#include <array>
#include <cstdint>
#include <exception>
#include <stdexcept>
#include <windows.h>
#include <rpc.h>
#ifdef DXX_ENABLE_WINDOWS_MINIDUMP
#include <dbghelp.h>
#endif
#include "vers_id.h"
using path_buffer = std::array<wchar_t, MAX_PATH>;
void d_set_exception_handler();
namespace {
class RAII_Windows_FILE_HANDLE
{
const HANDLE m_h;
public:
RAII_Windows_FILE_HANDLE(HANDLE &&h) :
m_h(h)
{
}
~RAII_Windows_FILE_HANDLE()
{
if (*this)
CloseHandle(m_h);
}
RAII_Windows_FILE_HANDLE(const RAII_Windows_FILE_HANDLE &) = delete;
RAII_Windows_FILE_HANDLE &operator=(const RAII_Windows_FILE_HANDLE &) = delete;
explicit operator bool() const
{
return m_h != INVALID_HANDLE_VALUE;
}
operator HANDLE() const
{
return m_h;
}
};
class RAII_Windows_DynamicSharedObject
{
HMODULE m_h;
RAII_Windows_DynamicSharedObject(HMODULE &&h) :
m_h(h)
{
}
static RAII_Windows_DynamicSharedObject LoadInternal(std::array<wchar_t, MAX_PATH> &pathbuf, const unsigned lws, const wchar_t *const filename)
{
wcscpy(&pathbuf[lws], filename);
return LoadLibraryW(pathbuf.data());
}
public:
~RAII_Windows_DynamicSharedObject()
{
if (*this)
FreeLibrary(m_h);
}
RAII_Windows_DynamicSharedObject(const RAII_Windows_DynamicSharedObject &) = delete;
RAII_Windows_DynamicSharedObject &operator=(const RAII_Windows_DynamicSharedObject &) = delete;
RAII_Windows_DynamicSharedObject(RAII_Windows_DynamicSharedObject &&) = default;
explicit operator bool() const
{
return m_h;
}
/*
* This leaks the loaded library. It is used to ensure the library
* will still be loaded when the termination handler runs, long
* after this object has gone out of scope.
*/
void release()
{
m_h = nullptr;
}
template <std::size_t N>
static RAII_Windows_DynamicSharedObject Load(std::array<wchar_t, MAX_PATH> &pathbuf, const unsigned lws, const wchar_t (&filename)[N])
{
if (lws >= MAX_PATH - N)
return nullptr;
return LoadInternal(pathbuf, lws, filename);
}
template <typename T>
T *GetProc(const char *const proc) const
{
union {
FARPROC gpa;
T *result;
};
gpa = GetProcAddress(m_h, proc);
return result;
}
};
struct dxx_trap_context
{
EXCEPTION_RECORD ExceptionRecord;
CONTEXT ContextRecord;
/* Pointer to the first inaccessible byte above the stack. */
const uint8_t *end_sp;
};
}
#define DXX_REPORT_TEXT_FORMAT_UUID "Format UUID: 0f7deda4-1122-4be8-97d5-afc91b7803d6"
#define DXX_REPORT_TEXT_LEADER_VERSION_PREFIX "Rebirth version: x"
#define DXX_REPORT_TEXT_LEADER_BUILD_DATETIME "Rebirth built: "
#define DXX_REPORT_TEXT_LEADER_EXCEPTION_MESSAGE "Exception message: "
constexpr unsigned dump_stack_bytes = 2048 * sizeof(void *);
constexpr unsigned dump_stack_stride = 16;
/*
* This includes leading text describing the UUID, so it must be bigger
* than a bare UUID would require.
*/
static std::array<char, 54> g_strctxuuid;
/*
* These labels are defined in asm() statements to record the address at
* which special instructions are placed. The array size must match the
* size of the assembly instruction. See `vectored_exception_handler`
* for how these are used.
