1 files changed, 99 insertions, 0 deletions
diff --git a/src/bootid.c b/src/bootid.c
new file mode 100644
index 0000000..c2f9d24
--- /dev/null
+++ b/src/bootid.c
@@ -0,0 +1,99 @@
+/*
+ *  Copyright (C) 2020 - Vito Caputo - <vcaputo@pengaru.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 3 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <fcntl.h>
+#include <liburing.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <iou.h>
+#include <thunk.h>
+
+#include "bootid.h"
+#include "readfile.h"
+
+/* Implements iou-based bootid retrieval.
+ *
+ * Note there's not really any reason for doing this async vio iou, it just
+ * served as the initial test/use case while iou was fleshed out, so here it
+ * is, no harm in using it.  I guess it's kind of convenient to have a little
+ * kicking of the tires iou/io_uring user at the start of the program anyways,
+ * rather than having something more complex to debug io_uring issues out of
+ * the hole.  At least if the bootid is retrieved there's some evidence of the
+ * basic machinery working.
+ */
+
+
+#define BOOTID_PATH "/proc/sys/kernel/random/boot_id"
+
+
+/* perform in-place removal of hyphens from str */
+static void dehyphen(char *str)
+{
+	char	*dest;
+
+	for (dest = str; *str; str++) {
+		if (*str == '-')
+			continue;
+
+		*dest++ = *str;
+	}
+
+	*dest = '\0';
+}
+
+/* call user-supplied closure now that buf is populated, after some baking of the data */
+THUNK_DEFINE_STATIC(have_bootid, iou_t *, iou, char *, buf, size_t *, size, char **, res_ptr, thunk_t *, closure)
+{
+	assert(iou);
+	assert(closure);
+
+	/* FIXME: I'm just assuming it's a proper nl-terminated bootid for now, null terminate it */
+	buf[*size - 1] = '\0';
+
+	dehyphen(buf);	/* replicating what systemd does with the bootid */
+
+	*res_ptr = strdup(buf);
+	if (!*res_ptr)
+		return -ENOMEM;
+
+	return thunk_dispatch(closure);
+}
+
+
+/* get a bootid via iou, scheduling closure once gotten */
+/* returns < 0 on error, 0 on successful queueing of operation */
+THUNK_DEFINE(bootid_get, iou_t *, iou, char **, res_ptr, thunk_t *, closure)
+{
+	thunk_t	*bootid_thunk;
+	struct {
+		char	buf[4096];
+		size_t	len;
+	}	*buf;
+
+	/* we need a buffer for readfiles, it only needs to last until have_bootid,
+	 * where it gets null terminated and strdup()d, so allocae it as part of
+	 * the have_bootid thunk.  The THUNK_ALLOC/THUNK_INIT interfaces are still
+	 * evolving.
+	 */
+	bootid_thunk = THUNK_ALLOC(have_bootid, (void **)&buf, sizeof(*buf));
+	buf->len = sizeof(buf->buf);
+	THUNK_INIT(have_bootid(bootid_thunk, iou, buf->buf, &buf->len, res_ptr, closure));
+
+	return readfile(iou, BOOTID_PATH, buf->buf, &buf->len, bootid_thunk);
+}