Simple dummy module that mimics what can be done with drivers to
bind/unbind them from the bus, which should trigger resource release.
This is mostly based on how i915 and (pending changes for) xe drivers
are interacting with perf pmu. A few differences due to not having
backing hardware or for simplicity:
- Instead of using BDF for bind/unbind, use a single number.
- Unbind is triggered either via debugfs or when removing the
module.
- event::destroy() is always assigned as there should only be a
few additional calls
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
---
kernel/events/Makefile | 1 +
kernel/events/dummy_pmu.c | 426 ++++++++++++++++++++++++++++++++++++++
2 files changed, 427 insertions(+)
create mode 100644 kernel/events/dummy_pmu.c
diff --git a/kernel/events/Makefile b/kernel/events/Makefile
index 91a62f566743..2993fed2d091 100644
--- a/kernel/events/Makefile
+++ b/kernel/events/Makefile
@@ -4,3 +4,4 @@ obj-y := core.o ring_buffer.o callchain.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_HW_BREAKPOINT_KUNIT_TEST) += hw_breakpoint_test.o
obj-$(CONFIG_UPROBES) += uprobes.o
+obj-m += dummy_pmu.o
diff --git a/kernel/events/dummy_pmu.c b/kernel/events/dummy_pmu.c
new file mode 100644
index 000000000000..cdba3a831e4a
--- /dev/null
+++ b/kernel/events/dummy_pmu.c
@@ -0,0 +1,426 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#define pr_fmt(fmt) "%s: " fmt, KBUILD_MODNAME
+
+#include <linux/debugfs.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/perf_event.h>
+#include <linux/random.h>
+#include <linux/seq_file.h>
+#include <linux/types.h>
+
+struct dummy_mod {
+ struct dentry *debugfs_root;
+
+ struct list_head device_list;
+ struct mutex mutex;
+};
+
+struct dummy_pmu {
+ struct pmu base;
+ char *name;
+ bool registered;
+};
+
+struct dummy_device {
+ unsigned int instance;
+ struct kref refcount;
+ struct list_head mod_entry;
+ struct dummy_pmu pmu;
+};
+
+static struct dummy_mod dm;
+
+static void device_release(struct kref *ref);
+
+static struct dummy_pmu *event_to_pmu(struct perf_event *event)
+{
+ return container_of(event->pmu, struct dummy_pmu, base);
+}
+
+static struct dummy_device *pmu_to_device(struct dummy_pmu *pmu)
+{
+ return container_of(pmu, struct dummy_device, pmu);
+}
+
+static ssize_t dummy_pmu_events_sysfs_show(struct device *dev,
+ struct device_attribute *attr,
+ char *page)
+{
+ struct perf_pmu_events_attr *pmu_attr;
+
+ pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);
+
+ return sprintf(page, "event=0x%04llx\n", pmu_attr->id);
+}
+
+#define DUMMY_PMU_EVENT_ATTR(name, config) \
+ PMU_EVENT_ATTR_ID(name, dummy_pmu_events_sysfs_show, config)
+
+PMU_FORMAT_ATTR(event, "config:0-63");
+
+#define DUMMY1_CONFIG 0x01
+#define DUMMY2_CONFIG 0x02
+
+static struct attribute *dummy_pmu_event_attrs[] = {
+ DUMMY_PMU_EVENT_ATTR(test-event-1, DUMMY1_CONFIG),
+ DUMMY_PMU_EVENT_ATTR(test-event-2, DUMMY2_CONFIG),
+ NULL,
+};
+
+static struct attribute *dummy_pmu_format_attrs[] = {
+ &format_attr_event.attr,
+ NULL,
+};
+static const struct attribute_group dummy_pmu_events_attr_group = {
+ .name = "events",
+ .attrs = dummy_pmu_event_attrs,
+};
+static const struct attribute_group dummy_pmu_format_attr_group = {
+ .name = "format",
+ .attrs = dummy_pmu_format_attrs,
+};
+static const struct attribute_group *attr_groups[] = {
+ &dummy_pmu_format_attr_group,
+ &dummy_pmu_events_attr_group,
+ NULL,
+};
+
