Re: [PATCH 1/1] tracing: Support reading trace event format file larger than PAGE_SIZE

Steven Rostedt
2025-01-06T22:10:24Z

On Mon, 6 Jan 2025 18:15:36 +0000
Shiju Jose <shiju.jose@huawei.com> wrote:

> >You see, it requires multiple reads to pull in an entire kernel pseudo file. None of
> >those reads are greater than PAGE_SIZE. Why should trace format files be any
> >different?
> Thanks for the reply.
> Yes. I had a fix/workaround in the userspace rasdaemon with multiple reads like above
> as reported previously in the following thread.
> https://lore.kernel.org/lkml/3c9808a694d242cab35bab67602edebf@huawei.com/
> However thought a solution in the common kernel code for the format file
> may be better. I will go ahead with the user space solution.

That would make it different than every other pseudo file in the kernel. I
rather not do that.

>
> Also shared an information in the above thread about libtraceevent __parse_event() does not
> return error when parse_format() fail with incomplete formt data, which resulted initialization for the
> trace event does not fail in the user space tool.

Hmm, can you send me the the format file that failed?

Just the output of "cat /sys/kernel/tracing/events/<system>/<event>/format"
will do.

-- Steve