[v5,11/12] livepatch: Add metadata runtime retrieval mechanism
diff mbox series

Message ID 20191114130653.51185-12-wipawel@amazon.de
State Superseded
Headers show
Series
  • livepatch: new features and fixes
Related show

Commit Message

Pawel Wieczorkiewicz Nov. 14, 2019, 1:06 p.m. UTC
Extend the livepatch list operation to fetch also payloads' metadata.
This is achieved by extending the sysctl list interface with 2 extra
guest handles:
* metadata     - an array of arbitrary size strings
* metadata_len - an array of metadata strings' lengths (uin32_t each)

Payloads' metadata is a string of arbitrary size and does not have an
upper bound limit. It may also vary in size between payloads.

In order to let the userland allocate enough space for the incoming
data add a metadata total size field to the list sysctl operation and
fill it with total size of all payloads' metadata.

Extend the libxc to handle the metadata back-to-back data transfers
as well as metadata length array data transfers.

The xen-livepatch userland tool is extended to always display the
metadata for each received module. The metadata is received with the
following format: key=value\0key=value\0...key=value\0. The format is
modified to the following one: key=value;key=value;...key=value.
The new format allows to easily parse the metadata for a given module
by a machine.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
Reviewed-by: Andra-Irina Paraschiv <andraprs@amazon.com>
Reviewed-by: Martin Pohlack <mpohlack@amazon.de>
Reviewed-by: Norbert Manthey <nmanthey@amazon.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
Changed since v4:
 * add 'pad' field to list sysctl

Changed since v3:
  * use uint32_t instead of uint64_t and off_t for
    metadata_total_size and related variables

Changed since v1:
  * added corresponding documentation
  * make metadata optional (do not display it when given payload
    does not have it)
---
 docs/misc/livepatch.pandoc    | 33 +++++++++++++++++-----
 tools/libxc/include/xenctrl.h | 22 +++++++++++----
 tools/libxc/xc_misc.c         | 64 +++++++++++++++++++++++++++++++++++--------
 tools/misc/xen-livepatch.c    | 41 +++++++++++++++++++++------
 xen/common/livepatch.c        | 25 +++++++++++++----
 xen/include/public/sysctl.h   | 20 ++++++++++----
 6 files changed, 162 insertions(+), 43 deletions(-)

Comments

Ross Lagerwall Nov. 19, 2019, 5:11 p.m. UTC | #1
On 11/14/19 1:06 PM, Pawel Wieczorkiewicz wrote:
> Extend the livepatch list operation to fetch also payloads' metadata.
> This is achieved by extending the sysctl list interface with 2 extra
> guest handles:
> * metadata     - an array of arbitrary size strings
> * metadata_len - an array of metadata strings' lengths (uin32_t each)
> 
> Payloads' metadata is a string of arbitrary size and does not have an
> upper bound limit. It may also vary in size between payloads.
> 
> In order to let the userland allocate enough space for the incoming
> data add a metadata total size field to the list sysctl operation and
> fill it with total size of all payloads' metadata.
> 
> Extend the libxc to handle the metadata back-to-back data transfers
> as well as metadata length array data transfers.
> 
> The xen-livepatch userland tool is extended to always display the
> metadata for each received module. The metadata is received with the
> following format: key=value\0key=value\0...key=value\0. The format is
> modified to the following one: key=value;key=value;...key=value.
> The new format allows to easily parse the metadata for a given module
> by a machine.
> 
> Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
> Reviewed-by: Andra-Irina Paraschiv <andraprs@amazon.com>
> Reviewed-by: Martin Pohlack <mpohlack@amazon.de>
> Reviewed-by: Norbert Manthey <nmanthey@amazon.de>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>

Patch
diff mbox series

diff --git a/docs/misc/livepatch.pandoc b/docs/misc/livepatch.pandoc
index 43d0896aa8..2f3f95ed37 100644
--- a/docs/misc/livepatch.pandoc
+++ b/docs/misc/livepatch.pandoc
@@ -707,8 +707,8 @@  The structure is as follow:
 
 ### XEN_SYSCTL_LIVEPATCH_LIST (2)
 
-Retrieve an array of abbreviated status and names of payloads that are loaded in the
-hypervisor.
+Retrieve an array of abbreviated status, names and metadata of payloads that are
+loaded in the hypervisor.
 
