[Xen-changelog] [qemu-xen master] osdep: Fix ROUND_UP(64-bit, 32-bit)

[patchbot@xxxxxxx]

commit 33a599667a9e70588483a31286dfff8cfc27d513
Author:     Eric Blake <eblake@xxxxxxxxxx>
AuthorDate: Thu Sep 14 08:49:23 2017 -0500
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu Sep 28 16:37:36 2017 -0500

    osdep: Fix ROUND_UP(64-bit, 32-bit)
    
    When using bit-wise operations that exploit the power-of-two
    nature of the second argument of ROUND_UP(), we still need to
    ensure that the mask is as wide as the first argument (done
    by using a ternary to force proper arithmetic promotion).
    Unpatched, ROUND_UP(2ULL*1024*1024*1024*1024, 512U) produces 0,
    instead of the intended 2TiB, because negation of an unsigned
    32-bit quantity followed by widening to 64-bits does not
    sign-extend the mask.
    
    Broken since its introduction in commit 292c8e50 (v1.5.0).
    Callers that passed the same width type to both macro parameters,
    or that had other code to ensure the first parameter's maximum
    runtime value did not exceed the second parameter's width, are
    unaffected, but I did not audit to see which (if any) existing
    clients of the macro could trigger incorrect behavior (I found
    the bug while adding a new use of the macro).
    
    While preparing the patch, checkpatch complained about poor
    spacing, so I also fixed that here and in the nearby DIV_ROUND_UP.
    
    CC: qemu-trivial@xxxxxxxxxx
    CC: qemu-stable@xxxxxxxxxx
    Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
    Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>
    Reviewed-by: Richard Henderson <richard.henderson@xxxxxxxxxx>
    Signed-off-by: Michael Tokarev <mjt@xxxxxxxxxx>
    (cherry picked from commit 2098b073f398cd628c09c5a78537a6854e85830d)
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 include/qemu/osdep.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 6855b94..f4ff372 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -189,13 +189,13 @@ extern int daemon(int, int);
 
 /* Round number up to multiple. Requires that d be a power of 2 (see
  * QEMU_ALIGN_UP for a safer but slower version on arbitrary
- * numbers) */
+ * numbers); works even if d is a smaller type than n.  */
 #ifndef ROUND_UP
-#define ROUND_UP(n,d) (((n) + (d) - 1) & -(d))
+#define ROUND_UP(n, d) (((n) + (d) - 1) & -(0 ? (n) : (d)))
 #endif
 
 #ifndef DIV_ROUND_UP
-#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
+#define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
 #endif
 
 /*
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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