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// -*- mode: C++ -*-
// Copyright (c) 2010, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
// cfi_frame_info.h: Define the CFIFrameInfo class, which holds the
// set of 'STACK CFI'-derived register recovery rules that apply at a
// given instruction.
#ifndef PROCESSOR_CFI_FRAME_INFO_H_
#define PROCESSOR_CFI_FRAME_INFO_H_
#include <map>
#include <string>
#include "common/using_std_string.h"
#include "google_breakpad/common/breakpad_types.h"
namespace google_breakpad {
using std::map;
class MemoryRegion;
// A set of rules for recovering the calling frame's registers'
// values, when the PC is at a given address in the current frame's
// function. See the description of 'STACK CFI' records at:
//
//
// To prepare an instance of CFIFrameInfo for use at a given
// instruction, first populate it with the rules from the 'STACK CFI
// INIT' record that covers that instruction, and then apply the
// changes given by the 'STACK CFI' records up to our instruction's
// address. Then, use the FindCallerRegs member function to apply the
// rules to the callee frame's register values, yielding the caller
// frame's register values.
class CFIFrameInfo {
public:
// A map from register names onto values.
template<typename ValueType> class RegisterValueMap:
public map<string, ValueType> { };
// Set the expression for computing a call frame address, return
// address, or register's value. At least the CFA rule and the RA
// rule must be set before calling FindCallerRegs.
void SetCFARule(const string &expression) { cfa_rule_ = expression; }
void SetRARule(const string &expression) { ra_rule_ = expression; }
void SetRegisterRule(const string ®ister_name, const string &expression) {
register_rules_[register_name] = expression;
}
// Compute the values of the calling frame's registers, according to
// this rule set. Use ValueType in expression evaluation; this
// should be uint32_t on machines with 32-bit addresses, or
// uint64_t on machines with 64-bit addresses.
//
// Return true on success, false otherwise.
//
// MEMORY provides access to the contents of the stack. REGISTERS is
// a dictionary mapping the names of registers whose values are
// known in the current frame to their values. CALLER_REGISTERS is
// populated with the values of the recoverable registers in the
// frame that called the current frame.
//
// In addition, CALLER_REGISTERS[".ra"] will be the return address,
// and CALLER_REGISTERS[".cfa"] will be the call frame address.
// These may be helpful in computing the caller's PC and stack
// pointer, if their values are not explicitly specified.
template<typename ValueType>
bool FindCallerRegs(const RegisterValueMap<ValueType> ®isters,
const MemoryRegion &memory,
RegisterValueMap<ValueType> *caller_registers) const;
// Serialize the rules in this object into a string in the format
// of STACK CFI records.
string Serialize() const;
private:
// A map from register names onto evaluation rules.
typedef map<string, string> RuleMap;
// In this type, a "postfix expression" is an expression of the sort
// interpreted by google_breakpad::PostfixEvaluator.
// A postfix expression for computing the current frame's CFA (call
// frame address). The CFA is a reference address for the frame that
// remains unchanged throughout the frame's lifetime. You should
// evaluate this expression with a dictionary initially populated
// with the values of the current frame's known registers.
string cfa_rule_;
// The following expressions should be evaluated with a dictionary
// initially populated with the values of the current frame's known
// registers, and with ".cfa" set to the result of evaluating the
// cfa_rule expression, above.
// A postfix expression for computing the current frame's return
// address.
string ra_rule_;
// For a register named REG, rules[REG] is a postfix expression
// which leaves the value of REG in the calling frame on the top of
// the stack. You should evaluate this expression
RuleMap register_rules_;
};
// A parser for STACK CFI-style rule sets.
// This may seem bureaucratic: there's no legitimate run-time reason
// to use a parser/handler pattern for this, as it's not a likely
// reuse boundary. But doing so makes finer-grained unit testing
// possible.
class CFIRuleParser {
public:
class Handler {
public:
Handler() { }
virtual ~Handler() { }
// The input specifies EXPRESSION as the CFA/RA computation rule.
virtual void CFARule(const string &expression) = 0;
virtual void RARule(const string &expression) = 0;
// The input specifies EXPRESSION as the recovery rule for register NAME.
virtual void RegisterRule(const string &name, const string &expression) = 0;
};
// Construct a parser which feeds its results to HANDLER.
