From cd8509637458c2e3ceedbe173ff20180ce0ea25a Mon Sep 17 00:00:00 2001 From: Benjamin Barenblat Date: Mon, 21 Oct 2019 10:56:55 -0400 Subject: xssxss, an LD_PRELOAD to suspend XScreenSaver with XScreenSaverSuspend --- .gitignore | 8 +++ CONTRIBUTING.md | 33 +++++++++ LICENSE | 202 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Makefile | 32 +++++++++ README.md | 54 +++++++++++++++ xssbase.c | 17 +++++ xssbase.h | 20 ++++++ xsslog.c | 61 +++++++++++++++++ xsslog.h | 27 ++++++++ xssxss.c | 141 +++++++++++++++++++++++++++++++++++++++ 10 files changed, 595 insertions(+) create mode 100644 .gitignore create mode 100644 CONTRIBUTING.md create mode 100644 LICENSE create mode 100644 Makefile create mode 100644 README.md create mode 100644 xssbase.c create mode 100644 xssbase.h create mode 100644 xsslog.c create mode 100644 xsslog.h create mode 100644 xssxss.c diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..ae5540b --- /dev/null +++ b/.gitignore @@ -0,0 +1,8 @@ +# Editor backup files +*~ +\#* +.\#* +.*.swp + +*.o +*.so diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md new file mode 100644 index 0000000..d0c4879 --- /dev/null +++ b/CONTRIBUTING.md @@ -0,0 +1,33 @@ +How to contribute +================= + +We'd love to accept your patches and contributions to this project. There are +just a few small guidelines you need to follow. + + +Contributor License Agreement +----------------------------- + +Contributions to this project must be accompanied by a Contributor License +Agreement. You (or your employer) retain the copyright to your contribution; +this simply gives us permission to use and redistribute your contributions as +part of the project. Head over to to see +your current agreements on file or to sign a new one. + +You generally only need to submit a CLA once, so if you've already submitted one +(even if it was for a different project), you probably don't need to do it +again. + + +Submitting code +--------------- + +Submit patches either via a GitHub pull request or by sending mail to +bbaren@google.com. + + +Community Guidelines +-------------------- + +This project follows +[Google's Open Source Community Guidelines](https://opensource.google.com/conduct/). diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..d645695 --- /dev/null +++ b/LICENSE @@ -0,0 +1,202 @@ + + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. 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We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + + Copyright [yyyy] [name of copyright owner] + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..05b4a83 --- /dev/null +++ b/Makefile @@ -0,0 +1,32 @@ +# Copyright 2019 Google LLC +# +# Licensed under the Apache License, Version 2.0 (the "License"); you may not +# use this file except in compliance with the License. You may obtain a copy of +# the License at +# +# https://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +# License for the specific language governing permissions and limitations under +# the License. + +CPPFLAGS = -D_GNU_SOURCE +CFLAGS = -O2 -flto -Wall -Werror=format-security -fvisibility=hidden -fpic -pthread +LDFLAGS = -Wl,-O2 -flto -Wl,-z,relro -Wl,-z,now -fpic -pthread -shared -s +LDLIBS = -lX11 -ldl + +.PHONY: all +all: libxssxss.so + +libxssxss.so: xssbase.o xsslog.o xssxss.o + $(LINK.o) $^ $(LDLIBS) -o $@ + +xssbase.o: xssbase.c xssbase.h +xsslog.o: xsslog.c xssbase.h xsslog.h +xssxss.o: xssxss.c xssbase.h xsslog.h + +.PHONY: clean +clean: + $(RM) xssbase.o xsslog.o xssxss.o libxssxss.so diff --git a/README.md b/README.md new file mode 100644 index 0000000..cd83dcf --- /dev/null +++ b/README.md @@ -0,0 +1,54 @@ +xssxss +====== + +Normally, [Chrome](https://www.google.com/chrome/) pauses your screensaver while +you’re watching video. If you use [xmonad](https://xmonad.org/) and +[XScreenSaver](https://www.jwz.org/xscreensaver/) together, though, it won’t. +xssxss fixes this behavior; simply run + + make + LD_PRELOAD=$PWD/libxssxss.so google-chrome + +and ta-da, Chrome will disable your screensaver like it’s supposed to. + +Motivation +---------- + +Chromium disables the screensaver through D-Bus. Neither XScreenSaver nor xmonad +implements a D-Bus interface, so [Chromium falls back][XSSSuspendSet] to calling +[`XScreenSaverSuspend`][Xss(3)]. Despite its name, this is an X library function +and [completely unrelated to XScreenSaver][Ubuntu 718176 comment 3], so +XScreenSaver never picks up on it and remains active. + +xssxss (“`XScreenSaver`/XScreenSaver”) translates between X’s `XScreenSaver` +functions and XScreenSaver’s interface by executing `xdg-screensaver reset` when +Chrome calls `XScreenSaverSuspend`. + +[Ubuntu 718176 comment 3]: https://bugs.launchpad.net/ubuntu/+source/xscreensaver/+bug/718176/comments/3 +[XSSSuspendSet]: https://cs.chromium.org/chromium/src/services/device/wake_lock/power_save_blocker/power_save_blocker_x11.cc?l=225&rcl=2edab67ba89b69c8b6117440faf1b8397a62ace6 +[Xss(3)]: https://www.x.org/releases/X11R7.7/doc/man/man3/Xss.3.xhtml + +Future work +----------- + +Ideally, users would be able to control XScreenSaver using D-Bus. However, I +think adding a D-Bus dependency to XScreenSaver is not the best approach; +instead, someone should write an adapter daemon that implements [a reasonable +D-Bus interface][idle-inhibition-spec] and executes `xscreensaver-command` to +control XScreenSaver. + +Once that daemon’s written, Chromium will need to use it. There are multiple +D-Bus interfaces for disabling various screensavers, and Chromium [currently +picks based on the running desktop environment][SelectAPI]. Chromium will need +modification to probe the available interfaces on the bus and select an +appropriate one. There’s a [`TODO` to this effect][SelectAPI TODO], which +suggests the project would be receptive to a patch. + +[idle-inhibition-spec]: https://people.freedesktop.org/~hadess/idle-inhibition-spec/re01.html +[SelectAPI]: https://cs.chromium.org/chromium/src/services/device/wake_lock/power_save_blocker/power_save_blocker_x11.cc?l=450&rcl=fdece9dd1e1f7840a643c85e2d89f356b153fe2c +[SelectAPI TODO]: https://cs.chromium.org/chromium/src/services/device/wake_lock/power_save_blocker/power_save_blocker_x11.cc?l=447-448&rcl=999b2f18d8c62250dd19c85f6c2bb370e68fba8f + +Disclaimer +---------- + +This is not an official Google product. diff --git a/xssbase.c b/xssbase.c new file mode 100644 index 0000000..f8b8055 --- /dev/null +++ b/xssbase.c @@ -0,0 +1,17 @@ +// Copyright 2019 Google LLC +// +// Licensed under the Apache License, Version 2.0 (the "License"); you may not +// use this file except in compliance with the License. You may obtain a copy of +// the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +// License for the specific language governing permissions and limitations under +// the License. + +#include "xssbase.h" + +const char kProjectName[] = "xssxss"; diff --git a/xssbase.h b/xssbase.h new file mode 100644 index 0000000..ec3ea87 --- /dev/null +++ b/xssbase.h @@ -0,0 +1,20 @@ +// Copyright 2019 Google LLC +// +// Licensed under the Apache License, Version 2.0 (the "License"); you may not +// use this file except in compliance with the License. You may obtain a copy of +// the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +// License for the specific language governing permissions and limitations under +// the License. + +#pragma once + +#define LOCAL __attribute__((visibility("hidden"))) +#define PUBLIC __attribute__((visibility("default"))) + +LOCAL