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//===-- GDBRegistrar.cpp - Registers objects with GDB ---------------------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
#include "JITRegistrar.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/MutexGuard.h"
#include "llvm/Support/ManagedStatic.h"
using namespace llvm;
// This must be kept in sync with gdb/gdb/jit.h .
extern "C" {
typedef enum {
} jit_actions_t;
struct jit_code_entry {
struct jit_code_entry *next_entry;
struct jit_code_entry *prev_entry;
const char *symfile_addr;
uint64_t symfile_size;
struct jit_descriptor {
uint32_t version;
// This should be jit_actions_t, but we want to be specific about the
// bit-width.
uint32_t action_flag;
struct jit_code_entry *relevant_entry;
struct jit_code_entry *first_entry;
// We put information about the JITed function in this global, which the
// debugger reads. Make sure to specify the version statically, because the
// debugger checks the version before we can set it during runtime.
struct jit_descriptor __jit_debug_descriptor = { 1, 0, nullptr, nullptr };
// Debuggers puts a breakpoint in this function.
LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
// The noinline and the asm prevent calls to this function from being
// optimized out.
#if !defined(_MSC_VER)
asm volatile("":::"memory");
namespace {
// Buffer for an in-memory object file in executable memory
typedef llvm::DenseMap< const char*,
std::pair<std::size_t, jit_code_entry*> >
/// Global access point for the JIT debugging interface designed for use with a
/// singleton toolbox. Handles thread-safe registration and deregistration of
/// object files that are in executable memory managed by the client of this
/// class.
class GDBJITRegistrar : public JITRegistrar {
/// A map of in-memory object files that have been registered with the
/// JIT interface.
RegisteredObjectBufferMap ObjectBufferMap;
/// Instantiates the JIT service.
GDBJITRegistrar() : ObjectBufferMap() {}
/// Unregisters each object that was previously registered and releases all
/// internal resources.
virtual ~GDBJITRegistrar();
/// Creates an entry in the JIT registry for the buffer @p Object,
/// which must contain an object file in executable memory with any
/// debug information for the debugger.
void registerObject(const ObjectBuffer &Object) override;
/// Removes the internal registration of @p Object, and
/// frees associated resources.
/// Returns true if @p Object was found in ObjectBufferMap.
bool deregisterObject(const ObjectBuffer &Object) override;
/// Deregister the debug info for the given object file from the debugger
/// and delete any temporary copies. This private method does not remove
/// the function from Map so that it can be called while iterating over Map.
void deregisterObjectInternal(RegisteredObjectBufferMap::iterator I);
/// Lock used to serialize all jit registration events, since they
/// modify global variables.
llvm::sys::Mutex JITDebugLock;
/// Do the registration.
void NotifyDebugger(jit_code_entry* JITCodeEntry) {
__jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
// Insert this entry at the head of the list.
JITCodeEntry->prev_entry = nullptr;
jit_code_entry* NextEntry = __jit_debug_descriptor.first_entry;
JITCodeEntry->next_entry = NextEntry;
if (NextEntry) {
NextEntry->prev_entry = JITCodeEntry;
__jit_debug_descriptor.first_entry = JITCodeEntry;
__jit_debug_descriptor.relevant_entry = JITCodeEntry;
GDBJITRegistrar::~GDBJITRegistrar() {
// Free all registered object files.
llvm::MutexGuard locked(JITDebugLock);
for (RegisteredObjectBufferMap::iterator I = ObjectBufferMap.begin(), E = ObjectBufferMap.end();
I != E; ++I) {
// Call the private method that doesn't update the map so our iterator
// doesn't break.
void GDBJITRegistrar::registerObject(const ObjectBuffer &Object) {
const char *Buffer = Object.getBufferStart();
size_t Size = Object.getBufferSize();
assert(Buffer && "Attempt to register a null object with a debugger.");
llvm::MutexGuard locked(JITDebugLock);
assert(ObjectBufferMap.find(Buffer) == ObjectBufferMap.end() &&
"Second attempt to perform debug registration.");
jit_code_entry* JITCodeEntry = new jit_code_entry();
if (!JITCodeEntry) {
"Allocation failed when registering a JIT entry!\n");
} else {
JITCodeEntry->symfile_addr = Buffer;
JITCodeEntry->symfile_size = Size;
ObjectBufferMap[Buffer] = std::make_pair(Size, JITCodeEntry);
bool GDBJITRegistrar::deregisterObject(const ObjectBuffer& Object) {
const char *Buffer = Object.getBufferStart();
llvm::MutexGuard locked(JITDebugLock);
RegisteredObjectBufferMap::iterator I = ObjectBufferMap.find(Buffer);
if (I != ObjectBufferMap.end()) {
return true;
return false;
void GDBJITRegistrar::deregisterObjectInternal(
RegisteredObjectBufferMap::iterator I) {
jit_code_entry*& JITCodeEntry = I->second.second;
// Do the unregistration.
__jit_debug_descriptor.action_flag = JIT_UNREGISTER_FN;
// Remove the jit_code_entry from the linked list.
jit_code_entry* PrevEntry = JITCodeEntry->prev_entry;
jit_code_entry* NextEntry = JITCodeEntry->next_entry;
if (NextEntry) {
NextEntry->prev_entry = PrevEntry;
if (PrevEntry) {
PrevEntry->next_entry = NextEntry;
else {
assert(__jit_debug_descriptor.first_entry == JITCodeEntry);
__jit_debug_descriptor.first_entry = NextEntry;
// Tell the debugger which entry we removed, and unregister the code.
__jit_debug_descriptor.relevant_entry = JITCodeEntry;
delete JITCodeEntry;
JITCodeEntry = nullptr;
llvm::ManagedStatic<GDBJITRegistrar> TheRegistrar;
} // end namespace
namespace llvm {
JITRegistrar& JITRegistrar::getGDBRegistrar() {
return *TheRegistrar;
} // namespace llvm