[S390] add breaking event address for user space

Copy the last breaking event address from the lowcore to a new
field in the thread_struct on each system entry. Add a new
ptrace request PTRACE_GET_LAST_BREAK and a new utrace regset
REGSET_LAST_BREAK to query the last breaking event.

This is useful for debugging wild branches in user space code.

Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/ptrace.h

···
 	psw_t psw;
 	unsigned long gprs[NUM_GPRS];
 	unsigned long orig_gpr2;
-	unsigned short svcnr;
 	unsigned short ilc;
+	unsigned short svcnr;
 };
 #endif
 
···
 #define PTRACE_PEEKDATA_AREA	      0x5003
 #define PTRACE_POKETEXT_AREA	      0x5004
 #define PTRACE_POKEDATA_AREA 	      0x5005
+#define PTRACE_GET_LAST_BREAK	      0x5006
 
 /*
  * PT_PROT definition is loosely based on hppa bsd definition in

arch/s390/include/asm/thread_info.h

···
 	struct restart_block	restart_block;
 	__u64			user_timer;
 	__u64			system_timer;
+	unsigned long		last_break;	/* last breaking-event-address. */
 };
 
 /*

arch/s390/kernel/asm-offsets.c

···
 	DEFINE(__TI_precount, offsetof(struct thread_info, preempt_count));
 	DEFINE(__TI_user_timer, offsetof(struct thread_info, user_timer));
 	DEFINE(__TI_system_timer, offsetof(struct thread_info, system_timer));
+	DEFINE(__TI_last_break, offsetof(struct thread_info, last_break));
 	BLANK();
 	DEFINE(__PT_ARGS, offsetof(struct pt_regs, args));
 	DEFINE(__PT_PSW, offsetof(struct pt_regs, psw));

arch/s390/kernel/entry.S

···
 	s	%r15,BASED(.Lc_spsize)	# make room for registers & psw
 	mvc	SP_PSW(8,%r15),0(%r12)	# move user PSW to stack
 	st	%r2,SP_ORIG_R2(%r15)	# store original content of gpr 2
-	icm	%r12,3,__LC_SVC_ILC
+	icm	%r12,12,__LC_SVC_ILC
 	stm	%r0,%r11,SP_R0(%r15)	# store gprs %r0-%r11 to kernel stack
-	st	%r12,SP_SVCNR(%r15)
+	st	%r12,SP_ILC(%r15)
 	mvc	SP_R12(16,%r15),\savearea # move %r12-%r15 to stack
 	la	%r12,0
 	st	%r12,__SF_BACKCHAIN(%r15)	# clear back chain

arch/s390/kernel/entry64.S

···
  *    R15 - kernel stack pointer
  */
 
-	.macro	SAVE_ALL_BASE savearea
-	stmg	%r12,%r15,\savearea
-	larl	%r13,system_call
-	.endm
-
 	.macro	SAVE_ALL_SVC psworg,savearea
-	la	%r12,\psworg
+	stmg	%r11,%r15,\savearea
 	lg	%r15,__LC_KERNEL_STACK	# problem state -> load ksp
+	aghi	%r15,-SP_SIZE		# make room for registers & psw
+	lg	%r11,__LC_LAST_BREAK
 	.endm
 
-	.macro	SAVE_ALL_SYNC psworg,savearea
-	la	%r12,\psworg
+	.macro	SAVE_ALL_PGM psworg,savearea
+	stmg	%r11,%r15,\savearea
 	tm	\psworg+1,0x01		# test problem state bit
-	jz	2f			# skip stack setup save
-	lg	%r15,__LC_KERNEL_STACK	# problem state -> load ksp
 #ifdef CONFIG_CHECK_STACK
-	j	3f
-2:	tml	%r15,STACK_SIZE - CONFIG_STACK_GUARD
-	jz	stack_overflow
-3:
+	jnz	1f
+	tml	%r15,STACK_SIZE - CONFIG_STACK_GUARD
+	jnz	2f
+	la	%r12,\psworg
+	j	stack_overflow
+#else
+	jz	2f
 #endif
-2:
+1:	lg	%r15,__LC_KERNEL_STACK	# problem state -> load ksp
+2:	aghi	%r15,-SP_SIZE		# make room for registers & psw
+	larl	%r13,system_call
+	lg	%r11,__LC_LAST_BREAK
 	.endm
 
