From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/12948 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] proposal adding explicit_bzero Date: Tue, 26 Jun 2018 16:53:37 -0400 Message-ID: <20180626205337.GA1392@brightrain.aerifal.cx> References: <20180626204341.GY1392@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1530046307 4707 195.159.176.226 (26 Jun 2018 20:51:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 26 Jun 2018 20:51:47 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-12964-gllmg-musl=m.gmane.org@lists.openwall.com Tue Jun 26 22:51:43 2018 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1fXuw9-00016I-Ae for gllmg-musl@m.gmane.org; Tue, 26 Jun 2018 22:51:41 +0200 Original-Received: (qmail 31956 invoked by uid 550); 26 Jun 2018 20:53:49 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 31934 invoked from network); 26 Jun 2018 20:53:49 -0000 Content-Disposition: inline In-Reply-To: Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:12948 Archived-At: On Tue, Jun 26, 2018 at 09:48:47PM +0100, David CARLIER wrote: > Yes true sorry :-|. No problem. Do you agree with my proposed fix and want me to make that change and apply it? Rich > On Tue, 26 Jun 2018 at 21:43, Rich Felker wrote: > > > On Fri, Jun 15, 2018 at 01:37:43PM +0000, David CARLIER wrote: > > > Hi dear lists, > > > this is my first message so forgive me if this idea had already been > > rejected. > > > > It's definitely not rejected outright, and I think the consensus is > > to adopt it. But.. > > > > > From c0a16cf96b96b009097d6ed656a2a7b8969e8399 Mon Sep 17 00:00:00 2001 > > > From: David Carlier > > > Date: Fri, 15 Jun 2018 13:30:09 +0000 > > > Subject: [PATCH] string: adding simple explicit_bzero implementation. > > > > > > glibc implementing it and modern security based code starting > > > using it widely, here a simple implementation using memory barrier. > > > --- > > > include/string.h | 1 + > > > src/string/explicit_bzero.c | 8 ++++++++ > > > 2 files changed, 9 insertions(+) > > > create mode 100644 src/string/explicit_bzero.c > > > > > > diff --git a/include/string.h b/include/string.h > > > index ce1dc300..795a2abc 100644 > > > --- a/include/string.h > > > +++ b/include/string.h > > > @@ -82,6 +82,7 @@ void *memccpy (void *__restrict, const void > > *__restrict, int, size_t); > > > char *strsep(char **, const char *); > > > size_t strlcat (char *, const char *, size_t); > > > size_t strlcpy (char *, const char *, size_t); > > > +void explicit_bzero (void *, size_t); > > > #endif > > > > > > #ifdef _GNU_SOURCE > > > diff --git a/src/string/explicit_bzero.c b/src/string/explicit_bzero.c > > > new file mode 100644 > > > index 00000000..47dba3c7 > > > --- /dev/null > > > +++ b/src/string/explicit_bzero.c > > > @@ -0,0 +1,8 @@ > > > +#define _BSD_SOURCE > > > +#include > > > + > > > +void explicit_bzero(void *d, size_t n) > > > +{ > > > + memset(d, 0, n); > > > + __asm__ volatile("": "r="(d) :: "memory"); > > > +} > > > -- > > > > The constraint here looks wrong. Normally = is written before the > > type, not after; I'm not sure if all compiler versions accept the > > unusual form with it after. But more importantly you have it as an > > output constraint, where it's essentially a dead store, such that the > > asm block does nothing to make explicit_bzero force the memset to > > happen. > > > > I think you meant for the constraint to be an input constraint "r"(d). > > Does that sound right? > > > > Rich > >