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 <[email protected]>
Reviewed-by: Kristian Høgsberg <[email protected]>
Tested-by: Alexandre Demers <[email protected]>
Tested-by: Mike Lothian <[email protected]>

2 files changed, 43 insertions, 4 deletions

diff --git a/src/loader/Makefile.am b/src/loader/Makefile.am
index 371dd575c09..bddf7ac35ed 100644
--- a/src/loader/Makefile.am
+++ b/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
 
diff --git a/src/loader/loader.c b/src/loader/loader.c
index a5bd7692e6e..63b977aa743 100644
--- a/src/loader/loader.c
+++ b/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);