10 files changed, 142 insertions, 91 deletions

diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h
index 62fd80c9e98c..93c907b4776f 100644
--- a/arch/s390/include/asm/ptrace.h
+++ b/arch/s390/include/asm/ptrace.h
@@ -328,8 +328,7 @@ struct pt_regs
         psw_t psw;
         unsigned long gprs[NUM_GPRS];
         unsigned long orig_gpr2;
-        unsigned short ilc;
-        unsigned short svcnr;
+        unsigned int svc_code;
 };
 
 /*
@@ -487,6 +486,8 @@ typedef struct
 #define PTRACE_POKETEXT_AREA          0x5004
 #define PTRACE_POKEDATA_AREA          0x5005
 #define PTRACE_GET_LAST_BREAK         0x5006
+#define PTRACE_PEEK_SYSTEM_CALL       0x5007
+#define PTRACE_POKE_SYSTEM_CALL       0x5008
 
 /*
  * PT_PROT definition is loosely based on hppa bsd definition in
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index 5c0246b955d8..614267f60713 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -13,6 +13,7 @@
 #define _ASM_SYSCALL_H  1
 
 #include <linux/sched.h>
+#include <linux/err.h>
 #include <asm/ptrace.h>
 
 /*
@@ -25,7 +26,7 @@ extern const unsigned int sys_call_table[];
 static inline long syscall_get_nr(struct task_struct *task,
                                   struct pt_regs *regs)
 {
-        return regs->svcnr ? regs->svcnr : -1;
+        return regs->svc_code ? (regs->svc_code & 0xffff) : -1;
 }
 
 static inline void syscall_rollback(struct task_struct *task,
@@ -37,7 +38,7 @@ static inline void syscall_rollback(struct task_struct *task,
 static inline long syscall_get_error(struct task_struct *task,
                                      struct pt_regs *regs)
 {
-        return (regs->gprs[2] >= -4096UL) ? -regs->gprs[2] : 0;
+        return IS_ERR_VALUE(regs->gprs[2]) ? regs->gprs[2] : 0;
 }
 
 static inline long syscall_get_return_value(struct task_struct *task,
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index f9a9a10979c9..0c4788eb5a65 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -48,6 +48,7 @@ struct thread_info {
         unsigned int            cpu;            /* current CPU */
         int                     preempt_count;  /* 0 => preemptable, <0 => BUG */
         struct restart_block    restart_block;
+        unsigned int            system_call;
         __u64                   user_timer;
         __u64                   system_timer;
         unsigned long           last_break;     /* last breaking-event-address. */
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index 1140035b1cd8..751318765e2e 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -45,8 +45,7 @@ int main(void)
         DEFINE(__PT_PSW, offsetof(struct pt_regs, psw));
         DEFINE(__PT_GPRS, offsetof(struct pt_regs, gprs));
         DEFINE(__PT_ORIG_GPR2, offsetof(struct pt_regs, orig_gpr2));
-        DEFINE(__PT_ILC, offsetof(struct pt_regs, ilc));
-        DEFINE(__PT_SVCNR, offsetof(struct pt_regs, svcnr));
+        DEFINE(__PT_SVC_CODE, offsetof(struct pt_regs, svc_code));
         DEFINE(__PT_SIZE, sizeof(struct pt_regs));
         BLANK();
         DEFINE(__SF_BACKCHAIN, offsetof(struct stack_frame, back_chain));
diff --git a/arch/s390/kernel/compat_signal.c b/arch/s390/kernel/compat_signal.c
index a9a285b8c4ad..d7c8e54c32e7 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->svcnr = 0;        /* disable syscall checks */
+        regs->svc_code = 0;     /* disable syscall checks */
         return 0;
 }
 