 	.macro	SAVE_ALL_ASYNC psworg,savearea
+	stmg	%r11,%r15,\savearea
+	larl	%r13,system_call
+	lg	%r11,__LC_LAST_BREAK
 	la	%r12,\psworg
 	tm	\psworg+1,0x01		# test problem state bit
 	jnz	1f			# from user -> load kernel stack
···
 0:	lg	%r14,__LC_ASYNC_STACK	# are we already on the async. stack ?
 	slgr	%r14,%r15
 	srag	%r14,%r14,STACK_SHIFT
-	jz	2f
-1:	lg	%r15,__LC_ASYNC_STACK	# load async stack
 #ifdef CONFIG_CHECK_STACK
-	j	3f
-2:	tml	%r15,STACK_SIZE - CONFIG_STACK_GUARD
-	jz	stack_overflow
-3:
+	jnz	1f
+	tml	%r15,STACK_SIZE - CONFIG_STACK_GUARD
+	jnz	2f
+	j	stack_overflow
+#else
+	jz	2f
 #endif
-2:
+1:	lg	%r15,__LC_ASYNC_STACK	# load async stack
+2:	aghi	%r15,-SP_SIZE		# make room for registers & psw
 	.endm
 
-	.macro	CREATE_STACK_FRAME psworg,savearea
-	aghi	%r15,-SP_SIZE		# make room for registers & psw
-	mvc	SP_PSW(16,%r15),0(%r12)	# move user PSW to stack
+	.macro	CREATE_STACK_FRAME savearea
+	xc	__SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
 	stg	%r2,SP_ORIG_R2(%r15)	# store original content of gpr 2
-	icm	%r12,3,__LC_SVC_ILC
-	stmg	%r0,%r11,SP_R0(%r15)	# store gprs %r0-%r11 to kernel stack
-	st	%r12,SP_SVCNR(%r15)
-	mvc	SP_R12(32,%r15),\savearea # move %r12-%r15 to stack
-	la	%r12,0
-	stg	%r12,__SF_BACKCHAIN(%r15)
+	mvc	SP_R11(40,%r15),\savearea # move %r11-%r15 to stack
+	stmg	%r0,%r10,SP_R0(%r15)	# store gprs %r0-%r10 to kernel stack
 	.endm
 
 	.macro	RESTORE_ALL psworg,sync
···
 	mvc	__VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
 	lmg	%r14,%r15,SP_R14(%r15)	# load grps 14-15 of user
 	lpswe	\psworg			# back to caller
+	.endm
+
+	.macro	LAST_BREAK
+	srag	%r10,%r11,23
+	jz	0f
+	stg	%r11,__TI_last_break(%r12)
+0:
 	.endm
 
