Hi,
On Fri, Jan 29, 2021 at 11:08 AM Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org wrote:
@@ -1202,6 +1207,13 @@ void etm4_config_trace_mode(struct etmv4_config *config) /* excluding kernel AND user space doesn't make sense */ WARN_ON_ONCE(mode == (ETM_MODE_EXCL_KERN | ETM_MODE_EXCL_USER));
if (!(mode & ETM_MODE_EXCL_KERN) && IS_ENABLED(CONFIG_EXCLUDE_KERNEL_HW_ITRACE)) {dev_err(&drvdata->csdev->dev,"Kernel mode tracing is not allowed, check your kernel config\n");config->mode |= ETM_MODE_EXCL_KERN;return;
So I'm not an expert on this code, but the above looks suspicious to me. Specifically you are still modifying "config->mode" even though printing an "error" (dev_err, not dev_warn) and then skipping the rest of this function. Since you're skipping the rest of this function you're not applying the access, right? Naively I'd have expected one of these:
1. Maybe the "dev_err" should be a "dev_warn" and then you shouldn't "return". In this case you're just implicitly adding "ETM_MODE_EXCL_KERN" (and shouting) but then making things work. Of course, then what happens if the user already specified "ETM_MODE_EXCL_USER" too? As per the comment above that "doesn't make sense". ...so maybe the code wouldn't behave properly...
2. Maybe you should be modifying this function to return an error code.
3. Maybe you should just be updating the one caller of this function to error check this right at the beginning of the function and then fail the sysfs write if the user did the wrong thing. Then in etm4_config_trace_mode you could just have a WARN_ON_ONCE if the kernel wasn't excluded...
-Doug