*/
extern const char dxx_rebirth_veh_ud2[2], dxx_rebirth_veh_sp[2];
/*
* 64 bit registers use an R prefix; 32 bit registers use an E prefix.
* For this handler, they can be treated the same. Use a macro to
* expand to the proper name.
*
* Win32 uses a leading underscore on names, relative to the C name.
* Win64 does not. Use a macro to cover that difference.
*/
#ifdef WIN64
#define DXX_NT_CONTEXT_REGISTER(n) R##n
#define DXX_ASM_LABEL(L) "" L
#define DXX_WINDOWS_HOST_ARCH_W L"64"
#define DXX_REPORT_TEXT_LEADER_VERSION DXX_REPORT_TEXT_LEADER_VERSION_PREFIX "64"
#else
#define DXX_NT_CONTEXT_REGISTER(n) E##n
#define DXX_ASM_LABEL(L) "_" L
#define DXX_WINDOWS_HOST_ARCH_W L"86"
#define DXX_REPORT_TEXT_LEADER_VERSION DXX_REPORT_TEXT_LEADER_VERSION_PREFIX "86"
#endif
static LONG CALLBACK vectored_exception_handler(EXCEPTION_POINTERS *const ep)
{
const auto ctx = ep->ContextRecord;
auto &ip = ctx->DXX_NT_CONTEXT_REGISTER(ip);
auto &ax = ctx->DXX_NT_CONTEXT_REGISTER(ax);
const auto t = reinterpret_cast<dxx_trap_context *>(ax);
/*
* If the fault address is dxx_rebirth_veh_ud2, this is an expected
* fault forced solely to capture register context. This fault must
* always happen.
*/
if (ip == reinterpret_cast<uintptr_t>(dxx_rebirth_veh_ud2))
{
/*
* Copy the captured data into the faulting function's local
* variable. The address of that local was loaded into ax before
* triggering the fault.
*/
t->ExceptionRecord = *ep->ExceptionRecord;
t->ContextRecord = *ctx;
/* Step past the faulting instruction. */
ip += sizeof(dxx_rebirth_veh_ud2);
return EXCEPTION_CONTINUE_EXECUTION;
}
/*
* If the fault address is dxx_rebirth_veh_sp, this is an expected
* fault triggered by scanning up off the top of the stack. This
* fault usually happens, but might not if the exception happened
* with a sufficiently deep stack.
*/
else if (ip == reinterpret_cast<uintptr_t>(dxx_rebirth_veh_sp))
{
/*
* The faulting function arranged for ax to hold the terminating
* address of the search and for bx to hold the currently tested
* address. When the fault happens, bx points to an
* inaccessible byte. Set ax to point to that byte. Decrement
* bx to counter the guaranteed increment in the faulting
* function. The combination of these changes ensures that the
* (current != end) test fails, terminating the loop without
* provoking an additional fault.
*/
ax = ctx->DXX_NT_CONTEXT_REGISTER(bx)--;
/* Step past the faulting instruction. */
ip += sizeof(dxx_rebirth_veh_sp);
return EXCEPTION_CONTINUE_EXECUTION;
}
return EXCEPTION_CONTINUE_SEARCH;
}
/* Ensure gcc does not clone the inline labels */
__attribute__((__noinline__,__noclone__,__warn_unused_result__))
static void *capture_exception_context(dxx_trap_context &dtc, const uint8_t *const sp)
{
const auto handler = AddVectoredExceptionHandler(1, &vectored_exception_handler);
if (handler)
{
dtc = {};
/*
* This block guarantees at least one and at most two faults to
* occur. Run it only if an exception handler was successfully
* added to catch these faults.
*/
asm volatile(
DXX_ASM_LABEL("dxx_rebirth_veh_ud2") ":\n"
/*
* Force a fault by executing a guaranteed undefined instruction. The
* fault handler will capture register context for a minidump, then step
* past this instruction.