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 195387ab7c98..afe3685d30e7 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -43,8 +43,7 @@ SP_R13	     =	STACK_FRAME_OVERHEAD + __PT_GPRS + 52
 SP_R14       =  STACK_FRAME_OVERHEAD + __PT_GPRS + 56
 SP_R15       =  STACK_FRAME_OVERHEAD + __PT_GPRS + 60
 SP_ORIG_R2   =  STACK_FRAME_OVERHEAD + __PT_ORIG_GPR2
-SP_ILC       =  STACK_FRAME_OVERHEAD + __PT_ILC
-SP_SVCNR     =  STACK_FRAME_OVERHEAD + __PT_SVCNR
+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 | \
@@ -229,7 +228,7 @@ sysc_saveall:
         SAVE_ALL_SVC __LC_SVC_OLD_PSW,__LC_SAVE_AREA
         CREATE_STACK_FRAME __LC_SAVE_AREA
         mvc     SP_PSW(8,%r15),__LC_SVC_OLD_PSW
-        mvc     SP_ILC(4,%r15),__LC_SVC_ILC
+        mvc     SP_SVC_CODE(4,%r15),__LC_SVC_ILC
         l       %r12,__LC_THREAD_INFO   # load pointer to thread_info struct
 sysc_vtime:
         UPDATE_VTIME __LC_EXIT_TIMER,__LC_SYNC_ENTER_TIMER,__LC_USER_TIMER
@@ -239,12 +238,12 @@ sysc_update:
         mvc     __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
 sysc_do_svc:
         xr      %r7,%r7
-        icm     %r7,3,SP_SVCNR(%r15)    # load svc number and test for svc 0
+        icm     %r7,3,SP_SVC_CODE+2(%r15)# load svc number and test for svc 0
         bnz     BASED(sysc_nr_ok)       # svc number > 0
         # svc 0: system call number in %r1
         cl      %r1,BASED(.Lnr_syscalls)
         bnl     BASED(sysc_nr_ok)
-        sth     %r1,SP_SVCNR(%r15)
+        sth     %r1,SP_SVC_CODE+2(%r15)
         lr      %r7,%r1           # copy svc number to %r7
 sysc_nr_ok:
         sll     %r7,2             # svc number *4
@@ -335,10 +334,11 @@ sysc_notify_resume:
 #
 sysc_restart:
         ni      __TI_flags+3(%r12),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
-        l       %r7,SP_R2(%r15)         # load new svc number
-        mvc     SP_R2(4,%r15),SP_ORIG_R2(%r15) # restore first argument
         lm      %r2,%r6,SP_R2(%r15)     # load svc arguments
-        sth     %r7,SP_SVCNR(%r15)
+        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
 
 #
@@ -346,7 +346,7 @@ sysc_restart:
 #
 sysc_singlestep:
         ni      __TI_flags+3(%r12),255-_TIF_PER_TRAP # clear TIF_PER_TRAP
-        xc      SP_SVCNR(2,%r15),SP_SVCNR(%r15)         # clear svc number
+        xc      SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)   # clear svc code
         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
@@ -361,7 +361,7 @@ sysc_tracesys:
         la      %r2,SP_PTREGS(%r15)     # load pt_regs
         la      %r3,0
         xr      %r0,%r0
-        icm     %r0,3,SP_SVCNR(%r15)
+        icm     %r0,3,SP_SVC_CODE(%r15)
         st      %r0,SP_R2(%r15)
         basr    %r14,%r1
         cl      %r2,BASED(.Lnr_syscalls)
@@ -454,7 +454,7 @@ 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_ILC(4,%r15),SP_ILC(%r15)
+        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 ?
@@ -531,7 +531,7 @@ pgm_svcper:
         SAVE_ALL_PGM __LC_SVC_OLD_PSW,__LC_SAVE_AREA
         CREATE_STACK_FRAME __LC_SAVE_AREA
         mvc     SP_PSW(8,%r15),__LC_SVC_OLD_PSW
-        mvc     SP_ILC(4,%r15),__LC_SVC_ILC
+        mvc     SP_SVC_CODE(4,%r15),__LC_SVC_ILC
         l       %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
@@ -550,7 +550,7 @@ pgm_svcper:
 #
 kernel_per:
         REENABLE_IRQS
-        xc      SP_SVCNR(2,%r15),SP_SVCNR(%r15)
+        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
@@ -966,7 +966,7 @@ cleanup_system_call:
         st      %r15,12(%r12)
         CREATE_STACK_FRAME __LC_SAVE_AREA
         mvc     SP_PSW(8,%r15),__LC_SVC_OLD_PSW
-        mvc     SP_ILC(4,%r15),__LC_SVC_ILC
+        mvc     SP_SVC_CODE(4,%r15),__LC_SVC_ILC
         mvc     0(4,%r12),__LC_THREAD_INFO
 cleanup_vtime:
         clc     __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn+12)
diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 3257f7f55551..7ff07d3a29c1 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -43,8 +43,7 @@ SP_R13	     =	STACK_FRAME_OVERHEAD + __PT_GPRS + 104
 SP_R14       =  STACK_FRAME_OVERHEAD + __PT_GPRS + 112
 SP_R15       =  STACK_FRAME_OVERHEAD + __PT_GPRS + 120
 SP_ORIG_R2   =  STACK_FRAME_OVERHEAD + __PT_ORIG_GPR2
-SP_ILC       =  STACK_FRAME_OVERHEAD + __PT_ILC
-SP_SVCNR      = STACK_FRAME_OVERHEAD + __PT_SVCNR
+SP_SVC_CODE  =  STACK_FRAME_OVERHEAD + __PT_SVC_CODE
 SP_SIZE      =  STACK_FRAME_OVERHEAD + __PT_SIZE
 
 STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
@@ -250,7 +249,7 @@ sysc_saveall:
         SAVE_ALL_SVC __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
+        mvc     SP_SVC_CODE(4,%r15),__LC_SVC_ILC
         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
@@ -260,14 +259,14 @@ sysc_update:
         mvc     __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
         LAST_BREAK
 sysc_do_svc:
-        llgh    %r7,SP_SVCNR(%r15)
+        llgh    %r7,SP_SVC_CODE+2(%r15)
         slag    %r7,%r7,2       # shift and test for svc 0
         jnz     sysc_nr_ok
         # svc 0: system call number in %r1
         llgfr   %r1,%r1         # clear high word in r1
         cghi    %r1,NR_syscalls
         jnl     sysc_nr_ok
-        sth     %r1,SP_SVCNR(%r15)
+        sth     %r1,SP_SVC_CODE+2(%r15)
         slag    %r7,%r1,2       # shift and test for svc 0
 sysc_nr_ok:
         larl    %r10,sys_call_table
@@ -358,11 +357,12 @@ sysc_notify_resume:
 #
 sysc_restart:
         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
-        sth     %r7,SP_SVCNR(%r15)
-        slag    %r7,%r7,2
+        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
 
 #
@@ -370,7 +370,7 @@ sysc_restart:
 #
 sysc_singlestep:
         ni      __TI_flags+7(%r12),255-_TIF_PER_TRAP    # clear TIF_PER_TRAP
-        xc      SP_SVCNR(2,%r15),SP_SVCNR(%r15)         # clear svc number
+        xc      SP_SVC_CODE(4,%r15),SP_SVC_CODE(%r15)   # clear svc code
         la      %r2,SP_PTREGS(%r15)     # address of register-save area
         larl    %r14,sysc_return        # load adr. of system return
         jg      do_per_trap
@@ -382,7 +382,7 @@ sysc_singlestep:
 sysc_tracesys:
         la      %r2,SP_PTREGS(%r15)     # load pt_regs
         la      %r3,0
-        llgh    %r0,SP_SVCNR(%r15)
+        llgh    %r0,SP_SVC_CODE+2(%r15)
         stg     %r0,SP_R2(%r15)
         brasl   %r14,do_syscall_trace_enter
         lghi    %r0,NR_syscalls
@@ -470,7 +470,7 @@ 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_ILC(4,%r15),SP_ILC(%r15)
+        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
@@ -551,7 +551,7 @@ pgm_svcper:
         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
+        mvc     SP_SVC_CODE(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
@@ -571,7 +571,7 @@ pgm_svcper:
 #
 kernel_per:
         REENABLE_IRQS
-        xc      SP_SVCNR(2,%r15),SP_SVCNR(%r15) # clear svc number
+        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
@@ -973,7 +973,7 @@ cleanup_system_call:
         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
+        mvc     SP_SVC_CODE(4,%r15),__LC_SVC_ILC
         mvc     8(8,%r12),__LC_THREAD_INFO
 cleanup_vtime:
         clc     __LC_RETURN_PSW+8(8),BASED(cleanup_system_call_insn+24)
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index ae0e14b8880c..bae1cc49fe96 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -42,6 +42,7 @@ enum s390_regset {
         REGSET_GENERAL,
         REGSET_FP,
         REGSET_LAST_BREAK,
+        REGSET_SYSTEM_CALL,
         REGSET_GENERAL_EXTENDED,
 };
 
@@ -303,6 +304,13 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
                            high order bit but older gdb's rely on it */
                         data |= PSW_ADDR_AMODE;
 #endif
+                if (addr == (addr_t) &dummy->regs.psw.addr)
+                        /*
+                         * The debugger changed the instruction address,
+                         * reset system call restart, see signal.c:do_signal
+                         */
+                        task_thread_info(child)->system_call = 0;
+
                 *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr) = data;
 
