perf buildid-cache: Add --debuginfod option to specify a server to fetch debug files

Add the --debuginfod option to specify debuginfod URL and support to do
that through config file as well.

Use the following in ~/.perfconfig file:

  [buildid-cache]
  debuginfod=http://192.168.122.174:8002

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201214105457.543111-14-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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

@@ -74,6 +74,12 @@ OPTIONS
 	used when creating a uprobe for a process that resides in a
 	different mount namespace from the perf(1) utility.
 
+--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
+
 SEE ALSO
 --------
 linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-buildid-list[1]

tools/perf/Documentation/perf-config.txt

@@ -238,6 +238,13 @@ buildid.*::
 		cache location, or to disable it altogether. If you want to disable it,
 		set buildid.dir to /dev/null. The default is $HOME/.debug
 
+buildid-cache.*::
+	buildid-cache.debuginfod=URLs
+		Specify debuginfod URLs 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
+
 annotate.*::
 	These are in control of addresses, jump function, source code
 	in lines of assembly code from a specific program.

tools/perf/builtin-buildid-cache.c

@@ -27,6 +27,7 @@
 #include "util/time-utils.h"
 #include "util/util.h"
 #include "util/probe-file.h"
+#include "util/config.h"
 #include <linux/string.h>
 #include <linux/err.h>
 
@@ -348,12 +349,21 @@ static int build_id_cache__show_all(void)
 	return 0;
 }
 
+static int perf_buildid_cache_config(const char *var, const char *value, void *cb)
+{
+	const char **debuginfod = cb;
+
+	if (!strcmp(var, "buildid-cache.debuginfod"))
+		*debuginfod = strdup(value);
+
+	return 0;
+}
+
 int cmd_buildid_cache(int argc, const char **argv)
 {
 	struct strlist *list;
 	struct str_node *pos;
-	int ret = 0;
+	int ret, ns_id = -1;
-	int ns_id = -1;
 	bool force = false;
 	bool list_files = false;
 	bool opts_flag = false;
@@ -363,7 +373,8 @@ int cmd_buildid_cache(int argc, const char **argv)
 		   *purge_name_list_str = NULL,
 		   *missing_filename = NULL,
 		   *update_name_list_str = NULL,
-		   *kcore_filename = NULL;
+		   *kcore_filename = NULL,
+		   *debuginfod = NULL;
 	char sbuf[STRERR_BUFSIZE];
 
 	struct perf_data data = {
@@ -388,6 +399,8 @@ int cmd_buildid_cache(int argc, const char **argv)
 	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_INCR('v', "verbose", &verbose, "be more verbose"),
 	OPT_INTEGER(0, "target-ns", &ns_id, "target pid for namespace context"),
 	OPT_END()
@@ -397,6 +410,10 @@ int cmd_buildid_cache(int argc, const char **argv)
 		NULL
 	};
 
+	ret = perf_config(perf_buildid_cache_config, &debuginfod);
+	if (ret)
+		return ret;
+
 	argc = parse_options(argc, argv, buildid_cache_options,
 			     buildid_cache_usage, 0);
 
@@ -408,6 +425,11 @@ int cmd_buildid_cache(int argc, const char **argv)
 	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);
+	}
+
 	/* -l is exclusive. It can not be used with other options. */
 	if (list_files && opts_flag) {
 		usage_with_options_msg(buildid_cache_usage,