Xen devel - Dec 2012 - [PATCH] memshr tools: use hypercall return value incorrectly

When programs in TOOLS call hypercall and fail, they will get return value -1
and find real error number in "errno". But in the following code, it
uses return value -1 to do switch-case incorrectly.

Signed-off-by: Yanzhang Li <liyz@pku.edu.cn>

diff -u xen-4.2.0/tools/memshr/interface.c
change/xen-4.2.0/tools/memshr/interface.c
--- xen-4.2.0/tools/memshr/interface.c  2012-09-17 18:21:18.000000000 +0800
+++ change/xen-4.2.0/tools/memshr/interface.c   2012-12-07 09:50:16.208705246
+0800
@@ -18,6 +18,7 @@
  */
 #include <string.h>
 #include <inttypes.h>
+#include <errno.h>

 #include "memshr.h"
 #include "memshr-priv.h"
@@ -184,7 +185,7 @@
         if(!ret) return 0;
         /* Handles failed to be shared => at least one of them must be
invalid,
            remove the relevant ones from the map */
-        switch(ret)
+        switch(-errno)
         {
             case XENMEM_SHARING_OP_S_HANDLE_INVALID:
                 ret = blockshr_shrhnd_remove(memshr.blks, source_st, NULL);