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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>
This commit is contained in:
Steven Rostedt 2025-10-28 19:11:23 -04:00 committed by Steven Rostedt (Google)
parent 299ea67e6a
commit e77ad6da90
1 changed files with 21 additions and 0 deletions
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21
kernel/trace/trace_syscalls.c
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@ -155,6 +155,8 @@ print_syscall_enter(struct trace_iterator *iter, int flags,
trace_seq_printf(s, "%s(", entry->name); trace_seq_printf(s, "%s(", entry->name);
for (i = 0; i < entry->nb_args; i++) { for (i = 0; i < entry->nb_args; i++) {
bool printable = false;
char *str;
if (trace_seq_has_overflowed(s)) if (trace_seq_has_overflowed(s))
goto end; goto end;
@ -193,8 +195,11 @@ print_syscall_enter(struct trace_iterator *iter, int flags,
val = trace->args[entry->user_arg_size]; val = trace->args[entry->user_arg_size];
str = ptr;
trace_seq_puts(s, " ("); trace_seq_puts(s, " (");
for (int x = 0; x < len; x++, ptr++) { for (int x = 0; x < len; x++, ptr++) {
if (isascii(*ptr) && isprint(*ptr))
printable = true;
if (x) if (x)
trace_seq_putc(s, ':'); trace_seq_putc(s, ':');
trace_seq_printf(s, "%02x", *ptr); 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_printf(s, ", %s", EXTRA);
trace_seq_putc(s, ')'); 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, ')'); trace_seq_putc(s, ')');