[lldb][LocateModuleCallback] Implement API, Python interface

RFC https://discourse.llvm.org/t/rfc-python-callback-for-target-get-module/71580

Use SWIG for the locate module callback the same as other Python callbacks.
TestLocateModuleCallback.py verifies the functionalities.

Differential Revision: https://reviews.llvm.org/D153735

Author: splhack

lldb/bindings/python/python-typemaps.swig

@@ -576,3 +576,54 @@ template <> bool SetNumberFromPyObject<double>(double &number, PyObject *obj) {
     return NULL;
   }
 }
+
+// For lldb::SBPlatformLocateModuleCallback
+%typemap(in) (lldb::SBPlatformLocateModuleCallback callback,
+              void *callback_baton) {
+  if (!($input == Py_None ||
+        PyCallable_Check(reinterpret_cast<PyObject *>($input)))) {
+    PyErr_SetString(PyExc_TypeError, "Need a callable object or None!");
+    SWIG_fail;
+  }
+
+  if ($input == Py_None) {
+    $1 = nullptr;
+    $2 = nullptr;
+  } else {
+    PythonCallable callable = Retain<PythonCallable>($input);
+    if (!callable.IsValid()) {
+      PyErr_SetString(PyExc_TypeError, "Need a valid callable object");
+      SWIG_fail;
+    }
+
+    llvm::Expected<PythonCallable::ArgInfo> arg_info = callable.GetArgInfo();
+    if (!arg_info) {
+      PyErr_SetString(PyExc_TypeError,
+                      ("Could not get arguments: " +
+                          llvm::toString(arg_info.takeError())).c_str());
+      SWIG_fail;
+    }
+
+    if (arg_info.get().max_positional_args != 3) {
+      PyErr_SetString(PyExc_TypeError, "Expected 3 argument callable object");
+      SWIG_fail;
+    }
+
+    // NOTE: When this is called multiple times, this will leak the Python
+    // callable object as other callbacks, because this does not call Py_DECREF
+    // the object. But it should be almost zero impact since this method is
+    // expected to be called only once.
+
+    // Don't lose the callback reference
+    Py_INCREF($input);
+
+    $1 = LLDBSwigPythonCallLocateModuleCallback;
+    $2 = $input;
+  }
+}
+
+%typemap(typecheck) (lldb::SBPlatformLocateModuleCallback callback,
+                     void *callback_baton) {
+  $1 = $input == Py_None;
+  $1 = $1 || PyCallable_Check(reinterpret_cast<PyObject *>($input));
+}

lldb/bindings/python/python-wrapper.swig

@@ -1118,4 +1118,54 @@ static void LLDBSwigPythonCallPythonSBDebuggerTerminateCallback(lldb::user_id_t
     SWIG_PYTHON_THREAD_END_BLOCK;
   }
 }
+
+static SBError LLDBSwigPythonCallLocateModuleCallback(
+    void *callback_baton, const SBModuleSpec &module_spec_sb,
+    SBFileSpec &module_file_spec_sb, SBFileSpec &symbol_file_spec_sb) {
+  SWIG_Python_Thread_Block swig_thread_block;
+
+  PyErr_Cleaner py_err_cleaner(true);
+  PythonObject module_spec_arg = SWIGBridge::ToSWIGWrapper(
+      std::move(std::make_unique<SBModuleSpec>(module_spec_sb)));
+  PythonObject module_file_spec_arg = SWIGBridge::ToSWIGWrapper(
+      std::move(std::make_unique<SBFileSpec>(module_file_spec_sb)));
+  PythonObject symbol_file_spec_arg = SWIGBridge::ToSWIGWrapper(
+      std::move(std::make_unique<SBFileSpec>(symbol_file_spec_sb)));
+
+  PythonCallable callable =
+      Retain<PythonCallable>(reinterpret_cast<PyObject *>(callback_baton));
+  if (!callable.IsValid()) {
+    return SBError("The callback callable is not valid.");
+  }
+
+  PythonObject result = callable(module_spec_arg, module_file_spec_arg,
+                                 symbol_file_spec_arg);
+
+  if (!result.IsAllocated())
+    return SBError("No result.");
+  lldb::SBError *sb_error_ptr = nullptr;
+  if (SWIG_ConvertPtr(result.get(), (void **)&sb_error_ptr,
+                      SWIGTYPE_p_lldb__SBError, 0) == -1) {
+    return SBError("Result is not SBError.");
+  }
+
+  if (sb_error_ptr->Success()) {
+    lldb::SBFileSpec *sb_module_file_spec_ptr = nullptr;
+    if (SWIG_ConvertPtr(module_file_spec_arg.get(),
+                        (void **)&sb_module_file_spec_ptr,
+                        SWIGTYPE_p_lldb__SBFileSpec, 0) == -1)
+      return SBError("module_file_spec is not SBFileSpec.");
+
+    lldb::SBFileSpec *sb_symbol_file_spec_ptr = nullptr;
+    if (SWIG_ConvertPtr(symbol_file_spec_arg.get(),
+                        (void **)&sb_symbol_file_spec_ptr,
+                        SWIGTYPE_p_lldb__SBFileSpec, 0) == -1)
+      return SBError("symbol_file_spec is not SBFileSpec.");
+
+    module_file_spec_sb = *sb_module_file_spec_ptr;
+    symbol_file_spec_sb = *sb_symbol_file_spec_ptr;
+  }
+
+  return *sb_error_ptr;
+}
 %}