+static void dummy_pmu_event_destroy(struct perf_event *event)
+{
+ struct dummy_pmu *pmu = event_to_pmu(event);
+ struct dummy_device *d = pmu_to_device(pmu);
+
+ kref_put(&d->refcount, device_release);
+}
+
+static int dummy_pmu_event_init(struct perf_event *event)
+{
+ struct dummy_pmu *pmu = event_to_pmu(event);
+ struct dummy_device *d = pmu_to_device(pmu);
+
+ if (!pmu->registered)
+ return -ENODEV;
+
+ if (event->attr.type != event->pmu->type)
+ return -ENOENT;
+
+ /* unsupported modes and filters */
+ if (event->attr.sample_period) /* no sampling */
+ return -EINVAL;
+
+ if (has_branch_stack(event))
+ return -EOPNOTSUPP;
+
+ if (event->cpu < 0)
+ return -EINVAL;
+
+ /* Event keeps a ref to maintain PMU allocated, even if it's unregistered */
+ kref_get(&d->refcount);
+ event->destroy = dummy_pmu_event_destroy;
+
+ return 0;
+}
+
+static void dummy_pmu_event_start(struct perf_event *event, int flags)
+{
+ struct dummy_pmu *pmu = event_to_pmu(event);
+
+ if (!pmu->registered)
+ return;
+
+ event->hw.state = 0;
+}
+
+static void dummy_pmu_event_read(struct perf_event *event)
+{
+ struct dummy_pmu *pmu = event_to_pmu(event);
+ u8 buf;
+
+ if (!pmu->registered) {
+ event->hw.state = PERF_HES_STOPPED;
+ return;
+ }
+
+ get_random_bytes(&buf, 1);
+ buf %= 10;
+
+ switch (event->attr.config & 0xf) {
+ case DUMMY1_CONFIG:
+ break;
+ case DUMMY2_CONFIG:
+ buf *= 2;
+ break;
+ }
+
+ local64_add(buf, &event->count);
+}
+
+static void dummy_pmu_event_stop(struct perf_event *event, int flags)
+{
+ struct dummy_pmu *pmu = event_to_pmu(event);
+
+ if (!pmu->registered)
+ goto out;
+
+ if (flags & PERF_EF_UPDATE)
+ dummy_pmu_event_read(event);
+
+out:
+ event->hw.state = PERF_HES_STOPPED;
+}
+
+static int dummy_pmu_event_add(struct perf_event *event, int flags)
+{
+ struct dummy_pmu *pmu = event_to_pmu(event);
+
+ if (!pmu->registered)
+ return -ENODEV;
+
+ if (flags & PERF_EF_START)
+ dummy_pmu_event_start(event, flags);
+
+ return 0;
+
+}
+
+static void dummy_pmu_event_del(struct perf_event *event, int flags)
+{
+ dummy_pmu_event_stop(event, PERF_EF_UPDATE);
+}
+
+static int device_init(struct dummy_device *d)
+{
+ int ret;
+
+ d->pmu.base = (struct pmu){
+ .attr_groups = attr_groups,
+ .module = THIS_MODULE,
+ .task_ctx_nr = perf_invalid_context,
+ .event_init = dummy_pmu_event_init,
+ .add = dummy_pmu_event_add,
+ .del = dummy_pmu_event_del,
+ .start = dummy_pmu_event_start,
+ .stop = dummy_pmu_event_stop,
+ .read = dummy_pmu_event_read,
+ };
+
+ d->pmu.name = kasprintf(GFP_KERNEL, "dummy_pmu_%u", d->instance);
+ if (!d->pmu.name)
+ return -ENOMEM;
+
+ ret = perf_pmu_register(&d->pmu.base, d->pmu.name, -1);
+ if (ret)
+ return ret;
+
+ d->pmu.registered = true;
+ pr_info("Device registered: %s\n", d->pmu.name);
+
+ return 0;
+}
+
+static void device_exit(struct dummy_device *d)
+{
+ d->pmu.registered = false;
+ perf_pmu_unregister(&d->pmu.base);
+
+ pr_info("Device released: %s\n", d->pmu.name);
+}
+
+static void device_release(struct kref *ref)
+{
+ struct dummy_device *d = container_of(ref, struct dummy_device, refcount);
+
+ kfree(d->pmu.name);
+ kfree(d);
+}
+
+static struct dummy_device *find_device_locked(struct dummy_mod *m, unsigned int instance)
+{
+ struct dummy_device *d;
+
+ list_for_each_entry(d, &m->device_list, mod_entry)
+ if (d->instance == instance)
+ return d;
+
+ return NULL;
+}
+
+static int dummy_add_device(struct dummy_mod *m, unsigned int instance)
+{
