Messages in this thread | | | Date | Sat, 08 Mar 2014 12:17:35 -0800 | From | Behan Webster <> | Subject | Re: [PATCH v2] mac80211: LLVMLinux: Remove VLAIS usage from mac80211 |
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On 03/07/14 18:27, Joe Perches wrote: > On Fri, 2014-03-07 at 18:15 -0800, Behan Webster wrote: >> On 03/07/14 17:56, Joe Perches wrote: >>> On Fri, 2014-03-07 at 17:26 -0800, behanw@converseincode.com wrote: >>>> From: Jan-Simon Möller <dl9pf@gmx.de> >>>> >>>> Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99 >>>> compliant equivalent. This is the original VLAIS struct. >>> [] >>>> diff --git a/net/mac80211/aes_ccm.c b/net/mac80211/aes_ccm.c >>> [] >>>> @@ -23,12 +23,14 @@ void ieee80211_aes_ccm_encrypt(struct crypto_aead *tfm, u8 *b_0, u8 *aad, >>>> u8 *data, size_t data_len, u8 *mic) >>>> { >>>> struct scatterlist assoc, pt, ct[2]; >>>> - struct { >>>> - struct aead_request req; >>>> - u8 priv[crypto_aead_reqsize(tfm)]; >>>> - } aead_req; >>>> >>>> - memset(&aead_req, 0, sizeof(aead_req)); >>>> + char aead_req_data[sizeof(struct aead_request) + >>>> + crypto_aead_reqsize(tfm) + >>>> + CRYPTO_MINALIGN] CRYPTO_MINALIGN_ATTR; >>> Can this be a too large amount of stack? >>> >>> Is crypto_aead_reqsize() limited to < ~1k? >>> >>> Perhaps it'd be better to use kzalloc for this >>> or another reserved pool >> No more stack being used than with the the original code. The stack >> memory use is identical. > I do understand that, but that's not my question. > > I appreciate you're getting this to compile for llvm. > > Any idea of the max value of crypto_aead_reqsize? And I understand your question, as well as why it is important.
Moving it from being stack based to alloacted memory may or may not be a good thing, but is orthogonal to the intention of this particular patch (which is just to remove the use of VLAIS from this code).
> $ grep-2.5.4 -rP --include=*.[ch] "(?:->|\.)\s*\breqsize\s*=[^=][^;]+;" * Very clever. I'm going to use this. :)
Behan
-- Behan Webster behanw@converseincode.com
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