[lldb] Add support for ScriptedFrame with real threads

This patch extends ScriptedFrame to work with real (non-scripted) threads,
enabling frame providers to synthesize frames for native processes.

Previously, ScriptedFrame only worked within ScriptedProcess/ScriptedThread
contexts. This patch decouples ScriptedFrame from ScriptedThread, allowing
users to augment or replace stack frames in real debugging sessions for use
cases like custom calling conventions, reconstructing corrupted frames from
core files, or adding diagnostic frames.

Key changes:

- ScriptedFrame::Create() now accepts ThreadSP instead of requiring
ScriptedThread, extracting architecture from the target triple rather
than ScriptedProcess.arch

- Added SBTarget::RegisterScriptedFrameProvider() and
ClearScriptedFrameProvider() APIs, with Target storing a
SyntheticFrameProviderDescriptor template for new threads

- Added "target frame-provider register/clear" commands for CLI access

- Thread class gains LoadScriptedFrameProvider(), ClearScriptedFrameProvider(),
and GetFrameProvider() methods for per-thread frame provider management

- New SyntheticStackFrameList overrides FetchFramesUpTo() to lazily provide
frames from either the frame provider or the real stack

This enables practical use of the SyntheticFrameProvider infrastructure in
real debugging workflows.

rdar://161834688

Signed-off-by: Med Ismail Bennani <[email protected]>

Author: medismailben

lldb/examples/python/templates/scripted_process.py

@@ -245,6 +245,7 @@ def __init__(self, process, args):
                 key/value pairs used by the scripted thread.
         """
         self.target = None
+        self.arch = None
         self.originating_process = None
         self.process = None
         self.args = None
@@ -266,6 +267,9 @@ def __init__(self, process, args):
             and process.IsValid()
         ):
             self.target = process.target
+            triple = self.target.triple
+            if triple:
+                self.arch = triple.split("-")[0]
             self.originating_process = process
             self.process = self.target.GetProcess()
             self.get_register_info()
@@ -352,17 +356,14 @@ def get_stackframes(self):
     def get_register_info(self):
         if self.register_info is None:
             self.register_info = dict()
-            if "x86_64" in self.originating_process.arch:
+            if "x86_64" in self.arch:
                 self.register_info["sets"] = ["General Purpose Registers"]
                 self.register_info["registers"] = INTEL64_GPR
-            elif (
-                "arm64" in self.originating_process.arch
-                or self.originating_process.arch == "aarch64"
-            ):
+            elif "arm64" in self.arch or self.arch == "aarch64":
                 self.register_info["sets"] = ["General Purpose Registers"]
                 self.register_info["registers"] = ARM64_GPR
             else:
-                raise ValueError("Unknown architecture", self.originating_process.arch)
+                raise ValueError("Unknown architecture", self.arch)
         return self.register_info
 
     @abstractmethod
@@ -405,11 +406,12 @@ def __init__(self, thread, args):
         """Construct a scripted frame.
 
         Args:
-            thread (ScriptedThread): The thread owning this frame.
+            thread (ScriptedThread/lldb.SBThread): The thread owning this frame.
             args (lldb.SBStructuredData): A Dictionary holding arbitrary
                 key/value pairs used by the scripted frame.
         """
         self.target = None
+        self.arch = None
         self.originating_thread = None
         self.thread = None
         self.args = None
@@ -424,10 +426,14 @@ def __init__(self, thread, args):
             or isinstance(thread, lldb.SBThread)
             and thread.IsValid()
         ):
-            self.target = thread.target
             self.process = thread.process
+            self.target = self.process.target
+            triple = self.target.triple
+            if triple:
+                self.arch = triple.split("-")[0]
+            tid = thread.tid if isinstance(thread, ScriptedThread) else thread.id
             self.originating_thread = thread
-            self.thread = self.process.GetThreadByIndexID(thread.tid)
+            self.thread = self.process.GetThreadByIndexID(tid)
             self.get_register_info()
 
