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Breakpad Linux dumper: Parse the .eh_frame section.

Browse source 
Extend google_breakpad::CFISection with the ability to produce
.eh_frame data. Entry headers have a different format, and pointers
can be encoded in new and fascinating ways.

Extend dwarf2reader::CallFrameInfo to be able to parse either DWARF
CFI or .eh_frame data, as determined by an argument to the
constructor. Cope with variations in header formats, encoded pointers,
and additional data in 'z' augmentation data blocks. Extend the unit
tests appropriately.

Extend dump_syms to look for a .eh_frame section, and if it is
present, find the necessary base addresess and parse its contents.

There's no need for DwarfCFIToModule to check the version numbers; if
CallFrameInfo can parse it, DwarfCFIToModule should be able to handle
it. Adjust tests accordingly.

a=jimblandy, r=nealsid


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@552 4c0a9323-5329-0410-9bdc-e9ce6186880e
This commit is contained in:
jimblandy 2010-03-16 16:37:50 +00:00
parent 0de9f43b87
commit a76aaa1442
11 changed files with 1335 additions and 142 deletions
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242
src/common/dwarf/dwarf2reader.h
View file

@ -46,6 +46,7 @@
#include <utility>
#include <vector>
#include "common/dwarf/bytereader.h"
#include "common/dwarf/dwarf2enums.h"
#include "common/dwarf/types.h"
@ -53,7 +54,6 @@ using namespace std;
namespace dwarf2reader {
struct LineStateMachine;
class ByteReader;
class Dwarf2Handler;
class LineInfoHandler;
@ -556,7 +556,7 @@ class CallFrameInfo {
public:
// The different kinds of entries one finds in CFI. Used internally,
// and for error reporting.
enum EntryKind { kUnknown, kCIE, kFDE };
enum EntryKind { kUnknown, kCIE, kFDE, kTerminator };
// The handler class to which the parser hands the parsed call frame
// information. Defined below.
@ -567,19 +567,75 @@ class CallFrameInfo {
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.
// .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)
: buffer_(buffer),
buffer_length_(buffer_length),
reader_(reader),
handler_(handler),
reporter_(reporter) { }
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.
@ -603,6 +659,13 @@ class CallFrameInfo {
// 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;
@ -616,16 +679,10 @@ class CallFrameInfo {
// simply buffer_ + offset + length.)
const char *end;
// The CIE pointer or CIE id field.
// 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 kind of entry we're parsing.
//
// This may be kUnknown at times, since we want to be able to
// count on it for error reporting even before we've finished
// parsing enough to tell what kind of entry we're looking at.
EntryKind kind;
// 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;
@ -638,12 +695,45 @@ class CallFrameInfo {
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.
@ -658,24 +748,27 @@ class CallFrameInfo {
class RuleMap;
class State;
// Parse the initial length and id of a CFI entry, either a CIE or an
// FDE. 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.
// 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. 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.
// 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. 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.
// 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
@ -683,6 +776,11 @@ class CallFrameInfo {
// 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_;
@ -695,6 +793,9 @@ class CallFrameInfo {
// 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
@ -786,6 +887,61 @@ class CallFrameInfo::Handler {
// 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
@ -811,6 +967,12 @@ class CallFrameInfo::Reporter {
// 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);
@ -830,6 +992,14 @@ class CallFrameInfo::Reporter {
virtual void UnrecognizedAugmentation(uint64 offset,
const 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);