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Message-ID: <CAMSMCx=11V-GMkAOdOJCK3C1M4bkERDc2esq6YZNU+ud5jwM4w@mail.gmail.com>
Date: Mon, 27 Jun 2016 21:49:35 +0000
From: Nathan McSween <nwmcsween@...il.com>
To: musl@...ts.openwall.com
Cc: Mark Winterrowd <markwinterrowd4@...il.com>
Subject: Re: request for help with aux
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@...il.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@...rogi.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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