Add shared library utils.

Add a few helpers to open shared libraries and load specific symbols
from there.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>

3 files changed, 186 insertions, 0 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index b8cc501..bae6e85 100755
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -47,6 +47,7 @@ driver_libs = \
 	$(NULL)
 
 source_c = \
+	dso_utils.c		\
 	gen6_mfc.c		\
 	gen6_mfd.c		\
 	gen6_vme.c		\
@@ -73,6 +74,7 @@ source_c = \
 	$(NULL)
 
 source_h = \
+	dso_utils.h		\
 	gen6_mfc.h		\
 	gen6_mfd.h		\
 	gen6_vme.h		\
diff --git a/src/dso_utils.c b/src/dso_utils.c
new file mode 100644
index 0000000..8fdea11
--- /dev/null
+++ b/src/dso_utils.c
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2012 Intel Corporation. All Rights Reserved.
+ *
+ * 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, sub license, 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 (including the
+ * next paragraph) 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 NON-INFRINGEMENT.
+ * IN NO EVENT SHALL PRECISION INSIGHT AND/OR ITS SUPPLIERS 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.
+ */
+
+#define _GNU_SOURCE 1
+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+#include "dso_utils.h"
+
+struct dso_handle {
+    void       *handle;
+};
+
+/* Opens the named shared library */
+struct dso_handle *
+dso_open(const char *path)
+{
+    struct dso_handle *h;
+
+    h = calloc(1, sizeof(*h));
+    if (!h)
+        return NULL;
+
+    if (path) {
+        h->handle = dlopen(path, RTLD_LAZY|RTLD_LOCAL);
+        if (!h->handle)
+            goto error;
+    }
+    else
+        h->handle = RTLD_DEFAULT;
+    return h;
+
+error:
+    dso_close(h);
+    return NULL;
+}
+
+/* Closes and disposed any allocated data */
+void
+dso_close(struct dso_handle *h)
+{
+    if (!h)
+        return;
+
+    if (h->handle) {
+        if (h->handle != RTLD_DEFAULT)
+            dlclose(h->handle);
+        h->handle = NULL;
+    }
+    free(h);
+}
+
+/* Load symbol into the supplied location */
+static bool
+get_symbol(struct dso_handle *h, void *func_vptr, const char *name)
+{
+    dso_generic_func func, * const func_ptr = func_vptr;
+    const char *error;
+
+    dlerror();
+    func = (dso_generic_func)dlsym(h->handle, name);
+    error = dlerror();
+    if (error) {
+        fprintf(stderr, "error: failed to resolve %s(): %s\n", name, error);
+        return false;
+    }
+    *func_ptr = func;
+    return true;
+}
+
+/* Loads symbols into the supplied vtable */
+bool
+dso_get_symbols(
+    struct dso_handle          *h,
+    void                       *vtable,
+    unsigned int                vtable_length,
+    const struct dso_symbol    *symbols
+)
+{
+    const struct dso_symbol *s;
+
+    for (s = symbols; s->name != NULL; s++) {
+        if (s->offset + sizeof(dso_generic_func) > vtable_length)
+            return false;
+        if (!get_symbol(h, ((char *)vtable) + s->offset, s->name))
+            return false;
+    }
+    return true;
+}
diff --git a/src/dso_utils.h b/src/dso_utils.h
new file mode 100644
index 0000000..9b8eba7
--- /dev/null
+++ b/src/dso_utils.h
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2012 Intel Corporation. All Rights Reserved.
+ *
+ * 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, sub license, 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 (including the
+ * next paragraph) 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 NON-INFRINGEMENT.
+ * IN NO EVENT SHALL PRECISION INSIGHT AND/OR ITS SUPPLIERS 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 DSO_UTILS_H
+#define DSO_UTILS_H
+
+#include <stdbool.h>
+
+/** Generic pointer to function. */
+typedef void (*dso_generic_func)(void);
+
+/** Library handle (opaque). */
+struct dso_handle;
+
+/** Symbol lookup table. */
+struct dso_symbol {
+    /** Symbol name */
+    const char  *name;
+    /** Offset into the supplied vtable where symbol is to be loaded. */
+    unsigned int offset;
+};
+
+/**
+ * Opens the named shared library.
+ *
+ * @param[in]  path  the library name, or NULL to lookup into loaded libraries
+ * @return the newly allocated library handle
+ */
+struct dso_handle *
+dso_open(const char *path);
+
+/** Closes and disposed any allocated data. */
+void
+dso_close(struct dso_handle *h);
+
+/**
+ * Loads symbols into the supplied vtable.
+ *
+ * @param[in]  handle           the DSO handle
+ * @param[in]  vtable           the function table to fill in
+ * @param[in]  vtable_length    the size (in bytes) of the function table
+ * @param[in]  symbols          the NULL terminated array of symbols to lookup
+ * @return true on success, false otherwise
+ **/
+bool
+dso_get_symbols(
+    struct dso_handle          *h,
+    void                       *vtable,
+    unsigned int                vtable_length,
+    const struct dso_symbol    *symbols
+);
+
+#endif /* DSO_UTILS_H */