perf record: Disable debuginfod by default

Fedora 35 sets DEBUGINFOD_URLS by default, which might lead to
unexpected stalls in perf record exit path, when we try to cache
profiled binaries.

# DEBUGINFOD_PROGRESS=1 ./perf record -a
^C[ perf record: Woken up 1 times to write data ]
Downloading from https://debuginfod.fedoraproject.org/ 447069
Downloading from https://debuginfod.fedoraproject.org/ 1502175
Downloading \^Z

Disabling DEBUGINFOD_URLS by default in perf record and adding
debuginfod option and .perfconfig variable support to enable id.

Default without debuginfo processing:
# perf record -a

Using system debuginfod setup:
# perf record -a --debuginfod

Using custom debuginfd url:
# perf record -a --debuginfod='https://evenbetterdebuginfodserver.krava'

Adding single perf_debuginfod_setup function and using
it also in perf buildid-cache command.

Signed-off-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Frank Ch. Eigler <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Michael Petlan <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-buildid-cache.txt

···
 	used when creating a uprobe for a process that resides in a
 	different mount namespace from the perf(1) utility.
 
---debuginfod=URLs::
+--debuginfod[=URLs]::
 	Specify debuginfod URL to be used when retrieving perf.data binaries,
 	it follows the same syntax as the DEBUGINFOD_URLS variable, like:
 
 	  buildid-cache.debuginfod=http://192.168.122.174:8002
+
+	If the URLs is not specified, the value of DEBUGINFOD_URLS
+	system environment variable is used.
 
 SEE ALSO
 --------

tools/perf/Documentation/perf-config.txt

···
 		Use 'n' control blocks in asynchronous (Posix AIO) trace writing
 		mode ('n' default: 1, max: 4).
 
+	record.debuginfod::
+		Specify debuginfod URL to be used when cacheing perf.data binaries,
+		it follows the same syntax as the DEBUGINFOD_URLS variable, like:
+
+		  http://192.168.122.174:8002
+
+		If the URLs is 'system', the value of DEBUGINFOD_URLS system environment
+		variable is used.
+
 diff.*::
 	diff.order::
 		This option sets the number of columns to sort the result.

tools/perf/Documentation/perf-record.txt

···
 
 include::intel-hybrid.txt[]
 
+--debuginfod[=URLs]::
+	Specify debuginfod URL to be used when cacheing perf.data binaries,
+	it follows the same syntax as the DEBUGINFOD_URLS variable, like:
+
+	  http://192.168.122.174:8002
+
+	If the URLs is not specified, the value of DEBUGINFOD_URLS
+	system environment variable is used.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1], linkperf:perf-intel-pt[1]

tools/perf/builtin-buildid-cache.c

···
 
 static int perf_buildid_cache_config(const char *var, const char *value, void *cb)
 {
-	const char **debuginfod = cb;
+	struct perf_debuginfod *di = cb;
 
-	if (!strcmp(var, "buildid-cache.debuginfod"))
-		*debuginfod = strdup(value);
+	if (!strcmp(var, "buildid-cache.debuginfod")) {
+		di->urls = strdup(value);
+		if (!di->urls)
+			return -ENOMEM;
+		di->set = true;
+	}
 
 	return 0;
 }
···
 		   *purge_name_list_str = NULL,
 		   *missing_filename = NULL,
 		   *update_name_list_str = NULL,
-		   *kcore_filename = NULL,
-		   *debuginfod = NULL;
+		   *kcore_filename = NULL;
+	struct perf_debuginfod debuginfod = { };
 	char sbuf[STRERR_BUFSIZE];
 
 	struct perf_data data = {
···
 	OPT_BOOLEAN('f', "force", &force, "don't complain, do it"),
 	OPT_STRING('u', "update", &update_name_list_str, "file list",
 		    "file(s) to update"),
-	OPT_STRING(0, "debuginfod", &debuginfod, "debuginfod url",
-		    "set debuginfod url"),
+	OPT_STRING_OPTARG_SET(0, "debuginfod", &debuginfod.urls,
+			&debuginfod.set, "debuginfod urls",
+			"Enable debuginfod data retrieval from DEBUGINFOD_URLS or specified urls",
+			"system"),
 	OPT_INCR('v', "verbose", &verbose, "be more verbose"),
 	OPT_INTEGER(0, "target-ns", &ns_id, "target pid for namespace context"),
 	OPT_END()
···
 	if (argc || !(list_files || opts_flag))
 		usage_with_options(buildid_cache_usage, buildid_cache_options);
 
-	if (debuginfod) {
-		pr_debug("DEBUGINFOD_URLS=%s\n", debuginfod);
-		setenv("DEBUGINFOD_URLS", debuginfod, 1);
-	}
+	perf_debuginfod_setup(&debuginfod);
 
 	/* -l is exclusive. It can not be used with other options. */
 	if (list_files && opts_flag) {

tools/perf/builtin-record.c

···
 	unsigned long long	samples;
 	struct mmap_cpu_mask	affinity_mask;
 	unsigned long		output_max_size;	/* = 0: unlimited */
+	struct perf_debuginfod	debuginfod;
 };
 
 static volatile int done;
···
 			rec->opts.nr_cblocks = nr_cblocks_default;
 	}
 #endif
+	if (!strcmp(var, "record.debuginfod")) {
+		rec->debuginfod.urls = strdup(value);
+		if (!rec->debuginfod.urls)
+			return -ENOMEM;
+		rec->debuginfod.set = true;
+	}
 
 	return 0;
 }
···
 		      parse_control_option),
 	OPT_CALLBACK(0, "synth", &record.opts, "no|all|task|mmap|cgroup",
 		     "Fine-tune event synthesis: default=all", parse_record_synth_option),
+	OPT_STRING_OPTARG_SET(0, "debuginfod", &record.debuginfod.urls,
+			  &record.debuginfod.set, "debuginfod urls",
+			  "Enable debuginfod data retrieval from DEBUGINFOD_URLS or specified urls",
+			  "system"),
 	OPT_END()
 };
 
···
 	err = symbol__validate_sym_arguments();
 	if (err)
 		return err;
+
+	perf_debuginfod_setup(&record.debuginfod);
 
 	/* Make system wide (-a) the default target. */
 	if (!argc && target__none(&rec->opts.target))

tools/perf/util/util.c

···
 	}
 	return strcpy(buf, "perf");
 }
+
+void perf_debuginfod_setup(struct perf_debuginfod *di)
+{
+	/*
+	 * By default '!di->set' we clear DEBUGINFOD_URLS, so debuginfod
+	 * processing is not triggered, otherwise we set it to 'di->urls'
+	 * value. If 'di->urls' is "system" we keep DEBUGINFOD_URLS value.
+	 */
+	if (!di->set)
+		setenv("DEBUGINFOD_URLS", "", 1);
+	else if (di->urls && strcmp(di->urls, "system"))
+		setenv("DEBUGINFOD_URLS", di->urls, 1);
+
+	pr_debug("DEBUGINFOD_URLS=%s\n", getenv("DEBUGINFOD_URLS"));
+}

tools/perf/util/util.h

···
 struct perf_event_attr;
 void test_attr__open(struct perf_event_attr *attr, pid_t pid, struct perf_cpu cpu,
 		     int fd, int group_fd, unsigned long flags);
+
+struct perf_debuginfod {
+	const char	*urls;
+	bool		 set;
+};
+void perf_debuginfod_setup(struct perf_debuginfod *di);
 #endif /* GIT_COMPAT_UTIL_H */