sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 407 insertions, 0 deletions

diff --git a/tools/perf/util/trace-event-scripting.c b/tools/perf/util/trace-event-scripting.c
new file mode 100644
index 000000000..dc584ac31
--- /dev/null
+++ b/tools/perf/util/trace-event-scripting.c
@@ -0,0 +1,407 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * trace-event-scripting.  Scripting engine common and initialization code.
+ *
+ * Copyright (C) 2009-2010 Tom Zanussi <tzanussi@gmail.com>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#ifdef HAVE_LIBTRACEEVENT
+#include <event-parse.h>
+#endif
+
+#include "debug.h"
+#include "event.h"
+#include "trace-event.h"
+#include "evsel.h"
+#include <linux/perf_event.h>
+#include <linux/zalloc.h>
+#include "util/sample.h"
+
+unsigned int scripting_max_stack = PERF_MAX_STACK_DEPTH;
+
+struct scripting_context *scripting_context;
+
+struct script_spec {
+	struct list_head	node;
+	struct scripting_ops	*ops;
+	char			spec[];
+};
+
+static LIST_HEAD(script_specs);
+
+static struct script_spec *script_spec__new(const char *spec,
+					    struct scripting_ops *ops)
+{
+	struct script_spec *s = malloc(sizeof(*s) + strlen(spec) + 1);
+
+	if (s != NULL) {
+		strcpy(s->spec, spec);
+		s->ops = ops;
+	}
+
+	return s;
+}
+
+static void script_spec__add(struct script_spec *s)
+{
+	list_add_tail(&s->node, &script_specs);
+}
+
+static struct script_spec *script_spec__find(const char *spec)
+{
+	struct script_spec *s;
+
+	list_for_each_entry(s, &script_specs, node)
+		if (strcasecmp(s->spec, spec) == 0)
+			return s;
+	return NULL;
+}
+
+static int script_spec_register(const char *spec, struct scripting_ops *ops)
+{
+	struct script_spec *s;
+
+	s = script_spec__find(spec);
+	if (s)
+		return -1;
+
+	s = script_spec__new(spec, ops);
+	if (!s)
+		return -1;
+
+	script_spec__add(s);
+	return 0;
+}
+
+struct scripting_ops *script_spec__lookup(const char *spec)
+{
+	struct script_spec *s = script_spec__find(spec);
+
+	if (!s)
+		return NULL;
+
+	return s->ops;
+}
+
+int script_spec__for_each(int (*cb)(struct scripting_ops *ops, const char *spec))
+{
+	struct script_spec *s;
+	int ret = 0;
+
+	list_for_each_entry(s, &script_specs, node) {
+		ret = cb(s->ops, s->spec);
+		if (ret)
+			break;
+	}
+	return ret;
+}
+
+void scripting_context__update(struct scripting_context *c,
+			       union perf_event *event,
+			       struct perf_sample *sample,
+			       struct addr_location *al,
+			       struct addr_location *addr_al)
+{
+#ifdef HAVE_LIBTRACEEVENT
+	const struct tep_event *tp_format = evsel__tp_format(sample->evsel);
+
+	c->pevent = tp_format ? tp_format->tep : NULL;
+#else
+	c->pevent = NULL;
+#endif
+	c->event_data = sample->raw_data;
+	c->event = event;
+	c->sample = sample;
+	c->al = al;
+	c->addr_al = addr_al;
+}
+
+static int flush_script_unsupported(void)
+{
+	return 0;
+}
+
+static int stop_script_unsupported(void)
+{
+	return 0;
+}
+
+static void process_event_unsupported(union perf_event *event __maybe_unused,
+				      struct perf_sample *sample __maybe_unused,
+				      struct addr_location *al __maybe_unused,
+				      struct addr_location *addr_al __maybe_unused)
+{
+}
+
+static void print_python_unsupported_msg(void)
+{
+	fprintf(stderr, "Python scripting not supported."
