Commit b6e5d971 authored Oct 28, 2025 by Steven Rostedt Committed by Steven Rostedt (Google) Oct 28, 2025

tracing: Check for printable characters when printing field dyn strings

When the "fields" option is enabled, it prints each trace event field
based on its type. But a dynamic array and a dynamic string can both have
a "char *" type. Printing it as a string can cause escape characters to be
printed and mess up the output of the trace.

For dynamic strings, test if there are any non-printable characters, and
if so, print both the string with the non printable characters as '.', and
the print the hex value of the array.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231148.929243047@kernel.org


Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

parent 64b627c8

kernel/trace/trace_output.c

+25 −2

Original line number	Diff line number	Diff line
		@@ -950,7 +950,9 @@ static void print_fields(struct trace_iterator iter, struct trace_event_call c
		int offset;
		int len;
		int ret;
		int i;
		void *pos;
		char *str;

		list_for_each_entry_reverse(field, head, link) {
		trace_seq_printf(&iter->seq, " %s=", field->name);
		@@ -977,8 +979,29 @@ static void print_fields(struct trace_iterator iter, struct trace_event_call c
		trace_seq_puts(&iter->seq, "<OVERFLOW>");
		break;
		}
		pos = (void *)iter->ent + offset;
		trace_seq_printf(&iter->seq, "%.s", len, (char )pos);
		str = (char *)iter->ent + offset;
		/* Check if there's any non printable strings */
		for (i = 0; i < len; i++) {
		if (str[i] && !(isascii(str[i]) && isprint(str[i])))
		break;
		}
		if (i < len) {
		for (i = 0; i < len; i++) {
		if (isascii(str[i]) && isprint(str[i]))
		trace_seq_putc(&iter->seq, str[i]);
		else
		trace_seq_putc(&iter->seq, '.');
		}
		trace_seq_puts(&iter->seq, " (");
		for (i = 0; i < len; i++) {
		if (i)
		trace_seq_putc(&iter->seq, ':');
		trace_seq_printf(&iter->seq, "%02x", str[i]);
		}
		trace_seq_putc(&iter->seq, ')');
		} else {
		trace_seq_printf(&iter->seq, "%.*s", len, str);
		}
		break;
		case FILTER_PTR_STRING:
		if (!iter->fmt_size)