On Thu, 12 Jun 2025 12:43:49 +0200 Gabriele Paoloni <gpaol...@redhat.com> wrote:
> This patch implements the documentation of event_enable_write and > event_enable_read in the form of testable function's expectations. > > Signed-off-by: Gabriele Paoloni <gpaol...@redhat.com> > --- > kernel/trace/trace_events.c | 72 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 72 insertions(+) > > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 5e84ef01d0c8..eb3c5e6e557d 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -1771,6 +1771,46 @@ static void p_stop(struct seq_file *m, void *p) > mutex_unlock(&event_mutex); > } > > +/** > + * event_enable_read - read from a trace event file to retrieve its status. > + * @filp: file pointer associated with the target trace event; > + * @ubuf: user space buffer where the event status is copied to; > + * @cnt: number of bytes to be copied to the user space buffer; Why is the above ending with semicolons? > + * @ppos: the current position in the buffer. > + * > + * This is a way for user space executables to retrieve the status of a > + * specific event > + * > + * Function's expectations: > + * - This function shall lock the global event_mutex before performing any > + * operation on the target event file and unlock it after all operations on > + * the target event file have completed; > + * - This function shall retrieve the status flags from the file associated > + * with the target event; > + * - This function shall format the string to report the event status to user > + * space: > + * - The first character of the string to be copied to user space shall be > + * set to "1" if the enabled flag is set AND the soft_disabled flag is > not > + * set, else it shall be set to "0"; > + * - The second character of the string to be copied to user space shall be > + * set to "*" if either the soft_disabled flag or the soft_mode flag is > + * set, else it shall be set to "\n"; > + * - The third character of the string to be copied to user space shall b > + * set to "\n" if either the soft_disabled flag or the soft_mode flag is > + * set, else it shall be set to "0"; > + * - Any other character in the string to be copied to user space shall be > + * set to "0"; The above could use some new lines. Like between each bullet. My eyesight isn't as good anymore and I find reading gobs of text more difficult. Newlines give my eyes a break. I know this is being written so that a tool could parse it, but also needs to be parsed by aging developers. ;-) > + * - This function shall check if the requested cnt bytes are equal or > greater > + * than the length of the string to be copied to user space (else a > + * corrupted event status could be reported); > + * - This function shall invoke simple_read_from_buffer() to perform the copy > + * of the kernel space string to ubuf. Hmm, and it is also verbose. This is a relatively simple function, and it caused quite a bit of requirements. I wonder if it could be shortened a bit. Otherwise more complex and larger functions are going to be overwhelming and likely not acceptable. And those are the functions that I think this will benefit the most! > + * > + * Returns the number of copied bytes on success, -ENODEV if the event file > + * cannot be retrieved from the input filp, -EINVAL if cnt is less than the > + * length of the string to be copied to ubuf, any error returned by > + * simple_read_from_buffer Returns should be formatted better where each return value is on a separate line. -- Steve > + */ > static ssize_t > event_enable_read(struct file *filp, char __user *ubuf, size_t cnt, > loff_t *ppos) > @@ -1808,6 +1848,38 @@ event_enable_read(struct file *filp, char __user > *ubuf, size_t cnt, > return simple_read_from_buffer(ubuf, cnt, ppos, buf, strlen(buf)); > } > > +/** > + * event_enable_write - write to a trace event file to enable/disable it. > + * @filp: file pointer associated with the target trace event; > + * @ubuf: user space buffer where the enable/disable value is copied from; > + * @cnt: number of bytes to be copied from the user space buffer; > + * @ppos: the current position in the buffer. > + * > + * This is a way for user space executables to enable or disable event > + * recording. > + * > + * Function's expectations: > + * - This function shall copy cnt bytes from the input ubuf buffer to a > kernel > + * space buffer (or the whole input ubuf if cnt is larger than ubuf size) > + * and shall convert the string within the kernel space buffer into a > decimal > + * base format number; > + * - This function shall lock the global event_mutex before performing any > + * operation on the target event file and unlock it after all operations on > + * the target event file have completed; > + * - This function shall check the size of the per-cpu ring-buffers used for > + * the event trace data and, if smaller than TRACE_BUF_SIZE_DEFAULT, expand > + * them to TRACE_BUF_SIZE_DEFAULT bytes (sizes larger than > + * TRACE_BUF_SIZE_DEFAULT are not allowed); > + * - This function shall invoke ftrace_event_enable_disable to enable or > + * disable the target trace event according to the value read from user > space > + * (0 - disable, 1 - enable); > + * > + * Returns 0 on success, any error returned by kstrtoul_from_user, -ENODEV if > + * the event file cannot be retrieved from the input filp, any error > returned by > + * tracing_update_buffers, any error returned by ftrace_event_enable_disable, > + * -EINVAL if the value copied from the user space ubuf is different from 0 > or > + * 1. > + */ > static ssize_t > event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt, > loff_t *ppos)
