Hi Sai,
On 04/09/2020 12:35 PM, Sai Prakash Ranjan wrote:
Reading TMC mode register in tmc_read_prepare_etb without
enabling the TMC hardware leads to async exceptions like
the one in the call trace below. This can happen if the
user tries to read the TMC etf data via device node without
setting up source and the sink first which enables the TMC
hardware in the path. So make sure that the TMC is enabled
before we try to read TMC data.
So, one can trigger the same SError by simply :
$ cat /sys/bus/coresight/device/tmc_etb0/mgmt/mode
And also :
Kernel panic - not syncing: Asynchronous SError Interrupt
CPU: 7 PID: 2605 Comm: hexdump Tainted: G S 5.4.30 #122
Call trace:
dump_backtrace+0x0/0x188
show_stack+0x20/0x2c
dump_stack+0xdc/0x144
panic+0x168/0x36c
panic+0x0/0x36c
arm64_serror_panic+0x78/0x84
do_serror+0x130/0x138
el1_error+0x84/0xf8
tmc_read_prepare_etb+0x88/0xb8
tmc_open+0x40/0xd8
misc_open+0x120/0x158
chrdev_open+0xb8/0x1a4
do_dentry_open+0x268/0x3a0
vfs_open+0x34/0x40
path_openat+0x39c/0xdf4
do_filp_open+0x90/0x10c
do_sys_open+0x150/0x3e8
__arm64_compat_sys_openat+0x28/0x34
el0_svc_common+0xa8/0x160
el0_svc_compat_handler+0x2c/0x38
el0_svc_compat+0x8/0x10
Fixes: 4525412a5046 ("coresight: tmc: making prepare/unprepare functions generic")
Reported-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
---
drivers/hwtracing/coresight/coresight-tmc.c | 5 +++++
drivers/hwtracing/coresight/coresight-tmc.h | 1 +
2 files changed, 6 insertions(+)
diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index 1cf82fa58289..7bae69748ab7 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -62,11 +62,13 @@ void tmc_flush_and_stop(struct tmc_drvdata *drvdata)
void tmc_enable_hw(struct tmc_drvdata *drvdata)
{
+ drvdata->enable = true;
writel_relaxed(TMC_CTL_CAPT_EN, drvdata->base + TMC_CTL);
}
void tmc_disable_hw(struct tmc_drvdata *drvdata)
{
+ drvdata->enable = false;
writel_relaxed(0x0, drvdata->base + TMC_CTL);
}
@@ -102,6 +104,9 @@ static int tmc_read_prepare(struct tmc_drvdata *drvdata)
{
int ret = 0;
+ if (!drvdata->enable)
+ return -EINVAL;
+
Does this check always guarantee that the TMC is enabled when
we actually get to reading the MODE ? This needs to be done
under the spinlock.
Cheers
Suzuki
