Implemented dlfcn functions

photon/libc/sys/horizon/dlfcn.c

@@ -1,30 +1,56 @@
 #include <magenta/types.h>
 #include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
 #include <dlfcn.h>
+#include <fcntl.h>
+#include <mio/fs.h>
 
-
-__attribute__((weak)) void *dyld_load_object(mx_handle_t handle, int mode) { return NULL; }
+__attribute__((weak)) void *dyld_load_object(const char *path, mx_handle_t handle, int mode) { return NULL; }
 __attribute__((weak)) void *dyld_get_symbol(void *handle, const char *name) { return NULL; }
 __attribute__((weak)) int dyld_close_object(void *handle) { return 0; }
 __attribute__((weak)) char *dyld_get_error(void) { return NULL; }
 
+static char dl_error[512] = {};
+
 void *dlopen(const char *path, int mode)
 {
-    dyld_load_object(MX_NULL_HANDLE, 0);
+    /* TODO include error message from errno */
+
+    int fd = open(path, O_RDONLY);
+    if (fd == -1) {
+        snprintf(dl_error, sizeof dl_error, "cannot open '%s'", path);
         return NULL;
     }
 
+    mx_handle_t image_vmo = MX_NULL_HANDLE;
+    int err = mio_map_file(fd, &image_vmo);
+    close(fd);
+
+    if (err != 0) {
+        snprintf(dl_error, sizeof dl_error, "cannot load '%s'", path);
+        return NULL;
+    }
+
+    dl_error[0] = '\0';
+    return dyld_load_object(path, image_vmo, mode);
+}
+
 void *dlsym(void *handle, const char *name)
 {
-    return NULL;
+    return dyld_get_symbol(handle, name);
 }
 
 int dlclose(void *handle)
 {
-    return 0;
+    return dyld_close_object(handle);
 }
 
 char *dlerror(void)
 {
-    return NULL;
+    if (dl_error[0] != '\0') {
+        return dl_error;
+    }
+
+    return dyld_get_error();
 }