*
* Before the fault, store the address of the `dxx_trap_context`
* instance `dtc` into ax for easy access by the fault handler. The
* fault handler then initializes dtc from the captured data. Mark
* memory as clobbered to prevent any speculative caching of `dtc`
* across the asm block. A narrower clobber could be used, but "memory"
* is sufficient and this code is not performance critical.
*/
" ud2\n"
:: "a" (&dtc) : "memory"
);
auto p = reinterpret_cast<uintptr_t>(sp);
for (auto e = p + dump_stack_bytes; p != e; ++p)
asm volatile(
DXX_ASM_LABEL("dxx_rebirth_veh_sp") ":\n"
/*
* Force a read of the address pointed at by [sp]. This must be done in
* assembly, not through a volatile C read, because the vectored
* exception handler must know the specific address of the read
* instruction.
*
* This may fault if the stack is not sufficiently deep. If a fault
* happens, the fault handler will adjust `e` and `p`, then step past
* the compare (although stepping past is not strictly necessary). On
* resume from the fault, the loop will find that the adjusted values
* make `++p` == `e`, causing the loop to terminate.
*/
" cmpb %%al,(%[sp])\n"
: "+a" (e),
[sp] "+b" (p)
:: "cc"
);
/*
* Save the address of the first inaccessible byte, rounded down
* to the nearest paragraph.
*/
dtc.end_sp = reinterpret_cast<const uint8_t *>(p & -dump_stack_stride);
RemoveVectoredExceptionHandler(handler);
}
return handler;
}
#undef DXX_ASM_LABEL
/*
* Initialize `path` with a path suitable to be used to write a minidump
* for the exception. Initialize `filename` to point to the first
* character in the filename (bypassing the directories).
*/
static unsigned prepare_exception_log_path(path_buffer &path, wchar_t *&filename, const unsigned pid)
{
const auto l = GetTempPathW(path.size(), path.data());
SYSTEMTIME st{};
GetSystemTime(&st);
/*
* Subsecond precision is not required. The program will terminate
* after writing this dump. No user is likely to be able to restart
* the game, and provoke a second dump, and on the same PID, within
* the same second.
*/
const auto r = l + _snwprintf(filename = path.data() + l, path.size() - l, L"%.4u-%.2u-%.2u-%.2u-%.2u-%.2u x" DXX_WINDOWS_HOST_ARCH_W L" P%u %hs.elog", st.wYear, st.wMonth, st.wDay, st.wHour, st.wMinute, st.wSecond, pid, g_descent_version);
const auto extension = path.data() + r - 5;
wchar_t *p;
/*
* NTFS does not allow star in filenames. The expected content of
* this part of the filename will never contain an 's', so replace
* '*' with 's'. The filename will contain at most one star, but
* possibly none if the version string reported no unstaged changes.
* The position of the star varies depending on whether the version
* string also included a plus to report staged uncommitted changes.
*/
if (*(p = &extension[-1]) == '*' ||
*(p = &extension[-2]) == '*')
*p = 's';
return r;
}
#ifdef DXX_ENABLE_WINDOWS_MINIDUMP
using MiniDumpWriteDump_type = decltype(MiniDumpWriteDump);
static MiniDumpWriteDump_type *g_pMiniDumpWriteDump;
/*
* Write a minidump to the open file `h`, reported as being from pid
* `pid` with context from `dtc`. If `what` is not empty, include it as
* a comment stream. The caller uses this to pass the exception text
* (as returned by `std::exception::what()`) so that it will be easy to
* find in the debugger.
