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The WinAPI `GetFinalPathNameByHandle` is used to retrieve the DLL file
name from the HANDLE provided to `LOAD_DLL_DEBUG_EVENT` in the debug
loop. When this API fails, lldb will simply ignore that module.
Certain ramdisk (e.g. ImDisk) does not work with this API, which means
it is impossible to use lldb to debug a process which loads DLLs located
on this type of ramdisk. In order to make this work, we need to use a
fallback routine which involves creating a file mapping, using
`GetMappedFileName` to get a device path, then substitutes the device
path with its drive letter.
References:
-
https://developercommunity.visualstudio.com/t/cannot-debug-program-when-compiled-to-ram-drive/43004#T-N109926
- https://github.com/jrfonseca/drmingw/issues/65
-
https://docs.microsoft.com/en-us/windows/win32/memory/obtaining-a-file-name-from-a-file-handle
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D126657
Files:
lldb/source/Plugins/Process/Windows/Common/DebuggerThread.cpp
Index: lldb/source/Plugins/Process/Windows/Common/DebuggerThread.cpp
===================================================================
--- lldb/source/Plugins/Process/Windows/Common/DebuggerThread.cpp
+++ lldb/source/Plugins/Process/Windows/Common/DebuggerThread.cpp
@@ -13,6 +13,7 @@
#include "lldb/Core/ModuleSpec.h"
#include "lldb/Host/ProcessLaunchInfo.h"
#include "lldb/Host/ThreadLauncher.h"
+#include "lldb/Host/windows/AutoHandle.h"
#include "lldb/Host/windows/HostProcessWindows.h"
#include "lldb/Host/windows/HostThreadWindows.h"
#include "lldb/Host/windows/ProcessLauncherWindows.h"
@@ -29,6 +30,8 @@
#include "llvm/Support/Threading.h"
#include "llvm/Support/raw_ostream.h"
+#include <psapi.h>
+
#ifndef STATUS_WX86_BREAKPOINT
#define STATUS_WX86_BREAKPOINT 0x4000001FL // For WOW64
#endif
@@ -409,6 +412,60 @@
return DBG_CONTINUE;
}
+static llvm::Optional<std::string> GetFileNameFromHandleFallback(HANDLE hFile) {
+ // Check that file is not empty as we cannot map a file with zero length.
+ DWORD dwFileSizeHi = 0;
+ DWORD dwFileSizeLo = ::GetFileSize(hFile, &dwFileSizeHi);
+ if (dwFileSizeLo == 0 && dwFileSizeHi == 0)
+ return llvm::None;
+
+ AutoHandle filemap(
+ ::CreateFileMappingW(hFile, nullptr, PAGE_READONLY, 0, 1, NULL), nullptr);
+ if (!filemap.IsValid())
+ return llvm::None;
+
+ auto view_deleter = [](void *pMem) { ::UnmapViewOfFile(pMem); };
+ std::unique_ptr<void, decltype(view_deleter)> pMem(
+ ::MapViewOfFile(filemap.get(), FILE_MAP_READ, 0, 0, 1), view_deleter);
+ if (!pMem)
+ return llvm::None;
+
+ std::array<wchar_t, MAX_PATH + 1> mapped_filename;
+ if (!::GetMappedFileNameW(::GetCurrentProcess(), pMem.get(),
+ mapped_filename.data(), mapped_filename.size()))
+ return llvm::None;
+
+ // A series of null-terminated strings, plus an additional null character
+ std::array<wchar_t, 512> drive_strings;
+ drive_strings[0] = L'\0';
+ if (!::GetLogicalDriveStringsW(drive_strings.size(), drive_strings.data()))
+ return llvm::None;
+
+ std::array<wchar_t, 3> drive = {L"_:"};
+ for (auto it = drive_strings.cbegin(); *it != L'\0'; it += wcslen(it) + 1) {
+ // Copy the drive letter to the template string
+ drive[0] = it[0];
+ std::array<wchar_t, MAX_PATH> device_name;
+ if (::QueryDosDeviceW(drive.data(), device_name.data(),
+ device_name.size())) {
+ size_t device_name_len = wcslen(device_name.data());
+ if (device_name_len < mapped_filename.size()) {
+ bool match = _wcsnicmp(mapped_filename.data(), device_name.data(),
+ device_name_len) == 0;
+ if (match && mapped_filename[device_name_len] == L'\\') {
+ // Replace device path with its drive letter
+ std::wstring rebuilt_path(drive.data());
+ rebuilt_path.append(&mapped_filename[device_name_len]);
+ std::string path_utf8;
+ llvm::convertWideToUTF8(rebuilt_path, path_utf8);
+ return path_utf8;
+ }
+ }
+ }
+ }
+ return llvm::None;
+}
+
DWORD
DebuggerThread::HandleLoadDllEvent(const LOAD_DLL_DEBUG_INFO &info,
DWORD thread_id) {
@@ -420,6 +477,17 @@
return DBG_CONTINUE;
}
+ auto on_load_dll = [&](llvm::StringRef path) {
+ FileSpec file_spec(path);
+ ModuleSpec module_spec(file_spec);
+ lldb::addr_t load_addr = reinterpret_cast<lldb::addr_t>(info.lpBaseOfDll);
+
+ LLDB_LOG(log, "Inferior {0} - DLL '{1}' loaded at address {2:x}...",
+ m_process.GetProcessId(), path, info.lpBaseOfDll);
+
+ m_debug_delegate->OnLoadDll(module_spec, load_addr);
+ };
+
std::vector<wchar_t> buffer(1);
DWORD required_size =
GetFinalPathNameByHandleW(info.hFile, &buffer[0], 0, VOLUME_NAME_DOS);
@@ -434,14 +502,10 @@
if (path_str.startswith("\\\\?\\"))
path += 4;
- FileSpec file_spec(path);
- ModuleSpec module_spec(file_spec);
- lldb::addr_t load_addr = reinterpret_cast<lldb::addr_t>(info.lpBaseOfDll);
-
- LLDB_LOG(log, "Inferior {0} - DLL '{1}' loaded at address {2:x}...",
- m_process.GetProcessId(), path, info.lpBaseOfDll);
-
- m_debug_delegate->OnLoadDll(module_spec, load_addr);
+ on_load_dll(path);
+ } else if (llvm::Optional<std::string> path =
+ GetFileNameFromHandleFallback(info.hFile)) {
+ on_load_dll(*path);
} else {
LLDB_LOG(
log,
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