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, 321 insertions, 0 deletions

diff --git a/tools/perf/util/pfm.c b/tools/perf/util/pfm.c
new file mode 100644
index 000000000..f80d6b0df
--- /dev/null
+++ b/tools/perf/util/pfm.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for libpfm4 event encoding.
+ *
+ * Copyright 2020 Google LLC.
+ */
+#include "util/cpumap.h"
+#include "util/debug.h"
+#include "util/event.h"
+#include "util/evlist.h"
+#include "util/evsel.h"
+#include "util/parse-events.h"
+#include "util/pmus.h"
+#include "util/pfm.h"
+#include "util/strbuf.h"
+#include "util/thread_map.h"
+
+#include <errno.h>
+#include <string.h>
+#include <linux/kernel.h>
+#include <perfmon/pfmlib_perf_event.h>
+
+static void libpfm_initialize(void)
+{
+	int ret;
+
+	ret = pfm_initialize();
+	if (ret != PFM_SUCCESS) {
+		ui__warning("libpfm failed to initialize: %s\n",
+			pfm_strerror(ret));
+	}
+}
+
+int parse_libpfm_events_option(const struct option *opt, const char *str,
+			int unset __maybe_unused)
+{
+	struct evlist *evlist = *(struct evlist **)opt->value;
+	struct perf_event_attr attr;
+	struct perf_pmu *pmu;
+	struct evsel *evsel, *grp_leader = NULL;
+	char *p, *q, *p_orig;
+	const char *sep;
+	int grp_evt = -1;
+	int ret;
+
+	libpfm_initialize();
+
+	p_orig = p = strdup(str);
+	if (!p)
+		return -1;
+
+	for (q = p; strsep(&p, ",{}"); q = p) {
+		sep = p ? str + (p - p_orig - 1) : "";
+		if (*sep == '{') {
+			if (grp_evt > -1) {
+				ui__error(
+					"nested event groups not supported\n");
+				goto error;
+			}
+			grp_evt++;
+		}
+
+		/* no event */
+		if (*q == '\0') {
+			if (*sep == '}') {
+				if (grp_evt < 0) {
+					ui__error("cannot close a non-existing event group\n");
+					goto error;
+				}
+				grp_evt--;
+			}
+			continue;
+		}
+
+		memset(&attr, 0, sizeof(attr));
+		event_attr_init(&attr);
+
+		ret = pfm_get_perf_event_encoding(q, PFM_PLM0|PFM_PLM3,
+						&attr, NULL, NULL);
+
+		if (ret != PFM_SUCCESS) {
+			ui__error("failed to parse event %s : %s\n", str,
+				  pfm_strerror(ret));
+			goto error;
+		}
+
+		pmu = perf_pmus__find_by_type((unsigned int)attr.type);
+		evsel = parse_events__add_event(evlist__nr_entries(evlist),
+						&attr, q, /*metric_id=*/NULL,
+						pmu);
+		if (evsel == NULL)
+			goto error;
+
+		evsel->is_libpfm_event = true;
+
+		evlist__add(evlist, evsel);
+
+		if (grp_evt == 0)
+			grp_leader = evsel;
+
+		if (grp_evt > -1) {
+			evsel__set_leader(evsel, grp_leader);
+			grp_leader->core.nr_members++;
+			grp_evt++;
+		}
+
+		if (*sep == '}') {
+			if (grp_evt < 0) {
+				ui__error(
+				   "cannot close a non-existing event group\n");
+				goto error;
+			}
+			grp_leader = NULL;
+			grp_evt = -1;
+		}
+	}
+	free(p_orig);
+	return 0;
+error:
+	free(p_orig);
+	return -1;
+}
+
+static bool is_libpfm_event_supported(const char *name, struct perf_cpu_map *cpus,
+				      struct perf_thread_map *threads)
+{
+	struct perf_pmu *pmu;
+	struct evsel *evsel;
+	struct perf_event_attr attr = {};
+	bool result = true;
+	int ret;
+
+	ret = pfm_get_perf_event_encoding(name, PFM_PLM0|PFM_PLM3,
+					  &attr, NULL, NULL);
+	if (ret != PFM_SUCCESS)
+		return false;
+
+	pmu = perf_pmus__find_by_type((unsigned int)attr.type);
+	evsel = parse_events__add_event(0, &attr, name, /*metric_id=*/NULL, pmu);
+	if (evsel == NULL)
+		return false;
+
+	evsel->is_libpfm_event = true;
+
+	ret = evsel__open(evsel, cpus, threads);
+	if (ret == -EACCES) {
+		/*
+		 * This happens if the paranoid value
+		 * /proc/sys/kernel/perf_event_paranoid is set to 2
+		 * Re-run with exclude_kernel set; we don't do that
+		 * by default as some ARM machines do not support it.
