1 //===-- UnwindAssembly-x86.cpp ----------------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "UnwindAssembly-x86.h"
11 #include "x86AssemblyInspectionEngine.h"
12 
13 #include "llvm-c/Disassembler.h"
14 #include "llvm/ADT/STLExtras.h"
15 #include "llvm/Support/TargetSelect.h"
16 
17 #include "lldb/Core/Address.h"
18 #include "lldb/Core/PluginManager.h"
19 #include "lldb/Symbol/UnwindPlan.h"
20 #include "lldb/Target/ABI.h"
21 #include "lldb/Target/ExecutionContext.h"
22 #include "lldb/Target/Process.h"
23 #include "lldb/Target/RegisterContext.h"
24 #include "lldb/Target/RegisterNumber.h"
25 #include "lldb/Target/Target.h"
26 #include "lldb/Target/Thread.h"
27 #include "lldb/Target/UnwindAssembly.h"
28 #include "lldb/Utility/ArchSpec.h"
29 #include "lldb/Utility/Status.h"
30 
31 using namespace lldb;
32 using namespace lldb_private;
33 
34 //-----------------------------------------------------------------------------------------------
35 //  UnwindAssemblyParser_x86 method definitions
36 //-----------------------------------------------------------------------------------------------
37 
38 UnwindAssembly_x86::UnwindAssembly_x86(const ArchSpec &arch)
39     : lldb_private::UnwindAssembly(arch),
40       m_assembly_inspection_engine(new x86AssemblyInspectionEngine(arch)) {}
41 
42 UnwindAssembly_x86::~UnwindAssembly_x86() {
43   delete m_assembly_inspection_engine;
44 }
45 
46 bool UnwindAssembly_x86::GetNonCallSiteUnwindPlanFromAssembly(
47     AddressRange &func, Thread &thread, UnwindPlan &unwind_plan) {
48   if (!func.GetBaseAddress().IsValid() || func.GetByteSize() == 0)
49     return false;
50   if (m_assembly_inspection_engine == nullptr)
51     return false;
52   ProcessSP process_sp(thread.GetProcess());
53   if (process_sp.get() == nullptr)
54     return false;
55   const bool prefer_file_cache = true;
56   std::vector<uint8_t> function_text(func.GetByteSize());
57   Status error;
58   if (process_sp->GetTarget().ReadMemory(
59           func.GetBaseAddress(), prefer_file_cache, function_text.data(),
60           func.GetByteSize(), error) == func.GetByteSize()) {
61     RegisterContextSP reg_ctx(thread.GetRegisterContext());
62     m_assembly_inspection_engine->Initialize(reg_ctx);
63     return m_assembly_inspection_engine->GetNonCallSiteUnwindPlanFromAssembly(
64         function_text.data(), func.GetByteSize(), func, unwind_plan);
65   }
66   return false;
67 }
68 
69 bool UnwindAssembly_x86::AugmentUnwindPlanFromCallSite(
70     AddressRange &func, Thread &thread, UnwindPlan &unwind_plan) {
71   bool do_augment_unwindplan = true;
72 
73   UnwindPlan::RowSP first_row = unwind_plan.GetRowForFunctionOffset(0);
74   UnwindPlan::RowSP last_row = unwind_plan.GetRowForFunctionOffset(-1);
75 
76   int wordsize = 8;
77   ProcessSP process_sp(thread.GetProcess());
78   if (process_sp.get() == nullptr)
79     return false;
80 
81   wordsize = process_sp->GetTarget().GetArchitecture().GetAddressByteSize();
82 
83   RegisterNumber sp_regnum(thread, eRegisterKindGeneric,
84                            LLDB_REGNUM_GENERIC_SP);
85   RegisterNumber pc_regnum(thread, eRegisterKindGeneric,
86                            LLDB_REGNUM_GENERIC_PC);
87 
88   // Does this UnwindPlan describe the prologue?  I want to see that the CFA is
89   // set in terms of the stack pointer plus an offset, and I want to see that
90   // rip is retrieved at the CFA-wordsize. If there is no description of the
91   // prologue, don't try to augment this eh_frame unwinder code, fall back to
92   // assembly parsing instead.
