Add support for loading shmoverride into Xwayland too

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="${PATH#*/wrappers:}"
+exec env LD_PRELOAD="@SHMOVERRIDE_LIB_PATH@" Xwayland "$@"

shmoverride/shmoverride.c

@@ -72,6 +72,8 @@ static int (*real_munmap) (void *shmaddr, size_t len);
 static int (*real_fstat64) (VER_ARG int fd, struct stat64 *buf);
 static int (*real_fstat)(VER_ARG int fd, struct stat *buf);
 
+static int try_init(void);
+
 static struct stat global_buf;
 static int gntdev_fd = -1;
 
@@ -84,7 +86,7 @@ static int xc_hnd;
 static xengnttab_handle *xgt;
 static char __shmid_filename[SHMID_FILENAME_LEN];
 static char *shmid_filename = NULL;
-static int idfd = -1, display = -1;
+static int idfd = -1, display = -1, init_called = 0;
 
 static uint8_t *mmap_mfns(struct shm_args_hdr *shm_args) {
     uint8_t *map;
@@ -151,6 +153,8 @@ ASM_DEF(void *, mmap,
         real_fstat = FSTAT;
     }
 
+    try_init();
+
 #if defined MAP_ANON && defined MAP_ANONYMOUS && (MAP_ANONYMOUS) != (MAP_ANON)
 # error header bug (def mismatch)
 #endif
@@ -217,6 +221,9 @@ ASM_DEF(int, munmap, void *addr, size_t len)
 {
     if (len > SIZE_MAX - XC_PAGE_SIZE)
         abort();
+
+    try_init();
+
     const uintptr_t addr_int = (uintptr_t)addr;
     const uintptr_t rounded_addr = addr_int & ~(uintptr_t)(XC_PAGE_SIZE - 1);
     return real_munmap((void *)rounded_addr, len + (addr_int - rounded_addr));
@@ -438,6 +445,7 @@ static int assign_off(off_t *off) {
 
 #define STAT(id)                                          \
 ASM_DEF(int, f ## id, int filedes, struct id *buf) {      \
+    try_init();                                           \
     int res = real_f ## id(VER filedes, buf);             \
     if (res ||                                            \
         !S_ISCHR(buf->st_mode) ||                         \
@@ -454,6 +462,7 @@ STAT(stat64)
 #ifdef _STAT_VER
 #define STAT(id)                                                    \
 ASM_DEF(int, __fx ## id, int ver, int filedes, struct id *buf) {    \
+    try_init();                                                     \
     if (ver != _STAT_VER) {                                         \
         fprintf(stderr,                                             \
                 "Wrong _STAT_VER: got %d, expected %d, libc has incompatibly changed\n", \
@@ -467,8 +476,13 @@ STAT(stat64)
 #undef STAT
 #endif
 
-int __attribute__ ((constructor)) initfunc(void)
+static int try_init(void)
 {
+    // Ideally it is being called in constructor, if something is calling this before
+    // constructor - we're assuming it is not multi-threaded code.
+    if (__builtin_expect(init_called, 1)) return 0;
+    init_called = 1;
+
     unsetenv("LD_PRELOAD");
     fprintf(stderr, "shmoverride constructor running\n");
     dlerror();
@@ -519,24 +533,26 @@ int __attribute__ ((constructor)) initfunc(void)
         fputs("snprintf() failed!\n", stderr);
         abort();
     }
-    shmid_filename = __shmid_filename;
-    fprintf(stderr, "shmoverride: running with shm file %s\n", shmid_filename);
+    fprintf(stderr, "shmoverride: running with shm file %s\n", __shmid_filename);
 
     /* Try to lock the shm.id file (don't rely on whether it exists, a previous
      * process might have crashed).
      */
-    idfd = open(shmid_filename, O_RDWR | O_CLOEXEC | O_CREAT | O_NOCTTY, 0600);
+    idfd = open(__shmid_filename, O_RDWR | O_CLOEXEC | O_CREAT | O_NOCTTY, 0600);
     if (idfd < 0) {
         fprintf(stderr, "shmoverride opening %s: %s\n",
-            shmid_filename, strerror(errno));
+            __shmid_filename, strerror(errno));
         goto cleanup;
     }
     if (flock(idfd, LOCK_EX | LOCK_NB) < 0) {
         fprintf(stderr, "shmoverride flock %s: %s\n",
-                shmid_filename, strerror(errno));
+                __shmid_filename, strerror(errno));
         /* There is probably an alive process holding the file, give up. */
         goto cleanup;
     }
+    /* Save shmid file for cleanup only after taking the lock */
+    shmid_filename = __shmid_filename;
+
     if (ftruncate(idfd, SHM_ARGS_SIZE) < 0) {
         perror("shmoverride ftruncate");
         goto cleanup;
@@ -581,6 +597,10 @@ int __attribute__ ((constructor)) initfunc(void)
     shm_args = NULL;
     return 0;
 }
+int __attribute__ ((constructor)) initfunc(void)
+{
+    return try_init();
+}
 
 int __attribute__ ((destructor)) descfunc(void)
 {