ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 191 insertions, 0 deletions

diff --git a/tools/perf/builtin-check.c b/tools/perf/builtin-check.c
new file mode 100644
index 000000000..60437650c
--- /dev/null
+++ b/tools/perf/builtin-check.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "builtin.h"
+#include "color.h"
+#include "util/bpf-utils.h"
+#include "util/debug.h"
+#include "util/header.h"
+#include <tools/config.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <subcmd/parse-options.h>
+
+static const char * const check_subcommands[] = { "feature", NULL };
+static struct option check_options[] = {
+	OPT_BOOLEAN('q', "quiet", &quiet, "do not show any warnings or messages"),
+	OPT_END()
+};
+static struct option check_feature_options[] = { OPT_PARENT(check_options) };
+
+static const char *check_usage[] = { NULL, NULL };
+static const char *check_feature_usage[] = {
+	"perf check feature <feature_list>",
+	NULL
+};
+
+#define FEATURE_STATUS(name_, macro_) {    \
+	.name = name_,                     \
+	.macro = #macro_,                  \
+	.is_builtin = IS_BUILTIN(macro_) }
+
+#define FEATURE_STATUS_TIP(name_, macro_, tip_) { \
+	.name = name_,				  \
+	.macro = #macro_,			  \
+	.tip = tip_,				  \
+	.is_builtin = IS_BUILTIN(macro_) }
+
+struct feature_status supported_features[] = {
+	FEATURE_STATUS("aio", HAVE_AIO_SUPPORT),
+	FEATURE_STATUS("bpf", HAVE_LIBBPF_SUPPORT),
+	FEATURE_STATUS("bpf_skeletons", HAVE_BPF_SKEL),
+	FEATURE_STATUS("debuginfod", HAVE_DEBUGINFOD_SUPPORT),
+	FEATURE_STATUS("dwarf", HAVE_LIBDW_SUPPORT),
+	FEATURE_STATUS("dwarf_getlocations", HAVE_LIBDW_SUPPORT),
+	FEATURE_STATUS("dwarf-unwind", HAVE_DWARF_UNWIND_SUPPORT),
+	FEATURE_STATUS_TIP("libbfd", HAVE_LIBBFD_SUPPORT, "Deprecated, license incompatibility, use BUILD_NONDISTRO=1 and install binutils-dev[el]"),
+	FEATURE_STATUS("babeltrace2-ctf-writer", HAVE_BABELTRACE2_CTF_WRITER_SUPPORT),
+	FEATURE_STATUS("libbpf-strings", HAVE_LIBBPF_STRINGS_SUPPORT),
+	FEATURE_STATUS("libcapstone", HAVE_LIBCAPSTONE_SUPPORT),
+	FEATURE_STATUS("libdw-dwarf-unwind", HAVE_LIBDW_SUPPORT),
+	FEATURE_STATUS("libelf", HAVE_LIBELF_SUPPORT),
+	FEATURE_STATUS("libLLVM", HAVE_LIBLLVM_SUPPORT),
+	FEATURE_STATUS("libnuma", HAVE_LIBNUMA_SUPPORT),
+	FEATURE_STATUS("libopencsd", HAVE_CSTRACE_SUPPORT),
+	FEATURE_STATUS_TIP("libperl", HAVE_LIBPERL_SUPPORT, "Deprecated, use LIBPERL=1 and install perl-ExtUtils-Embed/libperl-dev to build with it"),
+	FEATURE_STATUS("libpfm4", HAVE_LIBPFM),
+	FEATURE_STATUS("libpython", HAVE_LIBPYTHON_SUPPORT),
+	FEATURE_STATUS("libslang", HAVE_SLANG_SUPPORT),
+	FEATURE_STATUS("libtraceevent", HAVE_LIBTRACEEVENT),
+	FEATURE_STATUS_TIP("libunwind", HAVE_LIBUNWIND_SUPPORT, "Deprecated, use LIBUNWIND=1 and install libunwind-dev[el] to build with it"),
+	FEATURE_STATUS("lzma", HAVE_LZMA_SUPPORT),
+	FEATURE_STATUS("numa_num_possible_cpus", HAVE_LIBNUMA_SUPPORT),
+	FEATURE_STATUS("zlib", HAVE_ZLIB_SUPPORT),
+	FEATURE_STATUS("zstd", HAVE_ZSTD_SUPPORT),
+	FEATURE_STATUS("rust", HAVE_RUST_SUPPORT),
+
+	/* this should remain at end, to know the array end */
+	FEATURE_STATUS(NULL, _)
+};
+
