From: Steven Rostedt <rostedt@goodmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Tom Zanussi <zanussi@kernel.org>
Subject: Re: [PATCH 2/4] tracing/hist: Call hist functions directly via a switch statement
Date: Mon, 5 Sep 2022 11:29:00 -0400 [thread overview]
Message-ID: <20220905112900.79c8a387@gandalf.local.home> (raw)
In-Reply-To: <20220905224849.80af1cb24d9eed1c1cdbcaee@kernel.org>
On Mon, 5 Sep 2022 22:48:49 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> Hi Steve,
>
> I found this crashed the kernel if I ran
>
> # ftracetest test.d/trigger/trigger-hist-expressions.tc
>
> More specifically, here is the minimum reproduce command.
>
> # echo "hist:keys=common_pid:x=16-8-4" > events/sched/sched_process_fork/trigger
> [ 75.874402] BUG: kernel NULL pointer dereference, address: 0000000000000038
> [ 75.875378] #PF: supervisor read access in kernel mode
>
> I investigated it and found you missed to set correct fn_num for
> combined constant field;
>
> > @@ -2725,7 +2748,8 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
> > if (var2)
> > expr->operands[1] = var2;
> >
> > - expr->constant = op_fn(expr, NULL, NULL, NULL, NULL);
> > + expr->fn_num = op_fn;
> > + expr->constant = hist_fn_call(expr, NULL, NULL, NULL, NULL);
> >
> > expr->operands[0] = NULL;
> > expr->operands[1] = NULL;
>
> Here, we need this;
>
> expr->fn_num = HIST_FIELD_FN_CONST;
>
> Without this fix, the binary op_fn is kept on this const field and it
> causes the problem because the const field doesn't have operands.
>
Thanks Masami,
Today is a US holiday, and I'm only cleaning out some email (and working on
my LPC presentation for tomorrow's speaker's training), but not doing any
other work. I'll look at this tomorrow.
-- Steve
next prev parent reply other threads:[~2022-09-05 15:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-23 21:46 [PATCH 0/4] tracing: Have filters and histograms use a call table instead of pointers Steven Rostedt
2022-08-23 21:46 ` [PATCH 1/4] tracing: Add numeric delta time to the trace event benchmark Steven Rostedt
2022-08-23 21:46 ` [PATCH 2/4] tracing/hist: Call hist functions directly via a switch statement Steven Rostedt
2022-09-05 13:48 ` Masami Hiramatsu
2022-09-05 15:29 ` Steven Rostedt [this message]
2022-09-06 21:38 ` Steven Rostedt
2022-08-23 21:46 ` [PATCH 3/4] tracing: Move struct filter_pred into trace_events_filter.c Steven Rostedt
2022-08-23 21:46 ` [PATCH 4/4] tracing/filter: Call filter predicate functions directly via a switch statement Steven Rostedt
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