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Normalize paths better; improve backend-doesn't-start error handling
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Fixes #4
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@rprichard
rprichard committed Sep 28, 2016
1 parent 3eac9c3 commit 3dd52c8
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Showing 3 changed files with 104 additions and 21 deletions.
3 changes: 2 additions & 1 deletion backend/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -3,5 +3,6 @@ all : ../out/wslbridge-backend
../out/wslbridge-backend : wslbridge-backend.cc ../common/SocketIo.cc ../common/SocketIo.h ../VERSION.txt Makefile
mkdir -p ../out
g++ -std=c++11 -fno-exceptions \
-D_GNU_SOURCE -DWSLBRIDGE_VERSION=$(shell cat ../VERSION.txt) \
-D_GNU_SOURCE \
-DWSLBRIDGE_VERSION=$(shell cat ../VERSION.txt) \
-Wall -O2 $< ../common/SocketIo.cc -o $@ -lutil -pthread
3 changes: 2 additions & 1 deletion frontend/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -4,5 +4,6 @@ all : ../out/wslbridge.exe
mkdir -p ../out
g++ -std=c++11 -fno-exceptions \
-static -static-libgcc -static-libstdc++ \
-D_GNU_SOURCE -DWSLBRIDGE_VERSION=$(shell cat ../VERSION.txt) \
-D_GNU_SOURCE -D_WIN32_WINNT=0x0600 -DUNICODE -D_UNICODE \
-DWSLBRIDGE_VERSION=$(shell cat ../VERSION.txt) \
-Wall -O2 $< ../common/SocketIo.cc -o $@
119 changes: 100 additions & 19 deletions frontend/wslbridge.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@

#include <algorithm>
#include <array>
#include <atomic>
#include <memory>
#include <mutex>
#include <string>
Expand Down Expand Up @@ -456,7 +457,7 @@ static std::wstring getModuleFileName(HMODULE module) {
return std::wstring(path);
}

std::wstring findBackendProgram() {
static std::wstring findBackendProgram() {
std::wstring progDir = dirname(getModuleFileName(getCurrentModule()));
std::wstring ret = progDir + (L"\\" BACKEND_PROGRAM);
if (!pathExists(ret)) {
Expand All @@ -466,21 +467,77 @@ std::wstring findBackendProgram() {
return ret;
}

std::wstring convertPathToWsl(const std::wstring &path) {
const auto lowerDrive = [](wchar_t ch) -> wchar_t {
if (ch >= L'a' && ch <= L'z') {
return ch;
} else if (ch >= L'A' && ch <= 'Z') {
return ch - L'A' + L'a';
} else {
return L'\0';
static wchar_t lowerDrive(wchar_t ch) {
if (ch >= L'a' && ch <= L'z') {
return ch;
} else if (ch >= L'A' && ch <= 'Z') {
return ch - L'A' + L'a';
} else {
return L'\0';
}
}

static std::pair<std::wstring, std::wstring>
normalizePath(const std::wstring &path) {
const auto getFinalPathName = [&](HANDLE h) -> std::wstring {
std::wstring ret;
ret.resize(MAX_PATH + 1);
while (true) {
const auto sz = GetFinalPathNameByHandleW(h, &ret[0], ret.size(), 0);
if (sz == 0) {
fatal("error: GetFinalPathNameByHandle failed on '%s'",
wcsToMbs(path).c_str());
} else if (sz < ret.size()) {
ret.resize(sz);
return ret;
} else {
assert(sz > ret.size());
ret.resize(sz);
}
}
};
const auto h = CreateFileW(
path.c_str(),
GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
nullptr,
OPEN_EXISTING, 0, nullptr);
if (h == INVALID_HANDLE_VALUE) {
fatal("error: could not open '%s'", wcsToMbs(path).c_str());
}
auto npath = getFinalPathName(h);
std::array<wchar_t, MAX_PATH + 1> fsname;
fsname.back() = L'\0';
if (!GetVolumeInformationByHandleW(
h, nullptr, 0, nullptr, nullptr, nullptr,
&fsname[0], fsname.size())) {
fsname[0] = L'\0';
}
CloseHandle(h);
// Example of GetFinalPathNameByHandle result:
// \\?\C:\cygwin64\bin\wslbridge-backend
// 0123456
// \\?\UNC\server\share\file
// 01234567
if (npath.size() >= 7 &&
npath.substr(0, 4) == L"\\\\?\\" &&
lowerDrive(npath[4]) &&
npath.substr(5, 2) == L":\\") {
// Strip off the atypical \\?\ prefix.
npath = npath.substr(4);
} else if (npath.substr(0, 8) == L"\\\\?\\UNC\\") {
// Strip off the \\\\?\\UNC\\ prefix and replace it with \\.
npath = L"\\\\" + npath.substr(8);
}
return std::make_pair(std::move(npath), fsname.data());
}

