src: add commands to inspect the workqueue

Added two new commands (getactivehandles and getactiverequests)
which prints all pending handles and requests (same return
given by process._getActiveHandles() and process._getActiveRequests()).
Those changes were built upon the symbols added on nodejs/node#14901,
which means it's currently not working with node's latest build.

Fixes: nodejs#100
Ref: nodejs/node#14901

README.md

@@ -199,6 +199,11 @@ The following subcommands are supported:
                           * -n, --name  name     - all properties with the specified name
                           * -s, --string string  - all properties that refer to the specified JavaScript string value
 
+<!--- TODO fix indentation for the other commands --->
+      getactivehandles  -- *EXPERIMENTAL* Equivalent to running process._getActiveHandles. This command is still being
+                           developed and for now it only works building node from source.
+      getactiverequests -- *EXPERIMENTAL* Equivalent to running process._getActiveRequests. This command is still being
+                           developed and for now it only works building node from source.
       inspect         -- Print detailed description and contents of the JavaScript value.
 
                          Possible flags (all optional):

llnode.gyp.json

@@ -16,7 +16,10 @@
     ],
 
     "sources": [
+      "src/constants.cc",
       "src/llnode.cc",
+      "src/llnode-module.cc",
+      "src/llnode-constants.cc",
       "src/llv8.cc",
       "src/llv8-constants.cc",
       "src/llscan.cc",

src/constants.cc

@@ -0,0 +1,47 @@
+#include "src/constants.h"
+#include "src/llv8.h"
+
+namespace llnode {
+using v8::Error;
+using v8::constants::IsDebugMode;
+using v8::constants::LookupConstant;
+namespace constants {
+
+void ConstantsWrapper::Assign(SBTarget target) {
+  loaded_ = false;
+  target_ = target;
+}
+
+int64_t ConstantsWrapper::LoadRawConstant(const char* name, int64_t def) {
+  Error err;
+  int64_t v = LookupConstant(target_, name, def, err);
+  if (err.Fail() && IsDebugMode()) fprintf(stderr, "Failed to load %s\n", name);
+
+  return v;
+}
+
+
+int64_t ConstantsWrapper::LoadConstant(const char* name, int64_t def) {
+  Error err;
+  int64_t v =
+      LookupConstant(target_, (kConstantPrefix() + name).c_str(), def, err);
+  if (err.Fail() && IsDebugMode()) fprintf(stderr, "Failed to load %s\n", name);
+
+  return v;
+}
+
+
+int64_t ConstantsWrapper::LoadConstant(const char* name, const char* fallback,
+                                       int64_t def) {
+  Error err;
+  int64_t v =
+      LookupConstant(target_, (kConstantPrefix() + name).c_str(), def, err);
+  if (err.Fail())
+    v = LookupConstant(target_, (kConstantPrefix() + fallback).c_str(), def,
+                       err);
+  if (err.Fail() && IsDebugMode()) fprintf(stderr, "Failed to load %s\n", name);
+
+  return v;
+}
+}
+}

src/constants.h

@@ -0,0 +1,32 @@
+#ifndef SRC_CONSTANTS_H_
+#define SRC_CONSTANTS_H_
+
+#include <lldb/API/LLDB.h>
+using lldb::SBTarget;
+
+namespace llnode {
+namespace constants {
+
+class ConstantsWrapper {
+ public:
+  ConstantsWrapper() : loaded_(false) {}
+
+  inline bool is_loaded() const { return loaded_; }
+
+  void Assign(lldb::SBTarget target);
+
+  inline virtual std::string kConstantPrefix() { return ""; };
+
+ protected:
+  int64_t LoadRawConstant(const char* name, int64_t def = -1);
+  int64_t LoadConstant(const char* name, int64_t def = -1);
+  int64_t LoadConstant(const char* name, const char* fallback,
+                       int64_t def = -1);
+
+  lldb::SBTarget target_;
+  bool loaded_;
+};
+}
+}
+
+#endif