 /*
···
 system_call:
 	stpt	__LC_SYNC_ENTER_TIMER
 sysc_saveall:
-	SAVE_ALL_BASE __LC_SAVE_AREA
 	SAVE_ALL_SVC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
-	CREATE_STACK_FRAME __LC_SVC_OLD_PSW,__LC_SAVE_AREA
-	llgh	%r7,__LC_SVC_INT_CODE	# get svc number from lowcore
+	CREATE_STACK_FRAME __LC_SAVE_AREA
+	mvc	SP_PSW(16,%r15),__LC_SVC_OLD_PSW
+	mvc	SP_ILC(4,%r15),__LC_SVC_ILC
+	stg	%r7,SP_ARGS(%r15)
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 sysc_vtime:
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
 sysc_stime:
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 sysc_update:
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
+	LAST_BREAK
 sysc_do_svc:
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
-	ltgr	%r7,%r7		# test for svc 0
+	llgh	%r7,SP_SVCNR(%r15)
+	slag	%r7,%r7,2	# shift and test for svc 0
 	jnz	sysc_nr_ok
 	# svc 0: system call number in %r1
-	cl	%r1,BASED(.Lnr_syscalls)
+	llgfr	%r1,%r1		# clear high word in r1
+	cghi	%r1,NR_syscalls
 	jnl	sysc_nr_ok
-	lgfr	%r7,%r1 	# clear high word in r1
+	sth	%r1,SP_SVCNR(%r15)
+	slag	%r7,%r1,2	# shift and test for svc 0
 sysc_nr_ok:
-	mvc	SP_ARGS(8,%r15),SP_R7(%r15)
-sysc_do_restart:
-	sth	%r7,SP_SVCNR(%r15)
-	sllg	%r7,%r7,2	# svc number * 4
 	larl	%r10,sys_call_table
 #ifdef CONFIG_COMPAT
-	tm	__TI_flags+5(%r9),(_TIF_31BIT>>16)  # running in 31 bit mode ?
+	tm	__TI_flags+5(%r12),(_TIF_31BIT>>16)  # running in 31 bit mode ?
 	jno	sysc_noemu
 	larl	%r10,sys_call_table_emu  # use 31 bit emulation system calls
 sysc_noemu:
 #endif
-	tm	__TI_flags+6(%r9),_TIF_SYSCALL
+	tm	__TI_flags+6(%r12),_TIF_SYSCALL
 	lgf	%r8,0(%r7,%r10) # load address of system call routine
 	jnz	sysc_tracesys
 	basr	%r14,%r8	# call sys_xxxx
···
 sysc_return:
 	LOCKDEP_SYS_EXIT
 sysc_tif:
-	tm	__TI_flags+7(%r9),_TIF_WORK_SVC
+	tm	__TI_flags+7(%r12),_TIF_WORK_SVC
 	jnz	sysc_work	# there is work to do (signals etc.)
 sysc_restore:
 	RESTORE_ALL __LC_RETURN_PSW,1
···
 # One of the work bits is on. Find out which one.
 #
 sysc_work_tif:
-	tm	__TI_flags+7(%r9),_TIF_MCCK_PENDING
+	tm	__TI_flags+7(%r12),_TIF_MCCK_PENDING
 	jo	sysc_mcck_pending
-	tm	__TI_flags+7(%r9),_TIF_NEED_RESCHED
+	tm	__TI_flags+7(%r12),_TIF_NEED_RESCHED
 	jo	sysc_reschedule
-	tm	__TI_flags+7(%r9),_TIF_SIGPENDING
+	tm	__TI_flags+7(%r12),_TIF_SIGPENDING
 	jo	sysc_sigpending
-	tm	__TI_flags+7(%r9),_TIF_NOTIFY_RESUME
+	tm	__TI_flags+7(%r12),_TIF_NOTIFY_RESUME
 	jo	sysc_notify_resume
-	tm	__TI_flags+7(%r9),_TIF_RESTART_SVC
+	tm	__TI_flags+7(%r12),_TIF_RESTART_SVC
 	jo	sysc_restart
-	tm	__TI_flags+7(%r9),_TIF_SINGLE_STEP
+	tm	__TI_flags+7(%r12),_TIF_SINGLE_STEP
 	jo	sysc_singlestep
 	j	sysc_return		# beware of critical section cleanup
 
···
 # _TIF_SIGPENDING is set, call do_signal
 #
 sysc_sigpending:
-	ni	__TI_flags+7(%r9),255-_TIF_SINGLE_STEP # clear TIF_SINGLE_STEP
+	ni	__TI_flags+7(%r12),255-_TIF_SINGLE_STEP # clear TIF_SINGLE_STEP
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	brasl	%r14,do_signal		# call do_signal
-	tm	__TI_flags+7(%r9),_TIF_RESTART_SVC
+	tm	__TI_flags+7(%r12),_TIF_RESTART_SVC
 	jo	sysc_restart
-	tm	__TI_flags+7(%r9),_TIF_SINGLE_STEP
+	tm	__TI_flags+7(%r12),_TIF_SINGLE_STEP
 	jo	sysc_singlestep
 	j	sysc_return
 
···
 # _TIF_RESTART_SVC is set, set up registers and restart svc
 #
 sysc_restart:
-	ni	__TI_flags+7(%r9),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
+	ni	__TI_flags+7(%r12),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
 	lg	%r7,SP_R2(%r15)		# load new svc number
 	mvc	SP_R2(8,%r15),SP_ORIG_R2(%r15) # restore first argument
 	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
-	j	sysc_do_restart 	# restart svc
+	sth	%r7,SP_SVCNR(%r15)
+	slag	%r7,%r7,2
+	j	sysc_nr_ok		# restart svc
 
