[PATCH v9 04/25] libxc/migration: export read_record for common use

[Wen Congyang <wency@cn.fujitsu.com>]

read_record() could be used by primary to read dirty bitmap
record sent by secondary under COLO.
When used by save side, we need to pass the backchannel fd
instead of ctx->fd to read_record(), so we added a fd param to
it.

Signed-off-by: Yang Hongyang <hongyang.yang@easystack.cn>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
 tools/libxc/xc_sr_common.c  | 49 +++++++++++++++++++++++++++++++++++
 tools/libxc/xc_sr_common.h  | 14 ++++++++++
 tools/libxc/xc_sr_restore.c | 63 +--------------------------------------------
 3 files changed, 64 insertions(+), 62 deletions(-)

diff --git a/tools/libxc/xc_sr_common.c b/tools/libxc/xc_sr_common.c
index 8150140..42ee074 100644
--- a/tools/libxc/xc_sr_common.c
+++ b/tools/libxc/xc_sr_common.c
@@ -89,6 +89,55 @@ int write_split_record(struct xc_sr_context *ctx, struct xc_sr_record *rec,
     return -1;
 }
 
+int read_record(struct xc_sr_context *ctx, int fd, struct xc_sr_record *rec)
+{
+    xc_interface *xch = ctx->xch;
+    struct xc_sr_rhdr rhdr;
+    size_t datasz;
+
+    if ( read_exact(fd, &rhdr, sizeof(rhdr)) )
+    {
+        PERROR("Failed to read Record Header from stream");
+        return -1;
+    }
+    else if ( rhdr.length > REC_LENGTH_MAX )
+    {
+        ERROR("Record (0x%08x, %s) length %#x exceeds max (%#x)", rhdr.type,
+              rec_type_to_str(rhdr.type), rhdr.length, REC_LENGTH_MAX);
+        return -1;
+    }
+
+    datasz = ROUNDUP(rhdr.length, REC_ALIGN_ORDER);
+
+    if ( datasz )
+    {
+        rec->data = malloc(datasz);
+
+        if ( !rec->data )
+        {
+            ERROR("Unable to allocate %zu bytes for record data (0x%08x, %s)",
+                  datasz, rhdr.type, rec_type_to_str(rhdr.type));
+            return -1;
+        }
+
+        if ( read_exact(fd, rec->data, datasz) )
+        {
+            free(rec->data);
+            rec->data = NULL;
+            PERROR("Failed to read %zu bytes of data for record (0x%08x, %s)",
+                   datasz, rhdr.type, rec_type_to_str(rhdr.type));
+            return -1;
+        }
+    }
+    else
+        rec->data = NULL;
+
+    rec->type   = rhdr.type;
+    rec->length = rhdr.length;
+
+    return 0;
+};
+
 static void __attribute__((unused)) build_assertions(void)
 {
     XC_BUILD_BUG_ON(sizeof(struct xc_sr_ihdr) != 24);
diff --git a/tools/libxc/xc_sr_common.h b/tools/libxc/xc_sr_common.h
index bc99e9a..53d6129 100644
--- a/tools/libxc/xc_sr_common.h
+++ b/tools/libxc/xc_sr_common.h
@@ -370,6 +370,20 @@ static inline int write_record(struct xc_sr_context *ctx,
 }
 
 /*
+ * Reads a record from the stream, and fills in the record structure.
+ *
+ * Returns 0 on success and non-0 on failure.
+ *
+ * On success, the records type and size shall be valid.
+ * - If size is 0, data shall be NULL.
+ * - If size is non-0, data shall be a buffer allocated by malloc() which must
+ *   be passed to free() by the caller.
+ *
+ * On failure, the contents of the record structure are undefined.
+ */
+int read_record(struct xc_sr_context *ctx, int fd, struct xc_sr_record *rec);
+
+/*
  * This would ideally be private in restore.c, but is needed by
  * x86_pv_localise_page() if we receive pagetables frames ahead of the
  * contents of the frames they point at.
diff --git a/tools/libxc/xc_sr_restore.c b/tools/libxc/xc_sr_restore.c
index d4dc501..e543be3 100644
--- a/tools/libxc/xc_sr_restore.c
+++ b/tools/libxc/xc_sr_restore.c
@@ -69,67 +69,6 @@ static int read_headers(struct xc_sr_context *ctx)
 }
 
 /*
- * Reads a record from the stream, and fills in the record structure.
- *
- * Returns 0 on success and non-0 on failure.
- *
- * On success, the records type and size shall be valid.
- * - If size is 0, data shall be NULL.
- * - If size is non-0, data shall be a buffer allocated by malloc() which must
- *   be passed to free() by the caller.
- *
- * On failure, the contents of the record structure are undefined.
- */
-static int read_record(struct xc_sr_context *ctx, struct xc_sr_record *rec)
-{
-    xc_interface *xch = ctx->xch;
-    struct xc_sr_rhdr rhdr;
-    size_t datasz;
-
-    if ( read_exact(ctx->fd, &rhdr, sizeof(rhdr)) )
-    {
-        PERROR("Failed to read Record Header from stream");
-        return -1;
-    }
-    else if ( rhdr.length > REC_LENGTH_MAX )
-    {
-        ERROR("Record (0x%08x, %s) length %#x exceeds max (%#x)", rhdr.type,
-              rec_type_to_str(rhdr.type), rhdr.length, REC_LENGTH_MAX);
-        return -1;
-    }
-
-    datasz = ROUNDUP(rhdr.length, REC_ALIGN_ORDER);
-
-    if ( datasz )
-    {
-        rec->data = malloc(datasz);
-
-        if ( !rec->data )
-        {
-            ERROR("Unable to allocate %zu bytes for record data (0x%08x, %s)",
-                  datasz, rhdr.type, rec_type_to_str(rhdr.type));
-            return -1;
-        }
-
-        if ( read_exact(ctx->fd, rec->data, datasz) )
-        {
-            free(rec->data);
-            rec->data = NULL;
-            PERROR("Failed to read %zu bytes of data for record (0x%08x, %s)",
-                   datasz, rhdr.type, rec_type_to_str(rhdr.type));
-            return -1;
-        }
-    }
-    else
-        rec->data = NULL;
-
-    rec->type   = rhdr.type;
-    rec->length = rhdr.length;
-
-    return 0;
-};
-
-/*
  * Is a pfn populated?
  */
 static bool pfn_is_populated(const struct xc_sr_context *ctx, xen_pfn_t pfn)
@@ -646,7 +585,7 @@ static int restore(struct xc_sr_context *ctx)
 
     do
     {
-        rc = read_record(ctx, &rec);
+        rc = read_record(ctx, ctx->fd, &rec);
         if ( rc )
         {
             if ( ctx->restore.buffer_all_records )
-- 
2.5.0