[PATCH 3/4] tools/libxc: Avoid generating inappropriate zero-length records

[Andrew Cooper <andrew.cooper3@citrix.com>]

It was never intended for records such as these to be sent with zero content.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
 tools/libxc/xc_sr_save_x86_hvm.c |  4 ++++
 tools/libxc/xc_sr_save_x86_pv.c  | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/tools/libxc/xc_sr_save_x86_hvm.c b/tools/libxc/xc_sr_save_x86_hvm.c
index ba50a43..5401bf9 100644
--- a/tools/libxc/xc_sr_save_x86_hvm.c
+++ b/tools/libxc/xc_sr_save_x86_hvm.c
@@ -112,6 +112,10 @@ static int write_hvm_params(struct xc_sr_context *ctx)
         }
     }
 
+    /* No params? Skip this record. */
+    if ( hdr.count == 0 )
+        return 0;
+
     rc = write_split_record(ctx, &rec, entries, hdr.count * sizeof(*entries));
     if ( rc )
         PERROR("Failed to write HVM_PARAMS record");
diff --git a/tools/libxc/xc_sr_save_x86_pv.c b/tools/libxc/xc_sr_save_x86_pv.c
index 4a29460..5fb9f2f 100644
--- a/tools/libxc/xc_sr_save_x86_pv.c
+++ b/tools/libxc/xc_sr_save_x86_pv.c
@@ -607,6 +607,10 @@ static int write_one_vcpu_extended(struct xc_sr_context *ctx, uint32_t id)
         return -1;
     }
 
+    /* No content? Skip the record. */
+    if ( domctl.u.ext_vcpucontext.size == 0 )
+        return 0;
+
     return write_split_record(ctx, &rec, &domctl.u.ext_vcpucontext,
                               domctl.u.ext_vcpucontext.size);
 }
@@ -662,6 +666,10 @@ static int write_one_vcpu_xsave(struct xc_sr_context *ctx, uint32_t id)
         goto err;
     }
 
+    /* No xsave state? Skip this record. */
+    if ( domctl.u.vcpuextstate.size == 0 )
+        goto out;
+
     rc = write_split_record(ctx, &rec, buffer, domctl.u.vcpuextstate.size);
     if ( rc )
         goto err;
@@ -728,6 +736,10 @@ static int write_one_vcpu_msrs(struct xc_sr_context *ctx, uint32_t id)
         goto err;
     }
 
+    /* No MSRs? Skip this record. */
+    if ( domctl.u.vcpu_msrs.msr_count == 0 )
+        goto out;
+
     rc = write_split_record(ctx, &rec, buffer,
                             domctl.u.vcpu_msrs.msr_count *
                             sizeof(xen_domctl_vcpu_msr_t));
-- 
2.1.4


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