powerpc: Move the single step enable code to a generic path

This patch moves the single step enable code used by kprobe to a generic
routine header so that, it can be re-used by other code, in this case,
uprobes. No functional changes.

Signed-off-by: Suzuki K. Poulose <[e-mail]>
Cc: Ananth N Mavinakaynahalli <[e-mail]>
Cc: Kumar Gala <[e-mail]>
Cc: [e-mail]
Acked-by: Ananth N Mavinakayanahalli <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>

arch/powerpc/include/asm/probes.h

···
 #define is_trap(instr)		(IS_TW(instr) || IS_TWI(instr))
 #endif /* CONFIG_PPC64 */
 
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+#define MSR_SINGLESTEP	(MSR_DE)
+#else
+#define MSR_SINGLESTEP	(MSR_SE)
+#endif
+
+/* Enable single stepping for the current task */
+static inline void enable_single_step(struct pt_regs *regs)
+{
+	regs->msr |= MSR_SINGLESTEP;
+#ifdef CONFIG_PPC_ADV_DEBUG_REGS
+	/*
+	 * We turn off Critical Input Exception(CE) to ensure that the single
+	 * step will be for the instruction we have the probe on; if we don't,
+	 * it is possible we'd get the single step reported for CE.
+	 */
+	regs->msr &= ~MSR_CE;
+	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
+#ifdef CONFIG_PPC_47x
+	isync();
+#endif
+#endif
+}
+
+
 #endif /* __KERNEL__ */
 #endif	/* _ASM_POWERPC_PROBES_H */

arch/powerpc/kernel/kprobes.c

···
 #include <asm/sstep.h>
 #include <asm/uaccess.h>
 
-#ifdef CONFIG_PPC_ADV_DEBUG_REGS
-#define MSR_SINGLESTEP	(MSR_DE)
-#else
-#define MSR_SINGLESTEP	(MSR_SE)
-#endif
-
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
···
 
 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 {
-	regs->msr |= MSR_SINGLESTEP;
-#ifdef CONFIG_PPC_ADV_DEBUG_REGS
-	/*
-	 * We turn off Critical Input Exception(CE) to ensure that the single
-	 * step will be for the instruction we have the probe on; if we don't,
-	 * it is possible we'd get the single step reported for CE.
-	 */
-	regs->msr &= ~MSR_CE;
-	mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
-#ifdef CONFIG_PPC_47x
-	isync();
-#endif
-#endif
+	enable_single_step(regs);
 
 	/*
 	 * On powerpc we should single step on the original