perf trace: Support tracepoint dynamic char arrays

Things like:

  # grep __data_loc /sys/kernel/debug/tracing/events/sched/sched_process_exec/format
	field:__data_loc char[] filename;	offset:8;	size:4;	signed:1;
  #

That, at that offset (8) and with that size(8) have an integer that
contains the real length and offset for the contents of that array.

Now this works:

  # perf trace --max-events 1 -e sched:*exec -a
     0.000 sed/19441 sched:sched_process_exec(filename: "/usr/bin/sync", pid: 19441 (sync), old_pid: 19441 (sync))
  #

As when using the libtraceevent based beautifier:

  # perf trace --libtraceevent --max-events 1 -e sched:*exec -a
     0.000 sync/19463 sched:sched_process_exec(filename=/usr/bin/sync pid=19463 old_pid=19463)
  #

I.e. that 'filename' is implemented as a dynamic char array.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-950p0m842fe6n7sxsdwqj5i2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index cdee22d..907eaf3 100644 (file)
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -563,7 +563,7 @@ static size_t syscall_arg__scnprintf_char_array(char *bf, size_t size, struct sy
        // XXX Hey, maybe for sched:sched_switch prev/next comm fields we can
        //     fill missing comms using thread__set_comm()...
        //     here or in a special syscall_arg__scnprintf_pid_sched_tp...
-       return scnprintf(bf, size, "\"%-.*s\"", arg->fmt->nr_entries, arg->val);
+       return scnprintf(bf, size, "\"%-.*s\"", arg->fmt->nr_entries ?: arg->len, arg->val);
 }
 
 #define SCA_CHAR_ARRAY syscall_arg__scnprintf_char_array
@@ -1559,7 +1559,7 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
                        arg->scnprintf = SCA_PID;
                else if (strcmp(field->type, "umode_t") == 0)
                        arg->scnprintf = SCA_MODE_T;
-               else if ((field->flags & TEP_FIELD_IS_ARRAY) && strstarts(field->type, "char")) {
+               else if ((field->flags & TEP_FIELD_IS_ARRAY) && strstr(field->type, "char")) {
                        arg->scnprintf = SCA_CHAR_ARRAY;
                        arg->nr_entries = field->arraylen;
                } else if ((strcmp(field->type, "int") == 0 ||
@@ -2523,10 +2523,19 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct evsel *evsel,
                if (syscall_arg.mask & bit)
                        continue;
 
+               syscall_arg.len = 0;
                syscall_arg.fmt = arg;
-               if (field->flags & TEP_FIELD_IS_ARRAY)
-                       val = (uintptr_t)(sample->raw_data + field->offset);
-               else
+               if (field->flags & TEP_FIELD_IS_ARRAY) {
+                       int offset = field->offset;
+
+                       if (field->flags & TEP_FIELD_IS_DYNAMIC) {
+                               offset = format_field__intval(field, sample, evsel->needs_swap);
+                               syscall_arg.len = offset >> 16;
+                               offset &= 0xffff;
+                       }
+
+                       val = (uintptr_t)(sample->raw_data + offset);
+               } else
                        val = format_field__intval(field, sample, evsel->needs_swap);
                /*
                 * Some syscall args need some mask, most don't and

diff --git a/tools/perf/trace/beauty/beauty.h b/tools/perf/trace/beauty/beauty.h
index 77ad80a..0dee0cf 100644 (file)
--- a/tools/perf/trace/beauty/beauty.h
+++ b/tools/perf/trace/beauty/beauty.h
@@ -87,6 +87,7 @@ struct syscall_arg_fmt;
 
 /**
  * @val: value of syscall argument being formatted
+ * @len: for tracepoint dynamic arrays, if fmt->nr_entries == 0, then its not a fixed array, look at arg->len
  * @args: All the args, use syscall_args__val(arg, nth) to access one
  * @augmented_args: Extra data that can be collected, for instance, with eBPF for expanding the pathname for open, etc
  * @augmented_args_size: augmented_args total payload size
@@ -109,6 +110,7 @@ struct syscall_arg {
        struct thread *thread;
        struct trace  *trace;
        void          *parm;
+       u16           len;
        u8            idx;
        u8            mask;
        bool          show_string_prefix;