From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_MSPIKE_H2,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 4178 invoked from network); 15 Aug 2022 18:31:30 -0000 Received: from second.openwall.net (193.110.157.125) by inbox.vuxu.org with ESMTPUTF8; 15 Aug 2022 18:31:30 -0000 Received: (qmail 17588 invoked by uid 550); 15 Aug 2022 18:31:28 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 17556 invoked from network); 15 Aug 2022 18:31:27 -0000 Date: Mon, 15 Aug 2022 14:31:15 -0400 From: Rich Felker To: =?utf-8?B?w4lyaWNv?= Nogueira Cc: musl@lists.openwall.com Message-ID: <20220815183114.GZ7074@brightrain.aerifal.cx> References: <20220815182110.19039-1-ericonr@disroot.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220815182110.19039-1-ericonr@disroot.org> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] [PATCH] use __getauxval in mallocng On Mon, Aug 15, 2022 at 03:21:10PM -0300, Érico Nogueira wrote: > saves around 20 bytes of .text > --- > src/malloc/mallocng/glue.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/src/malloc/mallocng/glue.h b/src/malloc/mallocng/glue.h > index 151c48b8..4b988fb2 100644 > --- a/src/malloc/mallocng/glue.h > +++ b/src/malloc/mallocng/glue.h > @@ -12,6 +12,7 @@ > #include "libc.h" > #include "lock.h" > #include "dynlink.h" > +#include "sys/auxv.h" > > // use macros to appropriately namespace these. > #define size_classes __malloc_size_classes > @@ -42,9 +43,8 @@ > static inline uint64_t get_random_secret() > { > uint64_t secret = (uintptr_t)&secret * 1103515245; > - for (size_t i=0; libc.auxv[i]; i+=2) > - if (libc.auxv[i]==AT_RANDOM) > - memcpy(&secret, (char *)libc.auxv[i+1]+8, sizeof secret); > + const char *at_random = (void *)__getauxval(AT_RANDOM); > + if (at_random) memcpy(&secret, at_random+8, sizeof secret); > return secret; > } > > -- > 2.37.2 Hm, this might be worth doing. I'm trying to remember if there was a reason it wasn't done initially. It wasn't absence of a namespace-safe version because __getauxval already existed when mallocng was merged. And it doesn't look like there's an early-use issue before getauxval is usable either. Might it just be more expensive in the static linked case where __getauxval isn't otherwise used? Rich