xref: /llvm-project/llvm/examples/OrcV2Examples/LLJITWithRemoteDebugging/LLJITWithRemoteDebugging.cpp (revision b7d5b0d0eeda9bc0c7e8c4a6ee2d4ab6b48eb736) 
1 //===--- LLJITWithRemoteDebugging.cpp - LLJIT targeting a child process ---===//
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 // This example shows how to use LLJIT and JITLink for out-of-process execution
10 // with debug support.  A few notes beforehand:
11 //
12 //  * Debuggers must implement the GDB JIT interface (gdb, udb, lldb 12+).
13 //  * Debug support is currently limited to ELF on x86-64 platforms that run
14 //    Unix-like systems.
15 //  * There is a test for this example and it ships an IR file that is prepared
16 //    for the instructions below.
17 //
18 //
19 // The following command line session provides a complete walkthrough of the
20 // feature using LLDB 12:
21 //
22 // [Terminal 1] Prepare a debuggable out-of-process JIT session:
23 //
24 //    > cd llvm-project/build
25 //    > ninja LLJITWithRemoteDebugging llvm-jitlink-executor
26 //    > cp ../llvm/test/Examples/OrcV2Examples/Inputs/argc_sub1_elf.ll .
27 //    > bin/LLJITWithRemoteDebugging --wait-for-debugger argc_sub1_elf.ll
28 //    Found out-of-process executor: bin/llvm-jitlink-executor
29 //    Launched executor in subprocess: 65535
30 //    Attach a debugger and press any key to continue.
31 //
32 //
33 // [Terminal 2] Attach a debugger to the child process:
34 //
35 //    (lldb) log enable lldb jit
36 //    (lldb) settings set plugin.jit-loader.gdb.enable on
37 //    (lldb) settings set target.source-map Inputs/ \
38 //             /path/to/llvm-project/llvm/test/Examples/OrcV2Examples/Inputs/
39 //    (lldb) attach -p 65535
40 //     JITLoaderGDB::SetJITBreakpoint looking for JIT register hook
41 //     JITLoaderGDB::SetJITBreakpoint setting JIT breakpoint
42 //    Process 65535 stopped
43 //    (lldb) b sub1
44 //    Breakpoint 1: no locations (pending).
45 //    WARNING:  Unable to resolve breakpoint to any actual locations.
46 //    (lldb) c
47 //    Process 65535 resuming
48 //
49 //
50 // [Terminal 1] Press a key to start code generation and execution:
51 //
52 //    Parsed input IR code from: argc_sub1_elf.ll
53 //    Initialized LLJIT for remote executor
54 //    Running: argc_sub1_elf.ll
55 //
56 //
57 // [Terminal 2] Breakpoint hits; we change the argc value from 1 to 42:
58 //
59 //    (lldb)  JITLoaderGDB::JITDebugBreakpointHit hit JIT breakpoint
60 //     JITLoaderGDB::ReadJITDescriptorImpl registering JIT entry at 0x106b34000
61 //    1 location added to breakpoint 1
62 //    Process 65535 stopped
63 //    * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
64 //        frame #0: JIT(0x106b34000)`sub1(x=1) at argc_sub1.c:1:28
65 //    -> 1   	int sub1(int x) { return x - 1; }
66 //       2   	int main(int argc, char **argv) { return sub1(argc); }
67 //    (lldb) p x
68 //    (int) $0 = 1
69 //    (lldb) expr x = 42
70 //    (int) $1 = 42
71 //    (lldb) c
72 //
73 //
74 // [Terminal 1] Example output reflects the modified value:
75 //
76 //    Exit code: 41
77 //
78 //===----------------------------------------------------------------------===//
79 
80 #include "llvm/ExecutionEngine/Orc/Debugging/DebuggerSupport.h"
81 #include "llvm/ExecutionEngine/Orc/JITTargetMachineBuilder.h"
82 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
83 #include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
84 #include "llvm/ExecutionEngine/Orc/SimpleRemoteEPC.h"
85 #include "llvm/ExecutionEngine/Orc/ThreadSafeModule.h"
86 #include "llvm/Support/CommandLine.h"
87 #include "llvm/Support/Error.h"
88 #include "llvm/Support/FormatVariadic.h"
89 #include "llvm/Support/InitLLVM.h"
90 #include "llvm/Support/TargetSelect.h"
91 #include "llvm/Support/raw_ostream.h"
92 #include "llvm/TargetParser/Host.h"
93 
94 #include "../ExampleModules.h"
95 #include "RemoteJITUtils.h"
96 
97 #include <memory>
98 #include <string>
99 
100 using namespace llvm;
101 using namespace llvm::orc;
102 
103 // The LLVM IR file to run.
104 static cl::list<std::string> InputFiles(cl::Positional, cl::OneOrMore,
105                                         cl::desc("<input files>"));
106 
107 // Command line arguments to pass to the JITed main function.
