Prevent infinite recursion with Steam's overlay.

1 files changed, 72 insertions, 1 deletions

diff --git a/dispatch/glproc_gl.cpp b/dispatch/glproc_gl.cpp
index 1f3e9fc9..2516dab8 100644
--- a/dispatch/glproc_gl.cpp
+++ b/dispatch/glproc_gl.cpp
@@ -145,6 +145,73 @@ _getPrivateProcAddress(const char *procName)
 #else
 
 
+static inline void
+logSymbol(const char *name, void *ptr) {
+    if (0) {
+        if (ptr) {
+            Dl_info info;
+            if (ptr && dladdr(ptr, &info)) {
+                os::log("apitrace: %s -> \"%s\"\n", name, info.dli_fname);
+            }
+        } else {
+            os::log("apitrace: %s -> NULL\n", name);
+        }
+    }
+}
+
+
+#ifdef __GLIBC__
+extern "C" void * __libc_dlsym(void *, const char *);
+#endif
+
+
+/*
+ * Protect against dlsym interception.
+ *
+ * We implement the whole API, so we don't need to intercept dlsym -- dlopen is
+ * enough. However we need to protect against other dynamic libraries
+ * intercepting dlsym, to prevent infinite recursion,
+ *
+ * In particular the Steam Community Overlay advertises dlsym. See also
+ * http://lists.freedesktop.org/archives/apitrace/2013-March/000573.html
+ */
+static inline void *
+_dlsym(void *handle, const char *symbol)
+{
+    void *result;
+
+#ifdef __GLIBC__
+    /*
+     * We rely on glibc's internal __libc_dlsym.  See also
+     * http://www.linuxforu.com/2011/08/lets-hook-a-library-function/
+     *
+     * Use use it to obtain the true dlsym.  We don't use __libc_dlsym directly
+     * because it does not support things such as RTLD_NEXT.
+     */
+    typedef void * (*PFN_DLSYM)(void *, const char *);
+    static PFN_DLSYM dlsym_ptr = NULL;
+    if (!dlsym_ptr) {
+        void *libdl_handle = _dlopen("libdl.so.2", RTLD_LOCAL | RTLD_NOW);
+        if (libdl_handle) {
+            dlsym_ptr = (PFN_DLSYM)__libc_dlsym(libdl_handle, "dlsym");
+        }
+        if (!dlsym_ptr) {
+            os::log("apitrace: error: failed to look up real dlsym\n");
+            return NULL;
+        }
+
+        logSymbol("dlsym", (void*)dlsym_ptr);
+    }
+
+    result = dlsym_ptr(handle, symbol);
+#else
+    result = dlsym(handle, symbol);
+#endif
+
+    return result;
+}
+
+
 /*
  * Lookup a libGL symbol
  */
@@ -188,7 +255,11 @@ void * _libgl_sym(const char *symbol)
         }
     }
 
-    return dlsym(_libGlHandle, symbol);
+    result = _dlsym(_libGlHandle, symbol);
+
+    logSymbol(symbol, result);
+
+    return result;
 }