 #
 # _TIF_SINGLE_STEP is set, call do_single_step
 #
 sysc_singlestep:
-	ni	__TI_flags+7(%r9),255-_TIF_SINGLE_STEP	# clear TIF_SINGLE_STEP
+	ni	__TI_flags+7(%r12),255-_TIF_SINGLE_STEP	# clear TIF_SINGLE_STEP
 	xc	SP_SVCNR(2,%r15),SP_SVCNR(%r15)		# clear svc number
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	larl	%r14,sysc_return	# load adr. of system return
···
 sysc_tracesys:
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	la	%r3,0
-	srl	%r7,2
-	stg	%r7,SP_R2(%r15)
+	llgh	%r0,SP_SVCNR(%r15)
+	stg	%r0,SP_R2(%r15)
 	brasl	%r14,do_syscall_trace_enter
 	lghi	%r0,NR_syscalls
 	clgr	%r0,%r2
···
 	basr	%r14,%r8		# call sys_xxx
 	stg	%r2,SP_R2(%r15)		# store return value
 sysc_tracenogo:
-	tm	__TI_flags+6(%r9),_TIF_SYSCALL
+	tm	__TI_flags+6(%r12),_TIF_SYSCALL
 	jz	sysc_return
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	larl	%r14,sysc_return	# return point is sysc_return
···
 	.globl	ret_from_fork
 ret_from_fork:
 	lg	%r13,__LC_SVC_NEW_PSW+8
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	SP_PSW+1(%r15),0x01	# forking a kernel thread ?
 	jo	0f
 	stg	%r15,SP_R15(%r15)	# store stack pointer for new kthread
···
 	lg	%r15,__LC_KERNEL_STACK	# load ksp
 	aghi	%r15,-SP_SIZE		# make room for registers & psw
 	lg	%r13,__LC_SVC_NEW_PSW+8
-	lg	%r9,__LC_THREAD_INFO
 	mvc	SP_PTREGS(__PT_SIZE,%r15),0(%r12)	# copy pt_regs
+	lg	%r12,__LC_THREAD_INFO
 	xc	__SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
 #	TRACE_IRQS_ON
 	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts
···
  * for LPSW?).
  */
 	stpt	__LC_SYNC_ENTER_TIMER
-	SAVE_ALL_BASE __LC_SAVE_AREA
 	tm	__LC_PGM_INT_CODE+1,0x80 # check whether we got a per exception
 	jnz	pgm_per 		 # got per exception -> special case
-	SAVE_ALL_SYNC __LC_PGM_OLD_PSW,__LC_SAVE_AREA
-	CREATE_STACK_FRAME __LC_PGM_OLD_PSW,__LC_SAVE_AREA
+	SAVE_ALL_PGM __LC_PGM_OLD_PSW,__LC_SAVE_AREA
+	CREATE_STACK_FRAME __LC_SAVE_AREA
+	xc	SP_ILC(4,%r15),SP_ILC(%r15)
+	mvc	SP_PSW(16,%r15),__LC_PGM_OLD_PSW
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	SP_PSW+1(%r15),0x01	# interrupting from user ?
 	jz	pgm_no_vtime
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
+	LAST_BREAK
 pgm_no_vtime:
 	HANDLE_SIE_INTERCEPT
 	TRACE_IRQS_CHECK_OFF
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
-	mvc	SP_ARGS(8,%r15),__LC_LAST_BREAK
+	stg	%r11,SP_ARGS(%r15)
 	lgf	%r3,__LC_PGM_ILC	# load program interruption code
 	lghi	%r8,0x7f
 	ngr	%r8,%r3
···
 	clc	__LC_PGM_OLD_PSW(16),__LC_SVC_NEW_PSW
 	je	pgm_svcper
 # no interesting special case, ignore PER event
-	lmg	%r12,%r15,__LC_SAVE_AREA
 	lpswe	__LC_PGM_OLD_PSW
 
