x86: use wrmsrl in kprobes.c, step.c

Where x86_32 passed zero in the high 32 bits, use wrmsrl which
will zero extend for us.  This allows ifdefs for 32/64 bit to
be eliminated.

Eliminate ifdef in step.c.  Similar cleanup was done when unifying
kprobes_32|64.c and wrmsr() was chosen there over wrmsrl().  This
patch changes these to wrmsrl.
Signed-off-by: NHarvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/kprobes.c

@@ -410,13 +410,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 static void __kprobes clear_btf(void)
 {
 	if (test_thread_flag(TIF_DEBUGCTLMSR))
-		wrmsr(MSR_IA32_DEBUGCTLMSR, 0, 0);
+		wrmsrl(MSR_IA32_DEBUGCTLMSR, 0);
 }
 
 static void __kprobes restore_btf(void)
 {
 	if (test_thread_flag(TIF_DEBUGCTLMSR))
-		wrmsr(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr, 0);
+		wrmsrl(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr);
 }
 
 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)

arch/x86/kernel/step.c

@@ -229,11 +229,7 @@ static void write_debugctlmsr(struct task_struct *child, unsigned long val)
 	if (child != current)
 		return;
 
-#ifdef CONFIG_X86_64
 	wrmsrl(MSR_IA32_DEBUGCTLMSR, val);
-#else
-	wrmsr(MSR_IA32_DEBUGCTLMSR, val, 0);
-#endif
 }
 
 /*