[PATCH v2 1/8] tools/xenstore: add live update command to xenstore-control

["Edwin Török" <edvin.torok@citrix.com>]

From: Juergen Gross <jgross@suse.com>

Add the "live-update" command to xenstore-control enabling updating
xenstored to a new version in a running Xen system.

With -c <arg> it is possible to pass a different command line to the
new instance of xenstored. This will replace the command line used
for the invocation of the just running xenstored instance.

The running xenstored (or xenstore-stubdom) needs to support live
updating, of course.

For now just add a small dummy handler to C xenstore denying any
live update action.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Julien Grall <jgrall@amazon.com>
---
 docs/misc/xenstore.txt            |  21 ++
 tools/xenstore/Makefile           |   3 +-
 tools/xenstore/xenstore_control.c | 332 ++++++++++++++++++++++++++++--
 3 files changed, 339 insertions(+), 17 deletions(-)

diff --git a/docs/misc/xenstore.txt b/docs/misc/xenstore.txt
index 2081f20f55..1480742330 100644
--- a/docs/misc/xenstore.txt
+++ b/docs/misc/xenstore.txt
@@ -317,6 +317,27 @@ CONTROL			<command>|[<parameters>|]
 	Current commands are:
 	check
 		checks xenstored innards
+	live-update|<params>|+
+		perform a live-update of the Xenstore daemon, only to
+		be used via xenstore-control command.
+		<params> are implementation specific and are used for
+		different steps of the live-update processing. Currently
+		supported <params> are:
+		-f <file>  specify new daemon binary
+		-b <size>  specify size of new stubdom binary
+		-d <chunk-size> <binary-chunk>  transfer chunk of new
+			stubdom binary
+		-c <pars>  specify new command line to use
+		-s [-t <sec>] [-F]  start live update process (-t specifies
+			timeout in seconds to wait for active transactions
+			to finish, default is 60 seconds; -F will force
+			live update to happen even with running transactions
+			after timeout elapsed)
+		-a  abort live update handling
+		All sub-options will return "OK" in case of success or an
+		error string in case of failure. -s can return "BUSY" in case
+		of an active transaction, a retry of -s can be done in that
+		case.
 	log|on
 		turn xenstore logging on
 	log|off
diff --git a/tools/xenstore/Makefile b/tools/xenstore/Makefile
index 9a0f0d012d..ab89e22d3a 100644
--- a/tools/xenstore/Makefile
+++ b/tools/xenstore/Makefile
@@ -11,6 +11,7 @@ CFLAGS += -include $(XEN_ROOT)/tools/config.h
 CFLAGS += -I./include
 CFLAGS += $(CFLAGS_libxenevtchn)
 CFLAGS += $(CFLAGS_libxenctrl)
+CFLAGS += $(CFLAGS_libxenguest)
 CFLAGS += $(CFLAGS_libxentoolcore)
 CFLAGS += -DXEN_LIB_STORED="\"$(XEN_LIB_STORED)\""
 CFLAGS += -DXEN_RUN_STORED="\"$(XEN_RUN_STORED)\""
@@ -81,7 +82,7 @@ xenstore: xenstore_client.o
 	$(CC) $< $(LDFLAGS) $(LDLIBS_libxenstore) $(LDLIBS_libxentoolcore) $(SOCKET_LIBS) -o $@ $(APPEND_LDFLAGS)
 
 xenstore-control: xenstore_control.o
-	$(CC) $< $(LDFLAGS) $(LDLIBS_libxenstore) $(LDLIBS_libxentoolcore) $(SOCKET_LIBS) -o $@ $(APPEND_LDFLAGS)
+	$(CC) $< $(LDFLAGS) $(LDLIBS_libxenstore) $(LDLIBS_libxenctrl) $(LDLIBS_libxenguest) $(LDLIBS_libxentoolcore) $(SOCKET_LIBS) -o $@ $(APPEND_LDFLAGS)
 
 xs_tdb_dump: xs_tdb_dump.o utils.o tdb.o talloc.o
 	$(CC) $^ $(LDFLAGS) -o $@ $(APPEND_LDFLAGS)
diff --git a/tools/xenstore/xenstore_control.c b/tools/xenstore/xenstore_control.c
index afa04495a7..5ca015a07d 100644
--- a/tools/xenstore/xenstore_control.c
+++ b/tools/xenstore/xenstore_control.c
@@ -1,9 +1,311 @@
+#define _GNU_SOURCE
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
+#include <xenctrl.h>
+#include <xenguest.h>
 
 #include "xenstore.h"
 
