3 files changed, 27 insertions, 16 deletions

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 1d81bf9488ae..6e036bae9875 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -86,13 +86,13 @@ FixPerRegisters(struct task_struct *task)
                 per_info->control_regs.bits.storage_alt_space_ctl = 0;
 }
 
-static void set_single_step(struct task_struct *task)
+void user_enable_single_step(struct task_struct *task)
 {
         task->thread.per_info.single_step = 1;
         FixPerRegisters(task);
 }
 
-static void clear_single_step(struct task_struct *task)
+void user_disable_single_step(struct task_struct *task)
 {
         task->thread.per_info.single_step = 0;
         FixPerRegisters(task);
@@ -107,7 +107,7 @@ void
 ptrace_disable(struct task_struct *child)
 {
         /* make sure the single step bit is not set. */
-        clear_single_step(child);
+        user_disable_single_step(child);
 }
 
 #ifndef CONFIG_64BIT
@@ -651,7 +651,7 @@ do_ptrace(struct task_struct *child, long request, long addr, long data)
                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                 child->exit_code = data;
                 /* make sure the single step bit is not set. */
-                clear_single_step(child);
+                user_disable_single_step(child);
                 wake_up_process(child);
                 return 0;
 
@@ -665,7 +665,7 @@ do_ptrace(struct task_struct *child, long request, long addr, long data)
                         return 0;
                 child->exit_code = SIGKILL;
                 /* make sure the single step bit is not set. */
-                clear_single_step(child);
+                user_disable_single_step(child);
                 wake_up_process(child);
                 return 0;
 
@@ -675,10 +675,7 @@ do_ptrace(struct task_struct *child, long request, long addr, long data)
                         return -EIO;
                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                 child->exit_code = data;
-                if (data)
-                        set_tsk_thread_flag(child, TIF_SINGLE_STEP);
-                else
-                        set_single_step(child);
+                user_enable_single_step(child);
                 /* give it a chance to run. */
                 wake_up_process(child);
                 return 0;
diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index d264671c1b71..4449bf32cbf1 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -471,6 +471,7 @@ void do_signal(struct pt_regs *regs)
 
         if (signr > 0) {
                 /* Whee!  Actually deliver the signal.  */
+                int ret;
 #ifdef CONFIG_COMPAT
                 if (test_thread_flag(TIF_31BIT)) {
                         extern int handle_signal32(unsigned long sig,
@@ -478,15 +479,12 @@ void do_signal(struct pt_regs *regs)
                                                    siginfo_t *info,
                                                    sigset_t *oldset,
                                                    struct pt_regs *regs);
-                        if (handle_signal32(
-                                    signr, &ka, &info, oldset, regs) == 0) {
-                                if (test_thread_flag(TIF_RESTORE_SIGMASK))
-                                        clear_thread_flag(TIF_RESTORE_SIGMASK);
-                        }
-                        return;
+                        ret = handle_signal32(signr, &ka, &info, oldset, regs);
                 }
+                else
 #endif
-                if (handle_signal(signr, &ka, &info, oldset, regs) == 0) {
+                        ret = handle_signal(signr, &ka, &info, oldset, regs);
+                if (!ret) {
                         /*
                          * A signal was successfully delivered; the saved
                          * sigmask will have been stored in the signal frame,
@@ -495,6 +493,14 @@ void do_signal(struct pt_regs *regs)
                          */
                         if (test_thread_flag(TIF_RESTORE_SIGMASK))
                                 clear_thread_flag(TIF_RESTORE_SIGMASK);
+
+                        /*
+                         * If we would have taken a single-step trap
+                         * for a normal instruction, act like we took
+                         * one for the handler setup.
+                         */
+                        if (current->thread.per_info.single_step)
+                                set_thread_flag(TIF_SINGLE_STEP);
                 }
                 return;
         }
diff --git a/include/asm-s390/ptrace.h b/include/asm-s390/ptrace.h
index 332ee73688fc..61f6952f2e35 100644
--- a/include/asm-s390/ptrace.h
+++ b/include/asm-s390/ptrace.h
@@ -465,6 +465,14 @@ struct user_regs_struct
 #ifdef __KERNEL__
 #define __ARCH_SYS_PTRACE       1
 
+/*
+ * These are defined as per linux/ptrace.h, which see.
+ */
+#define arch_has_single_step()  (1)
+struct task_struct;
+extern void user_enable_single_step(struct task_struct *);
+extern void user_disable_single_step(struct task_struct *);
+
 #define user_mode(regs) (((regs)->psw.mask & PSW_MASK_PSTATE) != 0)
 #define instruction_pointer(regs) ((regs)->psw.addr & PSW_ADDR_INSN)
 #define regs_return_value(regs)((regs)->gprs[2])