On Tue, 7 Feb 2023 19:21:26 +0100
Florent Revest <revest@xxxxxxxxxxxx> wrote:
> The _multi API requires that users keep their own ops but can enforce
> that an op is only associated to one direct call.
>
> Signed-off-by: Florent Revest <revest@xxxxxxxxxxxx>
> Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
> Tested-by: Mark Rutland <mark.rutland@xxxxxxx>
> ---
> kernel/trace/trace_selftest.c | 11 +++++++----
> samples/ftrace/ftrace-direct-modify.c | 12 ++++++++----
> samples/ftrace/ftrace-direct-too.c | 12 +++++++-----
> samples/ftrace/ftrace-direct.c | 12 +++++++-----
> 4 files changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
> index ff0536cea968..57221f69a33b 100644
> --- a/kernel/trace/trace_selftest.c
> +++ b/kernel/trace/trace_selftest.c
> @@ -806,6 +806,9 @@ trace_selftest_startup_function_graph(struct tracer *trace,
> int ret;
> unsigned long count;
> char *func_name __maybe_unused;
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> + struct ftrace_ops direct = {};
Make this static to the file and move it above to where there's already an
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS block.
Less #ifdef is better, and also, I don't like having as an example an
ftrace_ops structure allocated on the stack. It can become increasingly
larger as time goes by. I don't want to encourage placing it on stacks.
> +#endif
>
> #ifdef CONFIG_DYNAMIC_FTRACE
> if (ftrace_filter_param) {
> @@ -870,8 +873,8 @@ trace_selftest_startup_function_graph(struct tracer *trace,
> * Register direct function together with graph tracer
> * and make sure we get graph trace.
> */
> - ret = register_ftrace_direct((unsigned long) DYN_FTRACE_TEST_NAME,
> - (unsigned long) trace_direct_tramp);
> + ftrace_set_filter_ip(&direct, (unsigned long)DYN_FTRACE_TEST_NAME, 0, 0);
> + ret = register_ftrace_direct_multi(&direct, (unsigned long)trace_direct_tramp);
> if (ret)
> goto out;
I had to rebase this code on top of the latest tree because of updates.
Which is good, because this patch requires those same. When using
ftrace_set_filter_ip() one needs to call
ftrace_free_filter(&direct);
Because the ftrace_set_filter_ip() allocates hashs on the ftrace_ops and
those need to be freed.
>
> @@ -891,8 +894,8 @@ trace_selftest_startup_function_graph(struct tracer *trace,
>
> unregister_ftrace_graph(&fgraph_ops);
>
> - ret = unregister_ftrace_direct((unsigned long) DYN_FTRACE_TEST_NAME,
> - (unsigned long) trace_direct_tramp);
> + ret = unregister_ftrace_direct_multi(&direct,
> + (unsigned long) trace_direct_tramp);
> if (ret)
> goto out;
>
> diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
> index de5a0f67f320..ecd76f75cb80 100644
> --- a/samples/ftrace/ftrace-direct-modify.c
> +++ b/samples/ftrace/ftrace-direct-modify.c
> @@ -96,6 +96,8 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +static struct ftrace_ops direct;
> +
> static unsigned long my_tramp = (unsigned long)my_tramp1;
> static unsigned long tramps[2] = {
> (unsigned long)my_tramp1,
> @@ -114,7 +116,7 @@ static int simple_thread(void *arg)
> if (ret)
> continue;
> t ^= 1;
> - ret = modify_ftrace_direct(my_ip, my_tramp, tramps[t]);
> + ret = modify_ftrace_direct_multi(&direct, tramps[t]);
> if (!ret)
> my_tramp = tramps[t];
> WARN_ON_ONCE(ret);
> @@ -129,7 +131,9 @@ static int __init ftrace_direct_init(void)
> {
> int ret;
>
> - ret = register_ftrace_direct(my_ip, my_tramp);
> + ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
> + ret = register_ftrace_direct_multi(&direct, my_tramp);
> +
> if (!ret)
> simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
> return ret;
> @@ -138,12 +142,12 @@ static int __init ftrace_direct_init(void)
> static void __exit ftrace_direct_exit(void)
> {
> kthread_stop(simple_tsk);
> - unregister_ftrace_direct(my_ip, my_tramp);
> + unregister_ftrace_direct_multi(&direct, my_tramp);
Same here.
> }
>
> module_init(ftrace_direct_init);
> module_exit(ftrace_direct_exit);
>
> MODULE_AUTHOR("Steven Rostedt");
> -MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()");
> +MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
> MODULE_LICENSE("GPL");
> diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
> index e13fb59a2b47..0e907092e2c0 100644
> --- a/samples/ftrace/ftrace-direct-too.c
> +++ b/samples/ftrace/ftrace-direct-too.c
> @@ -70,21 +70,23 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +static struct ftrace_ops direct;
> +
> static int __init ftrace_direct_init(void)
> {
> - return register_ftrace_direct((unsigned long)handle_mm_fault,
> - (unsigned long)my_tramp);
> + ftrace_set_filter_ip(&direct, (unsigned long) handle_mm_fault, 0, 0);
> +
> + return register_ftrace_direct_multi(&direct, (unsigned long) my_tramp);
> }
>
> static void __exit ftrace_direct_exit(void)
> {
> - unregister_ftrace_direct((unsigned long)handle_mm_fault,
> - (unsigned long)my_tramp);
> + unregister_ftrace_direct_multi(&direct, (unsigned long)my_tramp);
And here.
> }
>
> module_init(ftrace_direct_init);
> module_exit(ftrace_direct_exit);
>
> MODULE_AUTHOR("Steven Rostedt");
> -MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
> +MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct_multi()");
> MODULE_LICENSE("GPL");
> diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
> index 1f769d0db20f..e446c38f6b58 100644
> --- a/samples/ftrace/ftrace-direct.c
> +++ b/samples/ftrace/ftrace-direct.c
> @@ -63,21 +63,23 @@ asm (
>
> #endif /* CONFIG_S390 */
>
> +static struct ftrace_ops direct;
> +
> static int __init ftrace_direct_init(void)
> {
> - return register_ftrace_direct((unsigned long)wake_up_process,
> - (unsigned long)my_tramp);
> + ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
> +
> + return register_ftrace_direct_multi(&direct, (unsigned long) my_tramp);
> }
>
> static void __exit ftrace_direct_exit(void)
> {
> - unregister_ftrace_direct((unsigned long)wake_up_process,
> - (unsigned long)my_tramp);
> + unregister_ftrace_direct_multi(&direct, (unsigned long)my_tramp);
And here.
Maybe we could add a parameter to unregister_ftrace_direct_multi():
bool free_filters
when set, it will call the ftrace_free_filter(), as it looks like there's a
common code path here:
ftrace_set_filter_ip();
register_ftrace_direct_multi();
[..]
unregister_ftrace_direct_multi();
ftrace_free_filter();
Add the option will save people from having to do that last step, and also
remind people that the filters need to be freed.
-- Steve
> }
>
> module_init(ftrace_direct_init);
> module_exit(ftrace_direct_exit);
>
> MODULE_AUTHOR("Steven Rostedt");
> -MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
> +MODULE_DESCRIPTION("Example use case of using register_ftrace_direct_multi()");
> MODULE_LICENSE("GPL");