+/* Add a string plus terminating 0 byte to buf, returning new len. */
+static int add_to_buf(char **buf, const char *val, int len)
+{
+    int vallen = strlen(val) + 1;
+
+    if (len < 0)
+        return -1;
+
+    *buf = realloc(*buf, len + vallen);
+    if (!*buf)
+        return -1;
+
+    strcpy(*buf + len, val);
+
+    return len + vallen;
+}
+
+static int live_update_start(struct xs_handle *xsh, bool force, unsigned int to)
+{
+    int len = 0;
+    char *buf = NULL, *ret;
+    time_t time_start;
+
+    if (asprintf(&ret, "%u", to) < 0)
+        return 1;
+    len = add_to_buf(&buf, "-s", len);
+    len = add_to_buf(&buf, "-t", len);
+    len = add_to_buf(&buf, ret, len);
+    free(ret);
+    if (force)
+        len = add_to_buf(&buf, "-F", len);
+    if (len < 0)
+        return 1;
+
+    for (time_start = time(NULL); time(NULL) - time_start < to;) {
+        ret = xs_control_command(xsh, "live-update", buf, len);
+        if (!ret)
+            goto err;
+        if (strcmp(ret, "BUSY"))
+            break;
+    }
+
+    if (strcmp(ret, "OK"))
+        goto err;
+
+    free(buf);
+    free(ret);
+
+    return 0;
+
+ err:
+    fprintf(stderr, "Starting live update failed:\n%s\n",
+            ret ? : strerror(errno));
+    free(buf);
+    free(ret);
+
+    return 3;
+}
+
+static int live_update_cmdline(struct xs_handle *xsh, const char *cmdline)
+{
+    int len = 0, rc = 0;
+    char *buf = NULL, *ret;
+
+    len = add_to_buf(&buf, "-c", len);
+    len = add_to_buf(&buf, cmdline, len);
+    if (len < 0)
+        return 1;
+
+    ret = xs_control_command(xsh, "live-update", buf, len);
+    free(buf);
+    if (!ret || strcmp(ret, "OK")) {
+        fprintf(stderr, "Setting update binary failed:\n%s\n",
+                ret ? : strerror(errno));
+        rc = 3;
+    }
+    free(ret);
+
+    return rc;
+}
+
+static int send_kernel_blob(struct xs_handle *xsh, const char *binary)
+{
+    int rc = 0, len = 0;
+    xc_interface *xch;
+    struct xc_dom_image *dom;
+    char *ret, *buf = NULL;
+    size_t off, sz;
+#define BLOB_CHUNK_SZ 2048
+
+    xch = xc_interface_open(NULL, NULL, 0);
+    if (!xch) {
+        fprintf(stderr, "xc_interface_open() failed\n");
+        return 1;
+    }
+
+    dom = xc_dom_allocate(xch, NULL, NULL);
+    if (!dom) {
+        rc = 1;
+        goto out_close;
+    }
+
+    rc = xc_dom_kernel_file(dom, binary);
+    if (rc) {
+        rc = 1;
+        goto out_rel;
+    }
+
+    if (asprintf(&ret, "%zu", dom->kernel_size) < 0) {
+        rc = 1;
+        goto out_rel;
+    }
+    len = add_to_buf(&buf, "-b", len);
+    len = add_to_buf(&buf, ret, len);
+    free(ret);
+    if (len < 0) {
+        rc = 1;
+        goto out_rel;
+    }
+    ret = xs_control_command(xsh, "live-update", buf, len);
+    free(buf);
+    if (!ret || strcmp(ret, "OK")) {
+        fprintf(stderr, "Starting live update failed:\n%s\n",
+                ret ? : strerror(errno));
+        rc = 3;
+    }
+    free(ret);
+    if (rc)
+        goto out_rel;
+
+    /* buf capable to hold "-d" <1..2048> BLOB_CHUNK_SZ and a terminating 0. */
+    buf = malloc(3 + 5 + BLOB_CHUNK_SZ + 1);
+    if (!buf) {
+        rc = 1;
+        goto out_rel;
+    }
+
+    strcpy(buf, "-d");
+    sz = BLOB_CHUNK_SZ;
+    for (off = 0; off < dom->kernel_size; off += BLOB_CHUNK_SZ) {
+        if (dom->kernel_size - off < BLOB_CHUNK_SZ)
+            sz = dom->kernel_size - off;
+        sprintf(buf + 3, "%zu", sz);
+        len = 3 + strlen(buf + 3) + 1;
+        memcpy(buf + len, dom->kernel_blob + off, sz);
+        buf[len + sz] = 0;
+        len += sz + 1;
+        ret = xs_control_command(xsh, "live-update", buf, len);
+        if (!ret || strcmp(ret, "OK")) {
+            fprintf(stderr, "Transfer of new binary failed:\n%s\n",
+                    ret ? : strerror(errno));
+            rc = 3;
+            free(ret);
+            break;
+        }
+        free(ret);
+    }
+
+    free(buf);
+
+ out_rel:
+    xc_dom_release(dom);
+
+ out_close:
+    xc_interface_close(xch);
+
+    return rc;
+}
+
+/*
+ * Live update of Xenstore stubdom
+ *
+ * Sequence of actions:
+ * 1. transfer new stubdom binary
+ *    a) specify size
+ *    b) transfer unpacked binary in chunks
+ * 2. transfer new cmdline (optional)
+ * 3. start update (includes flags)
+ */
+static int live_update_stubdom(struct xs_handle *xsh, const char *binary,
+                               const char *cmdline, bool force, unsigned int to)
+{
+    int rc;
+
+    rc = send_kernel_blob(xsh, binary);
+    if (rc)
+        goto abort;
+
+    if (cmdline) {
+        rc = live_update_cmdline(xsh, cmdline);
+        if (rc)
+            goto abort;
+    }
+
+    rc = live_update_start(xsh, force, to);
+    if (rc)
+        goto abort;
+
+    return 0;
+
+ abort:
+    xs_control_command(xsh, "live-update", "-a", 3);
+    return rc;
+}
+
+/*
+ * Live update of Xenstore daemon
+ *
+ * Sequence of actions:
+ * 1. transfer new binary filename
+ * 2. transfer new cmdline (optional)
+ * 3. start update (includes flags)
+ */
+static int live_update_daemon(struct xs_handle *xsh, const char *binary,
+                              const char *cmdline, bool force, unsigned int to)
+{
+    int len = 0, rc;
+    char *buf = NULL, *ret;
+
+    len = add_to_buf(&buf, "-f", len);
+    len = add_to_buf(&buf, binary, len);
+    if (len < 0)
+        return 1;
+    ret = xs_control_command(xsh, "live-update", buf, len);
+    free(buf);
+    if (!ret || strcmp(ret, "OK")) {
+        fprintf(stderr, "Setting update binary failed:\n%s\n",
+                ret ? : strerror(errno));
+        free(ret);
+        return 3;
+    }
+    free(ret);
+
+    if (cmdline) {
+        rc = live_update_cmdline(xsh, cmdline);
+        if (rc)
+            goto abort;
+    }
+
+    rc = live_update_start(xsh, force, to);
+    if (rc)
+        goto abort;
+
+    return 0;
+
+ abort:
+    xs_control_command(xsh, "live-update", "-a", 3);
+    return rc;
+}
+
+static int live_update(struct xs_handle *xsh, int argc, char **argv)
+{
+    int rc = 0;
+    unsigned int i, to = 60;
+    char *binary = NULL, *cmdline = NULL, *val;
+    bool force = false;
+
+    for (i = 0; i < argc; i++) {
+        if (!strcmp(argv[i], "-c")) {
+            i++;
+            if (i == argc) {
+                fprintf(stderr, "Missing command line value\n");
+                rc = 2;
+                goto out;
+            }
+            cmdline = argv[i];
+        } else if (!strcmp(argv[i], "-t")) {
+            i++;
+            if (i == argc) {
+                fprintf(stderr, "Missing timeout value\n");
+                rc = 2;
+                goto out;
+            }
+            to = atoi(argv[i]);
+        } else if (!strcmp(argv[i], "-F"))
+            force = true;
+        else
+            binary = argv[i];
+    }
+
+    if (!binary) {
+        fprintf(stderr, "Missing binary specification\n");
+        rc = 2;
+        goto out;
+    }
+
+    val = xs_read(xsh, XBT_NULL, "/tool/xenstored/domid", &i);
+    if (val)
+        rc = live_update_stubdom(xsh, binary, cmdline, force, to);
+    else
+        rc = live_update_daemon(xsh, binary, cmdline, force, to);
+
+    free(val);
+
+ out:
+    return rc;
+}
 
