perf script: Allow adding and removing fields

With 'perf script' it is common that we just want to add or remove a field.

Currently this requires figuring out the long list of default fields and
specifying them first, and then adding/removing the new field.

This patch adds a new + - syntax to merely add or remove fields,
that allows more succint and clearer command lines

For example to remove the comm field from PMU samples:

Previously

  $ perf script -F tid,cpu,time,event,sym,ip,dso,period | head -1
  swapper  0 [000] 504345.383126:          1 cycles:  ffffffff90060c66 native_write_msr ([kernel.kallsyms])

with the new syntax

  perf script -F -comm | head -1
  0 [000] 504345.383126:          1 cycles:  ffffffff90060c66 native_write_msr ([kernel.kallsyms])

The new syntax cannot be mixed with normal overriding.

v2: Fix example in description. Use tid vs pid. No functional changes.
v3: Don't skip initialization when user specified explicit type.
v4: Rebase. Remove empty line.

Committer testing:

  # perf record -a usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.748 MB perf.data (14 samples) ]

Without a explicit field list specified via -F, defaults to:

  # perf script | head -2
      perf 6338 [000] 18467.058607: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
   swapper    0 [001] 18467.058617: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
  #

Which is equivalent to:

  # perf script -F comm,tid,cpu,time,period,event,ip,sym,dso | head -2
      perf 6338 [000] 18467.058607: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
   swapper    0 [001] 18467.058617: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
  #

So if we want to remove the comm, as in your original example, we would have to
figure out the default field list and remove ' comm' from it:

  # perf script -F tid,cpu,time,period,event,ip,sym,dso | head -2
   6338 [000] 18467.058607: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
      0 [001] 18467.058617: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
  #

With your patch this becomes simpler, one can remove fields by prefixing them
with '-':

  # perf script -F -comm | head -2
  6338 [000] 18467.058607: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
     0 [001] 18467.058617: 1 cycles: ffffffff89060c36 native_write_msr (/lib/modules/4.11.0-rc8+/build/vmlinux)
  #

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Milian Wolff <milian.wolff@kdab.com>
Link: http://lkml.kernel.org/r/20170602154810.15875-1-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-script.txt

@@ -130,6 +130,14 @@ OPTIONS
 	i.e., the specified fields apply to all event types if the type string
 	is not given.
 
+	In addition to overriding fields, it is also possible to add or remove
+	fields from the defaults. For example
+
+		-F -cpu,+insn
+
+	removes the cpu field and adds the insn field. Adding/removing fields
+	cannot be mixed with normal overriding.
+
 	The arguments are processed in the order received. A later usage can
 	reset a prior request. e.g.:
 

tools/perf/builtin-script.c

@@ -1727,6 +1727,7 @@ static int parse_output_fields(const struct option *opt __maybe_unused,
 	int rc = 0;
 	char *str = strdup(arg);
 	int type = -1;
+	enum { DEFAULT, SET, ADD, REMOVE } change = DEFAULT;
 
 	if (!str)
 		return -ENOMEM;
@@ -1772,6 +1773,10 @@ static int parse_output_fields(const struct option *opt __maybe_unused,
 			goto out;
 		}
 
+		/* Don't override defaults for +- */
+		if (strchr(str, '+') || strchr(str, '-'))
+			goto parse;
+
 		if (output_set_by_user())
 			pr_warning("Overriding previous field request for all events.\n");
 
@@ -1782,13 +1787,30 @@ static int parse_output_fields(const struct option *opt __maybe_unused,
 		}
 	}
 
+parse:
 	for (tok = strtok_r(tok, ",", &strtok_saveptr); tok; tok = strtok_r(NULL, ",", &strtok_saveptr)) {
+		if (*tok == '+') {
+			if (change == SET)
+				goto out_badmix;
+			change = ADD;
+			tok++;
+		} else if (*tok == '-') {
+			if (change == SET)
+				goto out_badmix;
+			change = REMOVE;
+			tok++;
+		} else {
+			if (change != SET && change != DEFAULT)
+				goto out_badmix;
+			change = SET;
+		}
+
 		for (i = 0; i < imax; ++i) {
 			if (strcmp(tok, all_output_options[i].str) == 0)
 				break;
 		}
 		if (i == imax && strcmp(tok, "flags") == 0) {
-			print_flags = true;
+			print_flags = change == REMOVE ? false : true;
 			continue;
 		}
 		if (i == imax) {
@@ -1805,8 +1827,12 @@ static int parse_output_fields(const struct option *opt __maybe_unused,
 				if (output[j].invalid_fields & all_output_options[i].field) {
 					pr_warning("\'%s\' not valid for %s events. Ignoring.\n",
 						   all_output_options[i].str, event_type(j));
-				} else
-					output[j].fields |= all_output_options[i].field;
+				} else {
+					if (change == REMOVE)
+						output[j].fields &= ~all_output_options[i].field;
+					else
+						output[j].fields |= all_output_options[i].field;
+				}
 			}
 		} else {
 			if (output[type].invalid_fields & all_output_options[i].field) {
@@ -1826,7 +1852,11 @@ static int parse_output_fields(const struct option *opt __maybe_unused,
 				 "Events will not be displayed.\n", event_type(type));
 		}
 	}
+	goto out;
 
+out_badmix:
+	fprintf(stderr, "Cannot mix +-field with overridden fields\n");
+	rc = -EINVAL;
 out:
 	free(str);
 	return rc;
@@ -2444,6 +2474,7 @@ int cmd_script(int argc, const char **argv)
 		     symbol__config_symfs),
 	OPT_CALLBACK('F', "fields", NULL, "str",
 		     "comma separated output fields prepend with 'type:'. "
+		     "+field to add and -field to remove."
 		     "Valid types: hw,sw,trace,raw. "
 		     "Fields: comm,tid,pid,time,cpu,event,trace,ip,sym,dso,"
 		     "addr,symoff,period,iregs,brstack,brstacksym,flags,"