 The caller provides:
 
@@ -717,11 +717,13 @@  The caller provides:
  * `idx` Index iterator. The index into the hypervisor's payload count. It is
     recommended that on first invocation zero be used so that `nr` (which the
     hypervisor will update with the remaining payload count) be provided.
-    Also the hypervisor will provide `version` with the most current value and
-    calculated total size for all payloads' names.
+    Also the hypervisor will provide `version` with the most current value,
+    calculated total size of all payloads' names and calculated total size of
+    all payload's metadata.
  * `nr` The max number of entries to populate. Can be zero which will result
     in the hypercall being a probing one and return the number of payloads
     (and update the `version`).
+ * `pad` - *MUST* be zero.
  * `status` Virtual address of where to write `struct xen_livepatch_status`
    structures. Caller *MUST* allocate up to `nr` of them.
  * `name` - Virtual address of where to write the unique name of the payloads.
@@ -733,14 +735,23 @@  The caller provides:
  * `len` - Virtual address of where to write the length of each unique name
    of the payload. Caller *MUST* allocate up to `nr` of them. Each *MUST* be
    of sizeof(uint32_t) (4 bytes).
+ * `metadata` - Virtual address of where to write the metadata of the payloads.
+   Caller *MUST* allocate enough space to be able to store all received data
+   (i.e. total allocated space *MUST* match the `metadata_total_size` value
+   provided by the hypervisor). Individual payload metadata string can be of
+   arbitrary length. The metadata string format is: key=value\0...key=value\0.
+ * `metadata_len` - Virtual address of where to write the length of each metadata
+   string of the payload. Caller *MUST* allocate up to `nr` of them. Each *MUST*
+   be of sizeof(uint32_t) (4 bytes).
 
 If the hypercall returns an positive number, it is the number (upto `nr`
 provided to the hypercall) of the payloads returned, along with `nr` updated
 with the number of remaining payloads, `version` updated (it may be the same
 across hypercalls - if it varies the data is stale and further calls could
-fail) and the `name_total_size` containing total size of transferred data for
-the array. The `status`, `name`, and `len` are updated at their designed index
-value (`idx`) with the returned value of data.
+fail), `name_total_size` and `metadata_total_size` containing total sizes of
+transferred data for both the arrays.
+The `status`, `name`, `len`, `metadata` and `metadata_len` are updated at their
+designed index value (`idx`) with the returned value of data.
 
 If the hypercall returns -XEN_E2BIG the `nr` is too big and should be
 lowered.
@@ -777,7 +788,9 @@  The structure is as follow:
                                                    should be filled out. Can be zero to get
                                                    amount of payloads and version.
                                                    OUT: How many payloads left. */
+        uint32_t pad;                           /* IN: Must be zero. */
         uint32_t name_total_size;               /* OUT: Total size of all transfer names */
+        uint32_t metadata_total_size;           /* OUT: Total size of all transfer metadata */
         XEN_GUEST_HANDLE_64(xen_livepatch_status_t) status;  /* OUT. Must have enough
                                                    space allocate for nr of them. */
         XEN_GUEST_HANDLE_64(char) name;         /* OUT: Array of names. Each member
@@ -786,6 +799,12 @@  The structure is as follow:
                                                    nr of them. */
         XEN_GUEST_HANDLE_64(uint32) len;        /* OUT: Array of lengths of name's.
                                                    Must have nr of them. */
+        XEN_GUEST_HANDLE_64(char) metadata;     /* OUT: Array of metadata strings. Each
+                                                   member may have an arbitrary length.
+                                                   Must have nr of them. */
+        XEN_GUEST_HANDLE_64(uint32) metadata_len;  /* OUT: Array of lengths of metadata's.
+                                                      Must have nr of them. */
+
     };
 
 ### XEN_SYSCTL_LIVEPATCH_ACTION (3)
diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index f490a6debc..e549702fdd 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2559,7 +2559,7 @@  int xc_livepatch_get(xc_interface *xch,
 
