplete; it provides a
// little brevity.
bool ReportIncomplete(Entry *entry);
// Return true if ENCODING has the DW_EH_PE_indirect bit set.
static bool IsIndirectEncoding(DwarfPointerEncoding encoding) {
return encoding & DW_EH_PE_indirect;
}
// The contents of the DWARF .debug_info section we're parsing.
const char *buffer_;
size_t buffer_length_;
// For reading multi-byte values with the appropriate endianness.
ByteReader *reader_;
// The handler to which we should report the data we find.
Handler *handler_;
// For reporting problems in the info we're parsing.
Reporter *reporter_;
// True if we are processing .eh_frame-format data.
bool eh_frame_;
};
// The handler class for CallFrameInfo. The a CFI parser calls the
// member functions of a handler object to report the data it finds.
class CallFrameInfo::Handler {
public:
// The pseudo-register number for the canonical frame address.
enum { kCFARegister = DW_REG_CFA };
Handler() { }
virtual ~Handler() { }
// The parser has found CFI for the machine code at ADDRESS,
// extending for LENGTH bytes. OFFSET is the offset of the frame
// description entry in the section, for use in error messages.
// VERSION is the version number of the CFI format. AUGMENTATION is
// a string describing any producer-specific extensions present in
// the data. RETURN_ADDRESS is the number of the register that holds
// the address to which the function should return.
//
// Entry should return true to process this CFI, or false to skip to
// the next entry.
//
// The parser invokes Entry for each Frame Description Entry (FDE)
// it finds. The parser doesn't report Common Information Entries
// to the handler explicitly; instead, if the handler elects to
// process a given FDE, the parser reiterates the appropriate CIE's
// contents at the beginning of the FDE's rules.
virtual bool Entry(size_t offset, uint64 address, uint64 length,
uint8 version, const std::string &augmentation,
unsigned return_address) = 0;
// When the Entry function returns true, the parser calls these
// handler functions repeatedly to describe the rules for recovering
// registers at each instruction in the given range of machine code.
// Immediately after a call to Entry, the handler should assume that
// the rule for each callee-saves register is "unchanged" --- that
// is, that the register still has the value it had in the caller.
//
// If a *Rule function returns true, we continue processing this entry's
// instructions. If a *Rule function returns false, we stop evaluating
// instructions, and skip to the next entry. Either way, we call End
// before going on to the next entry.
//
// In all of these functions, if the REG parameter is kCFARegister, then
// the rule describes how to find the canonical frame address.
// kCFARegister may be passed as a BASE_REGISTER argument, meaning that
// the canonical frame address should be used as the base address for the
// computation. All other REG values will be positive.
// At ADDRESS, register REG's value is not recoverable.
virtual bool UndefinedRule(uint64 address, int reg) = 0;
// At ADDRESS, register REG's value is the same as that it had in
// the caller.
virtual bool SameValueRule(uint64 address, int reg) = 0;
// At ADDRESS, register REG has been saved at offset OFFSET from
// BASE_REGISTER.
virtual bool OffsetRule(uint64 address, int reg,
int base_register, long offset) = 0;
// At ADDRESS, the caller's value of register REG is the current
// value of BASE_REGISTER plus OFFSET. (This rule doesn't provide an
// address at which the register's value is saved.)
virtual bool ValOffsetRule(uint64 address, int reg,
int base_register, long offset) = 0;
// At ADDRESS, register REG has been saved in BASE_REGISTER. This differs
// from ValOffsetRule(ADDRESS, REG, BASE_REGISTER, 0), in that
// BASE_REGISTER is the "home" for REG's saved value: if you want to
// assign to a variable whose home is REG in the calling frame, you
// should put the value in BASE_REGISTER.
virtual bool RegisterRule(uint64 address, int reg, int base_register) = 0;
// At ADDRESS, the DWARF expression EXPRESSION yields the address at
// which REG was saved.
virtual bool ExpressionRule(uint64 address, int reg,
const std::string &expression) = 0;
// At ADDRESS, the DWARF expression EXPRESSION yields the caller's
// value for REG. (This rule doesn't provide an address at which the
// register's value is saved.)
virtual bool ValExpressionRule(uint64 address, int reg,
const std::string &expression) = 0;
// Indicate that the rules for the address range reported by the
// last call to Entry are complete. End should return true if
// everything is okay, or false if an error has occurred and parsing
// should stop.
virtual bool End() = 0;
// Handler functions for Linux C++ exception handling data. These are
// only called if the data includes 'z' augmentation strings.
// The Linux C++ ABI uses an extension of the DWARF CFI format to
// walk the stack to propagate exceptions from the throw to the
// appropriate catch, and do the appropriate cleanups along the way.
