[S390] add TIF_SYSCALL thread flag

Add an explicit TIF_SYSCALL bit that indicates if a task is inside
a system call. The svc_code in the pt_regs structure is now only
valid if TIF_SYSCALL is set. With this definition TIF_RESTART_SVC
can be replaced with TIF_SYSCALL. Overall do_signal is a bit more
readable and it saves a few lines of code.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

5 files changed, 65 insertions, 91 deletions

diff --git a/arch/s390/kernel/compat_signal.c b/arch/s390/kernel/compat_signal.c
index d7c8e54c32e7..72a1c8d8d212 100644
--- a/arch/s390/kernel/compat_signal.c
+++ b/arch/s390/kernel/compat_signal.c
@@ -342,7 +342,7 @@ static int restore_sigregs32(struct pt_regs *regs,_sigregs32 __user *sregs)
 		return err;
 
 	restore_fp_regs(&current->thread.fp_regs);
-	regs->svc_code = 0;	/* disable syscall checks */
+	clear_thread_flag(TIF_SYSCALL);	/* No longer in a system call */
 	return 0;
 }
 
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index afe3685d30e7..b13157057e02 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -47,11 +47,11 @@ SP_SVC_CODE  =	STACK_FRAME_OVERHEAD + __PT_SVC_CODE
 SP_SIZE      =	STACK_FRAME_OVERHEAD + __PT_SIZE
 
 _TIF_WORK_SVC = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
-		 _TIF_MCCK_PENDING | _TIF_RESTART_SVC | _TIF_PER_TRAP )
+		 _TIF_MCCK_PENDING | _TIF_PER_TRAP )
 _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
 		 _TIF_MCCK_PENDING)
-_TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | \
-		_TIF_SECCOMP>>8 | _TIF_SYSCALL_TRACEPOINT>>8)
+_TIF_TRACE    = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
+		 _TIF_SYSCALL_TRACEPOINT)
 
 STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
 STACK_SIZE  = 1 << STACK_SHIFT
@@ -227,9 +227,10 @@ ENTRY(system_call)
 sysc_saveall:
 	SAVE_ALL_SVC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
 	CREATE_STACK_FRAME __LC_SAVE_AREA
+	l	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	mvc	SP_PSW(8,%r15),__LC_SVC_OLD_PSW
 	mvc	SP_SVC_CODE(4,%r15),__LC_SVC_ILC
-	l	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
+	oi	__TI_flags+3(%r12),_TIF_SYSCALL
 sysc_vtime:
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
 sysc_stime:
@@ -248,7 +249,7 @@ sysc_do_svc:
 sysc_nr_ok:
 	sll	%r7,2		  # svc number *4
 	l	%r10,BASED(.Lsysc_table)
-	tm	__TI_flags+2(%r12),_TIF_SYSCALL
+	tm	__TI_flags+2(%r12),_TIF_TRACE >> 8
 	mvc	SP_ARGS(4,%r15),SP_R7(%r15)
 	l	%r8,0(%r7,%r10)	  # get system call addr.
 	bnz	BASED(sysc_tracesys)
@@ -258,23 +259,19 @@ sysc_nr_ok:
 sysc_return:
 	LOCKDEP_SYS_EXIT
 sysc_tif:
+	tm	SP_PSW+1(%r15),0x01	# returning to user ?
+	bno	BASED(sysc_restore)
 	tm	__TI_flags+3(%r12),_TIF_WORK_SVC
 	bnz	BASED(sysc_work)  # there is work to do (signals etc.)
+	ni	__TI_flags+3(%r12),255-_TIF_SYSCALL
 sysc_restore:
 	RESTORE_ALL __LC_RETURN_PSW,1
 sysc_done:
 
