On May 29, 2008, at 5:56 AM, Benny Halevy wrote:
WRITEMEM zeroes the last word in the destination buffer
for padding purposes, but this must not be done if
no bytes are to be copied, as it would result
in zeroing of the word right before the array.
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
--
The current implementation works since it's always called
with non zero nbytes or it follows an encoding of the
string (or opaque) length which, if equal to zero,
can be overwritten with zero.
Another way of implementing that is the way it's done in
fs/nfsd/nfs4callback.c:
static inline __be32 *
xdr_writemem(__be32 *p, const void *ptr, int nbytes)
{
int tmp = XDR_QUADLEN(nbytes);
if (!tmp)
return p;
p[tmp-1] = 0;
memcpy(p, ptr, nbytes);
return p + tmp;
}
#define WRITEMEM(ptr,nbytes) do { \
p = xdr_writemem(p, ptr, nbytes); \
} while (0)
Also, is there any plan to clean up the xdr encoding definition
any time and define a cleaner static inline API?
I'd be happy to take a stab at it and come up with a
written and tested proposal.
By the way, here is a pointer to the old work:
http://git.linux-nfs.org/?p=cel/
cel-2.6.git;a=shortlog;h=drop-20070423
The work in this snapshot is only partially complete.
There are many many issues to fix up. One of the bigger ones is that
the RPC layer still takes the BKL during XDR encoding and decoding.
But I wanted to create something that could be fully or partially
shared by the client and server implementations, and that would be
more rigorous about static and dynamic type checking.
In addition, the NFSv4 routines use a new style of managing the RPC
buffer that I wanted to adopt for the other in-kernel XDR routines,
then convert the RPC client to use only the new style when invoking
XDR routines. I never got that far, but I still think it's a
reasonable goal.
git diff --stat -p
fs/nfsd/nfs4xdr.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index e8e27fb..588c9f6 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1712,7 +1712,7 @@ nfsd4_decode_compound(struct
nfsd4_compoundargs *argp)
*p++ = htonl((u32)((n) >> 32)); \
*p++ = htonl((u32)(n)); \
} while (0)
-#define WRITEMEM(ptr,nbytes) do { \
+#define WRITEMEM(ptr,nbytes) do if (nbytes > 0) { \
*(p + XDR_QUADLEN(nbytes) -1) = 0; \
memcpy(p, ptr, nbytes); \
p += XDR_QUADLEN(nbytes); \
--
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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