perf libbfd: Ensure libbfd is initialized prior to use

Multiple threads may be creating and destroying BFD objects in
situations like `perf top`.

Without appropriate initialization crashes may occur during libbfd's
cache management.

BFD's locks require recursive mutexes, add support for these.

Committer testing:

This happens only when building with 'make BUILD_NONDISTRO=1' and having
the binutils-devel package (or equivalent) installed, i.e. linking with
binutils devel files, an opt-in perf build.

Before:

root@x1:~# perf top
perf: Segmentation fault
-------- backtrace --------
<SNIP multiple failed attempts at printing a backtrace>
root@x1:~#

After this patch it works as before.

Closes: https://lore.kernel.org/lkml/[e-mail]/
Fixes: 95931d9a594dd0b5 ("perf libbfd: Move libbfd functionality to its own file")
Reported-by: Guilherme Amadio <[e-mail]>
Signed-off-by: Ian Rogers <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/libbfd.c

···
 	asymbol **syms;
 };
 
+static bool perf_bfd_lock(void *bfd_mutex)
+{
+	mutex_lock(bfd_mutex);
+	return true;
+}
+
+static bool perf_bfd_unlock(void *bfd_mutex)
+{
+	mutex_unlock(bfd_mutex);
+	return true;
+}
+
+static void perf_bfd_init(void)
+{
+	static struct mutex bfd_mutex;
+
+	mutex_init_recursive(&bfd_mutex);
+
+	if (bfd_init() != BFD_INIT_MAGIC) {
+		pr_err("Error initializing libbfd\n");
+		return;
+	}
+	if (!bfd_thread_init(perf_bfd_lock, perf_bfd_unlock, &bfd_mutex))
+		pr_err("Error initializing libbfd threading\n");
+}
+
+static void ensure_bfd_init(void)
+{
+	static pthread_once_t bfd_init_once = PTHREAD_ONCE_INIT;
+
+	pthread_once(&bfd_init_once, perf_bfd_init);
+}
+
 static int bfd_error(const char *string)
 {
 	const char *errmsg;
···
 	bfd *abfd;
 	struct a2l_data *a2l = NULL;
 
+	ensure_bfd_init();
 	abfd = bfd_openr(path, NULL);
 	if (abfd == NULL)
 		return NULL;
···
 	bfd *abfd;
 	u64 start, len;
 
+	ensure_bfd_init();
 	abfd = bfd_openr(debugfile, NULL);
 	if (!abfd)
 		return -1;
···
 	if (fd < 0)
 		return -1;
 
+	ensure_bfd_init();
 	abfd = bfd_fdopenr(filename, /*target=*/NULL, fd);
 	if (!abfd)
 		return -1;
···
 	asection *section;
 	bfd *abfd;
 
+	ensure_bfd_init();
 	abfd = bfd_openr(filename, NULL);
 	if (!abfd)
 		return -1;
···
 	memset(tpath, 0, sizeof(tpath));
 	perf_exe(tpath, sizeof(tpath));
 
+	ensure_bfd_init();
 	bfdf = bfd_openr(tpath, NULL);
 	if (bfdf == NULL)
 		abort();

tools/perf/util/mutex.c

···
 
 #define CHECK_ERR(err) check_err(__func__, err)
 
-static void __mutex_init(struct mutex *mtx, bool pshared)
+static void __mutex_init(struct mutex *mtx, bool pshared, bool recursive)
 {
 	pthread_mutexattr_t attr;
 
···
 	/* In normal builds enable error checking, such as recursive usage. */
 	CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK));
 #endif
+	if (recursive)
+		CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE));
 	if (pshared)
 		CHECK_ERR(pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
-
 	CHECK_ERR(pthread_mutex_init(&mtx->lock, &attr));
 	CHECK_ERR(pthread_mutexattr_destroy(&attr));
 }
 
 void mutex_init(struct mutex *mtx)
 {
-	__mutex_init(mtx, /*pshared=*/false);
+	__mutex_init(mtx, /*pshared=*/false, /*recursive=*/false);
 }
 
 void mutex_init_pshared(struct mutex *mtx)
 {
-	__mutex_init(mtx, /*pshared=*/true);
+	__mutex_init(mtx, /*pshared=*/true, /*recursive=*/false);
+}
+
+void mutex_init_recursive(struct mutex *mtx)
+{
+	__mutex_init(mtx, /*pshared=*/false, /*recursive=*/true);
 }
 
 void mutex_destroy(struct mutex *mtx)

tools/perf/util/mutex.h

···
  * process-private attribute.
  */
 void mutex_init_pshared(struct mutex *mtx);
+/* Initializes a mutex that may be recursively held on the same thread. */
+void mutex_init_recursive(struct mutex *mtx);
 void mutex_destroy(struct mutex *mtx);
 
 void mutex_lock(struct mutex *mtx) EXCLUSIVE_LOCK_FUNCTION(*mtx);