[PATCH 06/15] ARM: etm: Add some missing locks and error checks

John Stultz
2012-06-20T22:49:21Z

From: Arve Hjønnevåg <arve@android.com>

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.

CC: Russell King <linux@arm.linux.org.uk>
CC: Paul Gortmaker <paul.gortmaker@windriver.com>
CC: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
arch/arm/kernel/etm.c | 57 +++++++++++++++++++++++++++++++++----------------
1 file changed, 39 insertions(+), 18 deletions(-)

diff --git a/arch/arm/kernel/etm.c b/arch/arm/kernel/etm.c
index c651cf9..3d21cf6 100644
--- 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 __devinit 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 __devinit 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 __devinit 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 __devinit 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");
--
1.7.9.5