*/
static void write_exception_dump(dxx_trap_context &dtc, const unsigned pid, const std::string &what, const HANDLE h, const MiniDumpWriteDump_type *const pMiniDumpWriteDump)
{
MINIDUMP_EXCEPTION_INFORMATION mei;
MINIDUMP_USER_STREAM_INFORMATION musi;
EXCEPTION_POINTERS ep;
ep.ContextRecord = &dtc.ContextRecord;
ep.ExceptionRecord = &dtc.ExceptionRecord;
mei.ThreadId = GetCurrentThreadId();
mei.ExceptionPointers = &ep;
mei.ClientPointers = 0;
std::array<MINIDUMP_USER_STREAM, 5> mus;
std::array<char, 92> musTextVersion;
std::array<char, 44> musTextDateTime;
std::array<char, 512> musTextExceptionMessage;
unsigned UserStreamCount = 0;
{
auto &m = mus[UserStreamCount++];
m.Type = MINIDUMP_STREAM_TYPE::CommentStreamA;
static char leader[] = DXX_REPORT_TEXT_FORMAT_UUID;
m.BufferSize = sizeof(leader);
m.Buffer = leader;
}
{
auto &m = mus[UserStreamCount++];
m.Type = MINIDUMP_STREAM_TYPE::CommentStreamA;
m.BufferSize = g_strctxuuid.size();
m.Buffer = g_strctxuuid.data();
}
{
auto &m = mus[UserStreamCount++];
m.Type = MINIDUMP_STREAM_TYPE::CommentStreamA;
m.Buffer = musTextVersion.data();
m.BufferSize = 1 + std::snprintf(musTextVersion.data(), musTextVersion.size(), DXX_REPORT_TEXT_LEADER_VERSION " %s", g_descent_version);
}
{
auto &m = mus[UserStreamCount++];
m.Type = MINIDUMP_STREAM_TYPE::CommentStreamA;
m.Buffer = musTextDateTime.data();
m.BufferSize = 1 + std::snprintf(musTextDateTime.data(), musTextDateTime.size(), DXX_REPORT_TEXT_LEADER_BUILD_DATETIME "%s", g_descent_build_datetime);
}
if (!what.empty())
{
auto &m = mus[UserStreamCount++];
m.Type = MINIDUMP_STREAM_TYPE::CommentStreamA;
m.Buffer = musTextExceptionMessage.data();
m.BufferSize = 1 + std::snprintf(musTextExceptionMessage.data(), musTextExceptionMessage.size(), DXX_REPORT_TEXT_LEADER_EXCEPTION_MESSAGE "%s", what.c_str());
}
musi.UserStreamCount = UserStreamCount;
musi.UserStreamArray = mus.data();
(*pMiniDumpWriteDump)(GetCurrentProcess(), pid, h, MiniDumpWithFullMemory, &mei, &musi, nullptr);
}
/*
* Open the file named by `path` for write. On success, call
* `write_exception_dump` above with that handle. On failure, clear the
* path so that the later UI code does not tell the user about a file
* that does not exist.
*/
static void write_exception_dump(dxx_trap_context &dtc, const unsigned pid, const std::string &what, path_buffer &path, const MiniDumpWriteDump_type *const pMiniDumpWriteDump)
{
if (RAII_Windows_FILE_HANDLE h{CreateFileW(path.data(), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)})
write_exception_dump(dtc, pid, what, h, pMiniDumpWriteDump);
else
path.front() = 0;
}
#endif
/*
* Write a plain text dump of metadata and a hex dump of the faulting
* stack.
*/
static void write_exception_stack(const wchar_t *const filename, const unsigned pid, const uint8_t *const begin_sp, const dxx_trap_context &dtc, const std::string &what, const HANDLE h)
{
std::array<char, 4096> buf;
buf = {};
const auto len_header_text = std::snprintf(buf.data(), buf.size(),
"Rebirth exception printed context\n"
DXX_REPORT_TEXT_FORMAT_UUID "\n"
"%.50s\n"
DXX_REPORT_TEXT_LEADER_VERSION " %s\n"
DXX_REPORT_TEXT_LEADER_BUILD_DATETIME "%s\n"
"Rebirth PID: %u\n"
"Report date-time: %.19ls\n"
DXX_REPORT_TEXT_LEADER_EXCEPTION_MESSAGE "\"%s\"\n"
"UD2 IP: %p\n"
"SP: %p\n"
"\n"
, g_strctxuuid.data(), g_descent_version, g_descent_build_datetime, pid, filename, what.c_str(), reinterpret_cast<const uint8_t *>(dtc.ContextRecord.DXX_NT_CONTEXT_REGISTER(ip)), begin_sp
);
/*
* end_sp is rounded down to a paragraph boundary.
