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Re: [PATCH] Remove unnecessary IFUNC dispatch for __memset_chk.
- From: Alexander Monakov <amonakov at ispras dot ru>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Ondřej Bílka <neleai at seznam dot cz>, Zack Weinberg <zackw at panix dot com>, Andreas Schwab <schwab at linux-m68k dot org>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 11 Aug 2015 22:41:12 +0300 (MSK)
- Subject: Re: [PATCH] Remove unnecessary IFUNC dispatch for __memset_chk.
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On Tue, 11 Aug 2015, H.J. Lu wrote:
> > Didn't know its explicitly forbidden to use nonstatic resolvers. Do we document that requirement somewhere?
> > If not then we should add it to documentation.
>
> It makes no senses for IFUNC selector to return the address of
> a global function, which may be preempted at run-time.
That would be imposing a policy while providing a mechanism.
I think there are plausible scenarios where returning a global function from
an ifunc resolver would be natural.
To give a specific example, imagine an ifunc symbol
'printf_fortified_opportunistically', which resolves to 'printf_chk' if it is
available in the global namespace, or normal 'printf' otherwise.
Such a symbol could be in any DSO, not necessarily libc, and thus it has to be
able to pick up global symbol definitions.
Thanks.
Alexander