From: "Daniel Cegiełka" <daniel.cegielka@gmail.com>
To: musl@lists.openwall.com
Subject: Re: thoughts on reallocarray, explicit_bzero?
Date: Mon, 19 May 2014 18:45:08 +0200 [thread overview]
Message-ID: <CAPLrYERvsFF=0UN-gRchd7zY0ViKNf6QA5bt7Oj5mGcxpLzbdA@mail.gmail.com> (raw)
In-Reply-To: <20140519162556.GY12324@port70.net>
2014-05-19 18:25 GMT+02:00 Szabolcs Nagy <nsz@port70.net>:
> i don't see how the openbsd explicit_bzero stops the
> compiler to do optimizations..
>
> (i guess they rely on that their gcc does not do lto
> or that libc is dynamic linked and the compiler has no
> 'explicit_bzero' builtin, neither of which is a great
> solution..)
>
> the usual approach to this is volatile function pointer:
>
> static void *(*volatile force_memset)(void,int,size_t) = memset;
>
> in general in c one cannot be sure that the secret bits
> are not leaked somewhere since the languge spec cannot
> give such guarantees
>
> that said either the volatile funcptr or actually reusing
> the memory such that it cannot be optimized away works in
> practice
first version:
void explicit_bzero(void * const b, const size_t l)
{
volatile unsigned char *p = (volatile unsigned char *) b;
size_t i = (size_t) 0U;
while (i < l) {
p[i++] = 0U;
}
}
Of course, if someone has better ideas... I'm very curious :)
Daniel
next prev parent reply other threads:[~2014-05-19 16:45 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-19 15:31 Isaac Dunham
2014-05-19 15:43 ` Rich Felker
2014-05-19 16:19 ` Daniel Cegiełka
2014-05-20 6:19 ` Rich Felker
2014-05-20 15:50 ` Daniel Cegiełka
2014-05-19 15:44 ` Daniel Cegiełka
2014-05-19 16:16 ` Rich Felker
2014-05-19 16:30 ` Daniel Cegiełka
2014-05-19 16:32 ` Szabolcs Nagy
2015-01-28 22:01 ` Daniel Cegiełka
2015-01-28 22:34 ` Daniel Cegiełka
2015-01-28 22:38 ` Nathan McSween
2015-01-28 22:54 ` Daniel Cegiełka
2015-01-28 23:02 ` Josiah Worcester
2015-01-29 2:19 ` Rich Felker
2015-01-29 4:03 ` Brent Cook
2015-01-29 4:15 ` Rich Felker
2015-01-29 9:30 ` Daniel Cegiełka
2015-01-29 10:04 ` Szabolcs Nagy
2015-01-29 10:31 ` Daniel Cegiełka
2015-01-29 10:54 ` Daniel Cegiełka
2014-05-19 16:25 ` Szabolcs Nagy
2014-05-19 16:45 ` Daniel Cegiełka [this message]
2014-05-19 16:58 ` Rich Felker
2014-05-19 16:55 ` Rich Felker
2014-05-19 18:12 ` Szabolcs Nagy
2014-05-19 22:08 ` Andy Lutomirski
2014-05-20 0:41 ` Szabolcs Nagy
2014-06-11 9:59 ` Thorsten Glaser
2014-06-11 12:59 ` Rich Felker
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