s390/compat: correct ucontext layout for high gprs

The uc_sigmask definition in the kernel differs from the one in the
glibc, the kernel uc_sigmask has 64 bits while the glibc verison
is 1024 bits. The extension of the ucontext structure for 64-bit
register support for 31-bit compat processes added a new field
uc_gprs_high which starts 8 bytes after the uc_sigmask field.
As the glibc view of the ucontext assumes a size of 128 bytes for
uc_sigmask add a 120 byte padding to the kernel structure
ucontext_extended after the 8 byte uc_sigmask.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/uapi/asm/ucontext.h

@@ -16,7 +16,9 @@ struct ucontext_extended {
 	struct ucontext  *uc_link;
 	stack_t		  uc_stack;
 	_sigregs	  uc_mcontext;
-	unsigned long	  uc_sigmask[2];
+	sigset_t	  uc_sigmask;
+	/* Allow for uc_sigmask growth.  Glibc uses a 1024-bit sigset_t.  */
+	unsigned char	  __unused[128 - sizeof(sigset_t)];
 	unsigned long	  uc_gprs_high[16];
 };
 
@@ -27,7 +29,9 @@ struct ucontext {
 	struct ucontext  *uc_link;
 	stack_t		  uc_stack;
 	_sigregs          uc_mcontext;
-	sigset_t	  uc_sigmask;	/* mask last for extensibility */
+	sigset_t	  uc_sigmask;
+	/* Allow for uc_sigmask growth.  Glibc uses a 1024-bit sigset_t.  */
+	unsigned char	  __unused[128 - sizeof(sigset_t)];
 };
 
 #endif /* !_ASM_S390_UCONTEXT_H */

arch/s390/kernel/compat_linux.h

@@ -69,7 +69,9 @@ struct ucontext32 {
 	__u32			uc_link;	/* pointer */	
 	compat_stack_t		uc_stack;
 	_sigregs32		uc_mcontext;
-	compat_sigset_t		uc_sigmask;	/* mask last for extensibility */
+	compat_sigset_t		uc_sigmask;
+	/* Allow for uc_sigmask growth.  Glibc uses a 1024-bit sigset_t.  */
+	unsigned char		__unused[128 - sizeof(compat_sigset_t)];
 };
 
 struct stat64_emu31;