src/llnode-constants.cc

@@ -0,0 +1,173 @@
+#include <lldb/API/LLDB.h>
+
+#include "llnode-constants.h"
+#include "llv8-constants.h"
+#include "llv8-inl.h"
+#include "llv8.h"
+
+using lldb::SBProcess;
+using lldb::SBThread;
+using lldb::SBError;
+using lldb::SBFrame;
+using lldb::SBStream;
+
+namespace llnode {
+using v8::Error;
+using v8::constants::LookupConstant;
+namespace node {
+namespace constants {
+v8::LLV8 llv8;
+
+void Environment::Load() {
+  kIsolate = LoadRawConstant("node::node_isolate");
+  kReqWrapQueueOffset = LoadConstant("class__Environment__reqWrapQueue", 1256);
+  kHandleWrapQueueOffset =
+      LoadConstant("class__Environment__handleWrapQueue", 1240);
+  kEnvContextEmbedderDataIndex =
+      LoadConstant("environment_context_idx_embedder_data", 32);
+  kCurrentEnvironment = LoadCurrentEnvironment();
+}
+
+addr_t Environment::LoadCurrentEnvironment() {
+  addr_t currentEnvironment = DefaultLoadCurrentEnvironment();
+  if (currentEnvironment == -1) {
+    currentEnvironment = FallbackLoadCurrentEnvironment();
+  }
+
+  return currentEnvironment;
+}
+
+addr_t Environment::DefaultLoadCurrentEnvironment() {
+  llv8.Load(target_);
+
+  SBProcess process = target_.GetProcess();
+  SBError sberr;
+  uint64_t env = -1;
+  uint64_t isolate_thread = 0;
+  uint64_t thread_context_ptr = 0;
+  uint64_t thread_context = 0;
+  v8::Error err;
+
+  if (!(llv8.isolate()->kThreadLocalTopOffset != -1 &&
+        llv8.thread_local_top()->kContextOffset != -1)) {
+    return env;
+  }
+
+  isolate_thread = kIsolate + llv8.isolate()->kThreadLocalTopOffset;
+
+  thread_context_ptr = isolate_thread + llv8.thread_local_top()->kContextOffset;
+  thread_context = process.ReadPointerFromMemory(thread_context_ptr, sberr);
+  if (sberr.Fail()) {
+    return -1;
+  }
+  v8::Context ctx(&llv8, thread_context);
+  v8::Value native = ctx.Native(err);
+  if (err.Fail()) {
+    return -1;
+  }
+  env = CurrentEnvironmentFromContext(native);
+  return env;
+}
+
+addr_t Environment::CurrentEnvironmentFromContext(v8::Value context) {
+  llv8.Load(target_);
+  v8::Error err;
+
+  v8::FixedArray contextArray = v8::FixedArray(context);
+  v8::FixedArray embed =
+      contextArray.Get<v8::FixedArray>(llv8.context()->kEmbedderDataIndex, err);
+  if (err.Fail()) {
+    return -1;
+  }
+  v8::Smi encodedEnv = embed.Get<v8::Smi>(kEnvContextEmbedderDataIndex, err);
+  if (err.Fail()) {
+    return -1;
+  } else {
+    return encodedEnv.raw();
+  }
+}
+
+addr_t Environment::FallbackLoadCurrentEnvironment() {
+  addr_t env = -1;
+  SBProcess process = target_.GetProcess();
+  SBThread thread = process.GetSelectedThread();
+  if (!thread.IsValid()) {
+    return -1;
+  }
+
+  llv8.Load(target_);
+
+  SBStream desc;
+  if (!thread.GetDescription(desc)) {
+    return -1;
+  }
+  SBFrame selected_frame = thread.GetSelectedFrame();
+
+  uint32_t num_frames = thread.GetNumFrames();
+  for (uint32_t i = 0; i < num_frames; i++) {
+    SBFrame frame = thread.GetFrameAtIndex(i);
+
+    if (!frame.GetSymbol().IsValid()) {
+      v8::Error err;
+      v8::JSFrame v8_frame(&llv8, static_cast<int64_t>(frame.GetFP()));
+      v8::JSFunction v8_function = v8_frame.GetFunction(err);
+      if (err.Fail()) {
+        continue;
+      }
+      v8::Value val;
+      val = v8_function.GetContext(err);
+      if (err.Fail()) {
+        continue;
+      }
+      bool found = false;
+      while (!found) {
+        v8::Context context(val);
+        v8::Value native = context.Native(err);
+        if (err.Success()) {
+          if (native.raw() == context.raw()) {
+            found = true;
+            env = CurrentEnvironmentFromContext(native);
+            break;
+          }
+        }
+
+        val = context.Previous(err);
+        if (err.Fail()) {
+          break;
+        }
+      }
+      if (found) {
+        break;
+      }
+    }
+  }
+
+  return env;
+}
+
+
+void ReqWrapQueue::Load() {
+  kHeadOffset = LoadConstant("class__ReqWrapQueue__headOffset", (int64_t)0);
+  kNextOffset = LoadConstant("class__ReqWrapQueue__nextOffset", (int64_t)8);
+}
+
+void ReqWrap::Load() {
+  kListNodeOffset = LoadConstant("class__ReqWrap__node", (int64_t)48);
+}
+
+void HandleWrapQueue::Load() {
+  kHeadOffset = LoadConstant("class__HandleWrapQueue__headOffset", (int64_t)0);
+  kNextOffset = LoadConstant("class__HandleWrapQueue__nextOffset", (int64_t)8);
+}
+
+void HandleWrap::Load() {
+  kListNodeOffset = LoadConstant("class__HandleWrap__node", (int64_t)48);
+}
+
+void BaseObject::Load() {
+  kPersistentHandleOffset =
+      LoadConstant("class__BaseObject__persistent_handle", (int64_t)8);
+}
+}
+}
+}