 /*
  * Get a number of available payloads and get actual total size of
- * the payloads' name array.
+ * the payloads' name and metadata arrays.
  *
  * This functions is typically executed first before the xc_livepatch_list()
  * to obtain the sizes and correctly allocate all necessary data resources.
@@ -2570,13 +2570,16 @@  int xc_livepatch_get(xc_interface *xch,
  * will contain the hypercall error code value.
  */
 int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
-                                uint32_t *name_total_size);
+                                uint32_t *name_total_size,
+                                uint32_t *metadata_total_size);
 
 /*
  * The heart of this function is to get an array of the following objects:
  *   - xen_livepatch_status_t: states and return codes of payloads
  *   - name: names of payloads
  *   - len: lengths of corresponding payloads' names
+ *   - metadata: payloads' metadata
+ *   - metadata_len: lengths of corresponding payloads' metadata
  *
  * However it is complex because it has to deal with the hypervisor
  * returning some of the requested data or data being stale
@@ -2589,12 +2592,13 @@  int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
  *
  * It is expected that the caller of this function will first issue the
  * xc_livepatch_list_get_sizes() in order to obtain total sizes of names
- * as well as the current number of payload entries.
- * The total sizes are required and supplied via the 'name_total_size'
- * parameter.
+ * and all metadata as well as the current number of payload entries.
+ * The total sizes are required and supplied via the 'name_total_size' and
+ * 'metadata_total_size' parameters.
  *
  * The 'max' is to be provided by the caller with the maximum number of
- * entries that 'info', 'name', 'len' arrays can be filled up with.
+ * entries that 'info', 'name', 'len', 'metadata' and 'metadata_len' arrays
+ * can be filled up with.
  *
  * Each entry in the 'info' array is expected to be of xen_livepatch_status_t
  * structure size.
@@ -2603,6 +2607,10 @@  int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
  *
  * Each entry in the 'len' array is expected to be of uint32_t size.
  *
+ * Each entry in the 'metadata' array may have an arbitrary size.
+ *
+ * Each entry in the 'metadata_len' array is expected to be of uint32_t size.
+ *
  * The return value is zero if the hypercall completed successfully.
  * Note that the return value is _not_ the amount of entries filled
  * out - that is saved in 'done'.
@@ -2617,6 +2625,8 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
                       struct xen_livepatch_status *info,
                       char *name, uint32_t *len,
                       const uint32_t name_total_size,
+                      char *metadata, uint32_t *metadata_len,
+                      const uint32_t metadata_total_size,
                       unsigned int *done, unsigned int *left);
 
 /*
diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
index 4f26cdb623..7747ea83aa 100644
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -663,7 +663,7 @@  int xc_livepatch_get(xc_interface *xch,
 
 /*
  * Get a number of available payloads and get actual total size of
- * the payloads' name array.
+ * the payloads' name and metadata arrays.
  *
  * This functions is typically executed first before the xc_livepatch_list()
  * to obtain the sizes and correctly allocate all necessary data resources.
@@ -674,12 +674,13 @@  int xc_livepatch_get(xc_interface *xch,
  * will contain the hypercall error code value.
  */
 int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
-                                uint32_t *name_total_size)
+                                uint32_t *name_total_size,
+                                uint32_t *metadata_total_size)
 {
     DECLARE_SYSCTL;
     int rc;
 
-    if ( !nr || !name_total_size )
+    if ( !nr || !name_total_size || !metadata_total_size )
     {
         errno = EINVAL;
         return -1;
@@ -695,6 +696,7 @@  int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
 
     *nr = sysctl.u.livepatch.u.list.nr;
     *name_total_size = sysctl.u.livepatch.u.list.name_total_size;
+    *metadata_total_size = sysctl.u.livepatch.u.list.metadata_total_size;
 