 #
 # Normal per exception
 #
 pgm_per_std:
-	SAVE_ALL_SYNC __LC_PGM_OLD_PSW,__LC_SAVE_AREA
-	CREATE_STACK_FRAME __LC_PGM_OLD_PSW,__LC_SAVE_AREA
+	SAVE_ALL_PGM __LC_PGM_OLD_PSW,__LC_SAVE_AREA
+	CREATE_STACK_FRAME __LC_SAVE_AREA
+	mvc	SP_PSW(16,%r15),__LC_PGM_OLD_PSW
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	SP_PSW+1(%r15),0x01	# interrupting from user ?
 	jz	pgm_no_vtime2
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
+	LAST_BREAK
 pgm_no_vtime2:
 	HANDLE_SIE_INTERCEPT
 	TRACE_IRQS_CHECK_OFF
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
-	lg	%r1,__TI_task(%r9)
+	lg	%r1,__TI_task(%r12)
 	tm	SP_PSW+1(%r15),0x01	# kernel per event ?
 	jz	kernel_per
 	mvc	__THREAD_per+__PER_atmid(2,%r1),__LC_PER_ATMID
 	mvc	__THREAD_per+__PER_address(8,%r1),__LC_PER_ADDRESS
 	mvc	__THREAD_per+__PER_access_id(1,%r1),__LC_PER_ACCESS_ID
-	oi	__TI_flags+7(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
+	oi	__TI_flags+7(%r12),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
 	lgf	%r3,__LC_PGM_ILC	# load program interruption code
 	lghi	%r8,0x7f
 	ngr	%r8,%r3			# clear per-event-bit and ilc
···
 # it was a single stepped SVC that is causing all the trouble
 #
 pgm_svcper:
-	SAVE_ALL_SYNC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
-	CREATE_STACK_FRAME __LC_SVC_OLD_PSW,__LC_SAVE_AREA
+	SAVE_ALL_PGM __LC_SVC_OLD_PSW,__LC_SAVE_AREA
+	CREATE_STACK_FRAME __LC_SAVE_AREA
+	mvc	SP_PSW(16,%r15),__LC_SVC_OLD_PSW
+	mvc	SP_ILC(4,%r15),__LC_SVC_ILC
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
-	llgh	%r7,__LC_SVC_INT_CODE	# get svc number from lowcore
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
+	LAST_BREAK
 	TRACE_IRQS_OFF
-	lg	%r8,__TI_task(%r9)
+	lg	%r8,__TI_task(%r12)
 	mvc	__THREAD_per+__PER_atmid(2,%r8),__LC_PER_ATMID
 	mvc	__THREAD_per+__PER_address(8,%r8),__LC_PER_ADDRESS
 	mvc	__THREAD_per+__PER_access_id(1,%r8),__LC_PER_ACCESS_ID
-	oi	__TI_flags+7(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
+	oi	__TI_flags+7(%r12),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
 	TRACE_IRQS_ON
 	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts
 	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
···
 io_int_handler:
 	stck	__LC_INT_CLOCK
 	stpt	__LC_ASYNC_ENTER_TIMER
-	SAVE_ALL_BASE __LC_SAVE_AREA+32
-	SAVE_ALL_ASYNC __LC_IO_OLD_PSW,__LC_SAVE_AREA+32
-	CREATE_STACK_FRAME __LC_IO_OLD_PSW,__LC_SAVE_AREA+32
+	SAVE_ALL_ASYNC __LC_IO_OLD_PSW,__LC_SAVE_AREA+40
+	CREATE_STACK_FRAME __LC_SAVE_AREA+40
+	mvc	SP_PSW(16,%r15),0(%r12)	# move user PSW to stack
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	SP_PSW+1(%r15),0x01	# interrupting from user ?
 	jz	io_no_vtime
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_ASYNC_ENTER_TIMER,__LC_USER_TIMER
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_ASYNC_ENTER_TIMER
+	LAST_BREAK
 io_no_vtime:
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
 	HANDLE_SIE_INTERCEPT
 	TRACE_IRQS_OFF
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
···
 	LOCKDEP_SYS_EXIT
 	TRACE_IRQS_ON
 io_tif:
-	tm	__TI_flags+7(%r9),_TIF_WORK_INT
+	tm	__TI_flags+7(%r12),_TIF_WORK_INT
 	jnz	io_work 		# there is work to do (signals etc.)
 io_restore:
 	RESTORE_ALL __LC_RETURN_PSW,0
···
 	jo	io_work_user		# yes -> do resched & signal
 #ifdef CONFIG_PREEMPT
 	# check for preemptive scheduling
-	icm	%r0,15,__TI_precount(%r9)
+	icm	%r0,15,__TI_precount(%r12)
 	jnz	io_restore		# preemption is disabled
 	tm	__TI_flags+7(%r12),_TIF_NEED_RESCHED
 	jno	io_restore
···
 #	       and _TIF_MCCK_PENDING
 #
 io_work_tif:
-	tm	__TI_flags+7(%r9),_TIF_MCCK_PENDING
+	tm	__TI_flags+7(%r12),_TIF_MCCK_PENDING
 	jo	io_mcck_pending
-	tm	__TI_flags+7(%r9),_TIF_NEED_RESCHED
+	tm	__TI_flags+7(%r12),_TIF_NEED_RESCHED
 	jo	io_reschedule
-	tm	__TI_flags+7(%r9),_TIF_SIGPENDING
+	tm	__TI_flags+7(%r12),_TIF_SIGPENDING
 	jo	io_sigpending
-	tm	__TI_flags+7(%r9),_TIF_NOTIFY_RESUME
+	tm	__TI_flags+7(%r12),_TIF_NOTIFY_RESUME
 	jo	io_notify_resume
 	j	io_return		# beware of critical section cleanup
 
