sh: SHMLBA & cache shape info from auxvt

[Carmelo AMOROSO]

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Hi All, Paul
we are adding the code in uClibc ld.so to retrieve the value
of shm_alignment from the cache shape info passed to the user space
through the AUXVT for sh arch.

Currently in bits/shm.h we have

/* Segment low boundary address multiple.  */
/*
 * XXX: This is misleading, SH-4 and SH-3 7705 in 32kb mode have dcache
 * aliases to contend with in the 4k page case. This is not an issue for
 * the other parts. Leave this bumped up for sanity until this can be
 * accurately defined by the L1D shape through the auxiliary vector.
 */
#define SHMLBA      (__getpagesize() << 2)

The comment (I guess Paul added) is definitely clear.

We would like to have something like that

#define SHMLBA      __get_shm_alignment()

but this will add a reference to a new function into any binaries
compiled using the new header that will not work with older runtime libraries
(not a major problem because header and libraries should be always aligned).

My doubt is it is allowed to add/export a new function in lib C that is not
part of the POSIX API.

Another option could be to remap the macro with sysconf, so

#define SHMLBA      sysconf(_SC_SHM_ALIGNMENT)

or something like that, but also in this case we need to export a new
sysconf name in bits/confname.h; is this allowed ?

Cheers,
Carmelo

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