1 files changed, 49 insertions, 0 deletions
diff --git a/usr/klibc/realpath.c b/usr/klibc/realpath.c
new file mode 100644
index 0000000..1474b1e
--- /dev/null
+++ b/usr/klibc/realpath.c
@@ -0,0 +1,49 @@
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/*
+ * Note that this requires name to refer to an existing file.  This is
+ * correct according to POSIX.  However, BSD and GNU implementations
+ * also allow name to refer to a non-existing file in an existing
+ * directory.
+ */
+
+char *realpath(const char *name, char *resolved_name)
+{
+	static const char proc_fd_prefix[] = "/proc/self/fd/";
+	char proc_fd_name[sizeof(proc_fd_prefix) + sizeof(int) * 3];
+	int allocated = 0;
+	int fd;
+	ssize_t len;
+
+	/* Open for path lookup only */
+	fd = open(name, O_PATH);
+	if (fd < 0)
+		return NULL;
+
+	if (!resolved_name) {
+		resolved_name = malloc(PATH_MAX);
+		if (!resolved_name)
+			goto out_close;
+		allocated = 1;
+	}
+
+	/* Use procfs to read back the resolved name */
+	sprintf(proc_fd_name, "%s%d", proc_fd_prefix, fd);
+	len = readlink(proc_fd_name, resolved_name, PATH_MAX - 1);
+	if (len < 0) {
+		if (allocated)
+			free(resolved_name);
+		resolved_name = NULL;
+	} else {
+		resolved_name[len] = 0;
+	}
+
+out_close:
+	close(fd);
+	return resolved_name;
+}