On 12/06/16 22:06, Mathieu Poirier wrote:
On 10 June 2016 at 04:31, Suzuki K Poulose <[email protected]> wrote:
At the end of a trace collection, we try to clear the entire buffer
and enable the ETR back if it was already enabled. But, we would have
adjusted the drvdata->buf to point to the beginning of the trace data
in the trace buffer @drvdata->vaddr. So, the following code which
clears the buffer is dangerous and can cause crashes, like below :
memset(drvdata->buf, 0, drvdata->size);
Unable to handle kernel paging request at virtual address ffffff800a145000
pgd = ffffffc974726000
*pgd=00000009f3e91003, *pud=00000009f3e91003, *pmd=0000000000000000
PREEMPT SMP
Modules linked in:
CPU: 4 PID: 1692 Comm: dd Not tainted 4.7.0-rc2+ #1721
Hardware name: ARM Juno development board (r0) (DT)
task: ffffffc9734a0080 ti: ffffffc974460000 task.ti: ffffffc974460000
PC is at __memset+0x1ac/0x200
LR is at tmc_read_unprepare_etr+0x144/0x1bc
pc : [<ffffff80083a05ac>] lr : [<ffffff800859c984>] pstate: 200001c5
...
[<ffffff80083a05ac>] __memset+0x1ac/0x200
[<ffffff800859b2e4>] tmc_release+0x90/0x94
[<ffffff8008202f58>] __fput+0xa8/0x1ec
[<ffffff80082030f4>] ____fput+0xc/0x14
[<ffffff80080c3ef8>] task_work_run+0xb0/0xe4
[<ffffff8008088bf4>] do_notify_resume+0x64/0x6c
[<ffffff8008084d5c>] work_pending+0x10/0x14
Code: 91010108 54ffff4a 8b040108 cb050042 (d50b7428)
Since we clear the buffer anyway in the following call to
tmc_etr_enable_hw(), remove the erroneous memset().
Fixes: commit de5461970b3e9e1 ("coresight: tmc: allocating memory when needed")
Cc: Mathieu Poirier <[email protected]>
Signed-off-by: Suzuki K Poulose <[email protected]>
---
Mathieu,
I think this should go to 4.7. Please push it.
If this [1] didn't make it, this one won't make it either.
applied it to my tree for merging in the 4.8 cycle.
I think both should go to 4.7, as these fixes real crashes.
Greg,
We have two fixes [1],[2] for coresight driver which fixes Kernel crashes.
Could you
please pick them up ?
I could resend them, if you would like.
[1] https://patchwork.kernel.org/patch/9144589/
[2] https://patchwork.kernel.org/patch/9169407/
Thanks
Suzuki
Thanks,
Mathieu
---
drivers/hwtracing/coresight/coresight-tmc-etr.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c
b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 69e104b..24d99ed 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -306,13 +306,10 @@ int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata)
if (local_read(&drvdata->mode) == CS_MODE_SYSFS) {
/*
* The trace run will continue with the same allocated trace
- * buffer. As such zero-out the buffer so that we don't end
- * up with stale data.
- *
- * Since the tracer is still enabled drvdata::buf
- * can't be NULL.
+ * buffer. The trace buffer is cleared in tmc_etr_enable_hw(),
+ * so we don't have to explicitly clear it. Also, since the
Yes, very good.
+ * tracer is still enabled drvdata::buf can't be NULL.
*/
- memset(drvdata->buf, 0, drvdata->size);
tmc_etr_enable_hw(drvdata);
} else {
/*
--
1.9.1