 #
-# There is work to do, but first we need to check if we return to userspace.
-#
-sysc_work:
-	tm	SP_PSW+1(%r15),0x01	# returning to user ?
-	bno	BASED(sysc_restore)
-
-#
 # One of the work bits is on. Find out which one.
 #
-sysc_work_tif:
+sysc_work:
 	tm	__TI_flags+3(%r12),_TIF_MCCK_PENDING
 	bo	BASED(sysc_mcck_pending)
 	tm	__TI_flags+3(%r12),_TIF_NEED_RESCHED
@@ -283,8 +280,6 @@ sysc_work_tif:
 	bo	BASED(sysc_sigpending)
 	tm	__TI_flags+3(%r12),_TIF_NOTIFY_RESUME
 	bo	BASED(sysc_notify_resume)
-	tm	__TI_flags+3(%r12),_TIF_RESTART_SVC
-	bo	BASED(sysc_restart)
 	tm	__TI_flags+3(%r12),_TIF_PER_TRAP
 	bo	BASED(sysc_singlestep)
 	b	BASED(sysc_return)	# beware of critical section cleanup
@@ -313,11 +308,14 @@ sysc_sigpending:
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	l	%r1,BASED(.Ldo_signal)
 	basr	%r14,%r1		# call do_signal
-	tm	__TI_flags+3(%r12),_TIF_RESTART_SVC
-	bo	BASED(sysc_restart)
-	tm	__TI_flags+3(%r12),_TIF_PER_TRAP
-	bo	BASED(sysc_singlestep)
-	b	BASED(sysc_return)
+	tm	__TI_flags+3(%r12),_TIF_SYSCALL
+	bno	BASED(sysc_return)
+	lm	%r2,%r6,SP_R2(%r15)	# load svc arguments
+	xr	%r7,%r7			# svc 0 returns -ENOSYS
+	clc	SP_SVC_CODE+2(2,%r15),BASED(.Lnr_syscalls+2)
+	bnl	BASED(sysc_nr_ok)	# invalid svc number -> do svc 0
+	icm	%r7,3,SP_SVC_CODE+2(%r15)# load new svc number
+	b	BASED(sysc_nr_ok)	# restart svc
 
 #
 # _TIF_NOTIFY_RESUME is set, call do_notify_resume
@@ -328,25 +326,11 @@ sysc_notify_resume:
 	la	%r14,BASED(sysc_return)
 	br	%r1			# call do_notify_resume
 
-
-#
-# _TIF_RESTART_SVC is set, set up registers and restart svc
-#
-sysc_restart:
-	ni	__TI_flags+3(%r12),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
-	lm	%r2,%r6,SP_R2(%r15)	# load svc arguments
-	xr	%r7,%r7			# svc 0 returns -ENOSYS
-	clc	SP_SVC_CODE+2(%r15),BASED(.Lnr_syscalls+2)
-	bnl	BASED(sysc_nr_ok)	# invalid svc number -> do svc 0
-	icm	%r7,3,SP_SVC_CODE+2(%r15)# load new svc number
-	b	BASED(sysc_nr_ok)	# restart svc
-
 #
 # _TIF_PER_TRAP is set, call do_per_trap
 #
 sysc_singlestep:
-	ni	__TI_flags+3(%r12),255-_TIF_PER_TRAP # clear TIF_PER_TRAP
-	xc	SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)	# clear svc code
+	ni	__TI_flags+3(%r12),255-(_TIF_SYSCALL | _TIF_PER_TRAP)
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	l	%r1,BASED(.Lhandle_per)	# load adr. of per handler
 	la	%r14,BASED(sysc_return)	# load adr. of system return
@@ -376,7 +360,7 @@ sysc_tracego:
 	basr	%r14,%r8		# call sys_xxx
 	st	%r2,SP_R2(%r15)		# store return value
 sysc_tracenogo:
-	tm	__TI_flags+2(%r12),_TIF_SYSCALL
+	tm	__TI_flags+2(%r12),_TIF_TRACE >> 8
 	bz	BASED(sysc_return)
 	l	%r1,BASED(.Ltrace_exit)
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
@@ -454,7 +438,6 @@ ENTRY(pgm_check_handler)
 	bnz	BASED(pgm_per)		# got per exception -> special case
 	SAVE_ALL_PGM __LC_PGM_OLD_PSW,__LC_SAVE_AREA
 	CREATE_STACK_FRAME __LC_SAVE_AREA
-	xc	SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)
 	mvc	SP_PSW(8,%r15),__LC_PGM_OLD_PSW
 	l	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	tm	SP_PSW+1(%r15),0x01	# interrupting from user ?
@@ -530,9 +513,10 @@ pgm_exit2:
 pgm_svcper:
 	SAVE_ALL_PGM __LC_SVC_OLD_PSW,__LC_SAVE_AREA
 	CREATE_STACK_FRAME __LC_SAVE_AREA
+	l	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	mvc	SP_PSW(8,%r15),__LC_SVC_OLD_PSW
 	mvc	SP_SVC_CODE(4,%r15),__LC_SVC_ILC
-	l	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
+	oi	__TI_flags+3(%r12),(_TIF_SYSCALL | _TIF_PER_TRAP)
 	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
@@ -540,7 +524,6 @@ pgm_svcper:
 	mvc	__THREAD_per_cause(2,%r8),__LC_PER_CAUSE
 	mvc	__THREAD_per_address(4,%r8),__LC_PER_ADDRESS
 	mvc	__THREAD_per_paid(1,%r8),__LC_PER_PAID
-	oi	__TI_flags+3(%r12),_TIF_PER_TRAP # set TIF_PER_TRAP
 	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts
 	lm	%r2,%r6,SP_R2(%r15)	# load svc arguments
 	b	BASED(sysc_do_svc)
@@ -550,7 +533,6 @@ pgm_svcper:
 #
 kernel_per:
 	REENABLE_IRQS
-	xc	SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	l	%r1,BASED(.Lhandle_per)	# load adr. of per handler
 	basr	%r14,%r1		# branch to do_single_step
@@ -965,9 +947,11 @@ cleanup_system_call:
 	s	%r15,BASED(.Lc_spsize)	# make room for registers & psw
 	st	%r15,12(%r12)
 	CREATE_STACK_FRAME __LC_SAVE_AREA
+	mvc	0(4,%r12),__LC_THREAD_INFO
+	l	%r12,__LC_THREAD_INFO
 	mvc	SP_PSW(8,%r15),__LC_SVC_OLD_PSW
 	mvc	SP_SVC_CODE(4,%r15),__LC_SVC_ILC
-	mvc	0(4,%r12),__LC_THREAD_INFO
+	oi	__TI_flags+3(%r12),_TIF_SYSCALL
 cleanup_vtime:
 	clc	__LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn+12)
 	bhe	BASED(cleanup_stime)
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 7ff07d3a29c1..e34907560c23 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -50,11 +50,11 @@ STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
 STACK_SIZE  = 1 << STACK_SHIFT
 