extern const char kProjectName[]; diff --git a/xsslog.c b/xsslog.c new file mode 100644 index 0000000..e6d7a63 --- /dev/null +++ b/xsslog.c @@ -0,0 +1,61 @@ +// Copyright 2019 Google LLC +// +// Licensed under the Apache License, Version 2.0 (the "License"); you may not +// use this file except in compliance with the License. You may obtain a copy of +// the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +// License for the specific language governing permissions and limitations under +// the License. + +#include "xsslog.h" + +#include +#include +#include +#include +#include + +static void StrAppend4(char target[], const char a[], const char b[], + const char c[], const char d[]) { + stpcpy(stpcpy(stpcpy(stpcpy(target, a), b), c), d); +} + +void CheckErrnoImpl(const bool condition, const char description[]) { + if (condition) { + return; + } + const int e = errno; + char buf[128]; + fprintf(stderr, "%s: check %s failed: %s\n", kProjectName, description, + strerror_r(e, buf, 128)); + _Exit(1); +} + +void CheckRetImpl(const int e, const char description[]) { + if (e == 0) { + return; + } + char buf[128]; + fprintf(stderr, "%s: %s failed: %s\n", kProjectName, description, + strerror_r(e, buf, 128)); + _Exit(1); +} + +void LogDebug(const char* const format, ...) { + const char colon_space[] = ": "; + char* const prefixed_format = + calloc(strlen(kProjectName) + strlen(colon_space) + strlen(format) + 2, + sizeof(char)); + CHECK_ERRNO(prefixed_format != NULL); + StrAppend4(prefixed_format, kProjectName, ": ", format, "\n"); + va_list args; + va_start(args, format); + vfprintf(stderr, prefixed_format, args); + va_end(args); + free(prefixed_format); +} diff --git a/xsslog.h b/xsslog.h new file mode 100644 index 0000000..cc897c5 --- /dev/null +++ b/xsslog.h @@ -0,0 +1,27 @@ +// Copyright 2019 Google LLC +// +// Licensed under the Apache License, Version 2.0 (the "License"); you may not +// use this file except in compliance with the License. You may obtain a copy of +// the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +// License for the specific language governing permissions and limitations under +// the License. + +#pragma once + +#include + +#include "xssbase.h" + +LOCAL void CheckErrnoImpl(const bool condition, const char description[]); +#define CHECK_ERRNO(condition) (CheckErrnoImpl((condition), #condition)) + +LOCAL void CheckRetImpl(const int, const char description[]); +#define CHECK_RET(call) (CheckRetImpl((call), #call)) + +LOCAL void LogDebug(const char* const format, ...); diff --git a/xssxss.c b/xssxss.c new file mode 100644 index 0000000..17966de --- /dev/null +++ b/xssxss.c @@ -0,0 +1,141 @@ +// Copyright 2019 Google LLC +// +// Licensed under the Apache License, Version 2.0 (the "License"); you may not +// use this file except in compliance with the License. You may obtain a copy of +// the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +// License for the specific language governing permissions and limitations under +// the License. + +#include +#include +#include + +#include +#include +#include +#include +#include +#include + +#include "xssbase.h" +#include "xsslog.h" + +static const int kWakeupSeconds = 10; + +// Runs `xdg-screensaver reset` every `kWakeupSeconds` seconds. +static void* WakerThreadMain(void* const ignored) { + // We'd like the new process to start with all signals in the default state. + // Set up the appropriate attributes to pass to `posix_spawn`. + sigset_t sigset; + posix_spawnattr_t attr; + CHECK_RET(posix_spawnattr_init(&attr)); + CHECK_ERRNO(sigfillset(&sigset) == 0); + CHECK_RET(posix_spawnattr_setsigdefault(&attr, &sigset)); + CHECK_ERRNO(sigemptyset(&sigset) == 