// CFI entries used for exception handling have two additional data
// associated with them:
//
// - The "language-specific data area" describes which exception
// types the function has 'catch' clauses for, and indicates how
// to go about re-entering the function at the appropriate catch
// clause. If the exception is not caught, it describes the
// destructors that must run before the frame is popped.
//
// - The "personality routine" is responsible for interpreting the
// language-specific data area's contents, and deciding whether
// the exception should continue to propagate down the stack,
// perhaps after doing some cleanup for this frame, or whether the
// exception will be caught here.
//
// In principle, the language-specific data area is opaque to
// everybody but the personality routine. In practice, these values
// may be useful or interesting to readers with extra context, and
// we have to at least skip them anyway, so we might as well report
// them to the handler.
// This entry's exception handling personality routine's address is
// ADDRESS. If INDIRECT is true, then ADDRESS is the address at
// which the routine's address is stored. The default definition for
// this handler function simply returns true, allowing parsing of
// the entry to continue.
virtual bool PersonalityRoutine(uint64 address, bool indirect) {
return true;
}
// This entry's language-specific data area (LSDA) is located at
// ADDRESS. If INDIRECT is true, then ADDRESS is the address at
// which the area's address is stored. The default definition for
// this handler function simply returns true, allowing parsing of
// the entry to continue.
virtual bool LanguageSpecificDataArea(uint64 address, bool indirect) {
return true;
}
// This entry describes a signal trampoline --- this frame is the
// caller of a signal handler. The default definition for this
// handler function simply returns true, allowing parsing of the
// entry to continue.
//
// The best description of the rationale for and meaning of signal
// trampoline CFI entries seems to be in the GCC bug database:
// http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208
virtual bool SignalHandler() { return true; }
};
// The CallFrameInfo class makes calls on an instance of this class to
// report errors or warn about problems in the data it is parsing.
// These messages are sent to the message sink |aLog| provided to the
// constructor.
class CallFrameInfo::Reporter final {
public:
// Create an error reporter which attributes troubles to the section
// named SECTION in FILENAME.
//
// Normally SECTION would be .debug_frame, but the Mac puts CFI data
// in a Mach-O section named __debug_frame. If we support
// Linux-style exception handling data, we could be reading an
// .eh_frame section.
Reporter(void (*aLog)(const char*),
const std::string &filename,
const std::string &section = ".debug_frame")
: log_(aLog), filename_(filename), section_(section) { }
virtual ~Reporter() { }
// The CFI entry at OFFSET ends too early to be well-formed. KIND
// indicates what kind of entry it is; KIND can be kUnknown if we
// haven't parsed enough of the entry to tell yet.
virtual void Incomplete(uint64 offset, CallFrameInfo::EntryKind kind);
// The .eh_frame data has a four-byte zero at OFFSET where the next
// entry's length would be; this is a terminator. However, the buffer
// length as given to the CallFrameInfo constructor says there should be
// more data.
virtual void EarlyEHTerminator(uint64 offset);
// The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the
// section is not that large.
virtual void CIEPointerOutOfRange(uint64 offset, uint64 cie_offset);
// The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the entry
// there is not a CIE.
virtual void BadCIEId(uint64 offset, uint64 cie_offset);
// The FDE at OFFSET refers to a CIE with version number VERSION,
// which we don't recognize. We cannot parse DWARF CFI if it uses
// a version number we don't recognize.
virtual void UnrecognizedVersion(uint64 offset, int version);
// The FDE at OFFSET refers to a CIE with augmentation AUGMENTATION,
// which we don't recognize. We cannot parse DWARF CFI if it uses
// augmentations we don't recognize.
virtual void UnrecognizedAugmentation(uint64 offset,
const std::string &augmentation);
// The pointer encoding ENCODING, specified by the CIE at OFFSET, is not
// a valid encoding.
virtual void InvalidPointerEncoding(uint64 offset, uint8 encoding);
// The pointer encoding ENCODING, specified by the CIE at OFFSET, depends
// on a base address which has not been supplied.
virtual void UnusablePointerEncoding(uint64 offset, uint8 encoding);
// The CIE at OFFSET contains a DW_CFA_restore instruction at
// INSN_OFFSET, which may not appear in a CIE.
virtual void RestoreInCIE(uint64 offset, uint64 insn_offset);
// The entry at OFFSET, of kind KIND, has an unrecognized
// instruction at INSN_OFFSET.
virtual void BadInstruction(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
// The instruction at INSN_OFFSET in the entry at OFFSET, of kind
// KIND, establishes a rule that cites the CFA, but we have not
// established a CFA rule yet.
