ARM: etm: Add some missing locks and error checks

It is not safe to call etm_lock or etb_lock without holding the
mutex since another thread may also have unlocked the registers.

Also add some missing checks for valid etb_regs in the etm sysfs
entries.

Change-Id: I939f76a6ea7546a8fc0d4ddafa2fd2b6f38103bb
Signed-off-by: Arve Hjønnevåg <arve@android.com>

arch/arm/kernel/etm.c

@@ -263,8 +263,13 @@ static void etm_dump(void)
 
 static void sysrq_etm_dump(int key, struct tty_struct *tty)
 {
+	if (!mutex_trylock(&tracer.mutex)) {
+		printk(KERN_INFO "Tracing hardware busy\n");
+		return;
+	}
 	dev_dbg(tracer.dev, "Dumping ETB buffer\n");
 	etm_dump();
+	mutex_unlock(&tracer.mutex);
 }
 
 static struct sysrq_key_op sysrq_etm_op = {
@@ -372,6 +377,7 @@ static int __init etb_probe(struct amba_device *dev, struct amba_id *id)
 	if (ret)
 		goto out;
 
+	mutex_lock(&t->mutex);
 	t->etb_regs = ioremap_nocache(dev->res.start, resource_size(&dev->res));
 	if (!t->etb_regs) {
 		ret = -ENOMEM;
@@ -380,6 +386,16 @@ static int __init etb_probe(struct amba_device *dev, struct amba_id *id)
 
 	amba_set_drvdata(dev, t);
 
+	etb_unlock(t);
+	t->etb_bufsz = etb_readl(t, ETBR_DEPTH);
+	dev_dbg(&dev->dev, "Size: %x\n", t->etb_bufsz);
+
+	/* make sure trace capture is disabled */
+	etb_writel(t, 0, ETBR_CTRL);
+	etb_writel(t, 0x1000, ETBR_FORMATTERCTRL);
+	etb_lock(t);
+	mutex_unlock(&t->mutex);
+
 	etb_miscdev.parent = &dev->dev;
 
 	ret = misc_register(&etb_miscdev);
@@ -393,25 +409,19 @@ static int __init etb_probe(struct amba_device *dev, struct amba_id *id)
 	else
 		clk_enable(t->emu_clk);
 
-	etb_unlock(t);
-	t->etb_bufsz = etb_readl(t, ETBR_DEPTH);
-	dev_dbg(&dev->dev, "Size: %x\n", t->etb_bufsz);
-
-	/* make sure trace capture is disabled */
-	etb_writel(t, 0, ETBR_CTRL);
-	etb_writel(t, 0x1000, ETBR_FORMATTERCTRL);
-	etb_lock(t);
-
 	dev_dbg(&dev->dev, "ETB AMBA driver initialized.\n");
 
 out:
 	return ret;
 
 out_unmap:
+	mutex_lock(&t->mutex);
 	amba_set_drvdata(dev, NULL);
 	iounmap(t->etb_regs);
+	t->etb_regs = NULL;
 
 out_release:
+	mutex_unlock(&t->mutex);
 	amba_release_regions(dev);
 
 	return ret;
@@ -473,6 +483,9 @@ static ssize_t trace_running_store(struct kobject *kobj,
 		return -EINVAL;
 
 	mutex_lock(&tracer.mutex);
+	if (!tracer.etb_regs)
+		ret = -ENODEV;
+	else
 		ret = value ? trace_start(&tracer) : trace_stop(&tracer);
 	mutex_unlock(&tracer.mutex);
 
@@ -489,6 +502,8 @@ static ssize_t trace_info_show(struct kobject *kobj,
 	u32 etb_wa, etb_ra, etb_st, etb_fc, etm_ctrl, etm_st;
 	int datalen;
 
+	mutex_lock(&tracer.mutex);
+	if (tracer.etb_regs) {
 		etb_unlock(&tracer);
 		datalen = etb_getdatalen(&tracer);
 		etb_wa = etb_readl(&tracer, ETBR_WRITEADDR);
@@ -496,11 +511,16 @@ static ssize_t trace_info_show(struct kobject *kobj,
 		etb_st = etb_readl(&tracer, ETBR_STATUS);
 		etb_fc = etb_readl(&tracer, ETBR_FORMATTERCTRL);
 		etb_lock(&tracer);
+	} else {
+		etb_wa = etb_ra = etb_st = etb_fc = ~0;
+		datalen = -1;
+	}
 
 	etm_unlock(&tracer);
 	etm_ctrl = etm_readl(&tracer, ETMR_CTRL);
 	etm_st = etm_readl(&tracer, ETMR_STATUS);
 	etm_lock(&tracer);
+	mutex_unlock(&tracer.mutex);
 
 	return sprintf(buf, "Trace buffer len: %d\nComparator pairs: %d\n"
 			"ETBR_WRITEADDR:\t%08x\n"
@@ -650,7 +670,6 @@ static int __init etm_probe(struct amba_device *dev, struct amba_id *id)
 
 	amba_set_drvdata(dev, t);
 
-	mutex_init(&t->mutex);
 	t->dev = &dev->dev;
 	t->flags = TRACER_CYCLE_ACC | TRACER_TRACE_DATA;
 	t->etm_portsz = 1;
@@ -744,6 +763,8 @@ static int __init etm_init(void)
 {
 	int retval;
 
+	mutex_init(&tracer.mutex);
+
 	retval = amba_driver_register(&etb_driver);
 	if (retval) {
 		printk(KERN_ERR "Failed to register etb\n");