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SubjectRe: [PATCH v3] tracing: Ignore mmiotrace from kernel commandline
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On 09/11/2017 02:26 PM, Ziqian SUN (Zamir) wrote:
> From: "Ziqian SUN (Zamir)" <zsun@redhat.com>
>
> The mmiotrace tracer cannot be enabled with ftrace=mmiotrace in kernel
> commandline. With this patch, noboot is added to the tracer struct,
> and when system boot with a tracer that has noboot=true, it will print
> out a warning message and continue booting.
>
> Signed-off-by: Ziqian SUN (Zamir) <zsun@redhat.com>
> --
> v1 -> v2 : remove unessential comment
> v2 -> v3 : Use tracer struct instead of a separate list to store noboot
> ---
> kernel/trace/trace.c | 7 +++++++
> kernel/trace/trace.h | 2 ++
> kernel/trace/trace_mmiotrace.c | 1 +
> 3 files changed, 10 insertions(+)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 5360b7a..48c474f 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5358,6 +5358,13 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
> if (t == tr->current_trace)
> goto out;
>
> + /* Some tracers won't work on kernel command line */
> + if (system_state < SYSTEM_RUNNING && t->noboot) {
> + pr_warn("Tracer '%s' is not allowed on command line, ignored\n",
> + t->name);
I feel the core trace printed by WARN is not so meaningful, so I use
pr_warn instead.
> + goto out;
> + }
> +
> /* Some tracers are only allowed for the top level buffer */
> if (!trace_ok_for_array(t, tr)) {
> ret = -EINVAL;
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index fb5d54d..652c682 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -444,6 +444,8 @@ struct tracer {
> #ifdef CONFIG_TRACER_MAX_TRACE
> bool use_max_tr;
> #endif
> + /* True if tracer cannot be enabled in kernel param */
> + bool noboot;
> };
>
>
> diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
> index cd7480d..dca78fc 100644
> --- a/kernel/trace/trace_mmiotrace.c
> +++ b/kernel/trace/trace_mmiotrace.c
> @@ -282,6 +282,7 @@ static enum print_line_t mmio_print_line(struct trace_iterator *iter)
> .close = mmio_close,
> .read = mmio_read,
> .print_line = mmio_print_line,
> + .noboot = true,
> };
>
> __init static int init_mmio_trace(void)
>

This patch passed my own test on top of Fedora kernel 4.13.0-1.fc26.x86_64.
--
Ziqian SUN (Zamir)
9F Raycom office (NAY)
Red Hat Software (Beijing) Co.,Ltd
IRC: zsun (internal and freenode)
Tel: +86 10 65627458
GPG : 1D86 6D4A 49CE 4BBD 72CF FCF5 D856 6E11 F2A0 525E

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