     return 0;
 }
@@ -704,6 +706,8 @@  int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
  *   - xen_livepatch_status_t: states and return codes of payloads
  *   - name: names of payloads
  *   - len: lengths of corresponding payloads' names
+ *   - metadata: payloads' metadata
+ *   - metadata_len: lengths of corresponding payloads' metadata
  *
  * However it is complex because it has to deal with the hypervisor
  * returning some of the requested data or data being stale
@@ -716,12 +720,13 @@  int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
  *
  * It is expected that the caller of this function will first issue the
  * xc_livepatch_list_get_sizes() in order to obtain total sizes of names
- * as well as the current number of payload entries.
- * The total sizes are required and supplied via the 'name_total_size'
- * parameter.
+ * and all metadata as well as the current number of payload entries.
+ * The total sizes are required and supplied via the 'name_total_size' and
+ * 'metadata_total_size' parameters.
  *
  * The 'max' is to be provided by the caller with the maximum number of
- * entries that 'info', 'name', 'len' arrays can be filled up with.
+ * entries that 'info', 'name', 'len', 'metadata' and 'metadata_len' arrays
+ * can be filled up with.
  *
  * Each entry in the 'info' array is expected to be of xen_livepatch_status_t
  * structure size.
@@ -730,6 +735,10 @@  int xc_livepatch_list_get_sizes(xc_interface *xch, unsigned int *nr,
  *
  * Each entry in the 'len' array is expected to be of uint32_t size.
  *
+ * Each entry in the 'metadata' array may have an arbitrary size.
+ *
+ * Each entry in the 'metadata_len' array is expected to be of uint32_t size.
+ *
  * The return value is zero if the hypercall completed successfully.
  * Note that the return value is _not_ the amount of entries filled
  * out - that is saved in 'done'.
@@ -744,6 +753,8 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
                       struct xen_livepatch_status *info,
                       char *name, uint32_t *len,
                       const uint32_t name_total_size,
+                      char *metadata, uint32_t *metadata_len,
+                      const uint32_t metadata_total_size,
                       unsigned int *done, unsigned int *left)
 {
     int rc;
@@ -752,13 +763,16 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
     DECLARE_HYPERCALL_BOUNCE(info, 0, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
     DECLARE_HYPERCALL_BOUNCE(name, 0, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
     DECLARE_HYPERCALL_BOUNCE(len, 0, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
+    DECLARE_HYPERCALL_BOUNCE(metadata, 0, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
+    DECLARE_HYPERCALL_BOUNCE(metadata_len, 0, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
     uint32_t max_batch_sz, nr;
     uint32_t version = 0, retries = 0;
     uint32_t adjust = 0;
-    uint32_t name_off = 0;
-    uint32_t name_sz;
+    uint32_t name_off = 0, metadata_off = 0;
+    uint32_t name_sz, metadata_sz;
 
-    if ( !max || !info || !name || !len || !done || !left )
+    if ( !max || !info || !name || !len ||
+         !metadata || !metadata_len || !done || !left )
     {
         errno = EINVAL;
         return -1;
@@ -777,10 +791,11 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
 
     max_batch_sz = max;
     name_sz = name_total_size;
+    metadata_sz = metadata_total_size;
     *done = 0;
     *left = 0;
     do {
-        uint32_t _name_sz;
+        uint32_t _name_sz, _metadata_sz;
 
         /*
          * The first time we go in this loop our 'max' may be bigger
@@ -803,10 +818,14 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
         HYPERCALL_BOUNCE_SET_SIZE(info, nr * sizeof(*info));
         HYPERCALL_BOUNCE_SET_SIZE(name, name_sz);
         HYPERCALL_BOUNCE_SET_SIZE(len, nr * sizeof(*len));
+        HYPERCALL_BOUNCE_SET_SIZE(metadata, metadata_sz);
+        HYPERCALL_BOUNCE_SET_SIZE(metadata_len, nr * sizeof(*metadata_len));
         /* Move the pointer to proper offset into 'info'. */
         (HYPERCALL_BUFFER(info))->ubuf = info + *done;
         (HYPERCALL_BUFFER(name))->ubuf = name + name_off;
         (HYPERCALL_BUFFER(len))->ubuf = len + *done;
+        (HYPERCALL_BUFFER(metadata))->ubuf = metadata + metadata_off;
+        (HYPERCALL_BUFFER(metadata_len))->ubuf = metadata_len + *done;
         /* Allocate memory. */
         rc = xc_hypercall_bounce_pre(xch, info);
         if ( rc )
@@ -820,9 +839,19 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
         if ( rc )
             break;
 
