Commit e77ad6da authored Oct 28, 2025 by Steven Rostedt Committed by Steven Rostedt (Google) Oct 28, 2025

tracing: Show printable characters in syscall arrays

When displaying the contents of the user space data passed to the kernel,
instead of just showing the array values, also print any printable
content.

Instead of just:

  bash-1113    [003] .....  3433.290654: sys_write(fd: 2, buf: 0x555a8deeddb0 (72:6f:6f:74:40:64:65:62:69:61:6e:2d:78:38:36:2d:36:34:3a:7e:23:20), count: 0x16)

Display:

  bash-1113    [003] .....  3433.290654: sys_write(fd: 2, buf: 0x555a8deeddb0 (72:6f:6f:74:40:64:65:62:69:61:6e:2d:78:38:36:2d:36:34:3a:7e:23:20) "root@debian-x86-64:~# ", count: 0x16)

This only affects tracing and does not affect perf, as this only updates
the output from the kernel. The output from perf is via user space. This
may change by an update to libtraceevent that will then update perf to
have this as well.

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/20251028231148.429422865@kernel.org


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

parent 299ea67e

kernel/trace/trace_syscalls.c

+21 −0

Original line number	Diff line number	Diff line
		@@ -155,6 +155,8 @@ print_syscall_enter(struct trace_iterator *iter, int flags,
		trace_seq_printf(s, "%s(", entry->name);

		for (i = 0; i < entry->nb_args; i++) {
		bool printable = false;
		char *str;

		if (trace_seq_has_overflowed(s))
		goto end;
		@@ -193,8 +195,11 @@ print_syscall_enter(struct trace_iterator *iter, int flags,

		val = trace->args[entry->user_arg_size];

		str = ptr;
		trace_seq_puts(s, " (");
		for (int x = 0; x < len; x++, ptr++) {
		if (isascii(ptr) && isprint(ptr))
		printable = true;
		if (x)
		trace_seq_putc(s, ':');
		trace_seq_printf(s, "%02x", *ptr);
		@@ -203,6 +208,22 @@ print_syscall_enter(struct trace_iterator *iter, int flags,
		trace_seq_printf(s, ", %s", EXTRA);

		trace_seq_putc(s, ')');

		/* If nothing is printable, don't bother printing anything */
		if (!printable)
		continue;

		trace_seq_puts(s, " \"");
		for (int x = 0; x < len; x++) {
		if (isascii(str[x]) && isprint(str[x]))
		trace_seq_putc(s, str[x]);
		else
		trace_seq_putc(s, '.');
		}
		if (len < val)
		trace_seq_printf(s, "\"%s", EXTRA);
		else
		trace_seq_putc(s, '"');
		}

		trace_seq_putc(s, ')');