lldb/include/lldb/API/SBDefines.h

@@ -126,6 +126,10 @@ typedef bool (*SBBreakpointHitCallback)(void *baton, SBProcess &process,
 typedef void (*SBDebuggerDestroyCallback)(lldb::user_id_t debugger_id,
                                           void *baton);
 
+typedef SBError (*SBPlatformLocateModuleCallback)(
+    void *baton, const SBModuleSpec &module_spec, SBFileSpec &module_file_spec,
+    SBFileSpec &symbol_file_spec);
+
 typedef void *ScriptedObject;
 }
 

lldb/include/lldb/API/SBPlatform.h

@@ -169,6 +169,18 @@ class LLDB_API SBPlatform {
   ///     environment.
   SBEnvironment GetEnvironment();
 
+  /// Set a callback as an implementation for locating module in order to
+  /// implement own module cache system. For example, to leverage distributed
+  /// build system, to bypass pulling files from remote platform, or to search
+  /// symbol files from symbol servers. The target will call this callback to
+  /// get a module file and a symbol file, and it will fallback to the LLDB
+  /// implementation when this callback failed or returned non-existent file.
+  /// This callback can set either module_file_spec or symbol_file_spec, or both
+  /// module_file_spec and symbol_file_spec. The callback will be cleared if
+  /// nullptr or None is set.
+  SBError SetLocateModuleCallback(lldb::SBPlatformLocateModuleCallback callback,
+                                  void *callback_baton);
+
 protected:
   friend class SBDebugger;
   friend class SBTarget;

lldb/source/API/SBPlatform.cpp

@@ -11,6 +11,7 @@
 #include "lldb/API/SBError.h"
 #include "lldb/API/SBFileSpec.h"
 #include "lldb/API/SBLaunchInfo.h"
+#include "lldb/API/SBModuleSpec.h"
 #include "lldb/API/SBPlatform.h"
 #include "lldb/API/SBUnixSignals.h"
 #include "lldb/Host/File.h"
@@ -655,3 +656,41 @@ SBEnvironment SBPlatform::GetEnvironment() {
 
   return SBEnvironment();
 }
+
+SBError SBPlatform::SetLocateModuleCallback(
+    lldb::SBPlatformLocateModuleCallback callback, void *callback_baton) {
+  LLDB_INSTRUMENT_VA(this, callback, callback_baton);
+  PlatformSP platform_sp(GetSP());
+  if (!platform_sp)
+    return SBError("invalid platform");
+
+  if (!callback) {
+    // Clear the callback.
+    platform_sp->SetLocateModuleCallback(nullptr);
+    return SBError();
+  }
+
+  // Platform.h does not accept lldb::SBPlatformLocateModuleCallback directly
+  // because of the SBModuleSpec and SBFileSpec dependencies. Use a lambda to
+  // convert ModuleSpec/FileSpec <--> SBModuleSpec/SBFileSpec for the callback
+  // arguments.
+  platform_sp->SetLocateModuleCallback(
+      [callback, callback_baton](const ModuleSpec &module_spec,
+                                 FileSpec &module_file_spec,
+                                 FileSpec &symbol_file_spec) {
+        SBModuleSpec module_spec_sb(module_spec);
+        SBFileSpec module_file_spec_sb;
+        SBFileSpec symbol_file_spec_sb;
+
+        SBError error = callback(callback_baton, module_spec_sb,
+                                 module_file_spec_sb, symbol_file_spec_sb);
+
+        if (error.Success()) {
+          module_file_spec = module_file_spec_sb.ref();
+          symbol_file_spec = symbol_file_spec_sb.ref();
+        }
+
+        return error.ref();
+      });
+  return SBError();
+}