On Thu, May 29, 2008 at 12:56:08PM +0300, 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.
Thanks, applied.
>
> 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.
I also added the above paragraph to the changelog.
>
> 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?
Not currently.
> I'd be happy to take a stab at it and come up with a
> written and tested proposal.
That could be helpful, thanks.
--b.
>
> Benny
>
> 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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