+		 *
+		 */
+		evsel->core.attr.exclude_kernel = 1;
+		ret = evsel__open(evsel, cpus, threads);
+
+	}
+	if (ret < 0)
+		result = false;
+
+	evsel__close(evsel);
+	evsel__put(evsel);
+
+	return result;
+}
+
+static const char *srcs[PFM_ATTR_CTRL_MAX] = {
+	[PFM_ATTR_CTRL_UNKNOWN] = "???",
+	[PFM_ATTR_CTRL_PMU] = "PMU",
+	[PFM_ATTR_CTRL_PERF_EVENT] = "perf_event",
+};
+
+static void
+print_attr_flags(struct strbuf *buf, const pfm_event_attr_info_t *info)
+{
+	if (info->is_dfl)
+		strbuf_addf(buf, "[default] ");
+
+	if (info->is_precise)
+		strbuf_addf(buf, "[precise] ");
+}
+
+static void
+print_libpfm_event(const struct print_callbacks *print_cb, void *print_state,
+		const pfm_pmu_info_t *pinfo, const pfm_event_info_t *info,
+		struct strbuf *buf)
+{
+	int j, ret;
+	char topic[80], name[80];
+	struct perf_cpu_map *cpus = perf_cpu_map__empty_new(1);
+	struct perf_thread_map *threads = thread_map__new_by_tid(0);
+
+	strbuf_setlen(buf, 0);
+	snprintf(topic, sizeof(topic), "pfm %s", pinfo->name);
+
+	snprintf(name, sizeof(name), "%s::%s", pinfo->name, info->name);
+	strbuf_addf(buf, "Code: 0x%"PRIx64"\n", info->code);
+
+	pfm_for_each_event_attr(j, info) {
+		pfm_event_attr_info_t ainfo;
+		const char *src;
+
+		ainfo.size = sizeof(ainfo);
+		ret = pfm_get_event_attr_info(info->idx, j, PFM_OS_PERF_EVENT_EXT, &ainfo);
+		if (ret != PFM_SUCCESS)
+			continue;
+
+		if (ainfo.ctrl >= PFM_ATTR_CTRL_MAX)
+			ainfo.ctrl = PFM_ATTR_CTRL_UNKNOWN;
+
+		src = srcs[ainfo.ctrl];
+		switch (ainfo.type) {
+		case PFM_ATTR_UMASK: /* Ignore for now */
+			break;
+		case PFM_ATTR_MOD_BOOL:
+			strbuf_addf(buf, " Modif: %s: [%s] : %s (boolean)\n", src,
+				    ainfo.name, ainfo.desc);
+			break;
+		case PFM_ATTR_MOD_INTEGER:
+			strbuf_addf(buf, " Modif: %s: [%s] : %s (integer)\n", src,
+				    ainfo.name, ainfo.desc);
+			break;
+		case PFM_ATTR_NONE:
+		case PFM_ATTR_RAW_UMASK:
+		case PFM_ATTR_MAX:
+		default:
+			strbuf_addf(buf, " Attr: %s: [%s] : %s\n", src,
+				    ainfo.name, ainfo.desc);
+		}
+	}
+
+	if (is_libpfm_event_supported(name, cpus, threads)) {
+		print_cb->print_event(print_state, topic, pinfo->name,
+				      /*pmu_type=*/PERF_TYPE_RAW,
+				      name, info->equiv,
+				      /*scale_unit=*/NULL,
+				      /*deprecated=*/NULL, "PFM event",
+				      info->desc, /*long_desc=*/NULL,
+				      /*encoding_desc=*/buf->buf);
+	}
+
+	pfm_for_each_event_attr(j, info) {
+		pfm_event_attr_info_t ainfo;
+		const char *src;
+
+		strbuf_setlen(buf, 0);
+
+		ainfo.size = sizeof(ainfo);
+		ret = pfm_get_event_attr_info(info->idx, j, PFM_OS_PERF_EVENT_EXT, &ainfo);
+		if (ret != PFM_SUCCESS)
+			continue;
+
+		if (ainfo.ctrl >= PFM_ATTR_CTRL_MAX)
+			ainfo.ctrl = PFM_ATTR_CTRL_UNKNOWN;
+
+		src = srcs[ainfo.ctrl];
+		if (ainfo.type == PFM_ATTR_UMASK) {
+			strbuf_addf(buf, "Umask: 0x%02"PRIx64" : %s: ",
+				ainfo.code, src);
+			print_attr_flags(buf, &ainfo);
+			snprintf(name, sizeof(name), "%s::%s:%s",
+				 pinfo->name, info->name, ainfo.name);
+
+			if (!is_libpfm_event_supported(name, cpus, threads))
+				continue;
+
+			print_cb->print_event(print_state,
+					topic,
+					pinfo->name,
+					/*pmu_type=*/PERF_TYPE_RAW,
+					name, /*alias=*/NULL,
+					/*scale_unit=*/NULL,
+					/*deprecated=*/NULL, "PFM event",
+					ainfo.desc, /*long_desc=*/NULL,
+					/*encoding_desc=*/buf->buf);
+		}
+	}
+
+	perf_cpu_map__put(cpus);
+	perf_thread_map__put(threads);
+}
+
+void print_libpfm_events(const struct print_callbacks *print_cb, void *print_state)
+{
+	pfm_event_info_t info;
+	pfm_pmu_info_t pinfo;
+	int p, ret;
+	struct strbuf storage;
+
+	libpfm_initialize();
+
+	/* initialize to zero to indicate ABI version */
+	info.size  = sizeof(info);
+	pinfo.size = sizeof(pinfo);
+
+	strbuf_init(&storage, 2048);
+
+	pfm_for_all_pmus(p) {
+		ret = pfm_get_pmu_info(p, &pinfo);
+		if (ret != PFM_SUCCESS)
+			continue;
+
+		/* only print events that are supported by host HW */
+		if (!pinfo.is_present)
+			continue;
+
+		/* handled by perf directly */
+		if (pinfo.pmu == PFM_PMU_PERF_EVENT)
+			continue;
+
+		for (int i = pinfo.first_event; i != -1; i = pfm_get_event_next(i)) {
+			ret = pfm_get_event_info(i, PFM_OS_PERF_EVENT_EXT,
+						&info);
+			if (ret != PFM_SUCCESS)
+				continue;
+
+			print_libpfm_event(print_cb, print_state, &pinfo, &info, &storage);
+		}
+	}
+	strbuf_release(&storage);
+}