1 //===-- UnwindAssembly-x86.cpp --------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "UnwindAssembly-x86.h"
10 #include "x86AssemblyInspectionEngine.h"
11 
12 #include "llvm-c/Disassembler.h"
13 #include "llvm/ADT/STLExtras.h"
14 #include "llvm/Support/TargetSelect.h"
15 
16 #include "lldb/Core/Address.h"
17 #include "lldb/Core/PluginManager.h"
18 #include "lldb/Symbol/UnwindPlan.h"
19 #include "lldb/Target/ABI.h"
20 #include "lldb/Target/ExecutionContext.h"
21 #include "lldb/Target/Process.h"
22 #include "lldb/Target/RegisterContext.h"
23 #include "lldb/Target/RegisterNumber.h"
24 #include "lldb/Target/Target.h"
25 #include "lldb/Target/Thread.h"
26 #include "lldb/Target/UnwindAssembly.h"
27 #include "lldb/Utility/ArchSpec.h"
28 #include "lldb/Utility/Status.h"
29 
30 using namespace lldb;
31 using namespace lldb_private;
32 
33 LLDB_PLUGIN_DEFINE_ADV(UnwindAssembly_x86, UnwindAssemblyX86)
34 
35 //  UnwindAssemblyParser_x86 method definitions
36 
37 UnwindAssembly_x86::UnwindAssembly_x86(const ArchSpec &arch)
38     : lldb_private::UnwindAssembly(arch),
39       m_assembly_inspection_engine(new x86AssemblyInspectionEngine(arch)) {}
40 
41 UnwindAssembly_x86::~UnwindAssembly_x86() {
42   delete m_assembly_inspection_engine;
43 }
44 
45 bool UnwindAssembly_x86::GetNonCallSiteUnwindPlanFromAssembly(
46     AddressRange &func, Thread &thread, UnwindPlan &unwind_plan) {
47   if (!func.GetBaseAddress().IsValid() || func.GetByteSize() == 0)
48     return false;
49   if (m_assembly_inspection_engine == nullptr)
50     return false;
51   ProcessSP process_sp(thread.GetProcess());
52   if (process_sp.get() == nullptr)
53     return false;
54   std::vector<uint8_t> function_text(func.GetByteSize());
55   Status error;
56   if (process_sp->GetTarget().ReadMemory(
57           func.GetBaseAddress(), function_text.data(), func.GetByteSize(),
58           error) == func.GetByteSize()) {
59     RegisterContextSP reg_ctx(thread.GetRegisterContext());
60     m_assembly_inspection_engine->Initialize(reg_ctx);
61     return m_assembly_inspection_engine->GetNonCallSiteUnwindPlanFromAssembly(
62         function_text.data(), func.GetByteSize(), func, unwind_plan);
63   }
64   return false;
65 }
66 
67 bool UnwindAssembly_x86::AugmentUnwindPlanFromCallSite(
68     AddressRange &func, Thread &thread, UnwindPlan &unwind_plan) {
69   bool do_augment_unwindplan = true;
70 
71   UnwindPlan::RowSP first_row = unwind_plan.GetRowForFunctionOffset(0);
72   UnwindPlan::RowSP last_row = unwind_plan.GetRowForFunctionOffset(-1);
73 
74   int wordsize = 8;
75   ProcessSP process_sp(thread.GetProcess());
76   if (process_sp.get() == nullptr)
77     return false;
78 
79   wordsize = process_sp->GetTarget().GetArchitecture().GetAddressByteSize();
80 
81   RegisterNumber sp_regnum(thread, eRegisterKindGeneric,
82                            LLDB_REGNUM_GENERIC_SP);
83   RegisterNumber pc_regnum(thread, eRegisterKindGeneric,
84                            LLDB_REGNUM_GENERIC_PC);
85 
86   // Does this UnwindPlan describe the prologue?  I want to see that the CFA is
87   // set in terms of the stack pointer plus an offset, and I want to see that
88   // rip is retrieved at the CFA-wordsize. If there is no description of the
89   // prologue, don't try to augment this eh_frame unwinder code, fall back to
90   // assembly parsing instead.
91 
92   if (first_row->GetCFAValue().GetValueType() !=
93           UnwindPlan::Row::FAValue::isRegisterPlusOffset ||
94       RegisterNumber(thread, unwind_plan.GetRegisterKind(),
95                      first_row->GetCFAValue().GetRegisterNumber()) !=
96           sp_regnum ||
97       first_row->GetCFAValue().GetOffset() != wordsize) {
98     return false;
99   }
100   UnwindPlan::Row::RegisterLocation first_row_pc_loc;
101   if (!first_row->GetRegisterInfo(
102           pc_regnum.GetAsKind(unwind_plan.GetRegisterKind()),
103           first_row_pc_loc) ||
104       !first_row_pc_loc.IsAtCFAPlusOffset() ||
105       first_row_pc_loc.GetOffset() != -wordsize) {
106     return false;
107   }
108 
109   // It looks like the prologue is described. Is the epilogue described?  If it
110   // is, no need to do any augmentation.
111 
112   if (first_row != last_row &&
113       first_row->GetOffset() != last_row->GetOffset()) {
114     // The first & last row have the same CFA register and the same CFA offset
115     // value and the CFA register is esp/rsp (the stack pointer).
116 
117     // We're checking that both of them have an unwind rule like "CFA=esp+4" or
118     // CFA+rsp+8".
