s390: Set psw addr field in getcontext and friends.

So far if the ucontext structure was obtained by getcontext and co,
the return address was stored in general purpose register 14 as
it is defined as return address in the ABI.

In contrast, the context passed to a signal handler contains the address
in psw.addr field.

If somebody e.g. wants to dump the address of the context, the origin
needs to be known.

Now this patch adjusts getcontext and friends and stores the return address
also in psw.addr field.

Note that setcontext isn't adjusted and it is not supported to pass a
ucontext structure from signal-handler to setcontext.  We are not able to
restore all registers and branching to psw.addr without clobbering one
register.

sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S

@@ -71,6 +71,12 @@ ENTRY(__getcontext)
 	/* Store general purpose registers.  */
 	stm     %r0,%r15,SC_GPRS(%r1)
 
+	/* Store psw mask to 0x0 and addr to return address.  Then the address
+	   can be retrieved from the ucontext structure in the same way as if it
+	   is created by kernel and passed to a signal-handler.  */
+	st	%r2,SC_PSW+0(%r1)
+	st	%r14,SC_PSW+4(%r1)
+
 	/* Return.  */
 	br	%r14
 END(__getcontext)

sysdeps/unix/sysv/linux/s390/s390-32/makecontext.c

@@ -60,6 +60,11 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
 
   /* Set the return address to trampoline.  */
   ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
+  /* Store psw mask to 0x0 and addr to trampoline.  Then the address
+     can be retrieved from the ucontext structure in the same way as if it
+     is created by kernel and passed to a signal-handler.  */
+  ucp->uc_mcontext.psw.addr = (long int) __makecontext_ret;
+  ucp->uc_mcontext.psw.mask = 0;
 
   /* Set register parameters.  */
   va_start (ap, argc);

sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S

@@ -66,6 +66,12 @@ ENTRY(__swapcontext)
 	/* Store general purpose registers.  */
 	stm     %r0,%r15,SC_GPRS(%r1)
 
+	/* Store psw mask to 0x0 and addr to return address.  Then the address
+	   can be retrieved from the ucontext structure in the same way as if it
+	   is created by kernel and passed to a signal-handler.  */
+	st	%r2,SC_PSW+0(%r1)
+	st	%r14,SC_PSW+4(%r1)
+
 	/* rt_sigprocmask (SIG_SETMASK, &ucp->uc_sigmask, &oucp->uc_sigmask,
 	   sigsetsize).  */
 	la      %r2,SIG_SETMASK

sysdeps/unix/sysv/linux/s390/s390-64/getcontext.S

@@ -71,6 +71,12 @@ ENTRY(__getcontext)
 	/* Store general purpose registers.  */
 	stmg    %r0,%r15,SC_GPRS(%r1)
 
+	/* Store psw mask to 0x0 and addr to return address.  Then the address
+	   can be retrieved from the ucontext structure in the same way as if it
+	   is created by kernel and passed to a signal-handler.  */
+	stg	%r2,SC_PSW+0(%r1)
+	stg	%r14,SC_PSW+8(%r1)
+
 	/* Return.  */
 	br	%r14
 END(__getcontext)

sysdeps/unix/sysv/linux/s390/s390-64/makecontext.c

@@ -60,6 +60,11 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
 
   /* Set the return address to trampoline.  */
   ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
+  /* Store psw mask to 0x0 and addr to trampoline.  Then the address
+     can be retrieved from the ucontext structure in the same way as if it
+     is created by kernel and passed to a signal-handler.  */
+  ucp->uc_mcontext.psw.addr = (long int) __makecontext_ret;
+  ucp->uc_mcontext.psw.mask = 0;
 
   /* Set register parameters.  */
   va_start (ap, argc);

sysdeps/unix/sysv/linux/s390/s390-64/swapcontext.S

@@ -66,6 +66,12 @@ ENTRY(__swapcontext)
 	/* Store general purpose registers.  */
 	stmg    %r0,%r15,SC_GPRS(%r1)
 
+	/* Store psw mask to 0x0 and addr to return address.  Then the address
+	   can be retrieved from the ucontext structure in the same way as if it
+	   is created by kernel and passed to a signal-handler.  */
+	stg	%r2,SC_PSW+0(%r1)
+	stg	%r14,SC_PSW+8(%r1)
+
 	/* rt_sigprocmask (SIG_SETMASK, &ucp->uc_sigmask, &oucp->uc_sigmask,
 	   sigsetsize).  */
 	la      %r2,SIG_SETMASK