 _TIF_WORK_SVC = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
-		 _TIF_MCCK_PENDING | _TIF_RESTART_SVC | _TIF_PER_TRAP )
+		 _TIF_MCCK_PENDING | _TIF_PER_TRAP )
 _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
 		 _TIF_MCCK_PENDING)
-_TIF_SYSCALL = (_TIF_SYSCALL_TRACE>>8 | _TIF_SYSCALL_AUDIT>>8 | \
-		_TIF_SECCOMP>>8 | _TIF_SYSCALL_TRACEPOINT>>8)
+_TIF_TRACE    = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
+		 _TIF_SYSCALL_TRACEPOINT)
 _TIF_EXIT_SIE = (_TIF_SIGPENDING | _TIF_NEED_RESCHED | _TIF_MCCK_PENDING)
 
 #define BASED(name) name-system_call(%r13)
@@ -248,9 +248,10 @@ ENTRY(system_call)
 sysc_saveall:
 	SAVE_ALL_SVC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
 	CREATE_STACK_FRAME __LC_SAVE_AREA
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	mvc	SP_PSW(16,%r15),__LC_SVC_OLD_PSW
 	mvc	SP_SVC_CODE(4,%r15),__LC_SVC_ILC
-	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
+	oi	__TI_flags+7(%r12),_TIF_SYSCALL
 sysc_vtime:
 	UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
 sysc_stime:
@@ -276,7 +277,7 @@ sysc_nr_ok:
 	larl	%r10,sys_call_table_emu  # use 31 bit emulation system calls
 sysc_noemu:
 #endif
-	tm	__TI_flags+6(%r12),_TIF_SYSCALL
+	tm	__TI_flags+6(%r12),_TIF_TRACE >> 8
 	mvc	SP_ARGS(8,%r15),SP_R7(%r15)
 	lgf	%r8,0(%r7,%r10) # load address of system call routine
 	jnz	sysc_tracesys
@@ -286,23 +287,19 @@ sysc_noemu:
 sysc_return:
 	LOCKDEP_SYS_EXIT
 sysc_tif:
+	tm	SP_PSW+1(%r15),0x01	# returning to user ?
+	jno	sysc_restore
 	tm	__TI_flags+7(%r12),_TIF_WORK_SVC
 	jnz	sysc_work	# there is work to do (signals etc.)
+	ni	__TI_flags+7(%r12),255-_TIF_SYSCALL
 sysc_restore:
 	RESTORE_ALL __LC_RETURN_PSW,1
 sysc_done:
 