* Round sp the same way so that there will exist an integer N such
* that (`sp` + (N * `dump_stack_stride`)) == `end_sp`.
*/
const auto sp = reinterpret_cast<const uint8_t *>(reinterpret_cast<uintptr_t>(begin_sp) & -dump_stack_stride);
DWORD dwWritten;
WriteFile(h, buf.data(), len_header_text, &dwWritten, 0);
const auto end_sp = dtc.end_sp;
for (unsigned i = 0; i < dump_stack_bytes; i += dump_stack_stride)
{
char hexdump[dump_stack_stride + 1];
const auto base_paragraph_pointer = &sp[i];
if (base_paragraph_pointer == end_sp)
break;
hexdump[dump_stack_stride] = 0;
for (unsigned j = dump_stack_stride; j--;)
{
const uint8_t c = reinterpret_cast<const uint8_t *>(base_paragraph_pointer)[j];
hexdump[j] = (c >= ' ' && c <= '~') ? c : '.';
}
buf = {};
#define FORMAT_PADDED_UINT8_4 " %.2x %.2x %.2x %.2x "
#define VAR_PADDED_UINT8_4(I) sp[I], sp[I + 1], sp[I + 2], sp[I + 3]
const auto len_line_text = std::snprintf(buf.data(), buf.size(),
"%p: " FORMAT_PADDED_UINT8_4 FORMAT_PADDED_UINT8_4 FORMAT_PADDED_UINT8_4 FORMAT_PADDED_UINT8_4 " %s\n"
, base_paragraph_pointer, VAR_PADDED_UINT8_4(i), VAR_PADDED_UINT8_4(i + 4), VAR_PADDED_UINT8_4(i + 8), VAR_PADDED_UINT8_4(i + 12), hexdump);
#undef VAR_PADDED_UINT8_4
#undef FORMAT_PADDED_UINT8_4
WriteFile(h, buf.data(), len_line_text, &dwWritten, 0);
}
}
static void write_exception_stack(const wchar_t *const filename, const unsigned pid, const uint8_t *const sp, const dxx_trap_context &dtc, const std::string &what, path_buffer &path)
{
if (RAII_Windows_FILE_HANDLE h{CreateFileW(path.data(), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)})
write_exception_stack(filename, pid, sp, dtc, what, h);
else
path.front() = 0;
}
/*
* Prevent moving the large `dxx_trap_context` into the caller.
* The caller captures the stack pointer before this function begins.
* The captured value should exclude the locals of this function, so
* that the data printed from the captured value covers the stack used
* prior to the throw which triggered the terminate handler. If this
* function were inlined into the caller, the captured stack pointer
* would include the locals of this function.
*/
__attribute__((__noinline__,__noclone__))
static void write_exception_logs(const uint8_t *const sp)
{
std::string what;
try {
/*
* Rethrow the faulting exception, then catch it to extract its
* explanatory text.