···
 ext_int_handler:
 	stck	__LC_INT_CLOCK
 	stpt	__LC_ASYNC_ENTER_TIMER
-	SAVE_ALL_BASE __LC_SAVE_AREA+32
-	SAVE_ALL_ASYNC __LC_EXT_OLD_PSW,__LC_SAVE_AREA+32
-	CREATE_STACK_FRAME __LC_EXT_OLD_PSW,__LC_SAVE_AREA+32
+	SAVE_ALL_ASYNC __LC_EXT_OLD_PSW,__LC_SAVE_AREA+40
+	CREATE_STACK_FRAME __LC_SAVE_AREA+40
+	mvc	SP_PSW(16,%r15),0(%r12)	# move user PSW to stack
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	SP_PSW+1(%r15),0x01	# interrupting from user ?
 	jz	ext_no_vtime
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_ASYNC_ENTER_TIMER,__LC_USER_TIMER
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_ASYNC_ENTER_TIMER
+	LAST_BREAK
 ext_no_vtime:
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
 	HANDLE_SIE_INTERCEPT
 	TRACE_IRQS_OFF
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
···
 	la	%r1,4095		# revalidate r1
 	spt	__LC_CPU_TIMER_SAVE_AREA-4095(%r1)	# revalidate cpu timer
 	lmg	%r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)# revalidate gprs
-	SAVE_ALL_BASE __LC_SAVE_AREA+64
+	stmg	%r11,%r15,__LC_SAVE_AREA+80
+	larl	%r13,system_call
+	lg	%r11,__LC_LAST_BREAK
 	la	%r12,__LC_MCK_OLD_PSW
 	tm	__LC_MCCK_CODE,0x80	# system damage?
 	jo	mcck_int_main		# yes -> rest of mcck code invalid
···
 	srag	%r14,%r14,PAGE_SHIFT
 	jz	0f
 	lg	%r15,__LC_PANIC_STACK	# load panic stack
-0:	CREATE_STACK_FRAME __LC_MCK_OLD_PSW,__LC_SAVE_AREA+64
+0:	aghi	%r15,-SP_SIZE		# make room for registers & psw
+	CREATE_STACK_FRAME __LC_SAVE_AREA+80
+	mvc	SP_PSW(16,%r15),0(%r12)
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	__LC_MCCK_CODE+2,0x08	# mwp of old psw valid?
 	jno	mcck_no_vtime		# no -> no timer update
 	tm	SP_PSW+1(%r15),0x01	# interrupting from user ?
···
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_MCCK_ENTER_TIMER,__LC_USER_TIMER
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_MCCK_ENTER_TIMER
+	LAST_BREAK
 mcck_no_vtime:
-	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	brasl	%r14,s390_do_machine_check
 	tm	SP_PSW+1(%r15),0x01	# returning to user ?
···
 	xc	__SF_BACKCHAIN(8,%r1),__SF_BACKCHAIN(%r1) # clear back chain
 	lgr	%r15,%r1
 	stosm	__SF_EMPTY(%r15),0x04	# turn dat on
-	tm	__TI_flags+7(%r9),_TIF_MCCK_PENDING
+	tm	__TI_flags+7(%r12),_TIF_MCCK_PENDING
 	jno	mcck_return
 	HANDLE_SIE_INTERCEPT
 	TRACE_IRQS_OFF
···
 	jno	0f
 	stpt	__LC_EXIT_TIMER
 0:	lpswe	__LC_RETURN_MCCK_PSW	# back to caller
+mcck_done:
 