     @abstractmethod
@@ -508,7 +514,18 @@ def get_variables(self, filters):
 
     def get_register_info(self):
         if self.register_info is None:
-            self.register_info = self.originating_thread.get_register_info()
+            if isinstance(self.originating_thread, ScriptedThread):
+                self.register_info = self.originating_thread.get_register_info()
+            elif isinstance(self.originating_thread, lldb.SBThread):
+                self.register_info = dict()
+                if "x86_64" in self.arch:
+                    self.register_info["sets"] = ["General Purpose Registers"]
+                    self.register_info["registers"] = INTEL64_GPR
+                elif "arm64" in self.arch or self.arch == "aarch64":
+                    self.register_info["sets"] = ["General Purpose Registers"]
+                    self.register_info["registers"] = ARM64_GPR
+                else:
+                    raise ValueError("Unknown architecture", self.arch)
         return self.register_info
 
     @abstractmethod
@@ -642,12 +659,12 @@ def get_stop_reason(self):
 
             # TODO: Passthrough stop reason from driving process
             if self.driving_thread.GetStopReason() != lldb.eStopReasonNone:
-                if "arm64" in self.originating_process.arch:
+                if "arm64" in self.arch:
                     stop_reason["type"] = lldb.eStopReasonException
                     stop_reason["data"]["desc"] = (
                         self.driving_thread.GetStopDescription(100)
                     )
-                elif self.originating_process.arch == "x86_64":
+                elif self.arch == "x86_64":
                     stop_reason["type"] = lldb.eStopReasonSignal
                     stop_reason["data"]["signal"] = signal.SIGTRAP
                 else:

lldb/include/lldb/API/SBTarget.h

@@ -986,6 +986,34 @@ class LLDB_API SBTarget {
 
   lldb::SBMutex GetAPIMutex() const;
 
+  /// Register a scripted frame provider for this target.
+  ///
+  /// \param[in] class_name
+  ///     The name of the Python class that implements the frame provider.
+  ///
+  /// \param[in] args_dict
+  ///     A dictionary of arguments to pass to the frame provider class.
+  ///
+  /// \return
+  ///     An error object indicating success or failure.
+  lldb::SBError RegisterScriptedFrameProvider(const char *class_name,
+                                              lldb::SBStructuredData args_dict);
+
+  /// Remove a scripted frame provider from this target by name.
+  ///
+  /// \param[in] provider_name
+  ///     The name of the frame provider class to remove.
+  ///
+  /// \return
+  ///     An error object indicating success or failure.
+  lldb::SBError RemoveScriptedFrameProvider(const char *provider_name);
+
+  /// Clear the scripted frame provider for this target.
+  ///
+  /// \return
+  ///     An error object indicating success or failure.
+  lldb::SBError ClearScriptedFrameProvider();
+
 protected:
   friend class SBAddress;
   friend class SBAddressRange;

lldb/include/lldb/Target/StackFrame.h

@@ -442,7 +442,10 @@ class StackFrame : public ExecutionContextScope,
   uint32_t GetFrameIndex() const;
 
   /// Set this frame's synthetic frame index.
-  void SetFrameIndex(uint32_t index) { m_frame_index = index; }
+  void SetFrameIndex(uint32_t index) {
+    m_frame_index = index;
+    m_concrete_frame_index = index;
+  }
 
   /// Query this frame to find what frame it is in this Thread's
   /// StackFrameList, not counting inlined frames.

lldb/include/lldb/Target/StackFrameList.h

@@ -20,13 +20,13 @@ namespace lldb_private {
 
 class ScriptedThread;
 
-class StackFrameList {
+class StackFrameList : public std::enable_shared_from_this<StackFrameList> {
 public:
   // Constructors and Destructors
   StackFrameList(Thread &thread, const lldb::StackFrameListSP &prev_frames_sp,
                  bool show_inline_frames);
 
