1 files changed, 36 insertions, 0 deletions
diff --git a/mount.c b/mount.c
new file mode 100644
index 0000000..b4a6150
--- /dev/null
+++ b/mount.c
@@ -0,0 +1,36 @@
+/* See LICENSE file for copyright and license details. */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+int mount_overlay(uid_t uid, gid_t gid, const char *restrict lower, const char *restrict upper, const char *restrict workdir, const char *restrict mountpoint) {
+    if(access(mountpoint, W_OK) || access(upper, W_OK) || access(workdir, W_OK)) return -1;
+
+    char *options = malloc(
+        sizeof("lowerdir=") + strlen(lower) +
+        sizeof(",upperdir=") + strlen(upper) +
+        sizeof(",workdir=") + strlen(workdir)
+    );
+    sprintf(options, "lowerdir=%s,upperdir=%s,workdir=%s", lower, upper, workdir);
+    int mount_status = mount("overlay", mountpoint, "overlay", 0, options);
+    free(options);
+    if(mount_status) return -1;
+
+    /* When mounting an overlay, a folder named 'work' belonging to root:root is created inside workdirt. These next lines give the ownership back to the current user. */
+    char *other_work_dir = malloc(strlen(workdir) + sizeof("/work"));
+    sprintf(other_work_dir, "%s/work", workdir);
+    int status = chown(other_work_dir, uid, gid);
+    free(other_work_dir);
+    return status;
+}
+
+int mount_bind(const char *restrict source, const char *restrict dest) {
+    if(access(dest, W_OK)) return -1;
+    return mount(source, dest, "none", MS_BIND, NULL);
+}