[PATCH] S390: Fix backtrace in vdso functions.

[Stefan Liebler]

Hi,

On s390, GDB fails to show the complete backtrace from within vdso 
functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in 
r14 to r10 before branching to the vdso function. The branch-instruction 
updates r14 in order to let the vdso function return. Then the original 
address in r14 is restored from r10. Unfortunately, there are no 
cfi-rules and GDB fails.

Furthermore the call of the vdso function does not comply with the s390 
ABI as no stack-frame for the vdso-function is generated.

This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and 
the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is 
used. Then the vdso function is called via function-pointer and GCC 
generates a new stack-frame and emits all needed cfi-rules.

The defines CLOBBER_[0-6] are removed as they  were only used in macro 
INTERNAL_VSYSCALL_CALL.

The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The 
only user is power. Thus it is removed from s390 sysdep.h.

ChangeLog:

	* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
	(INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
	 CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
	INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
	* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
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