[PATCH] S390: Fix build with gcc configured with --enable-default-pie. [BZ #21537]

[Stefan Liebler]

Hi,

Building glibc with gcc configured with --enable-default-pie failed on s390
due to assembler messages:
../sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S:44:
Error: junk at end of line, first unrecognized character is `@'

HIDDEN_JUMPTARGET was expanded to exit@PLT@GOTOFF.
If SHARED is not defined, HIDDEN_JUMPTARGET is defined to JUMPTARGET
in sysdeps/s390/s390-32/sysdep.h.  There it expanded to exit@PLT
in non SHARED case as PIC is defined if gcc is configured with
--enable-default-pie. Thus I've changed the "ifdef PIC" to "ifdef SHARED"
as we do not want PLTs in the static obj files.  I've also changed this
in sysdeps/s390/s390-64/sysdep.h.

I've also adjusted sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S.
If glibc is configured with --disable-hidden-plt, then NO_HIDDEN is defined.
In SHARED case HIDDEN_JUMPTARGET would be expanded to exit@PLT@GOTOFF
instead of __GI_exit@GOTOFF.
Now we jump to:
- __GI_exit if SHARED is defined
- exit@PLT if SHARED and NO_HIDDEN is defined
- exit if both are not defined.
On s390 31bit we have to setup GOT pointer in r12 if we use a PLT stub.
Therefore I use SYSCALL_PIC_SETUP from sysdep.h and added the missing 
semicolons.

Question about glibc configure flag --disable-hidden-plt:
Is this option supported or is it used by somebody?
It defines NO_HIDDEN which influences the definition of HIDDEN_JUMPTARGET.
I've tried to build glibc with this configure flag on s390, but it fails 
due to several reasons.

The glibc internal symbols of the ifunc'ed symbols are generated by 
using __hidden_ver1 which does not exist if NO_HIDDEN is defined. Thus 
for further testing I've used --disable-multi-arch to avoid the ifuncs.

Furthermore I get undefined references to __GI_memset/cpy/move
due to asm ("memxyz = __GI_memxyz"); in sysdeps/generic/symbol-hacks.h.

There are also undefined references to __nss_next2 and 
__inet6_scopeid_pton while linking nscd/nscd. Usually libc.so contains 
those symbols: xyz@@GLIBC_PRIVATE.
But with --disable-hidden-plt those symbols are only local.
For testing I've removed attribute_hidden at those prototypes.
Then glibc builds and the testsuite runs without fails except 
elf/check-localplt which detects the PLTs due to --disable-hidden-plt.

ChangeLog:

	[BZ #21537]
	* sysdeps/s390/s390-32/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
	Check SHARED instead of PIC.
	(SYSCALL_PIC_SETUP): Add missing semicolons.
	* sysdeps/s390/s390-64/sysdep.h (JUMPTARGET, SYSCALL_PIC_SETUP):
	Check SHARED instead of PIC.
	* sysdeps/unix/sysv/linux/s390/s390-32/__makecontext_ret.S
	(__makecontext_ret): Adjust code to jump to exit.
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