0); + CHECK_RET(posix_spawnattr_setsigmask(&attr, &sigset)); + CHECK_RET(posix_spawnattr_setflags( + &attr, POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK)); + + while (true) { + LogDebug("resetting screensaver"); + + // Start the process to wake up xscreensaver. When it exits, we'll get + // SIGCHLD, but we don't care; see notes in `SpawnWakerThread`. + pid_t waker_pid; + char* const waker[] = {"xdg-screensaver", "reset", NULL}; + const int e = posix_spawnp(&waker_pid, waker[0], /*file_action=*/NULL, + &attr, waker, environ); + if (e != 0) { + char buf[128]; + LogDebug("failed to spawn waker: %d", strerror_r(e, buf, 128)); + } + sleep(kWakeupSeconds); + } + + CHECK_RET(posix_spawnattr_destroy(&attr)); + return NULL; +} + +// Starts a new thread at `WakerThreadMain`. +static pthread_t SpawnWakerThread(void) { + // We'd like the new thread to start with all signals masked. The new thread + // inherits the state of our signal mask, so we need to temporarily mask off + // all signals before we call pthread_create. + // + // The new thread is going to be launching new processes, so you might think + // we should attract `SIGCHLD` to it. If this process has left the `SIGCHLD` + // handler at its default (i.e., to ignore it), this isn't necessary. If, on + // the other hand, this process has some thread with an actual `SIGCHLD` + // handler, we're screwed: that handler's going to get called spuriously when + // the new thread's child exits, and attracting `SIGCHLD` to the new thread + // won't solve that problem (the kernel will deliver the signal to an + // arbitrary thread that accepts it, so the original `SIGCHLD` handler might + // get called anyway). Hope that this process has no `SIGCHLD` handler active, + // and just ignore it. + sigset_t parent, child; + CHECK_ERRNO(sigfillset(&child) == 0); + CHECK_ERRNO(pthread_sigmask(SIG_SETMASK, &child, &parent) == 0); + + pthread_t thread; + CHECK_ERRNO(pthread_create(&thread, /*attr=*/NULL, WakerThreadMain, + /*arg=*/NULL) == 0); + + CHECK_ERRNO(pthread_sigmask(SIG_SETMASK, &parent, /*oldset=*/NULL) == 0); + return thread; +} + +static void CancelThread(const pthread_t thread) { + CHECK_ERRNO(pthread_cancel(thread) == 0); + CHECK_ERRNO(pthread_join(thread, /*retval=*/NULL) == 0); +} + +// This function must be thread-safe (it overrides a function that is also +// thread-safe.) +PUBLIC void XScreenSaverSuspend(Display* const display, const Bool suspend) { + // These variables are guarded by the Xlib display lock. The real + // XScreenSaverSuspend also locks the Xlib display, but the lock is a + // recursive mutex, so the double-locking is safe. + static void (*real_XScreenSaverSuspend)(Display*, Bool) = NULL; + static int suspends_active = 0; + static pthread_t waker_thread; + + LogDebug("%s requested", suspend ? "suspend" : "resume"); + + XLockDisplay(display); + + if (real_XScreenSaverSuspend == NULL && + (real_XScreenSaverSuspend = dlsym(RTLD_NEXT, "XScreenSaverSuspend")) == + NULL) { + // We couldn't get the real function. This isn't a huge deal, because we can + // still shut off xscreensaver, but the user probably wants to know about + // it. + LogDebug("can't forward to real XScreenSaverSuspend: %s", dlerror()); + } + + if (real_XScreenSaverSuspend != NULL) { + real_XScreenSaverSuspend(display, suspend); + } + + if (suspends_active == 0) { + if (suspend) { + LogDebug("starting waker thread"); + waker_thread = SpawnWakerThread(); + } else { + LogDebug("resume requested, but no suspends are active; ignoring"); + } + } else if (suspends_active == 1 && !suspend) { + LogDebug("canceling waker thread"); + CancelThread(waker_thread); + } + suspends_active += suspend ? 1 : -1; + LogDebug("%d suspend%s now active", suspends_active, + suspends_active == 1 ? " is" : "s are"); + + XUnlockDisplay(display); +} -- cgit v1.2.3