 /*
  * Restart interruption handler, kick starter for additional CPUs
···
 	lg	%r15,__LC_PANIC_STACK	# change to panic stack
 	aghi	%r15,-SP_SIZE
 	mvc	SP_PSW(16,%r15),0(%r12)	# move user PSW to stack
-	stmg	%r0,%r11,SP_R0(%r15)	# store gprs %r0-%r11 to kernel stack
+	stmg	%r0,%r10,SP_R0(%r15)	# store gprs %r0-%r10 to kernel stack
 	la	%r1,__LC_SAVE_AREA
 	chi	%r12,__LC_SVC_OLD_PSW
 	je	0f
 	chi	%r12,__LC_PGM_OLD_PSW
 	je	0f
-	la	%r1,__LC_SAVE_AREA+32
-0:	mvc	SP_R12(32,%r15),0(%r1)	# move %r12-%r15 to stack
+	la	%r1,__LC_SAVE_AREA+40
+0:	mvc	SP_R11(40,%r15),0(%r1)	# move %r11-%r15 to stack
 	mvc	SP_ARGS(8,%r15),__LC_LAST_BREAK
 	xc	__SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15) # clear back chain
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
···
 	je	0f
 	mvc	__LC_SYNC_ENTER_TIMER(8),__LC_ASYNC_ENTER_TIMER
 0:	cghi	%r12,__LC_MCK_OLD_PSW
-	la	%r12,__LC_SAVE_AREA+64
+	la	%r12,__LC_SAVE_AREA+80
 	je	0f
-	la	%r12,__LC_SAVE_AREA+32
+	la	%r12,__LC_SAVE_AREA+40
 0:	clc	__LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn+16)
 	jhe	cleanup_vtime
 	clc	__LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn)
 	jh	0f
-	mvc	__LC_SAVE_AREA(32),0(%r12)
-0:	stg	%r13,8(%r12)
-	stg	%r12,__LC_SAVE_AREA+96	# argh
-	SAVE_ALL_SYNC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
-	CREATE_STACK_FRAME __LC_SVC_OLD_PSW,__LC_SAVE_AREA
-	lg	%r12,__LC_SAVE_AREA+96	# argh
-	stg	%r15,24(%r12)
-	llgh	%r7,__LC_SVC_INT_CODE
+	mvc	__LC_SAVE_AREA(40),0(%r12)
+0:	lg	%r15,__LC_KERNEL_STACK	# problem state -> load ksp
+	aghi	%r15,-SP_SIZE		# make room for registers & psw
+	stg	%r15,32(%r12)
+	stg	%r11,0(%r12)
+	CREATE_STACK_FRAME __LC_SAVE_AREA
+	mvc	SP_PSW(16,%r15),__LC_SVC_OLD_PSW
+	mvc	SP_ILC(4,%r15),__LC_SVC_ILC
+	stg	%r7,SP_ARGS(%r15)
+	mvc	8(8,%r12),__LC_THREAD_INFO
 cleanup_vtime:
 	clc	__LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn+24)
 	jhe	cleanup_stime
···
 	UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
 cleanup_update:
 	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
-	mvc	__LC_RETURN_PSW+8(8),BASED(cleanup_table_system_call+8)
+	srag	%r12,%r11,23
+	lg	%r12,__LC_THREAD_INFO
+	jz	0f
+	stg	%r11,__TI_last_break(%r12)
+0:	mvc	__LC_RETURN_PSW+8(8),BASED(cleanup_table_system_call+8)
 	la	%r12,__LC_RETURN_PSW
 	br	%r14
 cleanup_system_call_insn:
···
 	mvc	__LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
 0:	mvc	__LC_RETURN_PSW(16),SP_PSW(%r15)
 	cghi	%r12,__LC_MCK_OLD_PSW
-	la	%r12,__LC_SAVE_AREA+64
+	la	%r12,__LC_SAVE_AREA+80
 	je	1f
-	la	%r12,__LC_SAVE_AREA+32
-1:	mvc	0(32,%r12),SP_R12(%r15)
-	lmg	%r0,%r11,SP_R0(%r15)
+	la	%r12,__LC_SAVE_AREA+40
+1:	mvc	0(40,%r12),SP_R11(%r15)
+	lmg	%r0,%r10,SP_R0(%r15)
 	lg	%r15,SP_R15(%r15)
 2:	la	%r12,__LC_RETURN_PSW
 	br	%r14
···
 	jhe	0f
 	mvc	__LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
 0:	mvc	__LC_RETURN_PSW(16),SP_PSW(%r15)
-	mvc	__LC_SAVE_AREA+64(32),SP_R12(%r15)
-	lmg	%r0,%r11,SP_R0(%r15)
+	mvc	__LC_SAVE_AREA+80(40),SP_R11(%r15)
+	lmg	%r0,%r10,SP_R0(%r15)
 	lg	%r15,SP_R15(%r15)
 1:	la	%r12,__LC_RETURN_PSW
 	br	%r14
···
  * Integer constants
  */
 		.align	4
-.Lconst:
-.Lnr_syscalls:	.long	NR_syscalls
-.L0x0130:	.short	0x130
-.L0x0140:	.short	0x140
-.L0x0150:	.short	0x150
-.L0x0160:	.short	0x160
-.L0x0170:	.short	0x170
 .Lcritical_start:
 		.quad	__critical_start
 .Lcritical_end:

arch/s390/kernel/ptrace.c

···
 enum s390_regset {
 	REGSET_GENERAL,
 	REGSET_FP,
+	REGSET_LAST_BREAK,
 	REGSET_GENERAL_EXTENDED,
 };
 