static std::wstring convertPathToWsl(const std::wstring &path) {
const auto isSlash = [](wchar_t ch) -> bool {
return ch == L'/' || ch == L'\\';
};
if (path.size() >= 3) {
const wchar_t drive = lowerDrive(path[0]);
const auto drive = lowerDrive(path[0]);
if (drive && path[1] == L':' && isSlash(path[2])) {
// Acceptable path.
std::wstring ret = L"/mnt/";
Expand All @@ -495,12 +552,12 @@ std::wstring convertPathToWsl(const std::wstring &path) {
}
}
fatal(
"Error: the backend program '%s' must be located on a "
"letter drive so WSL can access it with a /mnt/<LTR> path.\n",
"error: the backend program '%s' must be located on a "
"letter drive so WSL can access it with a /mnt/<LTR> path\n",
wcsToMbs(path).c_str());
}

std::wstring findSystemProgram(const wchar_t *name) {
static std::wstring findSystemProgram(const wchar_t *name) {
std::array<wchar_t, MAX_PATH> windir;
windir[0] = L'\0';
if (GetWindowsDirectoryW(windir.data(), windir.size()) == 0) {
Expand Down Expand Up @@ -771,14 +828,17 @@ int main(int argc, char *argv[]) {
errorSocket = std::unique_ptr<Socket>(new Socket);
}

const std::wstring bashPath = findSystemProgram(L"bash.exe");
const std::wstring backendPath = convertPathToWsl(findBackendProgram());
const auto bashPath = findSystemProgram(L"bash.exe");
const auto backendPathInfo = normalizePath(findBackendProgram());
const auto backendPathWin = backendPathInfo.first;
const auto fsname = backendPathInfo.second;
const auto backendPathWsl = convertPathToWsl(backendPathWin);
const auto initialSize = terminalSize();
const std::string key = randomString();
const auto key = randomString();

// Prepare the backend command line.
std::wstring bashCmdLine;
appendBashArg(bashCmdLine, backendPath);
appendBashArg(bashCmdLine, backendPathWsl);
if (debugFork) {
appendBashArg(bashCmdLine, L"--debug-fork");
}
Expand Down Expand Up @@ -843,11 +903,30 @@ int main(int argc, char *argv[]) {
formatErrorMessage(GetLastError()).c_str());
}

std::atomic<bool> backendStarted = { false };

// If the backend process exits before the frontend, then something has
// gone wrong.
const auto watchdog = std::thread([=]() {
const auto watchdog = std::thread([&]() {
WaitForSingleObject(pi.hProcess, INFINITE);
g_terminalState.fatal("\nwslbridge error: backend process died\n");
if (backendStarted) {
g_terminalState.fatal("\nwslbridge error: backend process died\n");
}
std::string msg = "wslbridge error: failed to start backend process\n";
msg.append("note: backend program is at '");
msg.append(wcsToMbs(backendPathWin));
msg.append("'\n");
if (access(wcsToMbs(backendPathWin).c_str(), X_OK) == -1 && errno == EACCES) {
msg.append("note: the backend file is not executable "
"(use 'chmod +x' on it?)\n");
}
if (fsname != L"NTFS") {
msg.append("note: backend is on a volume of type '");
msg.append(wcsToMbs(fsname));
msg.append("', expected 'NTFS'\n"
"note: WSL only supports local NTFS volumes\n");
}
g_terminalState.fatal("%s", msg.c_str());
});

const int controlSocketC = acceptClientAndAuthenticate(controlSocket, key);
Expand All @@ -863,6 +942,8 @@ int main(int argc, char *argv[]) {
g_terminalState.enterRawMode();
}

backendStarted = true;

mainLoop(spawnProgName,
usePty, controlSocketC,
inputSocketC, outputSocketC, errorSocketC,
Expand Down

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