+        rc = xc_hypercall_bounce_pre(xch, metadata);
+        if ( rc )
+            break;
+
+        rc = xc_hypercall_bounce_pre(xch, metadata_len);
+        if ( rc )
+            break;
+
         set_xen_guest_handle(sysctl.u.livepatch.u.list.status, info);
         set_xen_guest_handle(sysctl.u.livepatch.u.list.name, name);
         set_xen_guest_handle(sysctl.u.livepatch.u.list.len, len);
+        set_xen_guest_handle(sysctl.u.livepatch.u.list.metadata, metadata);
+        set_xen_guest_handle(sysctl.u.livepatch.u.list.metadata_len, metadata_len);
 
         rc = do_sysctl(xch, &sysctl);
         /*
@@ -839,6 +868,8 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
             xc_hypercall_bounce_post(xch, info);
             xc_hypercall_bounce_post(xch, name);
             xc_hypercall_bounce_post(xch, len);
+            xc_hypercall_bounce_post(xch, metadata);
+            xc_hypercall_bounce_post(xch, metadata_len);
             continue;
         }
         else if ( rc < 0 ) /* For all other errors we bail out. */
@@ -863,6 +894,8 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
             xc_hypercall_bounce_post(xch, info);
             xc_hypercall_bounce_post(xch, name);
             xc_hypercall_bounce_post(xch, len);
+            xc_hypercall_bounce_post(xch, metadata);
+            xc_hypercall_bounce_post(xch, metadata_len);
             continue;
         }
 
@@ -875,17 +908,24 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
         }
         *left = sysctl.u.livepatch.u.list.nr; /* Total remaining count. */
         _name_sz = sysctl.u.livepatch.u.list.name_total_size; /* Total received name size. */
+        _metadata_sz = sysctl.u.livepatch.u.list.metadata_total_size; /* Total received metadata size. */
         /* Copy only up 'rc' of data' - we could add 'min(rc,nr) if desired. */
         HYPERCALL_BOUNCE_SET_SIZE(info, (rc * sizeof(*info)));
         HYPERCALL_BOUNCE_SET_SIZE(name, _name_sz);
         HYPERCALL_BOUNCE_SET_SIZE(len, (rc * sizeof(*len)));
+        HYPERCALL_BOUNCE_SET_SIZE(metadata, _metadata_sz);
+        HYPERCALL_BOUNCE_SET_SIZE(metadata_len, (rc * sizeof(*metadata_len)));
         /* Bounce the data and free the bounce buffer. */
         xc_hypercall_bounce_post(xch, info);
         xc_hypercall_bounce_post(xch, name);
         xc_hypercall_bounce_post(xch, len);
+        xc_hypercall_bounce_post(xch, metadata);
+        xc_hypercall_bounce_post(xch, metadata_len);
 
         name_sz -= _name_sz;
         name_off += _name_sz;
+        metadata_sz -= _metadata_sz;
+        metadata_off += _metadata_sz;
 
         /* And update how many elements of info we have copied into. */
         *done += rc;
@@ -898,6 +938,8 @@  int xc_livepatch_list(xc_interface *xch, const unsigned int max,
         xc_hypercall_bounce_post(xch, len);
         xc_hypercall_bounce_post(xch, name);
         xc_hypercall_bounce_post(xch, info);
+        xc_hypercall_bounce_post(xch, metadata);
+        xc_hypercall_bounce_post(xch, metadata_len);
     }
 
     return rc > 0 ? 0 : rc;
diff --git a/tools/misc/xen-livepatch.c b/tools/misc/xen-livepatch.c
index c93c50040c..16a4a47ab7 100644
--- a/tools/misc/xen-livepatch.c
+++ b/tools/misc/xen-livepatch.c
@@ -69,8 +69,10 @@  static int list_func(int argc, char *argv[])
     unsigned int nr, done, left, i;
     xen_livepatch_status_t *info = NULL;
     char *name = NULL;
+    char *metadata = NULL;
     uint32_t *len = NULL;
-    uint32_t name_total_size, name_off;
+    uint32_t *metadata_len = NULL;
+    uint32_t name_total_size, metadata_total_size, name_off, metadata_off;
     int rc = ENOMEM;
 
     if ( argc )
@@ -80,7 +82,7 @@  static int list_func(int argc, char *argv[])
     }
     done = left = 0;
 
