1 //===-- JITDebugRegisterer.cpp - Register debug symbols for JIT -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines a JITDebugRegisterer object that is used by the JIT to
11 // register debug info with debuggers like GDB.
13 //===----------------------------------------------------------------------===//
15 #include "JITDebugRegisterer.h"
16 #include "../../CodeGen/ELF.h"
17 #include "../../CodeGen/ELFWriter.h"
18 #include "llvm/LLVMContext.h"
19 #include "llvm/Function.h"
20 #include "llvm/Module.h"
21 #include "llvm/Target/TargetMachine.h"
22 #include "llvm/Target/TargetOptions.h"
23 #include "llvm/ADT/DenseMap.h"
24 #include "llvm/ADT/OwningPtr.h"
25 #include "llvm/Support/Compiler.h"
26 #include "llvm/Support/MutexGuard.h"
27 #include "llvm/Support/raw_ostream.h"
28 #include "llvm/System/Mutex.h"
34 // This must be kept in sync with gdb/gdb/jit.h .
37 // Debuggers puts a breakpoint in this function.
38 DISABLE_INLINE void __jit_debug_register_code() { }
40 // We put information about the JITed function in this global, which the
41 // debugger reads. Make sure to specify the version statically, because the
42 // debugger checks the version before we can set it during runtime.
43 struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
49 /// JITDebugLock - Used to serialize all code registration events, since they
50 /// modify global variables.
51 sys::Mutex JITDebugLock;
55 JITDebugRegisterer::JITDebugRegisterer(TargetMachine &tm) : TM(tm), FnMap() { }
57 JITDebugRegisterer::~JITDebugRegisterer() {
58 // Free all ELF memory.
59 for (RegisteredFunctionsMap::iterator I = FnMap.begin(), E = FnMap.end();
61 // Call the private method that doesn't update the map so our iterator
63 UnregisterFunctionInternal(I);
68 std::string JITDebugRegisterer::MakeELF(const Function *F, DebugInfo &I) {
69 // Stack allocate an empty module with an empty LLVMContext for the ELFWriter
70 // API. We don't use the real module because then the ELFWriter would write
71 // out unnecessary GlobalValues during finalization.
73 Module M("", Context);
75 // Make a buffer for the ELF in memory.
77 raw_string_ostream O(Buffer);
79 EW.doInitialization(M);
81 // Copy the binary into the .text section. This isn't necessary, but it's
82 // useful to be able to disassemble the ELF by hand.
83 ELFSection &Text = EW.getTextSection((Function *)F);
84 Text.Addr = (uint64_t)I.FnStart;
85 // TODO: We could eliminate this copy if we somehow used a pointer/size pair
86 // instead of a vector.
87 Text.getData().assign(I.FnStart, I.FnEnd);
89 // Copy the exception handling call frame information into the .eh_frame
90 // section. This allows GDB to get a good stack trace, particularly on
91 // linux x86_64. Mark this as a PROGBITS section that needs to be loaded
92 // into memory at runtime.
93 ELFSection &EH = EW.getSection(".eh_frame", ELFSection::SHT_PROGBITS,
94 ELFSection::SHF_ALLOC);
95 // Pointers in the DWARF EH info are all relative to the EH frame start,
96 // which is stored here.
97 EH.Addr = (uint64_t)I.EhStart;
98 // TODO: We could eliminate this copy if we somehow used a pointer/size pair
99 // instead of a vector.
100 EH.getData().assign(I.EhStart, I.EhEnd);
102 // Add this single function to the symbol table, so the debugger prints the
103 // name instead of '???'. We give the symbol default global visibility.
104 ELFSym *FnSym = ELFSym::getGV(F,
107 ELFSym::STV_DEFAULT);
108 FnSym->SectionIdx = Text.SectionIdx;
109 FnSym->Size = I.FnEnd - I.FnStart;
110 FnSym->Value = 0; // Offset from start of section.
111 EW.SymbolList.push_back(FnSym);
113 EW.doFinalization(M);
116 // When trying to debug why GDB isn't getting the debug info right, it's
117 // awfully helpful to write the object file to disk so that it can be
118 // inspected with readelf and objdump.
119 if (JITEmitDebugInfoToDisk) {
120 std::string Filename;
121 raw_string_ostream O2(Filename);
122 O2 << "/tmp/llvm_function_" << I.FnStart << "_" << F->getNameStr() << ".o";
125 raw_fd_ostream O3(Filename.c_str(), Errors);
133 void JITDebugRegisterer::RegisterFunction(const Function *F, DebugInfo &I) {
134 // TODO: Support non-ELF platforms.
135 if (!TM.getELFWriterInfo())
138 std::string Buffer = MakeELF(F, I);
140 jit_code_entry *JITCodeEntry = new jit_code_entry();
141 JITCodeEntry->symfile_addr = Buffer.c_str();
142 JITCodeEntry->symfile_size = Buffer.size();
144 // Add a mapping from F to the entry and buffer, so we can delete this
146 FnMap[F] = std::make_pair<std::string, jit_code_entry*>(Buffer, JITCodeEntry);
148 // Acquire the lock and do the registration.
150 MutexGuard locked(JITDebugLock);
151 __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
153 // Insert this entry at the head of the list.
154 JITCodeEntry->prev_entry = NULL;
155 jit_code_entry *NextEntry = __jit_debug_descriptor.first_entry;
156 JITCodeEntry->next_entry = NextEntry;
157 if (NextEntry != NULL) {
158 NextEntry->prev_entry = JITCodeEntry;
160 __jit_debug_descriptor.first_entry = JITCodeEntry;
161 __jit_debug_descriptor.relevant_entry = JITCodeEntry;
162 __jit_debug_register_code();
166 void JITDebugRegisterer::UnregisterFunctionInternal(
167 RegisteredFunctionsMap::iterator I) {
168 jit_code_entry *JITCodeEntry = I->second.second;
170 // Acquire the lock and do the unregistration.
172 MutexGuard locked(JITDebugLock);
173 __jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN;
175 // Remove the jit_code_entry from the linked list.
176 jit_code_entry *PrevEntry = JITCodeEntry->prev_entry;
177 jit_code_entry *NextEntry = JITCodeEntry->next_entry;
179 NextEntry->prev_entry = PrevEntry;
182 PrevEntry->next_entry = NextEntry;
184 assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
185 __jit_debug_descriptor.first_entry = NextEntry;
188 // Tell GDB which entry we removed, and unregister the code.
189 __jit_debug_descriptor.relevant_entry = JITCodeEntry;
190 __jit_debug_register_code();
193 // Free the ELF file in memory.
194 std::string &Buffer = I->second.first;
198 void JITDebugRegisterer::UnregisterFunction(const Function *F) {
199 // TODO: Support non-ELF platforms.
200 if (!TM.getELFWriterInfo())
203 RegisteredFunctionsMap::iterator I = FnMap.find(F);
204 if (I == FnMap.end()) return;
205 UnregisterFunctionInternal(I);
209 } // end namespace llvm