 #
-# There is work to do, but first we need to check if we return to userspace.
-#
-sysc_work:
-	tm	SP_PSW+1(%r15),0x01	# returning to user ?
-	jno	sysc_restore
-
-#
 # One of the work bits is on. Find out which one.
 #
-sysc_work_tif:
+sysc_work:
 	tm	__TI_flags+7(%r12),_TIF_MCCK_PENDING
 	jo	sysc_mcck_pending
 	tm	__TI_flags+7(%r12),_TIF_NEED_RESCHED
@@ -311,8 +308,6 @@ sysc_work_tif:
 	jo	sysc_sigpending
 	tm	__TI_flags+7(%r12),_TIF_NOTIFY_RESUME
 	jo	sysc_notify_resume
-	tm	__TI_flags+7(%r12),_TIF_RESTART_SVC
-	jo	sysc_restart
 	tm	__TI_flags+7(%r12),_TIF_PER_TRAP
 	jo	sysc_singlestep
 	j	sysc_return		# beware of critical section cleanup
@@ -338,11 +333,15 @@ sysc_sigpending:
 	ni	__TI_flags+7(%r12),255-_TIF_PER_TRAP # clear TIF_PER_TRAP
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	brasl	%r14,do_signal		# call do_signal
-	tm	__TI_flags+7(%r12),_TIF_RESTART_SVC
-	jo	sysc_restart
-	tm	__TI_flags+7(%r12),_TIF_PER_TRAP
-	jo	sysc_singlestep
-	j	sysc_return
+	tm	__TI_flags+7(%r12),_TIF_SYSCALL
+	jno	sysc_return
+	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
+	lghi	%r7,0			# svc 0 returns -ENOSYS
+	lh	%r1,SP_SVC_CODE+2(%r15)	# load new svc number
+	cghi	%r1,NR_syscalls
+	jnl	sysc_nr_ok		# invalid svc number -> do svc 0
+	slag	%r7,%r1,2
+	j	sysc_nr_ok		# restart svc
 
 #
 # _TIF_NOTIFY_RESUME is set, call do_notify_resume
@@ -353,24 +352,10 @@ sysc_notify_resume:
 	jg	do_notify_resume	# call do_notify_resume
 
 #
-# _TIF_RESTART_SVC is set, set up registers and restart svc
-#
-sysc_restart:
-	ni	__TI_flags+7(%r12),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
-	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
-	lghi	%r7,0			# svc 0 returns -ENOSYS
-	lh	%r1,SP_SVC_CODE+2(%r15)	# load new svc number
-	cghi	%r1,NR_syscalls
-	jnl	sysc_nr_ok		# invalid svc number -> do svc 0
-	slag	%r7,%r1,2
-	j	sysc_nr_ok		# restart svc
-
-#
 # _TIF_PER_TRAP is set, call do_per_trap
 #
 sysc_singlestep:
-	ni	__TI_flags+7(%r12),255-_TIF_PER_TRAP	# clear TIF_PER_TRAP
-	xc	SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)	# clear svc code
+	ni	__TI_flags+7(%r12),255-(_TIF_SYSCALL | _TIF_PER_TRAP)
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	larl	%r14,sysc_return	# load adr. of system return
 	jg	do_per_trap
@@ -397,7 +382,7 @@ sysc_tracego:
 	basr	%r14,%r8		# call sys_xxx
 	stg	%r2,SP_R2(%r15)		# store return value
 sysc_tracenogo:
-	tm	__TI_flags+6(%r12),_TIF_SYSCALL
+	tm	__TI_flags+6(%r12),_TIF_TRACE >> 8
 	jz	sysc_return
 	la	%r2,SP_PTREGS(%r15)	# load pt_regs
 	larl	%r14,sysc_return	# return point is sysc_return
@@ -470,7 +455,6 @@ ENTRY(pgm_check_handler)
 	jnz	pgm_per 		 # got per exception -> special case
 	SAVE_ALL_PGM __LC_PGM_OLD_PSW,__LC_SAVE_AREA
 	CREATE_STACK_FRAME __LC_SAVE_AREA
-	xc	SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)
 	mvc	SP_PSW(16,%r15),__LC_PGM_OLD_PSW
 	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	HANDLE_SIE_INTERCEPT
@@ -550,9 +534,10 @@ pgm_exit2:
 pgm_svcper:
 	SAVE_ALL_PGM __LC_SVC_OLD_PSW,__LC_SAVE_AREA
 	CREATE_STACK_FRAME __LC_SAVE_AREA
+	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
 	mvc	SP_PSW(16,%r15),__LC_SVC_OLD_PSW
 	mvc	SP_SVC_CODE(4,%r15),__LC_SVC_ILC
-	lg	%r12,__LC_THREAD_INFO	# load pointer to thread_info struct
+	oi	__TI_flags+7(%r12),(_TIF_SYSCALL | _TIF_PER_TRAP)
 	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
@@ -561,7 +546,6 @@ pgm_svcper:
 	mvc	__THREAD_per_cause(2,%r8),__LC_PER_CAUSE
 	mvc	__THREAD_per_address(8,%r8),__LC_PER_ADDRESS
 	mvc	__THREAD_per_paid(1,%r8),__LC_PER_PAID
-	oi	__TI_flags+7(%r12),_TIF_PER_TRAP # set TIF_PER_TRAP
 	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts
 	lmg	%r2,%r6,SP_R2(%r15)	# load svc arguments
 	j	sysc_do_svc
@@ -571,7 +555,6 @@ pgm_svcper:
 #
 kernel_per:
 	REENABLE_IRQS
-	xc	SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)	# clear svc number
 	la	%r2,SP_PTREGS(%r15)	# address of register-save area
 	brasl	%r14,do_per_trap
 	j	pgm_exit
@@ -972,9 +955,11 @@ cleanup_system_call:
 	stg	%r15,32(%r12)
 	stg	%r11,0(%r12)
 	CREATE_STACK_FRAME __LC_SAVE_AREA
+	mvc	8(8,%r12),__LC_THREAD_INFO
+	lg	%r12,__LC_THREAD_INFO
 	mvc	SP_PSW(16,%r15),__LC_SVC_OLD_PSW
 	mvc	SP_SVC_CODE(4,%r15),__LC_SVC_ILC
-	mvc	8(8,%r12),__LC_THREAD_INFO
+	oi	__TI_flags+7(%r12),_TIF_SYSCALL
 cleanup_vtime:
 	clc	__LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn+24)
 	jhe	cleanup_stime
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index bae1cc49fe96..3519c99ae0c0 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -750,7 +750,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 		 * debugger stored an invalid system call number. Skip
 		 * the system call and the system call restart handling.
 		 */
-		regs->svc_code = 0;
+		clear_thread_flag(TIF_SYSCALL);
 		ret = -1;
 	}
 