+		"  Install libpython and rebuild perf to enable it.\n"
+		"For example:\n  # apt-get install python-dev (ubuntu)"
+		"\n  # yum install python-devel (Fedora)"
+		"\n  etc.\n");
+}
+
+static int python_start_script_unsupported(const char *script __maybe_unused,
+					   int argc __maybe_unused,
+					   const char **argv __maybe_unused,
+					   struct perf_session *session __maybe_unused)
+{
+	print_python_unsupported_msg();
+
+	return -1;
+}
+
+static int python_generate_script_unsupported(struct tep_handle *pevent
+					      __maybe_unused,
+					      const char *outfile
+					      __maybe_unused)
+{
+	print_python_unsupported_msg();
+
+	return -1;
+}
+
+struct scripting_ops python_scripting_unsupported_ops = {
+	.name = "Python",
+	.dirname = "python",
+	.start_script = python_start_script_unsupported,
+	.flush_script = flush_script_unsupported,
+	.stop_script = stop_script_unsupported,
+	.process_event = process_event_unsupported,
+	.generate_script = python_generate_script_unsupported,
+};
+
+static void register_python_scripting(struct scripting_ops *scripting_ops)
+{
+	if (scripting_context == NULL)
+		scripting_context = malloc(sizeof(*scripting_context));
+
+       if (scripting_context == NULL ||
+	   script_spec_register("Python", scripting_ops) ||
+	   script_spec_register("py", scripting_ops)) {
+		pr_err("Error registering Python script extension: disabling it\n");
+		zfree(&scripting_context);
+	}
+}
+
+#ifndef HAVE_LIBPYTHON_SUPPORT
+void setup_python_scripting(void)
+{
+	register_python_scripting(&python_scripting_unsupported_ops);
+}
+#else
+extern struct scripting_ops python_scripting_ops;
+
+void setup_python_scripting(void)
+{
+	register_python_scripting(&python_scripting_ops);
+}
+#endif
+
+#ifdef HAVE_LIBTRACEEVENT
+static void print_perl_unsupported_msg(void)
+{
+	fprintf(stderr, "Perl scripting not supported."
+		"  Install libperl and rebuild perf to enable it.\n"
+		"For example:\n  # apt-get install libperl-dev (ubuntu)"
+		"\n  # yum install 'perl(ExtUtils::Embed)' (Fedora)"
+		"\n  etc.\n");
+}
+
+static int perl_start_script_unsupported(const char *script __maybe_unused,
+					 int argc __maybe_unused,
+					 const char **argv __maybe_unused,
+					 struct perf_session *session __maybe_unused)
+{
+	print_perl_unsupported_msg();
+
+	return -1;
+}
+
+static int perl_generate_script_unsupported(struct tep_handle *pevent
+					    __maybe_unused,
+					    const char *outfile __maybe_unused)
+{
+	print_perl_unsupported_msg();
+
+	return -1;
+}
+
+struct scripting_ops perl_scripting_unsupported_ops = {
+	.name = "Perl",
+	.dirname = "perl",
+	.start_script = perl_start_script_unsupported,
+	.flush_script = flush_script_unsupported,
+	.stop_script = stop_script_unsupported,
+	.process_event = process_event_unsupported,
+	.generate_script = perl_generate_script_unsupported,
+};
+
+static void register_perl_scripting(struct scripting_ops *scripting_ops)
+{
+	if (scripting_context == NULL)
+		scripting_context = malloc(sizeof(*scripting_context));
+
+       if (scripting_context == NULL ||
+	   script_spec_register("Perl", scripting_ops) ||
+	   script_spec_register("pl", scripting_ops)) {
+		pr_err("Error registering Perl script extension: disabling it\n");
+		zfree(&scripting_context);
+	}
+}
+
+#ifndef HAVE_LIBPERL_SUPPORT
+void setup_perl_scripting(void)
+{
+	register_perl_scripting(&perl_scripting_unsupported_ops);
+}
+#else
+extern struct scripting_ops perl_scripting_ops;
+
+void setup_perl_scripting(void)
+{
+	register_perl_scripting(&perl_scripting_ops);
+}
+#endif
+#endif
+
+static const struct {
+	u32 flags;
+	const char *name;
+} sample_flags[] = {
