Re: [PATCHv2] coresight: tmc: Fix TMC mode read in tmc_read_prepare_etb()

[Mathieu Poirier]

On Thu, Apr 16, 2020 at 09:44:59PM +0530, Sai Prakash Ranjan wrote:
> On some QCOM platforms like SC7180, SDM845 and SM8150,
> reading TMC mode register without proper coresight power
> management can lead to async exceptions like the one in
> the call trace below in tmc_read_prepare_etb(). This can
> happen if the user tries to read the TMC etf data via
> device node without setting up source and the sink first.
> Fix this by having a check for coresight sysfs mode
> before reading TMC mode management register.
> 
>  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>
> Suggested-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>

Applied - thanks,
Mathieu

> ---
> v2:
>  * Move the TMC mode read under CS_MODE_SYSFS as per Mathieu
> ---
>  drivers/hwtracing/coresight/coresight-tmc-etf.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index d0cc3985b72a..36cce2bfb744 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -596,13 +596,6 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
>  		goto out;
>  	}
>  
> -	/* There is no point in reading a TMC in HW FIFO mode */
> -	mode = readl_relaxed(drvdata->base + TMC_MODE);
> -	if (mode != TMC_MODE_CIRCULAR_BUFFER) {
> -		ret = -EINVAL;
> -		goto out;
> -	}
> -
>  	/* Don't interfere if operated from Perf */
>  	if (drvdata->mode == CS_MODE_PERF) {
>  		ret = -EINVAL;
> @@ -616,8 +609,15 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
>  	}
>  
>  	/* Disable the TMC if need be */
> -	if (drvdata->mode == CS_MODE_SYSFS)
> +	if (drvdata->mode == CS_MODE_SYSFS) {
> +		/* There is no point in reading a TMC in HW FIFO mode */
> +		mode = readl_relaxed(drvdata->base + TMC_MODE);
> +		if (mode != TMC_MODE_CIRCULAR_BUFFER) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
>  		__tmc_etb_disable_hw(drvdata);
> +	}
>  
>  	drvdata->reading = true;
>  out:
> -- 
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