new file mode 100644
@@ -0,0 +1 @@
+/xen-9pfsd
new file mode 100644
@@ -0,0 +1,38 @@
+#
+# tools/9pfsd/Makefile
+#
+
+XEN_ROOT = $(CURDIR)/../..
+include $(XEN_ROOT)/tools/Rules.mk
+
+CFLAGS += $(PTHREAD_CFLAGS)
+LDFLAGS += $(PTHREAD_LDFLAGS)
+
+TARGETS := xen-9pfsd
+
+XEN-9PFSD_OBJS = xen-9pfsd.o
+$(XEN-9PFSD_OBJS): CFLAGS += $(CFLAGS_libxenstore)
+$(XEN-9PFSD_OBJS): CFLAGS += $(CFLAGS_libxenevtchn)
+$(XEN-9PFSD_OBJS): CFLAGS += $(CFLAGS_libxengnttab)
+xen-9pfsd: LDLIBS += $(call xenlibs-ldlibs,store evtchn gnttab)
+
+.PHONY: all
+all: $(TARGETS)
+
+xen-9pfsd: $(XEN-9PFSD_OBJS)
+ $(CC) $(LDFLAGS) -o $@ $(XEN-9PFSD_OBJS) $(LDLIBS) $(APPEND_LDFLAGS)
+
+.PHONY: install
+install: all
+ $(INSTALL_DIR) $(DESTDIR)$(LIBEXEC_BIN)
+ for i in $(TARGETS); do $(INSTALL_PROG) $$i $(DESTDIR)$(LIBEXEC_BIN); done
+
+.PHONY: uninstall
+uninstall:
+ for i in $(TARGETS); do rm -f $(DESTDIR)$(LIBEXEC_BIN)/$$i; done
+
+.PHONY: clean
+clean:
+ $(RM) *.o $(TARGETS) $(DEPS_RM)
+
+distclean: clean
new file mode 100644
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+/*
+ * xen-9pfsd - Xen 9pfs daemon
+ *
+ * Copyright (C) 2024 Juergen Gross <jgross@suse.com>
+ *
+ * Daemon to enable guests to access a directory of the dom0 file system.
+ * Access is made via the 9pfs protocol (xen-9pfsd acts as a PV 9pfs backend).
+ *
+ * Usage: xen-9pfsd
+ *
+ * xen-9pfsd does NOT support writing any links (neither soft links nor hard
+ * links), and it is accepting only canonicalized file paths in order to
+ * avoid the possibility to "escape" from the guest specific directory.
+ *
+ * The backend device string is "xen_9pfs", the tag used for mounting the
+ * 9pfs device is "Xen".
+ *
+ * As an additional security measure the maximum file space used by the guest
+ * can be limited by the backend Xenstore node "max-size" specifying the size
+ * in MBytes. This size includes the size of the root directory of the guest.
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syslog.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <xenevtchn.h>
+#include <xengnttab.h>
+#include <xenstore.h>
+
+static volatile bool stop_me;
+static bool daemon_running;
+static struct xs_handle *xs;
+static xengnttab_handle *xg;
+static xenevtchn_handle *xe;
+
+static void handle_stop(int sig)
+{
+ stop_me = true;
+}
+
+static void close_all(void)
+{
+ if ( daemon_running )
+ xs_rm(xs, XBT_NULL, "libxl/xen-9pfs");
+ if ( xe )
+ xenevtchn_close(xe);
+ if ( xg )
+ xengnttab_close(xg);
+ if ( xs )
+ xs_close(xs);
+ closelog();
+}
+
+static void do_err(const char *msg)
+{
+ syslog(LOG_ALERT, "%s, errno = %d, %s", msg, errno, strerror(errno));
+ close_all();
+ exit(1);
+}
+
+static void xen_connect(void)
+{
+ xs_transaction_t t;
+ char *val;
+ unsigned int len;
+
+ xs = xs_open(0);
+ if ( xs == NULL )
+ do_err("xs_open() failed");
+
+ xg = xengnttab_open(NULL, 0);
+ if ( xg == NULL )
+ do_err("xengnttab_open() failed");
+
+ xe = xenevtchn_open(NULL, 0);
+ if ( xe == NULL )
+ do_err("xenevtchn_open() failed");
+
+ while ( true )
+ {
+ t = xs_transaction_start(xs);
+ if ( t == XBT_NULL )
+ do_err("xs_transaction_start() failed");
+
+ val = xs_read(xs, t, "libxl/xen-9pfs/state", &len);
+ if ( val )
+ {
+ free(val);
+ xs_transaction_end(xs, t, true);
+ syslog(LOG_INFO, "daemon already running");
+ close_all();
+ exit(0);
+ }
+
+ if ( !xs_write(xs, t, "libxl/xen-9pfs/state", "running",
+ strlen("running")) )
+ {
+ xs_transaction_end(xs, t, true);
+ do_err("xs_write() failed writing state");
+ }
+
+ if ( xs_transaction_end(xs, t, false) )
+ break;
+ if ( errno != EAGAIN )
+ do_err("xs_transaction_end() failed");
+ }
+
+ daemon_running = true;
+}
+
+int main(int argc, char *argv[])
+{
+ struct sigaction act = { .sa_handler = handle_stop, };
+ int syslog_mask = LOG_MASK(LOG_WARNING) | LOG_MASK(LOG_ERR) |
+ LOG_MASK(LOG_CRIT) | LOG_MASK(LOG_ALERT) |
+ LOG_MASK(LOG_EMERG);
+
+ umask(027);
+ if ( getenv("XEN_9PFSD_VERBOSE") )
+ syslog_mask |= LOG_MASK(LOG_NOTICE) | LOG_MASK(LOG_INFO);
+ openlog("xen-9pfsd", LOG_CONS, LOG_DAEMON);
+ setlogmask(syslog_mask);
+
+ sigemptyset(&act.sa_mask);
+ sigaction(SIGHUP, &act, NULL);
+
+ xen_connect();
+
+ while ( !stop_me )
+ {
+ sleep(60);
+ }
+
+ close_all();
+
+ return 0;
+}
@@ -32,6 +32,7 @@ SUBDIRS-y += xenpmd
SUBDIRS-$(CONFIG_GOLANG) += golang
SUBDIRS-y += xl
SUBDIRS-y += helpers
+SUBDIRS-y += 9pfsd
SUBDIRS-$(CONFIG_X86) += xenpaging
SUBDIRS-$(CONFIG_X86) += debugger
SUBDIRS-$(CONFIG_TESTS) += tests