Import a copy of dlwrap from libfips.

This is just cworth's code, reindented for this project.
11 years ago · dae231680e
parent 9efad17eb4
commit dae231680e
2 changed files with 310 additions and 0 deletions
--- a/test/dlwrap.c
+++ b/test/dlwrap.c
@ -0,0 +1,253 @@
+/* Copyright © 2013, Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/* dladdr is a glibc extension */
+#define _GNU_SOURCE
+#include <dlfcn.h>
+
+#include <assert.h>
+
+#include "fips.h"
+
+#include "dlwrap.h"
+
+#include "glwrap.h"
+
+void *libfips_handle;
+
+typedef void *(*fips_dlopen_t)(const char *filename, int flag);
+typedef void *(*fips_dlsym_t)(void *handle, const char *symbol);
+
+static const char *wrapped_libs[] = {
+    "libGL.so",
+    "libEGL.so",
+    "libGLESv2.so"
+};
+
+static void *orig_handles[ARRAY_SIZE(wrapped_libs)];
+
+/* Match 'filename' against an internal list of libraries for which
+ * libfips has wrappers.
+ *
+ * Returns true and sets *index_ret if a match is found.
+ * Returns false if no match is found. */
+static bool
+find_wrapped_library_index(const char *filename, unsigned *index_ret)
+{
+    unsigned i;
+
+    for (i = 0; i < ARRAY_SIZE(wrapped_libs); i++) {
+        if (strncmp(wrapped_libs[i], filename,
+                    strlen(wrapped_libs[i])) == 0)
+            {
+                *index_ret = i;
+                return true;
+            }
+    }
+
+    return false;
+}
+
+/* Perform a dlopen on the libfips library itself.
+ *
+ * Many places in fips need to lookup symbols within the libfips
+ * library itself, (and not in any other library). This function
+ * provides a reliable way to get a handle for performing such
+ * lookups.
+ *
+ * The returned handle can be passed to dlwrap_real_dlsym for the
+ * lookups. */
+void *
+dlwrap_dlopen_libfips(void)
+{
+    Dl_info info;
+
+    /* We first find our own filename by looking up a function
+     * known to exist only in libfips. This function itself
+     * (dlwrap_dlopen_libfips) is a good one for that purpose. */
+    if (dladdr(dlwrap_dlopen_libfips, &info) == 0) {
+        fprintf(stderr, "Internal error: Failed to lookup filename of "
+                "libfips library with dladdr\n");
+        exit(1);
+    }
+
+    return dlwrap_real_dlopen(info.dli_fname, RTLD_NOW);
+}
+
+/* Many (most?) OpenGL programs dlopen libGL.so.1 rather than linking
+ * against it directly, which means they would not be seeing our
+ * wrapped GL symbols via LD_PRELOAD. So we catch the dlopen in a
+ * wrapper here and redirect it to our library.
+ */
+void *
+dlopen(const char *filename, int flag)
+{
+    void *ret;
+    unsigned index;
+
+    /* Before deciding whether to redirect this dlopen to our own
+     * library, we call the real dlopen. This assures that any
+     * expected side-effects from loading the intended library are
+     * resolved. Below, we may still return a handle pointing to
+     * our own library, and not what is opened here. */
+    ret = dlwrap_real_dlopen(filename, flag);
+
+    /* If filename is not a wrapped library, just return real dlopen */
+    if (!find_wrapped_library_index(filename, &index))
+        return ret;
+
+    /* When the application dlopens any wrapped library starting
+     * with 'libGL', (whether libGL.so.1 or libGLESv2.so.2), let's
+     * continue to use that library handle for future lookups of
+     * OpenGL functions. */
+    if (STRNCMP_LITERAL(filename, "libGL") == 0)
+        glwrap_set_gl_handle(ret);
+
+    assert(index < ARRAY_SIZE(orig_handles));
+    orig_handles[index] = ret;
+
+    if (libfips_handle == NULL)
+        libfips_handle = dlwrap_dlopen_libfips();
+
+    /* Otherwise, we return our own handle so that we can intercept
+     * future calls to dlsym. We encode the index in the return value
+     * so that we can later map back to the originally requested
+     * dlopen-handle if necessary. */
+    return libfips_handle + index;
+}
+
+void *
+dlwrap_real_dlopen(const char *filename, int flag)
+{
+    static fips_dlopen_t real_dlopen = NULL;
+
+    if (!real_dlopen) {
+        real_dlopen = (fips_dlopen_t) dlwrap_real_dlsym(RTLD_NEXT, "dlopen");
+        if (!real_dlopen) {
+            fprintf(stderr, "Error: Failed to find symbol for dlopen.\n");
+            exit(1);
+        }
+    }
+
+    return real_dlopen(filename, flag);
+}
+
+/* Since we redirect dlopens of libGL.so and libEGL.so to libfips we
+ * need to ensure that dlysm succeeds for all functions that might be
+ * defined in the real, underlying libGL library. But we're far too
+ * lazy to implement wrappers for function that would simply
+ * pass-through, so instead we also wrap dlysm and arrange for it to
+ * pass things through with RTLD_next if libfips does not have the
+ * function desired.  */
+void *
+dlsym(void *handle, const char *name)
+{
+    static void *symbol;
+    unsigned index;
+
+    /* All gl* and egl* symbols are preferentially looked up in libfips. */
+    if (STRNCMP_LITERAL(name, "gl") == 0 || STRNCMP_LITERAL(name, "egl") == 0) {
+        symbol = dlwrap_real_dlsym(libfips_handle, name);
+        if (symbol)
+            return symbol;
+    }
+
+    /* Failing that, anything specifically requested from the
+     * libfips library should be redirected to a real GL
+     * library. */
+
+    /* We subtract the index back out of the handle (see the addition
+     * of the index in our wrapper for dlopen above) to then use the
+     * correct, original dlopen'ed handle for the library of
+     * interest. */
+    index = handle - libfips_handle;
+    if (index < ARRAY_SIZE(orig_handles)) {
+        return dlwrap_real_dlsym(orig_handles[index], name);
+    }
+
+    /* And anything else is some unrelated dlsym. Just pass it
+     * through.  (This also covers the cases of lookups with
+     * special handles such as RTLD_DEFAULT or RTLD_NEXT.)