+ struct dummy_device *d, *d2;
+ int ret = 0;
+
+ mutex_lock(&m->mutex);
+ d = find_device_locked(m, instance);
+ mutex_unlock(&m->mutex);
+ if (d)
+ return -EINVAL;
+
+ d = kcalloc(1, sizeof(*d), GFP_KERNEL);
+ if (!d)
+ return -ENOMEM;
+
+ kref_init(&d->refcount);
+ d->instance = instance;
+
+ ret = device_init(d);
+ if (ret < 0)
+ goto fail_put;
+
+ mutex_lock(&m->mutex);
+ d2 = find_device_locked(m, instance);
+ if (d2) {
+ mutex_unlock(&m->mutex);
+ ret = -EINVAL;
+ goto fail_exit;
+ }
+ list_add(&d->mod_entry, &m->device_list);
+ mutex_unlock(&m->mutex);
+
+ return 0;
+
+fail_exit:
+ device_exit(d);
+fail_put:
+ kref_put(&d->refcount, device_release);
+ return ret;
+}
+
+static int dummy_del_device(struct dummy_mod *m, unsigned int instance)
+{
+ struct dummy_device *d, *found = NULL;
+
+ mutex_lock(&m->mutex);
+ list_for_each_entry(d, &m->device_list, mod_entry) {
+ if (d->instance == instance) {
+ list_del(&d->mod_entry);
+ found = d;
+ break;
+ }
+ }
+ mutex_unlock(&m->mutex);
+
+ if (!found)
+ return -EINVAL;
+
+ device_exit(found);
+ kref_put(&found->refcount, device_release);
+
+ return 0;
+}
+
+static int parse_device(const char __user *ubuf, size_t size, u32 *instance)
+{
+ char buf[16];
+ ssize_t len;
+
+ if (size > sizeof(buf) - 1)
+ return -E2BIG;
+
+ len = strncpy_from_user(buf, ubuf, sizeof(buf));
+ if (len < 0 || len >= sizeof(buf) - 1)
+ return -E2BIG;
+
+ if (kstrtou32(buf, 0, instance))
+ return -EINVAL;
+
+ return size;
+}
+
+static int bind_show(struct seq_file *s, void *unused)
+{
+ struct dummy_mod *m = s->private;
+ struct dummy_device *d;
+
+ mutex_lock(&m->mutex);
+ list_for_each_entry(d, &m->device_list, mod_entry)
+ seq_printf(s, "%u\n", d->instance);
+ mutex_unlock(&m->mutex);
+
+ return 0;
+}
+
+static ssize_t bind_write(struct file *f, const char __user *ubuf,
+ size_t size, loff_t *pos)
+{
+ struct dummy_mod *m = file_inode(f)->i_private;
+ u32 instance;
+ ssize_t ret;
+
+ ret = parse_device(ubuf, size, &instance);
+ if (ret < 0)
+ return ret;
+
+ ret = dummy_add_device(m, instance);
+ if (ret < 0)
+ return ret;
+
+ return size;
+}
+DEFINE_SHOW_STORE_ATTRIBUTE(bind);
+
+static int unbind_show(struct seq_file *s, void *unused)
+{
+ return -EPERM;
+}
+
+static ssize_t unbind_write(struct file *f, const char __user *ubuf,
+ size_t size, loff_t *pos)
+{
+ struct dummy_mod *m = file_inode(f)->i_private;
+ unsigned int instance;
+ ssize_t ret;
+
+ ret = parse_device(ubuf, size, &instance);
+ if (ret < 0)
+ return ret;
+
+ ret = dummy_del_device(m, instance);
+ if (ret < 0)
+ return ret;
+
+ return size;
+}
+DEFINE_SHOW_STORE_ATTRIBUTE(unbind);
+
+static int __init dummy_init(void)
+{
+ struct dentry *dir;
+
+ dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
+ debugfs_create_file("bind", 0600, dir, &dm, &bind_fops);
+ debugfs_create_file("unbind", 0200, dir, &dm, &unbind_fops);
+
+ dm.debugfs_root = dir;
+ INIT_LIST_HEAD(&dm.device_list);
+ mutex_init(&dm.mutex);
+
+ return 0;
+}
+
+static void dummy_exit(void)
+{
+ struct dummy_device *d, *tmp;
+
+ debugfs_remove_recursive(dm.debugfs_root);
+
+ mutex_lock(&dm.mutex);
+ list_for_each_entry_safe(d, tmp, &dm.device_list, mod_entry) {
+ device_exit(d);
+ kref_put(&d->refcount, device_release);
+ }
+ mutex_unlock(&dm.mutex);
+}
+
+module_init(dummy_init);
+module_exit(dummy_exit);
+
+MODULE_AUTHOR("Lucas De Marchi <lucas.demarchi@xxxxxxxxx>");
+MODULE_LICENSE("GPL");
--
2.46.2