-    rc = xc_livepatch_list_get_sizes(xch, &nr, &name_total_size);
+    rc = xc_livepatch_list_get_sizes(xch, &nr, &name_total_size, &metadata_total_size);
     if ( rc )
     {
         rc = errno;
@@ -108,12 +110,23 @@  static int list_func(int argc, char *argv[])
     if ( !len )
         goto error_len;
 
+    metadata = malloc(metadata_total_size * sizeof(*metadata) + 1);
+    if ( !metadata )
+        goto error_metadata;
+
+    metadata_len = malloc(nr * sizeof(*metadata_len));
+    if ( !metadata_len )
+        goto error_metadata_len;
+
     memset(info, 'A', nr * sizeof(*info));
     memset(name, 'B', name_total_size * sizeof(*name));
     memset(len, 'C', nr * sizeof(*len));
-    name_off = 0;
+    memset(metadata, 'D', metadata_total_size * sizeof(*metadata) + 1);
+    memset(metadata_len, 'E', nr * sizeof(*metadata_len));
+    name_off = metadata_off = 0;
 
-    rc = xc_livepatch_list(xch, nr, 0, info, name, len, name_total_size, &done, &left);
+    rc = xc_livepatch_list(xch, nr, 0, info, name, len, name_total_size,
+                           metadata, metadata_len, metadata_total_size, &done, &left);
     if ( rc || done != nr || left > 0)
     {
         rc = errno;
@@ -123,23 +136,35 @@  static int list_func(int argc, char *argv[])
         goto error;
     }
 
-    fprintf(stdout," ID                                     | status\n"
-                   "----------------------------------------+------------\n");
+    fprintf(stdout," ID                                     | status     | metadata\n"
+                   "----------------------------------------+------------+---------------\n");
 
     for ( i = 0; i < done; i++ )
     {
+        unsigned int j;
         char *name_str = name + name_off;
+        char *metadata_str = metadata + metadata_off;
 
         printf("%-40.*s| %s", len[i], name_str, state2str(info[i].state));
         if ( info[i].rc )
-            printf(" (%d, %s)\n", -info[i].rc, strerror(-info[i].rc));
+            printf(" (%d, %s)    | ", -info[i].rc, strerror(-info[i].rc));
         else
-            puts("");
+            printf("    | ");
+
+        /* Replace all '\0' with semi-colons. */
+        for ( j = 0; metadata_len[i] && j < metadata_len[i] - 1; j++ )
+            metadata_str[j] = (metadata_str[j] ?: ';');
+        printf("%.*s\n", metadata_len[i], metadata_str);
 
         name_off += len[i];
+        metadata_off += metadata_len[i];
     }
 
 error:
+    free(metadata_len);
+error_metadata_len:
+    free(metadata);
+error_metadata:
     free(len);
 error_len:
     free(name);
diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c
index 76f5b72740..e21533bf2c 100644
--- a/xen/common/livepatch.c
+++ b/xen/common/livepatch.c
@@ -1159,9 +1159,13 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
     if ( list->nr > 1024 )
         return -E2BIG;
 
+    if ( list->pad )
+        return -EINVAL;
+
     if ( list->nr &&
          (!guest_handle_okay(list->status, list->nr) ||
-          !guest_handle_okay(list->len, list->nr)) )
+          !guest_handle_okay(list->len, list->nr) ||
+          !guest_handle_okay(list->metadata_len, list->nr)) )
         return -EINVAL;
 
     spin_lock(&payload_lock);
@@ -1172,13 +1176,14 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
     }
 
     list->name_total_size = 0;
+    list->metadata_total_size = 0;
     if ( list->nr )
     {
-        uint64_t name_offset = 0;
+        uint64_t name_offset = 0, metadata_offset = 0;
 
         list_for_each_entry( data, &payload_list, list )
         {
-            uint32_t name_len;
+            uint32_t name_len, metadata_len;
 
             if ( list->idx > i++ )
                 continue;
@@ -1189,8 +1194,13 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
             name_len = strlen(data->name) + 1;
             list->name_total_size += name_len;
 
