| Message ID | 1409957901-28962-1-git-send-email-behanw@converseincode.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On 09/05/2014 06:58 PM, behanw@converseincode.com wrote: > From: Vinícius Tinti <viniciustinti@gmail.com> > > Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99 > compliant equivalent. This is the original VLAIS struct. > > struct { > struct shash_desc shash; > char ctx[crypto_shash_descsize(tfm)]; > } desc; > > This patch instead allocates the appropriate amount of memory using an char > array. > > The new code can be compiled with both gcc and clang. > > struct shash_desc contains a flexible array member member ctx declared with > CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning > of the array declared after struct shash_desc with long long. > > No trailing padding is required because it is not a struct type that can > be used in an array. > > The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long > as would be the case for a struct containing a member with > CRYPTO_MINALIGN_ATTR. We copied this from one of the other crypto api users, and I'm sure cooking up all these patches was not a great way to your afternoon. But, can I talk you into making a helper macro of some kind for this and putting it into the crypto api headers? Honestly this setup seems really error prone. -chris > > Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de> > Signed-off-by: Behan Webster <behanw@converseincode.com> > Signed-off-by: Vinícius Tinti <viniciustinti@gmail.com> > Signed-off-by: Mark Charlebois <charlebm@gmail.com> > --- > fs/btrfs/hash.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c > index 85889aa..a62743f 100644 > --- a/fs/btrfs/hash.c > +++ b/fs/btrfs/hash.c > @@ -33,18 +33,18 @@ void btrfs_hash_exit(void) > > u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length) > { > - struct { > - struct shash_desc shash; > - char ctx[crypto_shash_descsize(tfm)]; > - } desc; > + char desc[sizeof(struct shash_desc) + > + crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR; > + struct shash_desc *shash = (struct shash_desc *)desc; > + u32 *ctx = (u32 *)shash_desc_ctx(shash); > int err; > > - desc.shash.tfm = tfm; > - desc.shash.flags = 0; > - *(u32 *)desc.ctx = crc; > + shash->tfm = tfm; > + shash->flags = 0; > + *ctx = crc; > > - err = crypto_shash_update(&desc.shash, address, length); > + err = crypto_shash_update(shash, address, length); > BUG_ON(err); > > - return *(u32 *)desc.ctx; > + return *ctx; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 09/11/14 09:34, Chris Mason wrote: > > On 09/05/2014 06:58 PM, behanw@converseincode.com wrote: >> From: Vinícius Tinti <viniciustinti@gmail.com> >> >> Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99 >> compliant equivalent. This is the original VLAIS struct. >> >> struct { >> struct shash_desc shash; >> char ctx[crypto_shash_descsize(tfm)]; >> } desc; >> >> This patch instead allocates the appropriate amount of memory using an char >> array. >> >> The new code can be compiled with both gcc and clang. >> >> struct shash_desc contains a flexible array member member ctx declared with >> CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning >> of the array declared after struct shash_desc with long long. >> >> No trailing padding is required because it is not a struct type that can >> be used in an array. >> >> The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long >> as would be the case for a struct containing a member with >> CRYPTO_MINALIGN_ATTR. > We copied this from one of the other crypto api users, and I'm sure > cooking up all these patches was not a great way to your afternoon. > > But, can I talk you into making a helper macro of some kind for this and > putting it into the crypto api headers? Honestly this setup seems > really error prone. You're not the only person to ask for this. I've got one already coded up based on suggestions from tglx. I've regenerated all the patches. I will resubmit soon. Will fix. Behan
diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c index 85889aa..a62743f 100644 --- a/fs/btrfs/hash.c +++ b/fs/btrfs/hash.c @@ -33,18 +33,18 @@ void btrfs_hash_exit(void) u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length) { - struct { - struct shash_desc shash; - char ctx[crypto_shash_descsize(tfm)]; - } desc; + char desc[sizeof(struct shash_desc) + + crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR; + struct shash_desc *shash = (struct shash_desc *)desc; + u32 *ctx = (u32 *)shash_desc_ctx(shash); int err; - desc.shash.tfm = tfm; - desc.shash.flags = 0; - *(u32 *)desc.ctx = crc; + shash->tfm = tfm; + shash->flags = 0; + *ctx = crc; - err = crypto_shash_update(&desc.shash, address, length); + err = crypto_shash_update(shash, address, length); BUG_ON(err); - return *(u32 *)desc.ctx; + return *ctx; }