src/llnode-constants.h

@@ -0,0 +1,104 @@
+#ifndef SRC_LLNODE_CONSTANTS_H_
+#define SRC_LLNODE_CONSTANTS_H_
+
+#include <lldb/API/LLDB.h>
+#include "src/constants.h"
+#include "src/llv8.h"
+
+using lldb::addr_t;
+
+namespace llnode {
+using constants::ConstantsWrapper;
+namespace node {
+namespace constants {
+#define MODULE_DEFAULT_METHODS(NAME) \
+  NAME() {}                          \
+  inline NAME* operator()() {        \
+    if (loaded_) return this;        \
+    loaded_ = true;                  \
+    Load();                          \
+    return this;                     \
+  }
+
+
+class Module : public ConstantsWrapper {
+ public:
+  inline std::string kConstantPrefix() override { return "nodedbg_"; };
+};
+
+class Environment : public Module {
+ public:
+  MODULE_DEFAULT_METHODS(Environment);
+
+  int64_t kIsolate;
+  int64_t kReqWrapQueueOffset;
+  int64_t kHandleWrapQueueOffset;
+  int64_t kEnvContextEmbedderDataIndex;
+  addr_t kCurrentEnvironment;
+
+ protected:
+  void Load();
+
+ private:
+  addr_t LoadCurrentEnvironment();
+  addr_t DefaultLoadCurrentEnvironment();
+  addr_t FallbackLoadCurrentEnvironment();
+  addr_t CurrentEnvironmentFromContext(v8::Value context);
+};
+
+class ReqWrapQueue : public Module {
+ public:
+  MODULE_DEFAULT_METHODS(ReqWrapQueue);
+
+  int64_t kHeadOffset;
+  int64_t kNextOffset;
+
+ protected:
+  void Load();
+};
+
+class ReqWrap : public Module {
+ public:
+  MODULE_DEFAULT_METHODS(ReqWrap);
+
+  int64_t kListNodeOffset;
+
+ protected:
+  void Load();
+};
+
+class HandleWrapQueue : public Module {
+ public:
+  MODULE_DEFAULT_METHODS(HandleWrapQueue);
+
+  int64_t kHeadOffset;
+  int64_t kNextOffset;
+
+ protected:
+  void Load();
+};
+
+class HandleWrap : public Module {
+ public:
+  MODULE_DEFAULT_METHODS(HandleWrap);
+
+  int64_t kListNodeOffset;
+
+ protected:
+  void Load();
+};
+
+class BaseObject : public Module {
+ public:
+  MODULE_DEFAULT_METHODS(BaseObject);
+
+  int64_t kPersistentHandleOffset;
+
+ protected:
+  void Load();
+};
+}
+}
+}
+
+#endif