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>

diff --git a/arch/arm/kernel/etm.c b/arch/arm/kernel/etm.c
index 6f0777661d681add3390dbabd86ee7ee13cdb9bc..4b92715b5c1332106fda247c0139b27a0858ac7d 100644 (file)
--- a/arch/arm/kernel/etm.c
+++ b/arch/arm/kernel/etm.c
@@ -264,8 +264,13 @@ static void etm_dump(void)
 
 static void sysrq_etm_dump(int key)
 {
+       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 = {
@@ -374,6 +379,7 @@ static int etb_probe(struct amba_device *dev, const 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;
@@ -382,6 +388,16 @@ static int etb_probe(struct amba_device *dev, const 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);
@@ -395,25 +411,19 @@ static int etb_probe(struct amba_device *dev, const 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;
@@ -475,7 +485,10 @@ static ssize_t trace_running_store(struct kobject *kobj,
                return -EINVAL;
 
        mutex_lock(&tracer.mutex);
-       ret = value ? trace_start(&tracer) : trace_stop(&tracer);
+       if (!tracer.etb_regs)
+               ret = -ENODEV;
+       else
+               ret = value ? trace_start(&tracer) : trace_stop(&tracer);
        mutex_unlock(&tracer.mutex);
 
        return ret ? : n;
@@ -491,18 +504,25 @@ static ssize_t trace_info_show(struct kobject *kobj,
        u32 etb_wa, etb_ra, etb_st, etb_fc, etm_ctrl, etm_st;
        int datalen;
 
-       etb_unlock(&tracer);
-       datalen = etb_getdatalen(&tracer);
-       etb_wa = etb_readl(&tracer, ETBR_WRITEADDR);
-       etb_ra = etb_readl(&tracer, ETBR_READADDR);
-       etb_st = etb_readl(&tracer, ETBR_STATUS);
-       etb_fc = etb_readl(&tracer, ETBR_FORMATTERCTRL);
-       etb_lock(&tracer);
+       mutex_lock(&tracer.mutex);
+       if (tracer.etb_regs) {
+               etb_unlock(&tracer);
+               datalen = etb_getdatalen(&tracer);
+               etb_wa = etb_readl(&tracer, ETBR_WRITEADDR);
+               etb_ra = etb_readl(&tracer, ETBR_READADDR);
+               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"
@@ -652,7 +672,6 @@ static int etm_probe(struct amba_device *dev, const 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;
@@ -746,6 +765,8 @@ 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");