diff options
Diffstat (limited to 'tools/profiler/lul/LulDwarfExt.h')
| -rw-r--r-- | tools/profiler/lul/LulDwarfExt.h | 1287 |
1 files changed, 1287 insertions, 0 deletions
diff --git a/tools/profiler/lul/LulDwarfExt.h b/tools/profiler/lul/LulDwarfExt.h new file mode 100644 index 000000000..f3555ac55 --- /dev/null +++ b/tools/profiler/lul/LulDwarfExt.h @@ -0,0 +1,1287 @@ +/* -*- 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 { + 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 §ion = ".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 §ion) + : 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 parseDwarfExpr could not + // convert it to a sequence of PfxInstrs. + virtual void ExpressionCouldNotBeSummarised(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 unsigned int I386(); + + // AMD x86_64, AMD64, Intel EM64T, or Intel 64 + static unsigned int X86_64(); + + // ARM. + static 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, + ByteReader* reader, + /*MOD*/UniqueStringUniverse* usu, + /*OUT*/Summariser* summ) + : summ_(summ), usu_(usu), num_dw_regs_(num_dw_regs), + reporter_(reporter), reader_(reader), 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 ByteReader to use for parsing Dwarf expressions. + ByteReader* reader_; + + // 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_; +}; + + +// Convert the Dwarf expression in |expr| into PfxInstrs stored in the +// SecMap referred to by |summ|, and return the index of the starting +// PfxInstr added, which must be >= 0. In case of failure return -1. +int32_t parseDwarfExpr(Summariser* summ, const ByteReader* reader, + string expr, bool debug, + bool pushCfaAtStart, bool derefAtEnd); + +} // namespace lul + +#endif // LulDwarfExt_h |