*/
std::rethrow_exception(std::current_exception());
} catch (const std::exception &ee) {
what = ee.what();
} catch (...) {
}
#ifdef DXX_ENABLE_WINDOWS_MINIDUMP
path_buffer path_dump;
#define DXX_PATH_DUMP_FORMAT_STRING L"%s%s\n"
#define DXX_PATH_DUMP_ARGUMENTS \
, path_dump.front() ? L"If possible, make available the binary file:\n " : L"No dump file could be generated." \
, path_dump.data()
#else
#define DXX_PATH_DUMP_FORMAT_STRING \
L"Dump file generation is not enabled in this build.\n"
#define DXX_PATH_DUMP_ARGUMENTS
#endif
path_buffer path_stack;
dxx_trap_context dtc;
if (capture_exception_context(dtc, sp))
{
const unsigned pid = GetCurrentProcessId();
wchar_t *filename;
const auto pl = prepare_exception_log_path(path_stack, filename, pid);
#ifdef DXX_ENABLE_WINDOWS_MINIDUMP
path_dump = path_stack;
wcscpy(&path_dump[pl - 4], L"mdmp");
if (const auto pMiniDumpWriteDump = g_pMiniDumpWriteDump)
write_exception_dump(dtc, pid, what, path_dump, pMiniDumpWriteDump);
else
path_dump.front() = 0;
#else
(void)pl;
#endif
write_exception_stack(filename, pid, sp, dtc, what, path_stack);
}
else
{
#ifdef DXX_ENABLE_WINDOWS_MINIDUMP
path_dump.front() = 0;
#endif
path_stack.front() = 0;
}
std::array<wchar_t, 1024> msg;
_snwprintf(msg.data(), msg.size(),
L"Rebirth encountered a fatal error. Please report this to the developers.\n"
L"\nInclude in your report:\n"
L"%s%hs%s"
L"* The level(s) played this session, including download URLs for any add-on missions\n"
L"%s%s\n\n"
DXX_PATH_DUMP_FORMAT_STRING
L"\nTo the extent possible, provide steps to reproduce, starting from the game main menu.",
what.empty() ? L"" : L"* The exception message text:\n \"", what.c_str(), what.empty() ? L"" : L"\"\n",
path_stack.front() ? L"* The contents of the text file:\n " : L"", path_stack.data()
DXX_PATH_DUMP_ARGUMENTS
);
#undef DXX_PATH_DUMP_ARGUMENTS
#undef DXX_PATH_DUMP_FORMAT_STRING
MessageBoxW(NULL, msg.data(), L"Rebirth - Fatal Error", MB_ICONERROR | MB_TOPMOST | MB_TASKMODAL);
}
[[noreturn]]
static void terminate_handler()
{
const uint8_t *sp;
asm(
#ifdef WIN64
"movq %%rsp, %[sp]"
#else
"movl %%esp, %[sp]"
#endif
: [sp] "=rm" (sp));
write_exception_logs(sp);
ExitProcess(0);
}
void d_set_exception_handler()
{
std::set_terminate(&terminate_handler);
std::array<wchar_t, MAX_PATH> ws;
if (const auto lws = GetSystemDirectoryW(ws.data(), ws.size()))
{
if (auto &&rpcrt4 = RAII_Windows_DynamicSharedObject::Load(ws, lws, L"\\rpcrt4.dll"))
{
if (const auto pUuidCreate = rpcrt4.GetProc<decltype(UuidCreate)>("UuidCreate"))
{
UUID ctxuuid;
/*
* Create a UUID specific to this run.
*/
if (SUCCEEDED((*pUuidCreate)(&ctxuuid)))
{
std::snprintf(g_strctxuuid.data(), g_strctxuuid.size(), "Context UUID: %08lx-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x", ctxuuid.Data1, ctxuuid.Data2, ctxuuid.Data3, ctxuuid.Data4[0], ctxuuid.Data4[1], ctxuuid.Data4[2], ctxuuid.Data4[3], ctxuuid.Data4[4], ctxuuid.Data4[5], ctxuuid.Data4[6], ctxuuid.Data4[7]);
}
}
}
#ifdef DXX_ENABLE_WINDOWS_MINIDUMP
if (auto &&dbghelp = RAII_Windows_DynamicSharedObject::Load(ws, lws, L"\\dbghelp.dll"))
{
if ((g_pMiniDumpWriteDump = dbghelp.GetProc<decltype(MiniDumpWriteDump)>("MiniDumpWriteDump")))
dbghelp.release();
}
#endif
}
}