[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>

7 files changed, 69 insertions, 94 deletions

diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index 614267f60713..b239ff53b189 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -26,7 +26,8 @@ extern const unsigned int sys_call_table[];
 static inline long syscall_get_nr(struct task_struct *task,
                                   struct pt_regs *regs)
 {
-        return regs->svc_code ? (regs->svc_code & 0xffff) : -1;
+        return test_tsk_thread_flag(task, TIF_SYSCALL) ?
+                (regs->svc_code & 0xffff) : -1;
 }
 
 static inline void syscall_rollback(struct task_struct *task,
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index 0c4788eb5a65..a23183423b14 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -85,10 +85,10 @@ static inline struct thread_info *current_thread_info(void)
 /*
  * thread information flags bit numbers
  */
+#define TIF_SYSCALL             0       /* inside a system call */
 #define TIF_NOTIFY_RESUME       1       /* callback before returning to user */
 #define TIF_SIGPENDING          2       /* signal pending */
 #define TIF_NEED_RESCHED        3       /* rescheduling necessary */
-#define TIF_RESTART_SVC         4       /* restart svc with new svc number */
 #define TIF_PER_TRAP            6       /* deliver sigtrap on return to user */
 #define TIF_MCCK_PENDING        7       /* machine check handling is pending */
 #define TIF_SYSCALL_TRACE       8       /* syscall trace active */
@@ -104,11 +104,11 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_SINGLE_STEP         20      /* This task is single stepped */
 #define TIF_FREEZE              21      /* thread is freezing for suspend */
 
+#define _TIF_SYSCALL            (1<<TIF_SYSCALL)
 #define _TIF_NOTIFY_RESUME      (1<<TIF_NOTIFY_RESUME)
 #define _TIF_RESTORE_SIGMASK    (1<<TIF_RESTORE_SIGMASK)
 #define _TIF_SIGPENDING         (1<<TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED       (1<<TIF_NEED_RESCHED)
-#define _TIF_RESTART_SVC        (1<<TIF_RESTART_SVC)
 #define _TIF_PER_TRAP           (1<<TIF_PER_TRAP)
 #define _TIF_MCCK_PENDING       (1<<TIF_MCCK_PENDING)
 #define _TIF_SYSCALL_TRACE      (1<<TIF_SYSCALL_TRACE)
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;
                 }
         }