119 
120     if (first_row->GetCFAValue().GetValueType() ==
121             last_row->GetCFAValue().GetValueType() &&
122         first_row->GetCFAValue().GetRegisterNumber() ==
123             last_row->GetCFAValue().GetRegisterNumber() &&
124         first_row->GetCFAValue().GetOffset() ==
125             last_row->GetCFAValue().GetOffset()) {
126       // Get the register locations for eip/rip from the first & last rows. Are
127       // they both CFA plus an offset?  Is it the same offset?
128 
129       UnwindPlan::Row::RegisterLocation last_row_pc_loc;
130       if (last_row->GetRegisterInfo(
131               pc_regnum.GetAsKind(unwind_plan.GetRegisterKind()),
132               last_row_pc_loc)) {
133         if (last_row_pc_loc.IsAtCFAPlusOffset() &&
134             first_row_pc_loc.GetOffset() == last_row_pc_loc.GetOffset()) {
135 
136           // One last sanity check:  Is the unwind rule for getting the caller
137           // pc value "deref the CFA-4" or "deref the CFA-8"?
138 
139           // If so, we have an UnwindPlan that already describes the epilogue
140           // and we don't need to modify it at all.
141 
142           if (first_row_pc_loc.GetOffset() == -wordsize) {
143             return true;
144           }
145         }
146       }
147     }
148   }
149 
150   if (do_augment_unwindplan) {
151     if (!func.GetBaseAddress().IsValid() || func.GetByteSize() == 0)
152       return false;
153     if (m_assembly_inspection_engine == nullptr)
154       return false;
155     std::vector<uint8_t> function_text(func.GetByteSize());
156     Status error;
157     if (process_sp->GetTarget().ReadMemory(
158             func.GetBaseAddress(), function_text.data(), func.GetByteSize(),
159             error) == func.GetByteSize()) {
160       RegisterContextSP reg_ctx(thread.GetRegisterContext());
161       m_assembly_inspection_engine->Initialize(reg_ctx);
162       return m_assembly_inspection_engine->AugmentUnwindPlanFromCallSite(
163           function_text.data(), func.GetByteSize(), func, unwind_plan, reg_ctx);
164     }
165   }
166 
167   return false;
168 }
169 
170 bool UnwindAssembly_x86::GetFastUnwindPlan(AddressRange &func, Thread &thread,
171                                            UnwindPlan &unwind_plan) {
172   // if prologue is
173   //   55     pushl %ebp
174   //   89 e5  movl %esp, %ebp
175   //  or
176   //   55        pushq %rbp
177   //   48 89 e5  movq %rsp, %rbp
178 
179   // We should pull in the ABI architecture default unwind plan and return that
180 
181   llvm::SmallVector<uint8_t, 4> opcode_data;
182 
183   ProcessSP process_sp = thread.GetProcess();
184   if (process_sp) {
185     Target &target(process_sp->GetTarget());
186     Status error;
187     if (target.ReadMemory(func.GetBaseAddress(), opcode_data.data(), 4,
188                           error) == 4) {
189       uint8_t i386_push_mov[] = {0x55, 0x89, 0xe5};
190       uint8_t x86_64_push_mov[] = {0x55, 0x48, 0x89, 0xe5};
191 
192       if (memcmp(opcode_data.data(), i386_push_mov, sizeof(i386_push_mov)) ==
193               0 ||
194           memcmp(opcode_data.data(), x86_64_push_mov,
195                  sizeof(x86_64_push_mov)) == 0) {
196         ABISP abi_sp = process_sp->GetABI();
197         if (abi_sp) {
198           return abi_sp->CreateDefaultUnwindPlan(unwind_plan);
199         }
200       }
201     }
202   }
203   return false;
204 }
205 
206 bool UnwindAssembly_x86::FirstNonPrologueInsn(
207     AddressRange &func, const ExecutionContext &exe_ctx,
208     Address &first_non_prologue_insn) {
209 
210   if (!func.GetBaseAddress().IsValid())
211     return false;
212 
213   Target *target = exe_ctx.GetTargetPtr();
214   if (target == nullptr)
215     return false;
216 
217   if (m_assembly_inspection_engine == nullptr)
218     return false;
219 
220   std::vector<uint8_t> function_text(func.GetByteSize());
221   Status error;
222   if (target->ReadMemory(func.GetBaseAddress(), function_text.data(),
223                          func.GetByteSize(), error) == func.GetByteSize()) {
224     size_t offset;
225     if (m_assembly_inspection_engine->FindFirstNonPrologueInstruction(
226             function_text.data(), func.GetByteSize(), offset)) {
227       first_non_prologue_insn = func.GetBaseAddress();
228       first_non_prologue_insn.Slide(offset);
229     }
230     return true;
231   }
232   return false;
233 }
234 
235 UnwindAssembly *UnwindAssembly_x86::CreateInstance(const ArchSpec &arch) {
236   const llvm::Triple::ArchType cpu = arch.GetMachine();
237   if (cpu == llvm::Triple::x86 || cpu == llvm::Triple::x86_64)
238     return new UnwindAssembly_x86(arch);
239   return nullptr;
240 }
241 
242 void UnwindAssembly_x86::Initialize() {
243   PluginManager::RegisterPlugin(GetPluginNameStatic(),
244                                 GetPluginDescriptionStatic(), CreateInstance);
245 }
246 
247 void UnwindAssembly_x86::Terminate() {
248   PluginManager::UnregisterPlugin(CreateInstance);
249 }
250 
251 llvm::StringRef UnwindAssembly_x86::GetPluginDescriptionStatic() {
252   return "i386 and x86_64 assembly language profiler plugin.";
253 }
254