[Lldb-commits] [lldb] [lldb][FreeBSD] Add dynamic loader handle class for FreeBSD Kernel (PR #67106)

[Alex Langford via lldb-commits]

================
@@ -0,0 +1,770 @@
+#include "lldb/Breakpoint/StoppointCallbackContext.h"
+#include "lldb/Core/Debugger.h"
+#include "lldb/Core/Module.h"
+#include "lldb/Core/ModuleSpec.h"
+#include "lldb/Core/PluginManager.h"
+#include "lldb/Core/Section.h"
+#include "lldb/Core/StreamFile.h"
+#include "lldb/Interpreter/OptionValueProperties.h"
+#include "lldb/Symbol/LocateSymbolFile.h"
+#include "lldb/Symbol/ObjectFile.h"
+#include "lldb/Target/OperatingSystem.h"
+#include "lldb/Target/RegisterContext.h"
+#include "lldb/Target/StackFrame.h"
+#include "lldb/Target/Target.h"
+#include "lldb/Target/Thread.h"
+#include "lldb/Target/ThreadPlanRunToAddress.h"
+#include "lldb/Utility/DataBuffer.h"
+#include "lldb/Utility/DataBufferHeap.h"
+#include "lldb/Utility/LLDBLog.h"
+#include "lldb/Utility/Log.h"
+#include "lldb/Utility/State.h"
+
+#include "Plugins/ObjectFile/ELF/ObjectFileELF.h"
+
+#include "DynamicLoaderFreeBSDKernel.h"
+#include <memory>
+#include <mutex>
+
+using namespace lldb;
+using namespace lldb_private;
+
+LLDB_PLUGIN_DEFINE(DynamicLoaderFreeBSDKernel)
+
+void DynamicLoaderFreeBSDKernel::Initialize() {
+  PluginManager::RegisterPlugin(GetPluginNameStatic(),
+                                GetPluginDescriptionStatic(), CreateInstance,
+                                DebuggerInit);
+}
+
+void DynamicLoaderFreeBSDKernel::Terminate() {
+  PluginManager::UnregisterPlugin(CreateInstance);
+}
+
+llvm::StringRef DynamicLoaderFreeBSDKernel::GetPluginDescriptionStatic() {
+  return "The Dynamic Loader Plugin For FreeBSD Kernel";
+}
+
+static bool is_kernel(Module *module) {
+  if (!module)
+    return false;
+
+  ObjectFile *objfile = module->GetObjectFile();
+  if (!objfile)
+    return false;
+  if (objfile->GetType() != ObjectFile::eTypeExecutable)
+    return false;
+  if (objfile->GetStrata() != ObjectFile::eStrataUnknown &&
+      objfile->GetStrata() != ObjectFile::eStrataUser)
+    return false;
+
+  return true;
+}
+
+static bool is_kmod(Module *module) {
+  if (!module)
+    return false;
+  if (!module->GetObjectFile())
+    return false;
+  ObjectFile *objfile = module->GetObjectFile();
+  if (objfile->GetType() != ObjectFile::eTypeObjectFile &&
+      objfile->GetType() != ObjectFile::eTypeSharedLibrary)
+    return false;
+
+  return true;
+}
+
+static bool is_reloc(Module *module) {
+  if (!module)
+    return false;
+  if (!module->GetObjectFile())
+    return false;
+  ObjectFile *objfile = module->GetObjectFile();
+  if (objfile->GetType() != ObjectFile::eTypeObjectFile)
+    return false;
+
+  return true;
+}
+
+// Instantiate Function of the FreeBSD Kernel Dynamic Loader Plugin called when
+// Register the Plugin
+DynamicLoader *
+DynamicLoaderFreeBSDKernel::CreateInstance(lldb_private::Process *process,
+                                           bool force) {
+  // Check the environment when the plugin is not force loaded
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+  LLDB_LOGF(log, "DynamicLoaderFreeBSDKernel::CreateInstance: "
+                 "Try to create instance");
+  if (!force) {
+    Module *exec = process->GetTarget().GetExecutableModulePointer();
+    // Check if the target is kernel
+    if (exec && !is_kernel(exec)) {
+      return nullptr;
+    }
+
+    const llvm::Triple &triple_ref =
+        process->GetTarget().GetArchitecture().GetTriple();
+    if (!triple_ref.isOSFreeBSD()) {
+      return nullptr;
+    }
+  }
+
+  // At this point we have checked the target is a FreeBSD kernel and all we
+  // have to do is to find the kernel address
+  const addr_t kernel_address = FindFreeBSDKernel(process);
+
+  if (CheckForKernelImageAtAddress(process, kernel_address).IsValid())
+    return new DynamicLoaderFreeBSDKernel(process, kernel_address);
+
+  return nullptr;
+}
+
+addr_t
+DynamicLoaderFreeBSDKernel::FindFreeBSDKernel(lldb_private::Process *process) {
+  addr_t kernel_addr = process->GetImageInfoAddress();
+  if (kernel_addr == LLDB_INVALID_ADDRESS)
+    kernel_addr = FindKernelAtLoadAddress(process);
+  return kernel_addr;
+}
+
+// Get the kernel address if the kernel is not loaded with a slide
+addr_t DynamicLoaderFreeBSDKernel::FindKernelAtLoadAddress(
+    lldb_private::Process *process) {
+  Module *exe_module = process->GetTarget().GetExecutableModulePointer();
+
