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      1 // -*- mode: C++ -*-
      2 
      3 // Copyright (c) 2010, Google Inc.
      4 // All rights reserved.
      5 //
      6 // Redistribution and use in source and binary forms, with or without
      7 // modification, are permitted provided that the following conditions are
      8 // met:
      9 //
     10 //     * Redistributions of source code must retain the above copyright
     11 // notice, this list of conditions and the following disclaimer.
     12 //     * Redistributions in binary form must reproduce the above
     13 // copyright notice, this list of conditions and the following disclaimer
     14 // in the documentation and/or other materials provided with the
     15 // distribution.
     16 //     * Neither the name of Google Inc. nor the names of its
     17 // contributors may be used to endorse or promote products derived from
     18 // this software without specific prior written permission.
     19 //
     20 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     21 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     22 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     23 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     24 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     25 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     26 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     30 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31 
     32 // Original author: Jim Blandy <jimb (at) mozilla.com> <jimb (at) red-bean.com>
     33 
     34 // cfi_frame_info-inl.h: Definitions for cfi_frame_info.h inlined functions.
     35 
     36 #ifndef PROCESSOR_CFI_FRAME_INFO_INL_H_
     37 #define PROCESSOR_CFI_FRAME_INFO_INL_H_
     38 
     39 #include <string.h>
     40 
     41 namespace google_breakpad {
     42 
     43 template <typename RegisterType, class RawContextType>
     44 bool SimpleCFIWalker<RegisterType, RawContextType>::FindCallerRegisters(
     45     const MemoryRegion &memory,
     46     const CFIFrameInfo &cfi_frame_info,
     47     const RawContextType &callee_context,
     48     int callee_validity,
     49     RawContextType *caller_context,
     50     int *caller_validity) const {
     51   typedef CFIFrameInfo::RegisterValueMap<RegisterType> ValueMap;
     52   ValueMap callee_registers;
     53   ValueMap caller_registers;
     54   // Just for brevity.
     55   typename ValueMap::const_iterator caller_none = caller_registers.end();
     56 
     57   // Populate callee_registers with register values from callee_context.
     58   for (size_t i = 0; i < map_size_; i++) {
     59     const RegisterSet &r = register_map_[i];
     60     if (callee_validity & r.validity_flag)
     61       callee_registers[r.name] = callee_context.*r.context_member;
     62   }
     63 
     64   // Apply the rules, and see what register values they yield.
     65   if (!cfi_frame_info.FindCallerRegs<RegisterType>(callee_registers, memory,
     66                                                    &caller_registers))
     67     return false;
     68 
     69   // Populate *caller_context with the values the rules placed in
     70   // caller_registers.
     71   memset(caller_context, 0xda, sizeof(*caller_context));
     72   *caller_validity = 0;
     73   for (size_t i = 0; i < map_size_; i++) {
     74     const RegisterSet &r = register_map_[i];
     75     typename ValueMap::const_iterator caller_entry;
     76 
     77     // Did the rules provide a value for this register by its name?
     78     caller_entry = caller_registers.find(r.name);
     79     if (caller_entry != caller_none) {
     80       caller_context->*r.context_member = caller_entry->second;
     81       *caller_validity |= r.validity_flag;
     82       continue;
     83     }
     84 
     85     // Did the rules provide a value for this register under its
     86     // alternate name?
     87     if (r.alternate_name) {
     88       caller_entry = caller_registers.find(r.alternate_name);
     89       if (caller_entry != caller_none) {
     90         caller_context->*r.context_member = caller_entry->second;
     91         *caller_validity |= r.validity_flag;
     92         continue;
     93       }
     94     }
     95 
     96     // Is this a callee-saves register? The walker assumes that these
     97     // still hold the caller's value if the CFI doesn't mention them.
     98     //
     99     // Note that other frame walkers may fail to recover callee-saves
    100     // registers; for example, the x86 "traditional" strategy only
    101     // recovers %eip, %esp, and %ebp, even though %ebx, %esi, and %edi
    102     // are callee-saves, too. It is not correct to blindly set the
    103     // valid bit for all callee-saves registers, without first
    104     // checking its validity bit in the callee.
    105     if (r.callee_saves && (callee_validity & r.validity_flag) != 0) {
    106       caller_context->*r.context_member = callee_context.*r.context_member;
    107       *caller_validity |= r.validity_flag;
    108       continue;
    109     }
    110 
    111     // Otherwise, the register's value is unknown.
    112   }
    113 
    114   return true;
    115 }
    116 
    117 } // namespace google_breakpad
    118 
    119 #endif // PROCESSOR_CFI_FRAME_INFO_INL_H_
    120