1 files changed, 131 insertions, 0 deletions
diff --git a/Userland/Libraries/LibC/dlfcn.cpp b/Userland/Libraries/LibC/dlfcn.cpp
new file mode 100644
index 0000000000..04f742fcc3
--- /dev/null
+++ b/Userland/Libraries/LibC/dlfcn.cpp
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <dlfcn.h>
+#include <fcntl.h>
+#include <mman.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+#include <AK/HashMap.h>
+#include <AK/LexicalPath.h>
+#include <AK/RefPtr.h>
+#include <AK/ScopeGuard.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <LibELF/DynamicLoader.h>
+
+// NOTE: The string here should never include a trailing newline (according to POSIX)
+String g_dlerror_msg;
+
+HashMap<String, RefPtr<ELF::DynamicLoader>> g_elf_objects;
+
+extern "C" {
+
+int dlclose(void*)
+{
+    g_dlerror_msg = "dlclose not implemented!";
+    return -1;
+}
+
+char* dlerror()
+{
+    return const_cast<char*>(g_dlerror_msg.characters());
+}
+
+void* dlopen(const char* filename, int flags)
+{
+    // FIXME: Create a global mutex/semaphore/lock for dlopen/dlclose/dlsym and (?) dlerror
+    // FIXME: refcount?
+
+    if (!filename) {
+        // FIXME: Return the handle for "the main executable"
+        //     The Serenity Kernel will keep a mapping of the main elf binary resident in memory,
+        //     But a future dynamic loader might have a different idea/way of letting us access this information
+        ASSERT_NOT_REACHED();
+    }
+
+    auto basename = LexicalPath(filename).basename();
+
+    auto existing_elf_object = g_elf_objects.get(basename);
+    if (existing_elf_object.has_value()) {
+        return const_cast<ELF::DynamicLoader*>(existing_elf_object.value());
+    }
+
+    int fd = open(filename, O_RDONLY);
+    if (!fd) {
+        g_dlerror_msg = String::format("Unable to open file %s", filename);
+        return nullptr;
+    }
+
+    ScopeGuard close_fd_guard([fd]() { close(fd); });
+
+    struct stat file_stats {
+    };
+
+    int ret = fstat(fd, &file_stats);
+    if (ret < 0) {
+        g_dlerror_msg = String::format("Unable to stat file %s", filename);
+        return nullptr;
+    }
+
+    auto loader = ELF::DynamicLoader::construct(filename, fd, file_stats.st_size);
+
+    if (!loader->is_valid()) {
+        g_dlerror_msg = String::format("%s is not a valid ELF dynamic shared object!", filename);
+        return nullptr;
+    }
+
+    if (!loader->load_from_image(flags,
+            0 // total_tls_size = 0, FIXME: Support TLS when using dlopen()
+            )) {
+        g_dlerror_msg = String::format("Failed to load ELF object %s", filename);
+        return nullptr;
+    }
+
+    g_elf_objects.set(basename, move(loader));
+    g_dlerror_msg = "Successfully loaded ELF object.";
+
+    // we have one refcount already
+    return const_cast<ELF::DynamicLoader*>(g_elf_objects.get(basename).value());
+}
+
+void* dlsym(void* handle, const char* symbol_name)
+{
+    // FIXME: When called with a NULL handle we're supposed to search every dso in the process... that'll get expensive
+    ASSERT(handle);
+    auto* dso = reinterpret_cast<ELF::DynamicLoader*>(handle);
+    void* symbol = dso->symbol_for_name(symbol_name);
+    if (!symbol) {
+        g_dlerror_msg = "Symbol not found";
+        return nullptr;
+    }
+    return symbol;
+}
+
+} // extern "C"