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29 
30 // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
31 
32 // cfi_frame_info.cc: Implementation of CFIFrameInfo class.
33 // See cfi_frame_info.h for details.
34 
35 #include "processor/cfi_frame_info.h"
36 
37 #include <string.h>
38 
39 #include <sstream>
40 
41 #include "common/scoped_ptr.h"
42 #include "processor/postfix_evaluator-inl.h"
43 
44 namespace google_breakpad {
45 
46 #ifdef _WIN32
47 #define strtok_r strtok_s
48 #endif
49 
50 template<typename V>
FindCallerRegs(const RegisterValueMap<V> & registers,const MemoryRegion & memory,RegisterValueMap<V> * caller_registers) const51 bool CFIFrameInfo::FindCallerRegs(const RegisterValueMap<V> &registers,
52                                   const MemoryRegion &memory,
53                                   RegisterValueMap<V> *caller_registers) const {
54   // If there are not rules for both .ra and .cfa in effect at this address,
55   // don't use this CFI data for stack walking.
56   if (cfa_rule_.empty() || ra_rule_.empty())
57     return false;
58 
59   RegisterValueMap<V> working;
60   PostfixEvaluator<V> evaluator(&working, &memory);
61 
62   caller_registers->clear();
63 
64   // First, compute the CFA.
65   V cfa;
66   working = registers;
67   if (!evaluator.EvaluateForValue(cfa_rule_, &cfa))
68     return false;
69 
70   // Then, compute the return address.
71   V ra;
72   working = registers;
73   working[".cfa"] = cfa;
74   if (!evaluator.EvaluateForValue(ra_rule_, &ra))
75     return false;
76 
77   // Now, compute values for all the registers register_rules_ mentions.
78   for (RuleMap::const_iterator it = register_rules_.begin();
79        it != register_rules_.end(); it++) {
80     V value;
81     working = registers;
82     working[".cfa"] = cfa;
83     if (!evaluator.EvaluateForValue(it->second, &value))
84       return false;
85     (*caller_registers)[it->first] = value;
86   }
87 
88   (*caller_registers)[".ra"] = ra;
89   (*caller_registers)[".cfa"] = cfa;
90 
91   return true;
92 }
93 
94 // Explicit instantiations for 32-bit and 64-bit architectures.
95 template bool CFIFrameInfo::FindCallerRegs<uint32_t>(
96     const RegisterValueMap<uint32_t> &registers,
97     const MemoryRegion &memory,
98     RegisterValueMap<uint32_t> *caller_registers) const;
99 template bool CFIFrameInfo::FindCallerRegs<uint64_t>(
100     const RegisterValueMap<uint64_t> &registers,
101     const MemoryRegion &memory,
102     RegisterValueMap<uint64_t> *caller_registers) const;
103 
Serialize() const104 string CFIFrameInfo::Serialize() const {
105   std::ostringstream stream;
106 
107   if (!cfa_rule_.empty()) {
108     stream << ".cfa: " << cfa_rule_;
109   }
110   if (!ra_rule_.empty()) {
111     if (static_cast<std::streamoff>(stream.tellp()) != 0)
112       stream << " ";
113     stream << ".ra: " << ra_rule_;
114   }
115   for (RuleMap::const_iterator iter = register_rules_.begin();
116        iter != register_rules_.end();
117        ++iter) {
118     if (static_cast<std::streamoff>(stream.tellp()) != 0)
119       stream << " ";
120     stream << iter->first << ": " << iter->second;
121   }
122 
123   return stream.str();
124 }
125 
Parse(const string & rule_set)126 bool CFIRuleParser::Parse(const string &rule_set) {
127   size_t rule_set_len = rule_set.size();
128   scoped_array<char> working_copy(new char[rule_set_len + 1]);
129   memcpy(working_copy.get(), rule_set.data(), rule_set_len);
130   working_copy[rule_set_len] = '\0';
131 
132   name_.clear();
133   expression_.clear();
134 
135   char *cursor;
136   static const char token_breaks[] = " \t\r\n";
137   char *token = strtok_r(working_copy.get(), token_breaks, &cursor);
138 
139   for (;;) {
140     // End of rule set?
141     if (!token) return Report();
142 
143     // Register/pseudoregister name?
144     size_t token_len = strlen(token);
145     if (token_len >= 1 && token[token_len - 1] == ':') {
146       // Names can't be empty.
147       if (token_len < 2) return false;
148       // If there is any pending content, report it.
149       if (!name_.empty() || !expression_.empty()) {
150         if (!Report()) return false;
151       }
152       name_.assign(token, token_len - 1);
153       expression_.clear();
154     } else {
155       // Another expression component.
156       assert(token_len > 0); // strtok_r guarantees this, I think.
157       if (!expression_.empty())
158         expression_ += ' ';
159       expression_ += token;
160     }
161     token = strtok_r(NULL, token_breaks, &cursor);
162   }
163 }
164 
Report()165 bool CFIRuleParser::Report() {
166   if (name_.empty() || expression_.empty()) return false;
167   if (name_ == ".cfa") handler_->CFARule(expression_);
168   else if (name_ == ".ra") handler_->RARule(expression_);
169   else handler_->RegisterRule(name_, expression_);
170   return true;
171 }
172 
CFARule(const string & expression)173 void CFIFrameInfoParseHandler::CFARule(const string &expression) {
174   frame_info_->SetCFARule(expression);
175 }
176 
RARule(const string & expression)177 void CFIFrameInfoParseHandler::RARule(const string &expression) {
178   frame_info_->SetRARule(expression);
179 }
180 
RegisterRule(const string & name,const string & expression)181 void CFIFrameInfoParseHandler::RegisterRule(const string &name,
182                                             const string &expression) {
183   frame_info_->SetRegisterRule(name, expression);
184 }
185 
186 } // namespace google_breakpad
187