         } else if (addr < (addr_t) (&dummy->regs.orig_gpr2)) {
@@ -610,6 +618,11 @@ static int __poke_user_compat(struct task_struct *child,
                         /* Build a 64 bit psw address from 31 bit address. */
                         task_pt_regs(child)->psw.addr =
                                 (__u64) tmp & PSW32_ADDR_INSN;
+                        /*
+                         * The debugger changed the instruction address,
+                         * reset system call restart, see signal.c:do_signal
+                         */
+                        task_thread_info(child)->system_call = 0;
                 } else {
                         /* gpr 0-15 */
                         *(__u32*)((addr_t) &task_pt_regs(child)->psw
@@ -737,7 +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->svcnr = 0;
+                regs->svc_code = 0;
                 ret = -1;
         }
 
@@ -899,6 +912,26 @@ static int s390_last_break_get(struct task_struct *target,
 
 #endif
 
+static int s390_system_call_get(struct task_struct *target,
+                                const struct user_regset *regset,
+                                unsigned int pos, unsigned int count,
+                                void *kbuf, void __user *ubuf)
+{
+        unsigned int *data = &task_thread_info(target)->system_call;
+        return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                   data, 0, sizeof(unsigned int));
+}
+
+static int s390_system_call_set(struct task_struct *target,
+                                const struct user_regset *regset,
+                                unsigned int pos, unsigned int count,
+                                const void *kbuf, const void __user *ubuf)
+{
+        unsigned int *data = &task_thread_info(target)->system_call;
+        return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+                                  data, 0, sizeof(unsigned int));
+}
+
 static const struct user_regset s390_regsets[] = {
         [REGSET_GENERAL] = {
                 .core_note_type = NT_PRSTATUS,
@@ -925,6 +958,14 @@ static const struct user_regset s390_regsets[] = {
                 .get = s390_last_break_get,
         },
 #endif
+        [REGSET_SYSTEM_CALL] = {
+                .core_note_type = NT_S390_SYSTEM_CALL,
+                .n = 1,
+                .size = sizeof(unsigned int),
+                .align = sizeof(unsigned int),
+                .get = s390_system_call_get,
+                .set = s390_system_call_set,
+        },
 };
 
 static const struct user_regset_view user_s390_view = {
@@ -1104,6 +1145,14 @@ static const struct user_regset s390_compat_regsets[] = {
                 .align = sizeof(long),
                 .get = s390_compat_last_break_get,
         },
+        [REGSET_SYSTEM_CALL] = {
+                .core_note_type = NT_S390_SYSTEM_CALL,
+                .n = 1,
+                .size = sizeof(compat_uint_t),
+                .align = sizeof(compat_uint_t),
+                .get = s390_system_call_get,
+                .set = s390_system_call_set,
+        },
         [REGSET_GENERAL_EXTENDED] = {
                 .core_note_type = NT_S390_HIGH_GPRS,
                 .n = sizeof(s390_compat_regs_high) / sizeof(compat_long_t),
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 9a40e1cc5ec3..e751cab80e04 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -30,6 +30,7 @@
 #include <asm/ucontext.h>
 #include <asm/uaccess.h>
 #include <asm/lowcore.h>
+#include <asm/compat.h>
 #include "entry.h"
 
 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
@@ -156,7 +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->svcnr = 0;        /* disable syscall checks */
+        regs->svc_code = 0;     /* disable syscall checks */
         return 0;
 }
 
@@ -401,7 +402,6 @@ static int handle_signal(unsigned long sig, struct k_sigaction *ka,
  */
 void do_signal(struct pt_regs *regs)
 {
-        unsigned long retval = 0, continue_addr = 0, restart_addr = 0;
         siginfo_t info;
         int signr;
         struct k_sigaction ka;
@@ -421,54 +421,43 @@ void do_signal(struct pt_regs *regs)
         else
                 oldset = &current->blocked;
 