CFIRuleParser(Handler *handler) : handler_(handler) { }
// Parse RULE_SET as a set of CFA computation and RA/register
// recovery rules, as appearing in STACK CFI records. Report the
// results of parsing by making the appropriate calls to handler_.
// Return true if parsing was successful, false otherwise.
bool Parse(const string &rule_set);
private:
// Report any accumulated rule to handler_
bool Report();
// The handler to which the parser reports its findings.
Handler *handler_;
// Working data.
string name_, expression_;
};
// A handler for rule set parsing that populates a CFIFrameInfo with
// the results.
class CFIFrameInfoParseHandler: public CFIRuleParser::Handler {
public:
// Populate FRAME_INFO with the results of parsing.
CFIFrameInfoParseHandler(CFIFrameInfo *frame_info)
: frame_info_(frame_info) { }
void CFARule(const string &expression);
void RARule(const string &expression);
void RegisterRule(const string &name, const string &expression);
private:
CFIFrameInfo *frame_info_;
};
// A utility class template for simple 'STACK CFI'-driven stack walkers.
// Given a CFIFrameInfo instance, a table describing the architecture's
// register set, and a context holding the last frame's registers, an
// instance of this class can populate a new context with the caller's
// registers.
//
// This class template doesn't use any internal knowledge of CFIFrameInfo
// or the other stack walking structures; it just uses the public interface
// of CFIFrameInfo to do the usual things. But the logic it handles should
// be common to many different architectures' stack walkers, so wrapping it
// up in a class should allow the walkers to share code.
//
// RegisterType should be the type of this architecture's registers, either
// uint32_t or uint64_t. RawContextType should be the raw context
// structure type for this architecture.
template <typename RegisterType, class RawContextType>
class SimpleCFIWalker {
public:
// A structure describing one architecture register.
struct RegisterSet {
// The register name, as it appears in STACK CFI rules.
const char *name;
// An alternate name that the register's value might be found
// under in a register value dictionary, or NULL. When generating
// names, prefer NAME to this value. It's common to list ".cfa" as
// an alternative name for the stack pointer, and ".ra" as an
// alternative name for the instruction pointer.
const char *alternate_name;
// True if the callee is expected to preserve the value of this
// register. If this flag is true for some register R, and the STACK
// CFI records provide no rule to recover R, then SimpleCFIWalker
// assumes that the callee has not changed R's value, and the caller's
// value for R is that currently in the callee's context.
bool callee_saves;
// The ContextValidity flag representing the register's presence.
int validity_flag;
// A pointer to the RawContextType member that holds the
// register's value.
RegisterType RawContextType::*context_member;
};
// Create a simple CFI-based frame walker, given a description of the
// architecture's register set. REGISTER_MAP is an array of
// RegisterSet structures; MAP_SIZE is the number of elements in the
// array.
SimpleCFIWalker(const RegisterSet *register_map, size_t map_size)
: register_map_(register_map), map_size_(map_size) { }
// Compute the calling frame's raw context given the callee's raw
// context.
//
// Given:
//
// - MEMORY, holding the stack's contents,
// - CFI_FRAME_INFO, describing the called function,
// - CALLEE_CONTEXT, holding the called frame's registers, and
// - CALLEE_VALIDITY, indicating which registers in CALLEE_CONTEXT are valid,
//
// fill in CALLER_CONTEXT with the caller's register values, and set
// CALLER_VALIDITY to indicate which registers are valid in
// CALLER_CONTEXT. Return true on success, or false on failure.
bool FindCallerRegisters(const MemoryRegion &memory,
const CFIFrameInfo &cfi_frame_info,
const RawContextType &callee_context,
int callee_validity,
RawContextType *caller_context,
int *caller_validity) const;
private:
const RegisterSet *register_map_;
size_t map_size_;
};
} // namespace google_breakpad
#include "cfi_frame_info-inl.h"
#endif // PROCESSOR_CFI_FRAME_INFO_H_