+  if (!is_kernel(exe_module))
+    return LLDB_INVALID_ADDRESS;
+
+  ObjectFile *exe_objfile = exe_module->GetObjectFile();
+
+  if (!exe_objfile->GetBaseAddress().IsValid())
+    return LLDB_INVALID_ADDRESS;
+
+  if (CheckForKernelImageAtAddress(
+          process, exe_objfile->GetBaseAddress().GetFileAddress())
+          .IsValid())
+    return exe_objfile->GetBaseAddress().GetFileAddress();
+
+  return LLDB_INVALID_ADDRESS;
+}
+
+// Read ELF header from memry and return
+bool DynamicLoaderFreeBSDKernel::ReadELFHeader(Process *process,
+                                               lldb::addr_t addr,
+                                               llvm::ELF::Elf32_Ehdr &header,
+                                               bool *read_error) {
+  Status error;
+  if (read_error)
+    *read_error = false;
+
+  if (process->ReadMemory(addr, &header, sizeof(header), error) !=
+      sizeof(header)) {
+    if (read_error)
+      *read_error = true;
+    return false;
+  }
+
+  if (!header.checkMagic())
+    return false;
+
+  return true;
+}
+
+// Check the correctness of Kernel and return UUID
+lldb_private::UUID DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress(
+    Process *process, lldb::addr_t addr, bool *read_error) {
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+
+  if (addr == LLDB_INVALID_ADDRESS) {
+    if (read_error)
+      *read_error = true;
+    return UUID();
+  }
+
+  LLDB_LOGF(log,
+            "DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress: "
+            "looking for kernel binary at 0x%" PRIx64,
+            addr);
+
+  llvm::ELF::Elf32_Ehdr header;
+  if (!ReadELFHeader(process, addr, header))
+    return UUID();
+
+  // Check header type
+  if (header.e_type != llvm::ELF::ET_EXEC)
+    return UUID();
+
+  ModuleSP memory_module_sp =
+      process->ReadModuleFromMemory(FileSpec("temp_freebsd_kernel"), addr);
+  if (!memory_module_sp.get())
+    return UUID();
+
+  ObjectFile *exe_objfile = memory_module_sp->GetObjectFile();
+  if (exe_objfile == nullptr) {
+    LLDB_LOGF(log,
+              "DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress "
+              "found a binary at 0x%" PRIx64
+              " but could not create an object file from memory",
+              addr);
+    return UUID();
+  }
+
+  if (is_kernel(memory_module_sp.get())) {
+    ArchSpec kernel_arch(
+        llvm::ELF::convertEMachineToArchName(header.e_machine));
+
+    if (!process->GetTarget().GetArchitecture().IsCompatibleMatch(kernel_arch))
+      process->GetTarget().SetArchitecture(kernel_arch);
+
+    if (log) {
+      std::string uuid_str;
+      if (memory_module_sp->GetUUID().IsValid()) {
+        uuid_str = "with UUID ";
+        uuid_str += memory_module_sp->GetUUID().GetAsString();
+      } else {
+        uuid_str = "and no LC_UUID found in load commands ";
+      }
+      LLDB_LOGF(log,
+                "DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress: "
+                "kernel binary image found at 0x%" PRIx64 " with arch '%s' %s",
+                addr, kernel_arch.GetTriple().str().c_str(), uuid_str.c_str());
+    }
+
+    return memory_module_sp->GetUUID();
+  }
+
+  return UUID();
+}
+
+void DynamicLoaderFreeBSDKernel::DebuggerInit(
+    lldb_private::Debugger &debugger) {}
+
+DynamicLoaderFreeBSDKernel::DynamicLoaderFreeBSDKernel(Process *process,
+                                                       addr_t kernel_address)
+    : DynamicLoader(process), m_process(process),
+      m_linker_file_list_struct_addr(LLDB_INVALID_ADDRESS),
+      m_linker_file_head_addr(LLDB_INVALID_ADDRESS),
+      m_kernel_load_address(kernel_address), m_mutex() {
+  process->SetCanRunCode(false);
+}
+
+DynamicLoaderFreeBSDKernel::~DynamicLoaderFreeBSDKernel() { Clear(true); }
+
+void DynamicLoaderFreeBSDKernel::Update() {
+  LoadKernelModules();
+  SetNotificationBreakPoint();
+}
+
+// Create in memory Module at the load address
+bool DynamicLoaderFreeBSDKernel::KModImageInfo::ReadMemoryModule(
+    lldb_private::Process *process) {
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+  if (m_memory_module_sp)
+    return true;
+  if (m_load_address == LLDB_INVALID_ADDRESS)
+    return false;
+
+  FileSpec file_spec(m_name.c_str());
----------------
bulbazord wrote:

You can create an `llvm::StringRef` out of a `std::string`. Creating one from a `const char *` involves doing a `strlen`.

https://github.com/llvm/llvm-project/pull/67106