virtual void NoCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
// The instruction at INSN_OFFSET in the entry at OFFSET, of kind
// KIND, is a DW_CFA_restore_state instruction, but the stack of
// saved states is empty.
virtual void EmptyStateStack(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
// The DW_CFA_remember_state instruction at INSN_OFFSET in the entry
// at OFFSET, of kind KIND, would restore a state that has no CFA
// rule, whereas the current state does have a CFA rule. This is
// bogus input, which the CallFrameInfo::Handler interface doesn't
// (and shouldn't) have any way to report.
virtual void ClearingCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
private:
// A logging sink function, as supplied by LUL's user.
void (*log_)(const char*);
protected:
// The name of the file whose CFI we're reading.
std::string filename_;
// The name of the CFI section in that file.
std::string section_;
};
using lul::CallFrameInfo;
using lul::Summariser;
// A class that accepts parsed call frame information from the DWARF
// CFI parser and populates a google_breakpad::Module object with the
// contents.
class DwarfCFIToModule: public CallFrameInfo::Handler {
public:
// DwarfCFIToModule uses an instance of this class to report errors
// detected while converting DWARF CFI to Breakpad STACK CFI records.
class Reporter {
public:
// Create a reporter that writes messages to the message sink
// |aLog|. FILE is the name of the file we're processing, and
// SECTION is the name of the section within that file that we're
// looking at (.debug_frame, .eh_frame, etc.).
Reporter(void (*aLog)(const char*),
const std::string &file, const std::string &section)
: log_(aLog), file_(file), section_(section) { }
virtual ~Reporter() { }
// The DWARF CFI entry at OFFSET says that REG is undefined, but the
// Breakpad symbol file format cannot express this.
virtual void UndefinedNotSupported(size_t offset,
const UniqueString* reg);
// The DWARF CFI entry at OFFSET says that REG uses a DWARF
// expression to find its value, but DwarfCFIToModule is not
// capable of translating DWARF expressions to Breakpad postfix
// expressions.
virtual void ExpressionsNotSupported(size_t offset,
const UniqueString* reg);
private:
// A logging sink function, as supplied by LUL's user.
void (*log_)(const char*);
protected:
std::string file_, section_;
};
// Register name tables. If TABLE is a vector returned by one of these
// functions, then TABLE[R] is the name of the register numbered R in
// DWARF call frame information.
class RegisterNames {
public:
// Intel's "x86" or IA-32.
static const unsigned int I386();
// AMD x86_64, AMD64, Intel EM64T, or Intel 64
static const unsigned int X86_64();
// ARM.
static const unsigned int ARM();
};
// Create a handler for the dwarf2reader::CallFrameInfo parser that
// records the stack unwinding information it receives in SUMM.
//
// Use REGISTER_NAMES[I] as the name of register number I; *this
// keeps a reference to the vector, so the vector should remain
// alive for as long as the DwarfCFIToModule does.
//
// Use REPORTER for reporting problems encountered in the conversion
// process.
DwarfCFIToModule(const unsigned int num_dw_regs,
Reporter *reporter,
/*MOD*/UniqueStringUniverse* usu,
/*OUT*/Summariser* summ)
: summ_(summ), usu_(usu), num_dw_regs_(num_dw_regs),
reporter_(reporter), return_address_(-1) {
}
virtual ~DwarfCFIToModule() {}
virtual bool Entry(size_t offset, uint64 address, uint64 length,
uint8 version, const std::string &augmentation,
unsigned return_address);
virtual bool UndefinedRule(uint64 address, int reg);
virtual bool SameValueRule(uint64 address, int reg);
virtual bool OffsetRule(uint64 address, int reg,
int base_register, long offset);
virtual bool ValOffsetRule(uint64 address, int reg,
int base_register, long offset);
virtual bool RegisterRule(uint64 address, int reg, int base_register);
virtual bool ExpressionRule(uint64 address, int reg,
const std::string &expression);
virtual bool ValExpressionRule(uint64 address, int reg,
const std::string &expression);
virtual bool End();
private:
// Return the name to use for register I.
const UniqueString* RegisterName(int i);
// The Summariser to which we should give entries
Summariser* summ_;
// Universe for creating UniqueStrings in, should that be necessary.
UniqueStringUniverse* usu_;
// The number of Dwarf-defined register names for this architecture.
const unsigned int num_dw_regs_;
// The reporter to use to report problems.
Reporter *reporter_;
// The section offset of the current frame description entry, for
// use in error messages.
size_t entry_offset_;
// The return address column for that entry.
unsigned return_address_;
};
} // namespace lul
#endif // LulDwarfExt_h
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