loader: Use dlsym to get our udev symbols instead of explicit linking.

Steam links against libudev.so.0, while we're linking against
libudev.so.1.  The result is that the symbol names (which are the same in
the two libraries) end up conflicting, and some of the usage of .so.1
calls the .so.0 bits, which have different internal structures, and
segfaults happen.

By using a dlopen() with RTLD_LOCAL, we can explicitly look for the
symbols we want, while they get the symbols they want.

Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Tested-by: Alexandre Demers <alexandre.f.demers@gmail.com>
Tested-by: Mike Lothian <mike@fireburn.co.uk>

configure.ac

@@ -858,7 +858,7 @@ xyesno)
 
     if test x"$enable_dri3$have_libudev" = xyesyes; then
         X11_INCLUDES="$X11_INCLUDES $LIBUDEV_CFLAGS"
-        GL_LIB_DEPS="$GL_LIB_DEPS $LIBUDEV_LIBS"
+        GL_LIB_DEPS="$GL_LIB_DEPS"
     fi
 
     # need DRM libs, $PTHREAD_LIBS, etc.

src/egl/main/Makefile.am

@@ -112,7 +112,7 @@ if HAVE_EGL_DRIVER_DRI2
 AM_CFLAGS += -D_EGL_BUILT_IN_DRIVER_DRI2
 AM_CFLAGS += -DHAVE_XCB_DRI2
 libEGL_la_LIBADD += ../drivers/dri2/libegl_dri2.la
-libEGL_la_LIBADD += $(LIBUDEV_LIBS) $(DLOPEN_LIBS) $(LIBDRM_LIBS)
+libEGL_la_LIBADD += $(DLOPEN_LIBS) $(LIBDRM_LIBS)
 endif
 
 # Provide compatibility with scripts for the old Mesa build system for

src/loader/Makefile.am

@@ -29,9 +29,6 @@ libloader_la_CPPFLAGS = \
 	$(VISIBILITY_CFLAGS) \
 	$(LIBUDEV_CFLAGS)
 
-libloader_la_LIBADD = \
-	$(LIBUDEV_LIBS)
-
 if !HAVE_LIBDRM
 libloader_la_CPPFLAGS += \
 	-D__NOT_HAVE_DRM_H
@@ -39,7 +36,7 @@ else
 libloader_la_CPPFLAGS += \
 	$(LIBDRM_CFLAGS)
 
-libloader_la_LIBADD += \
+libloader_la_LIBADD = \
 	$(LIBDRM_LIBS)
 endif
 

src/loader/loader.c

@@ -67,6 +67,8 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
+#include <assert.h>
+#include <dlfcn.h>
 #include "loader.h"
 
 #ifndef __NOT_HAVE_DRM_H
@@ -92,11 +94,37 @@ static void (*log_)(int level, const char *fmt, ...) = default_logger;
 #ifdef HAVE_LIBUDEV
 #include <libudev.h>
 
+static void *udev_handle = NULL;
+
+static void *
+udev_dlopen_handle(void)
+{
+   if (!udev_handle) {
+      udev_handle = dlopen("libudev.so.1", RTLD_LOCAL | RTLD_LAZY);
+   }
+
+   return udev_handle;
+}
+
+static void *
+asserted_dlsym(void *dlopen_handle, const char *name)
+{
+   void *result = dlsym(dlopen_handle, name);
+   assert(result);
+   return result;
+}
+
+#define UDEV_SYMBOL(ret, name, args) \
+   ret (*name) args = asserted_dlsym(udev_dlopen_handle(), #name);
+
+
 static inline struct udev_device *
 udev_device_new_from_fd(struct udev *udev, int fd)
 {
    struct udev_device *device;
    struct stat buf;
+   UDEV_SYMBOL(struct udev_device *, udev_device_new_from_devnum,
+               (struct udev *udev, char type, dev_t devnum));
 
    if (fstat(fd, &buf) < 0) {
       log_(_LOADER_WARNING, "MESA-LOADER: failed to stat fd %d", fd);
@@ -119,6 +147,14 @@ loader_get_pci_id_for_fd(int fd, int *vendor_id, int *chip_id)
    struct udev *udev = NULL;
    struct udev_device *device = NULL, *parent;
    const char *pci_id;
+   UDEV_SYMBOL(struct udev *, udev_new, (void));
+   UDEV_SYMBOL(struct udev_device *, udev_device_get_parent,
+               (struct udev_device *));
+   UDEV_SYMBOL(const char *, udev_device_get_property_value,
+               (struct udev_device *, const char *));
+   UDEV_SYMBOL(struct udev_device *, udev_device_unref,
+               (struct udev_device *));
+   UDEV_SYMBOL(struct udev *, udev_unref, (struct udev *));
 
    *chip_id = -1;
 
@@ -240,6 +276,12 @@ loader_get_device_name_for_fd(int fd)
    struct udev *udev;
    struct udev_device *device;
    const char *const_device_name;
+   UDEV_SYMBOL(struct udev *, udev_new, (void));
+   UDEV_SYMBOL(const char *, udev_device_get_devnode,
+               (struct udev_device *));
+   UDEV_SYMBOL(struct udev_device *, udev_device_unref,
+               (struct udev_device *));
+   UDEV_SYMBOL(struct udev *, udev_unref, (struct udev *));
 
    udev = udev_new();
    device = udev_device_new_from_fd(udev, fd);