-        /* Are we from a system call? */
-        if (regs->svcnr) {
-                continue_addr = regs->psw.addr;
-                restart_addr = continue_addr - regs->ilc;
-                retval = regs->gprs[2];
-
-                /* Prepare for system call restart.  We do this here so that a
-                   debugger will see the already changed PSW. */
-                switch (retval) {
-                case -ERESTARTNOHAND:
-                case -ERESTARTSYS:
-                case -ERESTARTNOINTR:
-                        regs->gprs[2] = regs->orig_gpr2;
-                        regs->psw.addr = restart_addr;
-                        break;
-                case -ERESTART_RESTARTBLOCK:
-                        regs->gprs[2] = -EINTR;
-                }
-                regs->svcnr = 0;        /* Don't deal with this again. */
-        }
-
-        /* Get signal to deliver.  When running under ptrace, at this point
-           the debugger may change all our registers ... */
+        /*
+         * Get signal to deliver. When running under ptrace, at this point
+         * the debugger may change all our registers, including the system
+         * call information.
+         */
+        current_thread_info()->system_call = regs->svc_code;
         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
-
-        /* Depending on the signal settings we may need to revert the
-           decision to restart the system call. */
-        if (signr > 0 && regs->psw.addr == restart_addr) {
-                if (retval == -ERESTARTNOHAND
-                    || (retval == -ERESTARTSYS
-                         && !(current->sighand->action[signr-1].sa.sa_flags
-                              & SA_RESTART))) {
-                        regs->gprs[2] = -EINTR;
-                        regs->psw.addr = continue_addr;
-                }
-        }
+        regs->svc_code = current_thread_info()->system_call;
 
         if (signr > 0) {
                 /* Whee!  Actually deliver the signal.  */
-                int ret;
-#ifdef CONFIG_COMPAT
-                if (is_compat_task()) {
-                        ret = handle_signal32(signr, &ka, &info, oldset, regs);
-                }
-                else
-#endif
-                        ret = handle_signal(signr, &ka, &info, oldset, regs);
-                if (!ret) {
+                if (regs->svc_code > 0) {
+                        /* Check for system call restarting. */
+                        switch (regs->gprs[2]) {
+                        case -ERESTART_RESTARTBLOCK:
+                        case -ERESTARTNOHAND:
+                                regs->gprs[2] = -EINTR;
+                                break;
+                        case -ERESTARTSYS:
+                                if (!(ka.sa.sa_flags & SA_RESTART)) {
+                                        regs->gprs[2] = -EINTR;
+                                        break;
+                                }
+                        /* fallthrough */
+                        case -ERESTARTNOINTR:
+                                regs->gprs[2] = regs->orig_gpr2;
+                                regs->psw.addr = regs->psw.addr -
+                                        (regs->svc_code >> 16);
+                                break;
+                        }
+                        /* No longer in a system call */
+                        regs->svc_code = 0;
+                }
+
+                if ((is_compat_task() ?
+                     handle_signal32(signr, &ka, &info, oldset, regs) :
+                     handle_signal(signr, &ka, &info, oldset, regs)) == 0) {
                         /*
                          * A signal was successfully delivered; the saved
                          * sigmask will have been stored in the signal frame,
@@ -482,11 +471,28 @@ void do_signal(struct pt_regs *regs)
                          * Let tracing know that we've done the handler setup.
                          */
                         tracehook_signal_handler(signr, &info, &ka, regs,
-                                        test_thread_flag(TIF_SINGLE_STEP));
+                                         test_thread_flag(TIF_SINGLE_STEP));
                 }
                 return;
         }
 
+        /* No handlers present - check for system call restart */
+        if (regs->svc_code > 0) {
+                switch (regs->gprs[2]) {
+                case -ERESTART_RESTARTBLOCK:
+                        /* Restart with sys_restart_syscall */
+                        regs->svc_code = __NR_restart_syscall;
+                /* fallthrough */
+                case -ERESTARTNOHAND:
+                case -ERESTARTSYS:
+                case -ERESTARTNOINTR:
+                        /* Restart system call with magic TIF bit. */
+                        regs->gprs[2] = regs->orig_gpr2;
+                        set_thread_flag(TIF_RESTART_SVC);
+                        break;
+                }
+        }
+
         /*
          * If there's no signal to deliver, we just put the saved sigmask back.
          */
@@ -494,13 +500,6 @@ void do_signal(struct pt_regs *regs)
                 clear_thread_flag(TIF_RESTORE_SIGMASK);
                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
         }
-
-        /* Restart a different system call. */
-        if (retval == -ERESTART_RESTARTBLOCK
-            && regs->psw.addr == continue_addr) {
-                regs->gprs[2] = __NR_restart_syscall;
-                set_thread_flag(TIF_RESTART_SVC);
-        }
 }
 
 void do_notify_resume(struct pt_regs *regs)
diff --git a/include/linux/elf.h b/include/linux/elf.h
index 110821cb6ea5..31f0508d7da7 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -395,6 +395,7 @@ typedef struct elf64_shdr {
 #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 */
+#define NT_S390_SYSTEM_CALL     0x307   /* s390 system call restart data */
 #define NT_ARM_VFP      0x400           /* ARM VFP/NEON registers */