/thirdparty/breakpad/processor/cfi_frame_info-inl.h

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 32// Original author: Jim Blandy <jimb@mozilla.com> <jimb@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
 41namespace google_breakpad {
 42
 43template <typename RegisterType, class RawContextType>
 44bool 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_