108 static cl::list<std::string> InputArgv("args", cl::Positional,
109                                        cl::desc("<program arguments>..."),
110                                        cl::PositionalEatsArgs);
111 
112 // Given paths must exist on the remote target.
113 static cl::list<std::string>
114     Dylibs("dlopen", cl::desc("Dynamic libraries to load before linking"),
115            cl::value_desc("filename"));
116 
117 // File path of the executable to launch for execution in a child process.
118 // Inter-process communication will go through stdin/stdout pipes.
119 static cl::opt<std::string>
120     OOPExecutor("executor", cl::desc("Set the out-of-process executor"),
121                 cl::value_desc("filename"));
122 
123 // Network address of a running executor process that we can connect via TCP. It
124 // may run locally or on a remote machine.
125 static cl::opt<std::string> OOPExecutorConnectTCP(
126     "connect",
127     cl::desc("Connect to an out-of-process executor through a TCP socket"),
128     cl::value_desc("<hostname>:<port>"));
129 
130 // Give the user a chance to connect a debugger. Once we connected the executor
131 // process, wait for the user to press a key (and print out its PID if it's a
132 // child process).
133 static cl::opt<bool>
134     WaitForDebugger("wait-for-debugger",
135                     cl::desc("Wait for user input before entering JITed code"),
136                     cl::init(false));
137 
138 ExitOnError ExitOnErr;
139 
main(int argc,char * argv[])140 int main(int argc, char *argv[]) {
141   InitLLVM X(argc, argv);
142 
143   InitializeNativeTarget();
144   InitializeNativeTargetAsmPrinter();
145 
146   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
147   cl::ParseCommandLineOptions(argc, argv, "LLJITWithRemoteDebugging");
148 
149   std::unique_ptr<SimpleRemoteEPC> EPC;
150   if (OOPExecutorConnectTCP.getNumOccurrences() > 0) {
151     // Connect to a running out-of-process executor through a TCP socket.
152     EPC = ExitOnErr(connectTCPSocket(OOPExecutorConnectTCP));
153     outs() << "Connected to executor at " << OOPExecutorConnectTCP << "\n";
154   } else {
155     // Launch an out-of-process executor locally in a child process.
156     std::string Path =
157         OOPExecutor.empty() ? findLocalExecutor(argv[0]) : OOPExecutor;
158     outs() << "Found out-of-process executor: " << Path << "\n";
159 
160     uint64_t PID;
161     std::tie(EPC, PID) = ExitOnErr(launchLocalExecutor(Path));
162     outs() << "Launched executor in subprocess: " << PID << "\n";
163   }
164 
165   if (WaitForDebugger) {
166     outs() << "Attach a debugger and press any key to continue.\n";
167     fflush(stdin);
168     getchar();
169   }
170 
171   // Load the given IR files.
172   std::vector<ThreadSafeModule> TSMs;
173   for (const std::string &Path : InputFiles) {
174     outs() << "Parsing input IR code from: " << Path << "\n";
175     TSMs.push_back(ExitOnErr(parseExampleModuleFromFile(Path)));
176   }
177 
178   // Create LLJIT and destroy it before disconnecting the target process.
179   outs() << "Initializing LLJIT for remote executor\n";
180   auto J = ExitOnErr(
181       LLJITBuilder().setExecutorProcessControl(std::move(EPC)).create());
182 
183   // Add plugin for debug support.
184   ExitOnErr(enableDebuggerSupport(*J));
185 
186   // Load required shared libraries on the remote target and add a generator
187   // for each of it, so the compiler can lookup their symbols.
188   for (const std::string &Path : Dylibs)
189     J->getMainJITDylib().addGenerator(
190         ExitOnErr(loadDylib(J->getExecutionSession(), Path)));
191 
192   // Add the loaded IR module to the JIT. This will set up symbol tables and
193   // prepare for materialization.
194   for (ThreadSafeModule &TSM : TSMs)
195     ExitOnErr(J->addIRModule(std::move(TSM)));
196 
197   // The example uses a non-lazy JIT for simplicity. Thus, looking up the main
198   // function will materialize all reachable code. It also triggers debug
199   // registration in the remote target process.
200   auto MainAddr = ExitOnErr(J->lookup("main"));
201 
202   outs() << "Running: main(";
203   int Pos = 0;
204   std::vector<std::string> ActualArgv{"LLJITWithRemoteDebugging"};
205   for (const std::string &Arg : InputArgv) {
206     outs() << (Pos++ == 0 ? "" : ", ") << "\"" << Arg << "\"";
207     ActualArgv.push_back(Arg);
208   }
209   outs() << ")\n";
210 
211   // Execute the code in the remote target process and dump the result. With
212   // the debugger attached to the target, it should be possible to inspect the
213   // JITed code as if it was compiled statically.
214   {
215     ExecutorProcessControl &EPC =
216         J->getExecutionSession().getExecutorProcessControl();
217     int Result = ExitOnErr(EPC.runAsMain(MainAddr, ActualArgv));
218     outs() << "Exit code: " << Result << "\n";
219   }
220 
221   return 0;
222 }
223