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL, "call"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_RETURN, "return"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CONDITIONAL, "jcc"},
+	{PERF_IP_FLAG_BRANCH, "jmp"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL | PERF_IP_FLAG_INTERRUPT, "int"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_RETURN | PERF_IP_FLAG_INTERRUPT, "iret"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL | PERF_IP_FLAG_SYSCALLRET, "syscall"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_RETURN | PERF_IP_FLAG_SYSCALLRET, "sysret"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_ASYNC, "async"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL | PERF_IP_FLAG_ASYNC |	PERF_IP_FLAG_INTERRUPT,
+	 "hw int"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_TX_ABORT, "tx abrt"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_TRACE_BEGIN, "tr strt"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_TRACE_END, "tr end"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL | PERF_IP_FLAG_VMENTRY, "vmentry"},
+	{PERF_IP_FLAG_BRANCH | PERF_IP_FLAG_CALL | PERF_IP_FLAG_VMEXIT, "vmexit"},
+	{0, NULL}
+};
+
+static const struct {
+	u32 flags;
+	const char *name;
+} branch_events[] = {
+	{PERF_IP_FLAG_BRANCH_MISS, "miss"},
+	{PERF_IP_FLAG_NOT_TAKEN, "not_taken"},
+	{0, NULL}
+};
+
+static int sample_flags_to_name(u32 flags, char *str, size_t size)
+{
+	int i;
+	const char *prefix;
+	int pos = 0, ret, ev_idx = 0;
+	u32 xf = flags & PERF_ADDITIONAL_STATE_MASK;
+	u32 types, events;
+	char xs[16] = { 0 };
+
+	/* Clear additional state bits */
+	flags &= ~PERF_ADDITIONAL_STATE_MASK;
+
+	if (flags & PERF_IP_FLAG_TRACE_BEGIN)
+		prefix = "tr strt ";
+	else if (flags & PERF_IP_FLAG_TRACE_END)
+		prefix = "tr end  ";
+	else
+		prefix = "";
+
+	ret = snprintf(str + pos, size - pos, "%s", prefix);
+	if (ret < 0)
+		return ret;
+	pos += ret;
+
+	flags &= ~(PERF_IP_FLAG_TRACE_BEGIN | PERF_IP_FLAG_TRACE_END);
+
+	types = flags & ~PERF_IP_FLAG_BRANCH_EVENT_MASK;
+	for (i = 0; sample_flags[i].name; i++) {
+		if (sample_flags[i].flags != types)
+			continue;
+
+		ret = snprintf(str + pos, size - pos, "%s", sample_flags[i].name);
+		if (ret < 0)
+			return ret;
+		pos += ret;
+		break;
+	}
+
+	events = flags & PERF_IP_FLAG_BRANCH_EVENT_MASK;
+	for (i = 0; branch_events[i].name; i++) {
+		if (!(branch_events[i].flags & events))
+			continue;
+
+		ret = snprintf(str + pos, size - pos, !ev_idx ? "/%s" : ",%s",
+			       branch_events[i].name);
+		if (ret < 0)
+			return ret;
+		pos += ret;
+		ev_idx++;
+	}
+
+	/* Add an end character '/' for events */
+	if (ev_idx) {
+		ret = snprintf(str + pos, size - pos, "/");
+		if (ret < 0)
+			return ret;
+		pos += ret;
+	}
+
+	if (!xf)
+		return pos;
+
+	snprintf(xs, sizeof(xs), "(%s%s%s)",
+		 flags & PERF_IP_FLAG_IN_TX ? "x" : "",
+		 flags & PERF_IP_FLAG_INTR_DISABLE ? "D" : "",
+		 flags & PERF_IP_FLAG_INTR_TOGGLE ? "t" : "");
+
+	/* Right align the string if its length is less than the limit */
+	if ((pos + strlen(xs)) < SAMPLE_FLAGS_STR_ALIGNED_SIZE)
+		ret = snprintf(str + pos, size - pos, "%*s",
+			       (int)(SAMPLE_FLAGS_STR_ALIGNED_SIZE - ret), xs);
+	else
+		ret = snprintf(str + pos, size - pos, " %s", xs);
+	if (ret < 0)
+		return ret;
+
+	return pos + ret;
+}
+
+int perf_sample__sprintf_flags(u32 flags, char *str, size_t sz)
+{
+	const char *chars = PERF_IP_FLAG_CHARS;
+	const size_t n = strlen(PERF_IP_FLAG_CHARS);
+	size_t i, pos = 0;
+	int ret;
+
+	ret = sample_flags_to_name(flags, str, sz);
+	if (ret > 0)
+		return ret;
+
+	for (i = 0; i < n; i++, flags >>= 1) {
+		if ((flags & 1) && pos < sz)
+			str[pos++] = chars[i];
+	}
+	for (; i < 32; i++, flags >>= 1) {
+		if ((flags & 1) && pos < sz)
+			str[pos++] = '?';
+	}
+	if (pos < sz)
+		str[pos] = 0;
+
+	return pos;
+}