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Subject[PATCH] tracing/histograms: Fix parsing of "sym-offset" modifier
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.
+ */
+ if (op - str >= 4 && !strncmp(op - 4, ".sym-offset", 11))
+ return FIELD_OP_NONE;
+
if (*str == '-')
field_op = FIELD_OP_UNARY_MINUS;
else
--
2.31.1
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