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SubjectRe: [PATCH] tracing/histograms: Fix parsing of "sym-offset" modifier
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Hi Steve,

On Wed, 2021-07-07 at 11:08 -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
>
> With the addition of simple mathematical operations (plus and minus),
> the
> parsing of the "sym-offset" modifier broke, as it took the '-' part
> of the
> "sym-offset" as a minus, and tried to break it up into a mathematical
> operation of "field.sym - offset", in which case it failed to parse
> (unless the event had a field called "offset").
>
> Both .sym and .sym-offset modifiers should not be entered into
> mathematical calculations anyway. If ".sym-offset" is found in the
> modifier, then simply make it not an operation that can be calculated
> on.
>
> Cc: stable@vger.kernel.org
> Fixes: 100719dcef447 ("tracing: Add simple expression support to hist
> triggers")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> kernel/trace/trace_events_hist.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/kernel/trace/trace_events_hist.c
> b/kernel/trace/trace_events_hist.c
> index ba03b7d84fc2..0207aeed31e6 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -1555,6 +1555,13 @@ static int contains_operator(char *str)
>
> switch (*op) {
> case '-':
> + /*
> + * Unfortunately, the modifier ".sym-offset"
> + * can confuse things.
> + */

Good catch.

> + if (op - str >= 4 && !strncmp(op - 4, ".sym-offset",
> 11))
> + return FIELD_OP_NONE;
> +
> if (*str == '-')
> field_op = FIELD_OP_UNARY_MINUS;
> else

Reviewed-by: Tom Zanussi <zanussi@kernel.org>


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