[Xen-devel] [PATCH] only use legitimate shift counts in bitmap shifting

["Jan Beulich" <JBeulich@xxxxxxxx>]

An alternative would be to remove these implicitly unused functions.

Coverity ID 1192174 (__bitmap_shift_right)
Coverity ID 1192175 (__bitmap_shift_left)

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/bitmap.c
+++ b/xen/common/bitmap.c
@@ -144,7 +144,9 @@ void __bitmap_shift_right(unsigned long 
                lower = src[off + k];
                if (left && off + k == lim - 1)
                        lower &= mask;
-               dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
+               dst[k] = rem
+                        ? (upper << (BITS_PER_LONG - rem)) | (lower >> rem)
+                        : lower;
                if (left && k == lim - 1)
                        dst[k] &= mask;
        }
@@ -185,7 +187,9 @@ void __bitmap_shift_left(unsigned long *
                upper = src[k];
                if (left && k == lim - 1)
                        upper &= (1UL << left) - 1;
-               dst[k + off] = lower  >> (BITS_PER_LONG - rem) | upper << rem;
+               dst[k + off] = rem ? (lower >> (BITS_PER_LONG - rem))
+                                     | (upper << rem)
+                                  : upper;
                if (left && k + off == lim - 1)
                        dst[k + off] &= (1UL << left) - 1;
        }

Attachment: bitmap-shift-counts.patch
Description: Text document

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