+            metadata_len = data->metadata.len;
+            list->metadata_total_size += metadata_len;
+
             if ( !guest_handle_subrange_okay(list->name, name_offset,
-                                             name_offset + name_len - 1) )
+                                             name_offset + name_len - 1) ||
+                 !guest_handle_subrange_okay(list->metadata, metadata_offset,
+                                             metadata_offset + metadata_len - 1) )
             {
                 rc = -EINVAL;
                 break;
@@ -1200,7 +1210,10 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
             if ( __copy_to_guest_offset(list->name, name_offset,
                                         data->name, name_len) ||
                 __copy_to_guest_offset(list->len, idx, &name_len, 1) ||
-                __copy_to_guest_offset(list->status, idx, &status, 1) )
+                __copy_to_guest_offset(list->status, idx, &status, 1) ||
+                __copy_to_guest_offset(list->metadata, metadata_offset,
+                                       data->metadata.data, metadata_len) ||
+                __copy_to_guest_offset(list->metadata_len, idx, &metadata_len, 1) )
             {
                 rc = -EFAULT;
                 break;
@@ -1208,6 +1221,7 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
 
             idx++;
             name_offset += name_len;
+            metadata_offset += metadata_len;
 
             if ( (idx >= list->nr) || hypercall_preempt_check() )
                 break;
@@ -1218,6 +1232,7 @@  static int livepatch_list(struct xen_sysctl_livepatch_list *list)
         list_for_each_entry( data, &payload_list, list )
         {
             list->name_total_size += strlen(data->name) + 1;
+            list->metadata_total_size += data->metadata.len;
         }
     }
     list->nr = payload_cnt - i; /* Remaining amount. */
diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 4bfd1475bf..7e43bfe1bd 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -934,16 +934,17 @@  struct xen_sysctl_livepatch_get {
 };
 
 /*
- * Retrieve an array of abbreviated status and names of payloads that are
- * loaded in the hypervisor.
+ * Retrieve an array of abbreviated status, names and metadata of payloads that
+ * are loaded in the hypervisor.
  *
  * If the hypercall returns an positive number, it is the number (up to `nr`)
  * of the payloads returned, along with `nr` updated with the number of remaining
  * payloads, `version` updated (it may be the same across hypercalls. If it varies
- * the data is stale and further calls could fail) and the name_total_size
- * containing total size of transferred data for the array.
- * The `status`, `name`, `len` are updated at their designed index value (`idx`)
- * with the returned value of data.
+ * the data is stale and further calls could fail), `name_total_size` and
+ * `metadata_total_size` containing total sizes of transferred data for both the
+ * arrays.
+ * The `status`, `name`, `len`, `metadata` and `metadata_len` are updated at their
+ * designed index value (`idx`) with the returned value of data.
  *
  * If the hypercall returns E2BIG the `nr` is too big and should be
  * lowered. The upper limit of `nr` is left to the implemention.
@@ -965,7 +966,9 @@  struct xen_sysctl_livepatch_list {
                                                should fill out. Can be zero to get
                                                amount of payloads and version.
                                                OUT: How many payloads left. */
+    uint32_t pad;                           /* IN: Must be zero. */
     uint32_t name_total_size;               /* OUT: Total size of all transfer names */
+    uint32_t metadata_total_size;           /* OUT: Total size of all transfer metadata */
     XEN_GUEST_HANDLE_64(xen_livepatch_status_t) status;  /* OUT. Must have enough
                                                space allocate for nr of them. */
     XEN_GUEST_HANDLE_64(char) name;         /* OUT: Array of names. Each member
@@ -974,6 +977,11 @@  struct xen_sysctl_livepatch_list {
                                                nr of them. */
     XEN_GUEST_HANDLE_64(uint32) len;        /* OUT: Array of lengths of name's.
                                                Must have nr of them. */
+    XEN_GUEST_HANDLE_64(char) metadata;     /* OUT: Array of metadata strings. Each
+                                               member may have an arbitrary length.
+                                               Must have nr of them. */
+    XEN_GUEST_HANDLE_64(uint32) metadata_len;  /* OUT: Array of lengths of metadata's.
+                                                  Must have nr of them. */
 };
 
 /*