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 058e372bada1..0e905cb7604a 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -157,7 +157,7 @@ static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
 	current->thread.fp_regs.fpc &= FPC_VALID_MASK;
 
 	restore_fp_regs(&current->thread.fp_regs);
-	regs->svc_code = 0;	/* disable syscall checks */
+	clear_thread_flag(TIF_SYSCALL);	/* No longer in a system call */
 	return 0;
 }
 
@@ -426,13 +426,14 @@ void do_signal(struct pt_regs *regs)
 	 * the debugger may change all our registers, including the system
 	 * call information.
 	 */
-	current_thread_info()->system_call = regs->svc_code;
+	current_thread_info()->system_call =
+		test_thread_flag(TIF_SYSCALL) ? regs->svc_code : 0;
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
-	regs->svc_code = current_thread_info()->system_call;
 
 	if (signr > 0) {
 		/* Whee!  Actually deliver the signal.  */
-		if (regs->svc_code > 0) {
+		if (current_thread_info()->system_call) {
+			regs->svc_code = current_thread_info()->system_call;
 			/* Check for system call restarting. */
 			switch (regs->gprs[2]) {
 			case -ERESTART_RESTARTBLOCK:
@@ -453,7 +454,7 @@ void do_signal(struct pt_regs *regs)
 				break;
 			}
 			/* No longer in a system call */
-			regs->svc_code = 0;
+			clear_thread_flag(TIF_SYSCALL);
 		}
 
 		if ((is_compat_task() ?
@@ -478,7 +479,8 @@ void do_signal(struct pt_regs *regs)
 	}
 
 	/* No handlers present - check for system call restart */
-	if (regs->svc_code > 0) {
+	if (current_thread_info()->system_call) {
+		regs->svc_code = current_thread_info()->system_call;
 		switch (regs->gprs[2]) {
 		case -ERESTART_RESTARTBLOCK:
 			/* Restart with sys_restart_syscall */
@@ -489,7 +491,10 @@ void do_signal(struct pt_regs *regs)
 		case -ERESTARTNOINTR:
 			/* Restart system call with magic TIF bit. */
 			regs->gprs[2] = regs->orig_gpr2;
-			set_thread_flag(TIF_RESTART_SVC);
+			set_thread_flag(TIF_SYSCALL);
+			break;
+		default:
+			clear_thread_flag(TIF_SYSCALL);
 			break;
 		}
 	}