[PATCH for-4.9] x86/mm: Placate DEADCODE Coverity warning

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <JBeulich@suse.com>
Subject: [PATCH for-4.9] x86/mm: Placate DEADCODE Coverity warning
Date: Mon, 22 May 2017 14:12:55 +0100	[thread overview]
Message-ID: <1495458775-20946-1-git-send-email-andrew.cooper3@citrix.com> (raw)

_PAGE_GNTTAB is only used in debug builds of Xen; in release builds, it has
the value 0.  Coverity complains that "l1e_get_flags(l1e) & 0" is logically
dead.

Add an extra condition into the logic to skip the flag check if _PAGE_GNTTAB
is 0.

No functional change.

Coverity-ID: 1362036
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Julien Grall <julien.grall@arm.com>
---
 xen/arch/x86/mm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 77b0af1..b588653 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -1252,7 +1252,7 @@ void put_page_from_l1e(l1_pgentry_t l1e, struct domain *l1e_owner)
      * (Note that the undestroyable active grants are not a security hole in
      * Xen. All active grants can safely be cleaned up when the domain dies.)
      */
-    if ( (l1e_get_flags(l1e) & _PAGE_GNTTAB) &&
+    if ( _PAGE_GNTTAB && (l1e_get_flags(l1e) & _PAGE_GNTTAB) &&
          !l1e_owner->is_shutting_down && !l1e_owner->is_dying )
     {
         gdprintk(XENLOG_WARNING,
-- 
2.1.4


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