| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20110205090451.GA2315@cmpxchg.org>
Date: Sat, 5 Feb 2011 10:04:51 +0100
From: Johannes Weiner <hannes@...xchg.org>
To: Randy Dunlap <randy.dunlap@...cle.com>
Cc: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: [patch fixup] memcg: remove direct page_cgroup-to-page pointer fix
On Fri, Feb 04, 2011 at 06:38:10PM -0800, Randy Dunlap wrote:
> On Fri, 04 Feb 2011 15:15:17 -0800 akpm@...ux-foundation.org wrote:
>
> > The mm-of-the-moment snapshot 2011-02-04-15-15 has been uploaded to
> >
> > http://userweb.kernel.org/~akpm/mmotm/
> >
> > and will soon be available at
> >
> > git://zen-kernel.org/kernel/mmotm.git
> >
> > It contains the following patches against 2.6.38-rc3:
>
>
> Lots of these warnings in some kernel configs:
>
> mmotm-2011-0204-1515/include/linux/page_cgroup.h:144: warning: left shift count >= width of type
> mmotm-2011-0204-1515/include/linux/page_cgroup.h:145: warning: left shift count >= width of type
> mmotm-2011-0204-1515/include/linux/page_cgroup.h:150: warning: right shift count >= width of type
Thanks for the report, Randy, and sorry for the breakage. Here is the
fixup:
---
Since the non-flags field for pc array ids in pc->flags is offset from
the end of the word, we end up with a shift count of BITS_PER_LONG in
case the field width is zero.
This results in a compiler warning as we shift in both directions a
long int by BITS_PER_LONG.
There is no real harm -- the mask is zero -- but fix up the compiler
warning by also making the shift count zero for a non-existant field.
Reported-by: Randy Dunlap <randy.dunlap@...cle.com>
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index 05d8618..f5de21d 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -123,31 +123,36 @@ static inline void move_unlock_page_cgroup(struct page_cgroup *pc,
}
#ifdef CONFIG_SPARSEMEM
-#define PCG_ARRAYID_SHIFT SECTIONS_SHIFT
+#define PCG_ARRAYID_WIDTH SECTIONS_SHIFT
#else
-#define PCG_ARRAYID_SHIFT NODES_SHIFT
+#define PCG_ARRAYID_WIDTH NODES_SHIFT
#endif
-#if (PCG_ARRAYID_SHIFT > BITS_PER_LONG - NR_PCG_FLAGS)
+#if (PCG_ARRAYID_WIDTH > BITS_PER_LONG - NR_PCG_FLAGS)
#error Not enough space left in pc->flags to store page_cgroup array IDs
#endif
/* pc->flags: ARRAY-ID | FLAGS */
-#define PCG_ARRAYID_MASK ((1UL << PCG_ARRAYID_SHIFT) - 1)
+#define PCG_ARRAYID_MASK ((1UL << PCG_ARRAYID_WIDTH) - 1)
-#define PCG_ARRAYID_OFFSET (sizeof(unsigned long) * 8 - PCG_ARRAYID_SHIFT)
+#define PCG_ARRAYID_OFFSET (BITS_PER_LONG - PCG_ARRAYID_WIDTH)
+/*
+ * Zero the shift count for non-existant fields, to prevent compiler
+ * warnings and ensure references are optimized away.
+ */
+#define PCG_ARRAYID_SHIFT (PCG_ARRAYID_OFFSET * (PCG_ARRAYID_WIDTH != 0))
static inline void set_page_cgroup_array_id(struct page_cgroup *pc,
unsigned long id)
{
- pc->flags &= ~(PCG_ARRAYID_MASK << PCG_ARRAYID_OFFSET);
- pc->flags |= (id & PCG_ARRAYID_MASK) << PCG_ARRAYID_OFFSET;
+ pc->flags &= ~(PCG_ARRAYID_MASK << PCG_ARRAYID_SHIFT);
+ pc->flags |= (id & PCG_ARRAYID_MASK) << PCG_ARRAYID_SHIFT;
}
static inline unsigned long page_cgroup_array_id(struct page_cgroup *pc)
{
- return (pc->flags >> PCG_ARRAYID_OFFSET) & PCG_ARRAYID_MASK;
+ return (pc->flags >> PCG_ARRAYID_SHIFT) & PCG_ARRAYID_MASK;
}
#else /* CONFIG_CGROUP_MEM_RES_CTLR */
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists