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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,

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 // 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 "common/unique_string.h"

 #include "google_breakpad/common/breakpad_types.h"

 #include "common/module.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:

 //

 // http://code.google.com/p/google-breakpad/wiki/SymbolFiles

 //

 // 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 UniqueStringMap<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 Module::Expr& rule) { cfa_rule_ = rule; }

   void SetRARule(const Module::Expr& rule)  { ra_rule_ = rule; }

   void SetRegisterRule(const UniqueString* register_name,

                        const Module::Expr& rule) {

     register_rules_[register_name] = rule;

   }

   // 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> &registers,

                       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<const UniqueString*, Module::Expr> RuleMap;

   // An 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.

   Module::Expr 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.

   // An expression for computing the current frame's return address.

   Module::Expr 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 UniqueString* 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.

   const UniqueString* name_;

   string 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 UniqueString* 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 UniqueString* 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 UniqueString* 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_