Add Xwayland wrapper similar to the one for Xorg

Add a wrapper that sets LD_PRELOAD=.../shmoverride.so. Since suid
binaries are not involved with Xwayland, it can be a simple shell
script.

Place the wrapper as Xwayland in /usr/libexec/qubes/wrappers. Processes
that are supposed to use it need to have /usr/libexec/qubes/wrappers
prepended to PATH.

QubesOS/qubes-issues#8515

Makefile

@@ -35,7 +35,9 @@ selinux_policies ::= qubes-gui-daemon.pp
 
 all_targets := gui-daemon/qubes-guid gui-daemon/qubes-guid.1 \
      shmoverride/shmoverride.so \
-     shmoverride/X-wrapper-qubes pulse/pacat-simple-vchan \
+     shmoverride/X-wrapper-qubes \
+	 shmoverride/Xwayland-wrapper \
+	 pulse/pacat-simple-vchan \
      screen-layout-handler/watch-screen-layout-changes
 
 
@@ -52,6 +54,9 @@ shmoverride/shmoverride.so:
 shmoverride/X-wrapper-qubes:
 	(cd shmoverride; $(MAKE) X-wrapper-qubes)
 
+shmoverride/Xwayland-wrapper:
+	(cd shmoverride; $(MAKE) Xwayland-wrapper)
+
 pulse/pacat-simple-vchan:
 	$(MAKE) -C pulse pacat-simple-vchan
 
@@ -67,6 +72,7 @@ install:
 	install -D pulse/pacat-simple-vchan $(DESTDIR)/usr/bin/pacat-simple-vchan
 	install -D shmoverride/X-wrapper-qubes $(DESTDIR)/usr/bin/X-wrapper-qubes
 	install -D shmoverride/shmoverride.so $(DESTDIR)$(LIBDIR)/qubes-gui-daemon/shmoverride.so
+	install -D shmoverride/Xwayland-wrapper $(DESTDIR)/usr/libexec/qubes/wrappers/Xwayland
 	install -D -m 0644 gui-daemon/guid.conf $(DESTDIR)/etc/qubes/guid.conf
 	install -D gui-daemon/qubes-localgroup.sh $(DESTDIR)/etc/X11/xinit/xinitrc.d/qubes-localgroup.sh
 	install -D -m 0644 common/90-default-gui-daemon.policy $(DESTDIR)/etc/qubes/policy.d/90-default-gui-daemon.policy

debian/qubes-gui-daemon.install

@@ -1,6 +1,7 @@
 usr/bin/X.qubes
 usr/bin/qubes-guid
 usr/libexec/qubes/watch-screen-layout-changes
+usr/libexec/qubes/wrappers/Xwayland
 usr/share/man/man1/qubes-guid.1
 usr/lib/*/qubes-gui-daemon/shmoverride.so
 usr/lib/qubes/icon-receiver

rpm_spec/gui-daemon.spec.in

@@ -178,6 +178,7 @@ rm -f %{name}-%{version}
 /etc/xdg/autostart/qubes-icon-receiver.desktop
 /etc/X11/xinit/xinitrc.d/qubes-localgroup.sh
 /usr/libexec/qubes/watch-screen-layout-changes
+/usr/libexec/qubes/wrappers/Xwayland
 /usr/lib/qubes/icon-receiver
 %config %{_sysconfdir}/qubes-rpc/qubes.WindowIconUpdater
 %config %{_sysconfdir}/qubes/rpc-config/qubes.WindowIconUpdater

shmoverride/.gitignore

@@ -1,3 +1,3 @@
 X_wrapper_qubes
 shmoverride.so
-
+Xwayland-wrapper

shmoverride/Makefile

@@ -33,7 +33,7 @@ extra_cflags := -g -O2 -I../include/ -fPIC -Wall -Wextra -Werror \
 		-I../include -fvisibility=hidden -pthread
 CC=gcc
 
-all: shmoverride.so X-wrapper-qubes
+all: shmoverride.so X-wrapper-qubes Xwayland-wrapper
 
 shmoverride.so: shmoverride.o ./list.o
 	$(CC) $(CFLAGS) $(extra_cflags) -shared -o shmoverride.so \
@@ -43,8 +43,11 @@ vpath %.c ../common
 
 X-wrapper-qubes: X-wrapper-qubes.o
 
+Xwayland-wrapper: Xwayland-wrapper.in
+	sed -e "s,@SHMOVERRIDE_LIB_PATH@,$(LIBDIR)/qubes-gui-daemon/shmoverride.so," < $< > $@
+
 clean:
-	rm -f ./*~ ./*.o shmoverride.so X-wrapper-qubes
+	rm -f ./*~ ./*.o shmoverride.so X-wrapper-qubes Xwayland-wrapper
 
 %.o: %.c Makefile
 	$(CC) -MD -MP -MF $@.dep -c -o $@ $(extra_cflags) $(CFLAGS) $<

shmoverride/Xwayland-wrapper.in

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+export PATH="${PATH#*/wrappers:}"
+exec env LD_PRELOAD="@SHMOVERRIDE_LIB_PATH@" Xwayland "$@"