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From: Nathan McSween <nwmcsween@gmail.com>
To: musl@lists.openwall.com
Cc: Mark Winterrowd <markwinterrowd4@gmail.com>
Subject: Re: request for help with aux
Date: Mon, 27 Jun 2016 21:49:35 +0000	[thread overview]
Message-ID: <CAMSMCx=11V-GMkAOdOJCK3C1M4bkERDc2esq6YZNU+ud5jwM4w@mail.gmail.com> (raw)
In-Reply-To: <CALzRTRnqJ+oRs=4n=jvJprDTvbaTGiT07BwS50xvWBufQSNQyA@mail.gmail.com>

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Aux vec is used in things like SSP, so disabling aux would use a guessable
value for SSP, iirc static linking still uses the aux vec for SSP

On Mon, Jun 27, 2016, 2:34 PM Daniel Wilkerson <daniel.wilkerson@gmail.com>
wrote:

> Ah, thank you.  From that page:
>
>        This function is a nonstandard glibc extension.
>
> And:
>
>        The primary consumer of the information in the auxiliary vector is
>        the dynamic linker ld-linux.so(8).  The auxiliary vector is a
>        convenient and efficient shortcut that allows the kernel to
>        communicate a certain set of standard information that the dynamic
>        linker usually or always needs.  In some cases, the same information
>        could be obtained by system calls, but using the auxiliary vector is
>        cheaper.
>
> It seems therefore that if I am doing static linking that it is safe
> to simply provide an empty aux vector?
>
> Daniel
>
> On Mon, Jun 27, 2016 at 2:00 PM, Bobby Bingham <koorogi@koorogi.info>
> wrote:
> > On Mon, Jun 27, 2016 at 01:07:59PM -0700, Daniel Wilkerson wrote:
> >> This seems to initalize aux to be all zeros, so it seems that in
> >> theory all of the aux values could be optional:
> >>
> >>         size_t i, *auxv, aux[AUX_CNT] = { 0 };
> >>
> >> What I'm wondering is where to find the semantics of all of the aux
> >> names; I could hunt through all of the code, but any high-level
> >> suggestions you could provide could help a lot.  As a bonus, which
> >> ones might not have sensible defaults and are actually non-optional,
> >> if any.
> >
> > The getauxval man page is a good starting point:
> > http://man7.org/linux/man-pages/man3/getauxval.3.html
> >
> > --
> > Bobby
>

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  reply	other threads:[~2016-06-27 21:49 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-27 20:07 Daniel Wilkerson
2016-06-27 21:00 ` Bobby Bingham
2016-06-27 21:33   ` Daniel Wilkerson
2016-06-27 21:49     ` Nathan McSween [this message]
2016-06-27 21:58 ` Rich Felker
2016-06-28  0:22 ` Patrick Oppenlander

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