On production systems with ETMs enabled, it is preferred to exclude kernel mode(NS EL1) tracing for security concerns and support only userspace(NS EL0) tracing. Perf subsystem interface uses the newly introduced kernel config CONFIG_EXCLUDE_KERNEL_PMU_TRACE to exclude kernel mode tracing, but there is an additional interface via sysfs for ETMs which also needs to be handled to exclude kernel mode tracing. So we use this same generic kernel config to handle the sysfs mode of tracing. This config is disabled by default and would not affect the current configuration which has both kernel and userspace tracing enabled by default.
Signed-off-by: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org --- drivers/hwtracing/coresight/coresight-etm3x-core.c | 3 +++ drivers/hwtracing/coresight/coresight-etm3x-sysfs.c | 6 ++++++ 2 files changed, 9 insertions(+)
diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c index cf64ce73a741..d94f6b01ca09 100644 --- a/drivers/hwtracing/coresight/coresight-etm3x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c @@ -195,6 +195,9 @@ void etm_set_default(struct etm_config *config) if (WARN_ON_ONCE(!config)) return;
+ if (IS_ENABLED(CONFIG_EXCLUDE_KERNEL_PMU_TRACE)) + config->mode |= ETM_MODE_EXCL_KERN; + /* * Taken verbatim from the TRM: * diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c index e8c7649f123e..f522fc2e01b3 100644 --- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c @@ -116,6 +116,12 @@ static ssize_t mode_store(struct device *dev, if (ret) return ret;
+ if (IS_ENABLED(CONFIG_EXCLUDE_KERNEL_PMU_TRACE) && (!(val & ETM_MODE_EXCL_KERN))) { + dev_warn(dev, + "Kernel mode tracing is not allowed, check your kernel config\n"); + return -EACCES; + } + spin_lock(&drvdata->spinlock); config->mode = val & ETM_MODE_ALL;