[PATCH] Use libc_hidden_proto / _def for hidden wchar ifunc symbols.

[Stefan Liebler]

Hi,

on s390 (31bit) various debug/tst-*chk* testcases are failing as the 
tests are ending with a segmentation fault.

One test is e.g. calling wcsnrtombs in debug/tst-chk1.c:1549.
The function wcsnrtombs itself calls __wcsnlen. This function is called 
via PLT! The PLT-stub itself loads the address from GOT (r12 is assumed 
to be the GOT-pointer). In this case the loaded address is zero and the 
following branch leads to the segmentation fault.

Due to the attribute-hidden in commit 
44af8a32c341672b5160fdc2839767e9a837ad26 "Mark internal wchar functions 
with attribute_hidden [BZ #18822]" for e.g. the __wcsnlen function, r12 
is not loaded with the GOT-pointer in wcsnrtombs.

On s390x (64bit), this __wcsnlen call is also using the PLT-stub. But it 
is not failing as the GOT-pointer is setup with larl-instruction by the 
PLT-stub itself.
Note: On s390x/s390, __wcsnlen is an IFUNC symbol.

On x86_64, __wcsnlen is also an IFUNC symbol and is called via PLT, too.

Further IFUNC symbols on s390 which were marked as hidden by the 
mentioned commit are: __wcscat, __wcsncpy, __wcpncpy, __wcschrnul.

This patch adds the libc_hidden_proto / libc_hidden_def construct.
Then the __GI_* symbols are the default-ifunc-variants which can be 
called without PLT.

Okay to commit?

Bye.
Stefan

ChangeLog:

	* include/wchar.h (__wcsnlen, __wcscat, __wcsncpy, __wcpncpy,
	__wcschrnul): Add libc_hidden_proto.
	* wcsmbs/wcsnlen.c (__wcsnlen): Add libc_hidden_def.
	* wcsmbs/wcscat.c (__wcscat): Likewise.
	* wcsmbs/wcschrnul.c (__wcschrnul): Likewise.
	* wcsmbs/wcsncpy.c (__wcsncpy): Likewise.
	* wcsmbs/wcpncpy.c (__wcpncpy): Likewise.
	* sysdeps/x86_64/multiarch/wcsnlen-c.c (__wcsnlen): Add libc_hidden_def
	which aliases to default ifunc-variant.
	* sysdeps/s390/multiarch/wcsnlen-c.c (__wcsnlen):  Likewise.
	* sysdeps/s390/multiarch/wcscat-c.c (__wcscat): Likewise.
	* sysdeps/s390/multiarch/wcschrnul-c.c  (__wcschrnul): Likewise.
	* sysdeps/s390/multiarch/wcsncpy-c.c (__wcsncpy): Likewise.
	* sysdeps/s390/multiarch/wcpncpy-c.c (__wcpncpy): Likewise.
	* sysdeps/s390/multiarch/wcsnlen.c (__wcsnlen): Redirect symbol in
	header and use s390_vx_libc_ifunc_redirected instead of
	s390_vx_libc_ifunc.
	* sysdeps/s390/multiarch/wcscat.c (__wcscat): Likewise.
	* sysdeps/s390/multiarch/wcschrnul.c (__wcschrnul): Likewise.
	* sysdeps/s390/multiarch/wcsncpy.c (__wcsncpy): Likewise.
	* sysdeps/s390/multiarch/wcpncpy.c (__wcpncpy): Likewise.
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