+     */
+    return dlwrap_real_dlsym(handle, name);
+}
+
+void *
+dlwrap_real_dlsym(void *handle, const char *name)
+{
+    static fips_dlsym_t real_dlsym = NULL;
+
+    if (!real_dlsym) {
+        /* FIXME: This brute-force, hard-coded searching for a versioned
+         * symbol is really ugly. The only reason I'm doing this is because
+         * I need some way to lookup the "dlsym" function in libdl, but
+         * I can't use 'dlsym' to do it. So dlvsym works, but forces me
+         * to guess what the right version is.
+         *
+         * Potential fixes here:
+         *
+         *   1. Use libelf to actually inspect libdl.so and
+         *      find the right version, (finding the right
+         *      libdl.so can be made easier with
+         *      dl_iterate_phdr).
+         *
+         *   2. Use libelf to find the offset of the 'dlsym'
+         *      symbol within libdl.so, (and then add this to
+         *      the base address at which libdl.so is loaded
+         *      as reported by dl_iterate_phdr).
+         *
+         * In the meantime, I'll just keep augmenting this
+         * hard-coded version list as people report bugs. */
+        const char *version[] = {
+            "GLIBC_2.2.5",
+            "GLIBC_2.0"
+        };
+        int num_versions = sizeof(version) / sizeof(version[0]);
+        int i;
+        for (i = 0; i < num_versions; i++) {
+            real_dlsym = (fips_dlsym_t) dlvsym(RTLD_NEXT, "dlsym", version[i]);
+            if (real_dlsym)
+                break;
+        }
+        if (i == num_versions) {
+            fprintf(stderr, "Internal error: Failed to find real dlsym\n");
+            fprintf(stderr,
+                    "This may be a simple matter of fips not knowing about the version of GLIBC that\n"
+                    "your program is using. Current known versions are:\n\n\t");
+            for (i = 0; i < num_versions; i++)
+                fprintf(stderr, "%s ", version[i]);
+            fprintf(stderr,
+                    "\n\nYou can inspect your version by first finding libdl.so.2:\n"
+                    "\n"
+                    "\tldd <your-program> | grep libdl.so\n"
+                    "\n"
+                    "And then inspecting the version attached to the dlsym symbol:\n"
+                    "\n"
+                    "\treadelf -s /path/to/libdl.so.2 | grep dlsym\n"
+                    "\n"
+                    "And finally, adding the version to dlwrap.c:dlwrap_real_dlsym.\n");
+
+            exit(1);
+        }
+    }
+
+    return real_dlsym(handle, name);
+}
--- a/test/dlwrap.h
+++ b/test/dlwrap.h
@ -0,0 +1,57 @@
+/* Copyright © 2013, Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef DLWRAP_H
+#define DLWRAP_H
+
+#define _GNU_SOURCE
+#include <dlfcn.h>
+
+/* Call the *real* dlopen. We have our own wrapper for dlopen that, of
+ * necessity must use claim the symbol 'dlopen'. So whenever anything
+ * internal needs to call the real, underlying dlopen function, the
+ * thing to call is dlwrap_real_dlopen.
+ */
+void *
+dlwrap_real_dlopen(const char *filename, int flag);
+
+/* Perform a dlopen on the libfips library itself.
+ *
+ * Many places in fips need to lookup symbols within the libfips
+ * library itself, (and not in any other library). This function
+ * provides a reliable way to get a handle for performing such
+ * lookups.
+ *
+ * The returned handle can be passed to dlwrap_real_dlsym for the
+ * lookups. */
+void *
+dlwrap_dlopen_libfips(void);
+
+/* Call the *real* dlsym. We have our own wrapper for dlsym that, of
+ * necessity must use claim the symbol 'dlsym'. So whenever anything
+ * internal needs to call the real, underlying dlysm function, the
+ * thing to call is dlwrap_real_dlsym.
+ */
+void *
+dlwrap_real_dlsym(void *handle, const char *symbol);
+
+#endif
+