[XEN PATCH v3 RESEND] tools/lsevtchn: Use errno macro to handle hypercall error cases

[Matthew Barnes <matthew.barnes@xxxxxxxxx>]

Currently, lsevtchn aborts its event channel enumeration when it hits
its first hypercall error, namely:
* When an event channel doesn't exist at the specified port
* When the event channel is owned by Xen

lsevtchn does not distinguish between different hypercall errors, which
results in lsevtchn missing potential relevant event channels with
higher port numbers.

Use the errno macro to distinguish between hypercall errors, and
continue event channel enumeration if the hypercall error is not
critical to enumeration.

Signed-off-by: Matthew Barnes <matthew.barnes@xxxxxxxxx>
---
 tools/xcutils/lsevtchn.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/xcutils/lsevtchn.c b/tools/xcutils/lsevtchn.c
index d1710613ddc5..e4b3f88fe4ec 100644
--- a/tools/xcutils/lsevtchn.c
+++ b/tools/xcutils/lsevtchn.c
@@ -3,6 +3,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <stdio.h>
+#include <errno.h>
 
 #include <xenctrl.h>
 
@@ -24,7 +25,18 @@ int main(int argc, char **argv)
         status.port = port;
         rc = xc_evtchn_status(xch, &status);
         if ( rc < 0 )
-            break;
+        {
+            if ( errno == ESRCH )
+            {
+                fprintf(stderr, "Domain ID '%d' does not correspond to valid 
domain.\n", domid);
+                break;
+            }
+
+            if ( errno == EINVAL )
+                break;
+
+            continue;
+        }
 
         if ( status.status == EVTCHNSTAT_closed )
             continue;
-- 
2.34.1