/* -*- 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