perf path: Make mkpath thread safe, remove 16384 bytes from .bss

Avoid 4 static arrays for paths, pass in a char[] buffer to use. Makes
mkpath thread safe for the small number of users. Also removes 16,384
bytes from .bss.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Ross Zwisler <zwisler@chromium.org>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Yang Jihong <yangjihong1@huawei.com>
Link: https://lore.kernel.org/r/20230526183401.2326121-13-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 8 insertions, 32 deletions

diff --git a/tools/perf/util/cache.h b/tools/perf/util/cache.h
index 9f2e36ef5072..0b61840d4226 100644
--- a/tools/perf/util/cache.h
+++ b/tools/perf/util/cache.h
@@ -26,6 +26,6 @@ static inline int is_absolute_path(const char *path)
 	return path[0] == '/';
 }
 
-char *mkpath(const char *fmt, ...) __printf(1, 2);
+char *mkpath(char *path_buf, size_t sz, const char *fmt, ...) __printf(3, 4);
 
 #endif /* __PERF_CACHE_H */
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 658170b8dcef..f340dc73db6d 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -543,6 +543,7 @@ static char *home_perfconfig(void)
 	const char *home = NULL;
 	char *config;
 	struct stat st;
+	char path[PATH_MAX];
 
 	home = getenv("HOME");
 
@@ -554,7 +555,7 @@ static char *home_perfconfig(void)
 	if (!home || !*home || !perf_config_global())
 		return NULL;
 
-	config = strdup(mkpath("%s/.perfconfig", home));
+	config = strdup(mkpath(path, sizeof(path), "%s/.perfconfig", home));
 	if (config == NULL) {
 		pr_warning("Not enough memory to process %s/.perfconfig, ignoring it.\n", home);
 		return NULL;
diff --git a/tools/perf/util/path.c b/tools/perf/util/path.c
index ce80b79be103..00adf872bf00 100644
--- a/tools/perf/util/path.c
+++ b/tools/perf/util/path.c
@@ -1,16 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0
-/*
- * I'm tired of doing "vsnprintf()" etc just to open a
- * file, so here's a "return static buffer with printf"
- * interface for paths.
- *
- * It's obviously not thread-safe. Sue me. But it's quite
- * useful for doing things like
- *
- *   f = open(mkpath("%s/%s.perf", base, name), O_RDONLY);
- *
- * which is what it's designed for.
- */
 #include "path.h"
 #include "cache.h"
 #include <linux/kernel.h>
@@ -22,18 +10,6 @@
 #include <dirent.h>
 #include <unistd.h>
 
-static char bad_path[] = "/bad-path/";
-/*
- * One hack:
- */
-static char *get_pathname(void)
-{
-	static char pathname_array[4][PATH_MAX];
-	static int idx;
-
-	return pathname_array[3 & ++idx];
-}
-
 static char *cleanup_path(char *path)
 {
 	/* Clean it up */
@@ -45,18 +21,17 @@ static char *cleanup_path(char *path)
 	return path;
 }
 
-char *mkpath(const char *fmt, ...)
+char *mkpath(char *path_buf, size_t sz, const char *fmt, ...)
 {
 	va_list args;
 	unsigned len;
-	char *pathname = get_pathname();
 
 	va_start(args, fmt);
-	len = vsnprintf(pathname, PATH_MAX, fmt, args);
+	len = vsnprintf(path_buf, sz, fmt, args);
 	va_end(args);
-	if (len >= PATH_MAX)
-		return bad_path;
-	return cleanup_path(pathname);
+	if (len >= sz)
+		strncpy(path_buf, "/bad-path/", sz);
+	return cleanup_path(path_buf);
 }
 
 int path__join(char *bf, size_t size, const char *path1, const char *path2)