-  ~StackFrameList();
+  virtual ~StackFrameList();
 
   /// Get the number of visible frames. Frames may be created if \p can_create
   /// is true. Synthetic (inline) frames expanded from the concrete frame #0
@@ -106,6 +106,7 @@ class StackFrameList {
 
 protected:
   friend class Thread;
+  friend class ScriptedFrameProvider;
   friend class ScriptedThread;
 
   /// Use this API to build a stack frame list (used for scripted threads, for
@@ -211,18 +212,20 @@ class StackFrameList {
   /// Whether or not to show synthetic (inline) frames. Immutable.
   const bool m_show_inlined_frames;
 
+  /// These two Fetch frames APIs and SynthesizeTailCallFrames are called in
+  /// GetFramesUpTo, they are the ones that actually add frames.  They must be
+  /// called with the writer end of the list mutex held.
+
+  /// Returns true if fetching frames was interrupted, false otherwise.
+  virtual bool FetchFramesUpTo(uint32_t end_idx,
+                               InterruptionControl allow_interrupt);
+
 private:
   uint32_t SetSelectedFrameNoLock(lldb_private::StackFrame *frame);
   lldb::StackFrameSP
   GetFrameAtIndexNoLock(uint32_t idx,
                         std::shared_lock<std::shared_mutex> &guard);
 
-  /// These two Fetch frames APIs and SynthesizeTailCallFrames are called in
-  /// GetFramesUpTo, they are the ones that actually add frames.  They must be
-  /// called with the writer end of the list mutex held.
-
-  /// Returns true if fetching frames was interrupted, false otherwise.
-  bool FetchFramesUpTo(uint32_t end_idx, InterruptionControl allow_interrupt);
   /// Not currently interruptible so returns void.
   void FetchOnlyConcreteFramesUpTo(uint32_t end_idx);
   void SynthesizeTailCallFrames(StackFrame &next_frame);
@@ -231,6 +234,27 @@ class StackFrameList {
   const StackFrameList &operator=(const StackFrameList &) = delete;
 };
 
+/// A StackFrameList that wraps another StackFrameList and uses a
+/// SyntheticFrameProvider to lazily provide frames from either the provider
+/// or the underlying real stack frame list.
+class SyntheticStackFrameList : public StackFrameList {
+public:
+  SyntheticStackFrameList(Thread &thread, lldb::StackFrameListSP input_frames,
+                          const lldb::StackFrameListSP &prev_frames_sp,
+                          bool show_inline_frames);
+
+protected:
+  /// Override FetchFramesUpTo to lazily return frames from the provider
+  /// or from the actual stack frame list.
+  bool FetchFramesUpTo(uint32_t end_idx,
+                       InterruptionControl allow_interrupt) override;
+
+private:
+  /// The input stack frame list that the provider transforms.
+  /// This could be a real StackFrameList or another SyntheticStackFrameList.
+  lldb::StackFrameListSP m_input_frames;
+};
+
 } // namespace lldb_private
 
 #endif // LLDB_TARGET_STACKFRAMELIST_H

lldb/include/lldb/Target/SyntheticFrameProvider.h

@@ -64,6 +64,7 @@ struct SyntheticFrameProviderDescriptor {
   /// Check if this descriptor has valid metadata for script-based providers.
   bool IsValid() const { return scripted_metadata_sp != nullptr; }
 
+  /// Dump a description of this descriptor to the given stream.
   void Dump(Stream *s) const;
 };
 

lldb/include/lldb/Target/Target.h

@@ -32,6 +32,7 @@
 #include "lldb/Target/PathMappingList.h"
 #include "lldb/Target/SectionLoadHistory.h"
 #include "lldb/Target/Statistics.h"
+#include "lldb/Target/SyntheticFrameProvider.h"
 #include "lldb/Target/ThreadSpec.h"
 #include "lldb/Utility/ArchSpec.h"
 #include "lldb/Utility/Broadcaster.h"
@@ -697,6 +698,39 @@ class Target : public std::enable_shared_from_this<Target>,
   Status Attach(ProcessAttachInfo &attach_info,
                 Stream *stream); // Optional stream to receive first stop info
 
