[Xen-changelog] [qemu-xen master] hbitmap: Fix shifts of constants by granularity

[patchbot@xxxxxxx]

commit 6725f887acc023fc8850d62e1aaef083fdb4f3d4
Author:     Max Reitz <mreitz@xxxxxxxxxx>
AuthorDate: Tue Nov 15 23:47:32 2016 +0100
Commit:     Fam Zheng <famz@xxxxxxxxxx>
CommitDate: Tue Nov 29 17:46:36 2016 +0800

    hbitmap: Fix shifts of constants by granularity
    
    An hbitmap's granularity may be anything from 0 to 63, so when shifting
    constants by its value, they should not be plain ints.
    
    Even having changed the types, hbitmap_serialization_granularity() still
    tries to shift 64 to the right by the granularity. This operation is
    undefined if the granularity is greater than 57. Adding an assertion is
    fine for now, because serializing is done only in tests so far, but this
    means that only bitmaps with a granularity below 58 can be serialized
    and we should thus add a hbitmap_is_serializable() function later.
    
    One of the two places touched in this patch uses
    QEMU_ALIGN_UP(x, 1 << y). We can use ROUND_UP() there, since the second
    parameter is obviously a power of two.
    
    Signed-off-by: Max Reitz <mreitz@xxxxxxxxxx>
    Message-Id: <20161115224732.1334-1-mreitz@xxxxxxxxxx>
    Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
    Signed-off-by: Fam Zheng <famz@xxxxxxxxxx>
---
 util/hbitmap.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/util/hbitmap.c b/util/hbitmap.c
index 5d1a21c..9f691b7 100644
--- a/util/hbitmap.c
+++ b/util/hbitmap.c
@@ -399,9 +399,13 @@ bool hbitmap_get(const HBitmap *hb, uint64_t item)
 
 uint64_t hbitmap_serialization_granularity(const HBitmap *hb)
 {
+    /* Must hold true so that the shift below is defined
+     * (ld(64) == 6, i.e. 1 << 6 == 64) */
+    assert(hb->granularity < 64 - 6);
+
     /* Require at least 64 bit granularity to be safe on both 64 bit and 32 bit
      * hosts. */
-    return 64 << hb->granularity;
+    return UINT64_C(64) << hb->granularity;
 }
 
 /* Start should be aligned to serialization granularity, chunk size should be
@@ -594,7 +598,7 @@ void hbitmap_truncate(HBitmap *hb, uint64_t size)
     if (shrink) {
         /* Don't clear partial granularity groups;
          * start at the first full one. */
-        uint64_t start = QEMU_ALIGN_UP(num_elements, 1 << hb->granularity);
+        uint64_t start = ROUND_UP(num_elements, UINT64_C(1) << 
hb->granularity);
         uint64_t fix_count = (hb->size << hb->granularity) - start;
 
         assert(fix_count);
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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