93 
94   if (first_row->GetCFAValue().GetValueType() !=
95           UnwindPlan::Row::FAValue::isRegisterPlusOffset ||
96       RegisterNumber(thread, unwind_plan.GetRegisterKind(),
97                      first_row->GetCFAValue().GetRegisterNumber()) !=
98           sp_regnum ||
99       first_row->GetCFAValue().GetOffset() != wordsize) {
100     return false;
101   }
102   UnwindPlan::Row::RegisterLocation first_row_pc_loc;
103   if (first_row->GetRegisterInfo(
104           pc_regnum.GetAsKind(unwind_plan.GetRegisterKind()),
105           first_row_pc_loc) == false ||
106       first_row_pc_loc.IsAtCFAPlusOffset() == false ||
107       first_row_pc_loc.GetOffset() != -wordsize) {
108     return false;
109   }
110 
111   // It looks like the prologue is described. Is the epilogue described?  If it
112   // is, no need to do any augmentation.
113 
114   if (first_row != last_row &&
115       first_row->GetOffset() != last_row->GetOffset()) {
116     // The first & last row have the same CFA register and the same CFA offset
117     // value and the CFA register is esp/rsp (the stack pointer).
118 
119     // We're checking that both of them have an unwind rule like "CFA=esp+4" or
120     // CFA+rsp+8".
121 
122     if (first_row->GetCFAValue().GetValueType() ==
123             last_row->GetCFAValue().GetValueType() &&
124         first_row->GetCFAValue().GetRegisterNumber() ==
125             last_row->GetCFAValue().GetRegisterNumber() &&
126         first_row->GetCFAValue().GetOffset() ==
127             last_row->GetCFAValue().GetOffset()) {
128       // Get the register locations for eip/rip from the first & last rows. Are
129       // they both CFA plus an offset?  Is it the same offset?
130 
131       UnwindPlan::Row::RegisterLocation last_row_pc_loc;
132       if (last_row->GetRegisterInfo(
133               pc_regnum.GetAsKind(unwind_plan.GetRegisterKind()),
134               last_row_pc_loc)) {
135         if (last_row_pc_loc.IsAtCFAPlusOffset() &&
136             first_row_pc_loc.GetOffset() == last_row_pc_loc.GetOffset()) {
137 
138           // One last sanity check:  Is the unwind rule for getting the caller
139           // pc value "deref the CFA-4" or "deref the CFA-8"?
140 
141           // If so, we have an UnwindPlan that already describes the epilogue
142           // and we don't need to modify it at all.
143 
144           if (first_row_pc_loc.GetOffset() == -wordsize) {
145             do_augment_unwindplan = false;
146           }
147         }
148       }
149     }
150   }
151 
152   if (do_augment_unwindplan) {
153     if (!func.GetBaseAddress().IsValid() || func.GetByteSize() == 0)
154       return false;
155     if (m_assembly_inspection_engine == nullptr)
156       return false;
157     const bool prefer_file_cache = true;
158     std::vector<uint8_t> function_text(func.GetByteSize());
159     Status error;
160     if (process_sp->GetTarget().ReadMemory(
161             func.GetBaseAddress(), prefer_file_cache, function_text.data(),
162             func.GetByteSize(), error) == func.GetByteSize()) {
163       RegisterContextSP reg_ctx(thread.GetRegisterContext());
164       m_assembly_inspection_engine->Initialize(reg_ctx);
165       return m_assembly_inspection_engine->AugmentUnwindPlanFromCallSite(
166           function_text.data(), func.GetByteSize(), func, unwind_plan, reg_ctx);
167     }
168   }
169 
170   return false;
171 }
172 
173 bool UnwindAssembly_x86::GetFastUnwindPlan(AddressRange &func, Thread &thread,
174                                            UnwindPlan &unwind_plan) {