···
 			copied += sizeof(unsigned long);
 		}
 		return 0;
+	case PTRACE_GET_LAST_BREAK:
+		put_user(task_thread_info(child)->last_break,
+			 (unsigned long __user *) data);
+		return 0;
 	default:
 		/* Removing high order bit from addr (only for 31 bit). */
 		addr &= PSW_ADDR_INSN;
···
 			copied += sizeof(unsigned int);
 		}
 		return 0;
+	case PTRACE_GET_LAST_BREAK:
+		put_user(task_thread_info(child)->last_break,
+			 (unsigned int __user *) data);
+		return 0;
 	}
 	return compat_ptrace_request(child, request, addr, data);
 }
···
 	return rc;
 }
 
+#ifdef CONFIG_64BIT
+
+static int s390_last_break_get(struct task_struct *target,
+			       const struct user_regset *regset,
+			       unsigned int pos, unsigned int count,
+			       void *kbuf, void __user *ubuf)
+{
+	if (count > 0) {
+		if (kbuf) {
+			unsigned long *k = kbuf;
+			*k = task_thread_info(target)->last_break;
+		} else {
+			unsigned long  __user *u = ubuf;
+			if (__put_user(task_thread_info(target)->last_break, u))
+				return -EFAULT;
+		}
+	}
+	return 0;
+}
+
+#endif
+
 static const struct user_regset s390_regsets[] = {
 	[REGSET_GENERAL] = {
 		.core_note_type = NT_PRSTATUS,
···
 		.get = s390_fpregs_get,
 		.set = s390_fpregs_set,
 	},
+#ifdef CONFIG_64BIT
+	[REGSET_LAST_BREAK] = {
+		.core_note_type = NT_S390_LAST_BREAK,
+		.n = 1,
+		.size = sizeof(long),
+		.align = sizeof(long),
+		.get = s390_last_break_get,
+	},
+#endif
 };
 
 static const struct user_regset_view user_s390_view = {
···
 	return rc;
 }
 
+static int s390_compat_last_break_get(struct task_struct *target,
+				      const struct user_regset *regset,
+				      unsigned int pos, unsigned int count,
+				      void *kbuf, void __user *ubuf)
+{
+	compat_ulong_t last_break;
+
+	if (count > 0) {
+		last_break = task_thread_info(target)->last_break;
+		if (kbuf) {
+			unsigned long *k = kbuf;
+			*k = last_break;
+		} else {
+			unsigned long  __user *u = ubuf;
+			if (__put_user(last_break, u))
+				return -EFAULT;
+		}
+	}
+	return 0;
+}
+
 static const struct user_regset s390_compat_regsets[] = {
 	[REGSET_GENERAL] = {
 		.core_note_type = NT_PRSTATUS,
···
 		.align = sizeof(compat_long_t),
 		.get = s390_fpregs_get,
 		.set = s390_fpregs_set,
+	},
+	[REGSET_LAST_BREAK] = {
+		.core_note_type = NT_S390_LAST_BREAK,
+		.n = 1,
+		.size = sizeof(long),
+		.align = sizeof(long),
+		.get = s390_compat_last_break_get,
 	},
 	[REGSET_GENERAL_EXTENDED] = {
 		.core_note_type = NT_S390_HIGH_GPRS,

arch/s390/kernel/signal.c

···
 	   To avoid breaking binary compatibility, they are passed as args. */
 	regs->gprs[4] = current->thread.trap_no;
 	regs->gprs[5] = current->thread.prot_addr;
+	regs->gprs[6] = task_thread_info(current)->last_break;
 
 	/* Place signal number on stack to allow backtrace from handler.  */
 	if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
···
 	regs->gprs[2] = map_signal(sig);
 	regs->gprs[3] = (unsigned long) &frame->info;
 	regs->gprs[4] = (unsigned long) &frame->uc;
+	regs->gprs[5] = task_thread_info(current)->last_break;
 	return 0;
 
 give_sigsegv:

include/linux/elf.h

···
 #define NT_S390_TODPREG	0x303		/* s390 TOD programmable register */
 #define NT_S390_CTRS	0x304		/* s390 control registers */
 #define NT_S390_PREFIX	0x305		/* s390 prefix register */
+#define NT_S390_LAST_BREAK	0x306	/* s390 breaking event address */
 
 
 /* Note header in a PT_NOTE section */