 int main(int argc, char **argv)
 {
@@ -20,22 +322,6 @@ int main(int argc, char **argv)
         goto out;
     }
 
-    for (p = 2; p < argc; p++)
-        len += strlen(argv[p]) + 1;
-    if (len) {
-        par = malloc(len);
-        if (!par) {
-            fprintf(stderr, "Allocation error.\n");
-            rc = 1;
-            goto out;
-        }
-        len = 0;
-        for (p = 2; p < argc; p++) {
-            memcpy(par + len, argv[p], strlen(argv[p]) + 1);
-            len += strlen(argv[p]) + 1;
-        }
-    }
-
     xsh = xs_open(0);
     if (xsh == NULL) {
         fprintf(stderr, "Failed to contact Xenstored.\n");
@@ -43,6 +329,19 @@ int main(int argc, char **argv)
         goto out;
     }
 
+    if (!strcmp(argv[1], "live-update")) {
+        rc = live_update(xsh, argc - 2, argv + 2);
+        goto out_close;
+    }
+
+    for (p = 2; p < argc; p++)
+        len = add_to_buf(&par, argv[p], len);
+    if (len < 0) {
+        fprintf(stderr, "Allocation error.\n");
+        rc = 1;
+        goto out_close;
+    }
+
     ret = xs_control_command(xsh, argv[1], par, len);
     if (!ret) {
         rc = 3;
@@ -59,6 +358,7 @@ int main(int argc, char **argv)
     } else if (strlen(ret) > 0)
         printf("%s\n", ret);
 
+ out_close:
     xs_close(xsh);
 
  out:
-- 
2.29.2