+  // Frame provider methods
+
+  /// Add or update a scripted frame provider descriptor for this target.
+  /// The descriptor's name is extracted from its scripted metadata class name.
+  /// All new threads in this target will check if they match any descriptors
+  /// to create their frame providers.
+  ///
+  /// \param[in] descriptor
+  ///     The descriptor to add or update.
+  Status AddScriptedFrameProviderDescriptor(
+      const SyntheticFrameProviderDescriptor &descriptor);
+
+  /// Remove a scripted frame provider descriptor by name.
+  ///
+  /// \param[in] name
+  ///     The name/key of the descriptor to remove (the class name).
+  ///
+  /// \return
+  ///     True if a descriptor was removed, false if no descriptor with that
+  ///     name existed.
+  bool RemoveScriptedFrameProviderDescriptor(llvm::StringRef name);
+
+  /// Clear all scripted frame provider descriptors for this target.
+  void ClearScriptedFrameProviderDescriptors();
+
+  /// Get all scripted frame provider descriptors for this target.
+  const llvm::StringMap<SyntheticFrameProviderDescriptor> &
+  GetScriptedFrameProviderDescriptors() const;
+
+  /// Get a specific scripted frame provider descriptor by name.
+  std::optional<SyntheticFrameProviderDescriptor>
+  GetScriptedFrameProviderDescriptor(llvm::StringRef name) const;
+
   // This part handles the breakpoints.
 
   BreakpointList &GetBreakpointList(bool internal = false);
@@ -1689,6 +1723,13 @@ class Target : public std::enable_shared_from_this<Target>,
   PathMappingList m_image_search_paths;
   TypeSystemMap m_scratch_type_system_map;
 
+  /// Map of scripted frame provider descriptors for this target.
+  /// Keys are the provider class names, values are the descriptors.
+  /// Used to initialize frame providers for new threads.
+  llvm::StringMap<SyntheticFrameProviderDescriptor>
+      m_frame_provider_descriptors;
+  mutable std::recursive_mutex m_frame_provider_descriptors_mutex;
+
   typedef std::map<lldb::LanguageType, lldb::REPLSP> REPLMap;
   REPLMap m_repl_map;
 

lldb/include/lldb/Target/Thread.h

@@ -1297,6 +1297,15 @@ class Thread : public std::enable_shared_from_this<Thread>,
 
   lldb::StackFrameListSP GetStackFrameList();
 
+  llvm::Error
+  LoadScriptedFrameProvider(const SyntheticFrameProviderDescriptor &descriptor);
+
+  void ClearScriptedFrameProvider();
+
+  lldb::SyntheticFrameProviderSP GetFrameProvider() const {
+    return m_frame_provider_sp;
+  }
+
 protected:
   friend class ThreadPlan;
   friend class ThreadList;
@@ -1400,6 +1409,9 @@ class Thread : public std::enable_shared_from_this<Thread>,
   /// The Thread backed by this thread, if any.
   lldb::ThreadWP m_backed_thread;
 
+  /// The Scripted Frame Provider, if any.
+  lldb::SyntheticFrameProviderSP m_frame_provider_sp;
+
 private:
   bool m_extended_info_fetched; // Have we tried to retrieve the m_extended_info
                                 // for this thread?

lldb/include/lldb/Utility/ScriptedMetadata.h

@@ -27,6 +27,9 @@ class ScriptedMetadata {
     }
   }
 
+  ScriptedMetadata(const ScriptedMetadata &other)
+      : m_class_name(other.m_class_name), m_args_sp(other.m_args_sp) {}
+
   explicit operator bool() const { return !m_class_name.empty(); }
 
   llvm::StringRef GetClassName() const { return m_class_name; }