175   // if prologue is
176   //   55     pushl %ebp
177   //   89 e5  movl %esp, %ebp
178   //  or
179   //   55        pushq %rbp
180   //   48 89 e5  movq %rsp, %rbp
181 
182   // We should pull in the ABI architecture default unwind plan and return that
183 
184   llvm::SmallVector<uint8_t, 4> opcode_data;
185 
186   ProcessSP process_sp = thread.GetProcess();
187   if (process_sp) {
188     Target &target(process_sp->GetTarget());
189     const bool prefer_file_cache = true;
190     Status error;
191     if (target.ReadMemory(func.GetBaseAddress(), prefer_file_cache,
192                           opcode_data.data(), 4, error) == 4) {
193       uint8_t i386_push_mov[] = {0x55, 0x89, 0xe5};
194       uint8_t x86_64_push_mov[] = {0x55, 0x48, 0x89, 0xe5};
195 
196       if (memcmp(opcode_data.data(), i386_push_mov, sizeof(i386_push_mov)) ==
197               0 ||
198           memcmp(opcode_data.data(), x86_64_push_mov,
199                  sizeof(x86_64_push_mov)) == 0) {
200         ABISP abi_sp = process_sp->GetABI();
201         if (abi_sp) {
202           return abi_sp->CreateDefaultUnwindPlan(unwind_plan);
203         }
204       }
205     }
206   }
207   return false;
208 }
209 
210 bool UnwindAssembly_x86::FirstNonPrologueInsn(
211     AddressRange &func, const ExecutionContext &exe_ctx,
212     Address &first_non_prologue_insn) {
213 
214   if (!func.GetBaseAddress().IsValid())
215     return false;
216 
217   Target *target = exe_ctx.GetTargetPtr();
218   if (target == nullptr)
219     return false;
220 
221   if (m_assembly_inspection_engine == nullptr)
222     return false;
223 
224   const bool prefer_file_cache = true;
225   std::vector<uint8_t> function_text(func.GetByteSize());
226   Status error;
227   if (target->ReadMemory(func.GetBaseAddress(), prefer_file_cache,
228                          function_text.data(), func.GetByteSize(),
229                          error) == func.GetByteSize()) {
230     size_t offset;
231     if (m_assembly_inspection_engine->FindFirstNonPrologueInstruction(
232             function_text.data(), func.GetByteSize(), offset)) {
233       first_non_prologue_insn = func.GetBaseAddress();
234       first_non_prologue_insn.Slide(offset);
235     }
236     return true;
237   }
238   return false;
239 }
240 
241 UnwindAssembly *UnwindAssembly_x86::CreateInstance(const ArchSpec &arch) {
242   const llvm::Triple::ArchType cpu = arch.GetMachine();
243   if (cpu == llvm::Triple::x86 || cpu == llvm::Triple::x86_64)
244     return new UnwindAssembly_x86(arch);
245   return NULL;
246 }
247 
248 //------------------------------------------------------------------
249 // PluginInterface protocol in UnwindAssemblyParser_x86
250 //------------------------------------------------------------------
251 
252 ConstString UnwindAssembly_x86::GetPluginName() {
253   return GetPluginNameStatic();
254 }
255 
256 uint32_t UnwindAssembly_x86::GetPluginVersion() { return 1; }
257 
258 void UnwindAssembly_x86::Initialize() {
259   PluginManager::RegisterPlugin(GetPluginNameStatic(),
260                                 GetPluginDescriptionStatic(), CreateInstance);
261 }
262 
263 void UnwindAssembly_x86::Terminate() {
264   PluginManager::UnregisterPlugin(CreateInstance);
265 }
266 
267 lldb_private::ConstString UnwindAssembly_x86::GetPluginNameStatic() {
268   static ConstString g_name("x86");
269   return g_name;
270 }
271 
272 const char *UnwindAssembly_x86::GetPluginDescriptionStatic() {
273   return "i386 and x86_64 assembly language profiler plugin.";
274 }
275