[Xen-devel] [PATCH] xen: Avoid left shifting into a sign bit

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Clang 3.8 notices, and objects because it is undefined behaviour.

"error: shifting a negative signed value is undefined 
[-Werror,-Wshift-negative-value]"

Use unsigned constants rather than signed ones.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Kevin Tian <kevin.tian@xxxxxxxxx>
CC: Feng Wu <feng.wu@xxxxxxxxx>
---
 xen/common/page_alloc.c               | 2 +-
 xen/drivers/passthrough/vtd/x86/ats.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 624a266..7179d67 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1675,7 +1675,7 @@ void *alloc_xenheap_pages(unsigned int order, unsigned 
int memflags)
     ASSERT(!in_irq());
 
     if ( xenheap_bits && (memflags >> _MEMF_bits) > xenheap_bits )
-        memflags &= ~MEMF_bits(~0);
+        memflags &= ~MEMF_bits(~0U);
     if ( !(memflags >> _MEMF_bits) )
         memflags |= MEMF_bits(xenheap_bits);
 
diff --git a/xen/drivers/passthrough/vtd/x86/ats.c 
b/xen/drivers/passthrough/vtd/x86/ats.c
index 7c797f6..334b9c1 100644
--- a/xen/drivers/passthrough/vtd/x86/ats.c
+++ b/xen/drivers/passthrough/vtd/x86/ats.c
@@ -133,7 +133,7 @@ int dev_invalidate_iotlb(struct iommu *iommu, u16 did,
         case DMA_TLB_GLOBAL_FLUSH:
             /* invalidate all translations: sbit=1,bit_63=0,bit[62:12]=1 */
             sbit = 1;
-            addr = (~0 << PAGE_SHIFT_4K) & 0x7FFFFFFFFFFFFFFF;
+            addr = (~0UL << PAGE_SHIFT_4K) & 0x7FFFFFFFFFFFFFFF;
             rc = qinval_device_iotlb(iommu, pdev->ats_queue_depth,
                                      sid, sbit, addr);
             break;
@@ -145,7 +145,7 @@ int dev_invalidate_iotlb(struct iommu *iommu, u16 did,
             sbit = size_order ? 1 : 0;
 
             /* clear lower bits */
-            addr &= ~0 << PAGE_SHIFT_4K;
+            addr &= ~0UL << PAGE_SHIFT_4K;
 
             /* if sbit == 1, zero out size_order bit and set lower bits to 1 */
             if ( sbit )
-- 
2.1.4


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