+static void on_off_print(const char *status)
+{
+	printf("[ ");
+
+	if (!strcmp(status, "OFF"))
+		color_fprintf(stdout, PERF_COLOR_RED, "%-3s", status);
+	else
+		color_fprintf(stdout, PERF_COLOR_GREEN, "%-3s", status);
+
+	printf(" ]");
+}
+
+/* Helper function to print status of a feature along with name/macro */
+void feature_status__printf(const struct feature_status *feature)
+{
+	const char *name = feature->name, *macro = feature->macro,
+		   *status = feature->is_builtin ? "on" : "OFF";
+
+	printf("%22s: ", name);
+	on_off_print(status);
+	printf("  # %s", macro);
+
+	if (!feature->is_builtin && feature->tip)
+		printf(" ( tip: %s )", feature->tip);
+
+	putchar('\n');
+}
+
+/**
+ * check whether "feature" is built-in with perf
+ *
+ * returns:
+ *    0: NOT built-in or Feature not known
+ *    1: Built-in
+ */
+static int has_support(const char *feature)
+{
+	for (int i = 0; supported_features[i].name; ++i) {
+		if ((strcasecmp(feature, supported_features[i].name) == 0) ||
+		    (strcasecmp(feature, supported_features[i].macro) == 0)) {
+			if (!quiet)
+				feature_status__printf(&supported_features[i]);
+			return supported_features[i].is_builtin;
+		}
+	}
+
+	if (!quiet)
+		pr_err("Unknown feature '%s', please use 'perf version --build-options' to see which ones are available.\n", feature);
+
+	return 0;
+}
+
+
+/**
+ * Usage: 'perf check feature <feature_list>'
+ *
+ * <feature_list> can be a single feature name/macro, or a comma-separated list
+ * of feature names/macros
+ * eg. argument can be "libtraceevent" or "libtraceevent,bpf" etc
+ *
+ * In case of a comma-separated list, feature_enabled will be 1, only if
+ * all features passed in the string are supported
+ *
+ * Note that argv will get modified
+ */
+static int subcommand_feature(int argc, const char **argv)
+{
+	char *feature_list;
+	char *feature_name;
+	int feature_enabled;
+
+	argc = parse_options(argc, argv, check_feature_options,
+			check_feature_usage, 0);
+
+	if (!argc)
+		usage_with_options(check_feature_usage, check_feature_options);
+
+	if (argc > 1) {
+		pr_err("Too many arguments passed to 'perf check feature'\n");
+		return -1;
+	}
+
+	feature_enabled = 1;
+	/* feature_list is a non-const copy of 'argv[0]' */
+	feature_list = strdup(argv[0]);
+	if (!feature_list) {
+		pr_err("ERROR: failed to allocate memory for feature list\n");
+		return -1;
+	}
+
+	feature_name = strtok(feature_list, ",");
+
+	while (feature_name) {
+		feature_enabled &= has_support(feature_name);
+		feature_name = strtok(NULL, ",");
+	}
+
+	free(feature_list);
+
+	return !feature_enabled;
+}
+
+int cmd_check(int argc, const char **argv)
+{
+	argc = parse_options_subcommand(argc, argv, check_options,
+			check_subcommands, check_usage, 0);
+
+	if (!argc)
+		usage_with_options(check_usage, check_options);
+
+	if (strcmp(argv[0], "feature") == 0)
+		return subcommand_feature(argc, argv);
+
+	/* If no subcommand matched above, print usage help */
+	pr_err("Unknown subcommand: %s\n", argv[0]);
+	usage_with_options(check_usage, check_options);
+
+	/* free usage string allocated by parse_options_subcommand */
+	free((void *)check_usage[0]);
+
+	return 0;
+}