[PATCH v7 02/13] user_events: Add minimal support for trace_event into ftrace

Beau Belgrave
2021-12-09T22:32:32Z

Minimal support for interacting with dynamic events, trace_event and
ftrace. Core outline of flow between user process, ioctl and trace_event
APIs.

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
kernel/trace/Kconfig | 14 +
kernel/trace/Makefile | 1 +
kernel/trace/trace_events_user.c | 1194 ++++++++++++++++++++++++++++++
3 files changed, 1209 insertions(+)
create mode 100644 kernel/trace/trace_events_user.c

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 420ff4bc67fd..a0ae2640f391 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -724,6 +724,20 @@ config SYNTH_EVENTS

If in doubt, say N.

+config USER_EVENTS
+ bool "User trace events"
+ select TRACING
+ select DYNAMIC_EVENTS
+ help
+ User trace events are user-defined trace events that
+ can be used like an existing kernel trace event. User trace
+ events are generated by writing to a tracefs file. User
+ processes can determine if their tracing events should be
+ generated by memory mapping a tracefs file and checking for
+ an associated byte being non-zero.
+
+ If in doubt, say N.
+
config HIST_TRIGGERS
bool "Histogram triggers"
depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index bedc5caceec7..19ef3758da95 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_PROBE_EVENTS) += trace_eprobe.o
obj-$(CONFIG_TRACE_EVENT_INJECT) += trace_events_inject.o
obj-$(CONFIG_SYNTH_EVENTS) += trace_events_synth.o
obj-$(CONFIG_HIST_TRIGGERS) += trace_events_hist.o
+obj-$(CONFIG_USER_EVENTS) += trace_events_user.o
obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o
obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe.o
obj-$(CONFIG_TRACEPOINTS) += error_report-traces.o
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
new file mode 100644
index 000000000000..1d96d1c85147
--- /dev/null
+++ b/kernel/trace/trace_events_user.c
@@ -0,0 +1,1194 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021, Microsoft Corporation.
+ *
+ * Authors:
+ * Beau Belgrave <beaub@linux.microsoft.com>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/cdev.h>
+#include <linux/hashtable.h>
+#include <linux/list.h>
+#include <linux/io.h>
+#include <linux/uio.h>
+#include <linux/ioctl.h>
+#include <linux/jhash.h>
+#include <linux/trace_events.h>
+#include <linux/tracefs.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/user_events.h>
+#include "trace.h"
+#include "trace_dynevent.h"
+
+#define USER_EVENTS_PREFIX_LEN (sizeof(USER_EVENTS_PREFIX)-1)
+
+#define FIELD_DEPTH_TYPE 0
+#define FIELD_DEPTH_NAME 1
+#define FIELD_DEPTH_SIZE 2
+
+/*
+ * Limits how many trace_event calls user processes can create:
+ * Must be multiple of PAGE_SIZE.
+ */
+#define MAX_PAGES 1
+#define MAX_EVENTS (MAX_PAGES * PAGE_SIZE)
+
+/* Limit how long of an event name plus args within the subsystem. */
+#define MAX_EVENT_DESC 512
+#define EVENT_NAME(user_event) ((user_event)->tracepoint.name)
+#define MAX_FIELD_ARRAY_SIZE (2 * PAGE_SIZE)
+
+static char *register_page_data;
+
+static DEFINE_MUTEX(reg_mutex);
+static DEFINE_HASHTABLE(register_table, 4);
+static DECLARE_BITMAP(page_bitmap, MAX_EVENTS);
+
+/*
+ * Stores per-event properties, as users register events
+ * within a file a user_event might be created if it does not
+ * already exist. These are globally used and their lifetime
+ * is tied to the refcnt member. These cannot go away until the
+ * refcnt reaches zero.
+ */
+struct user_event {
+ struct tracepoint tracepoint;
+ struct trace_event_call call;
+ struct trace_event_class class;
+ struct dyn_event devent;
+ struct hlist_node node;
+ struct list_head fields;
+ atomic_t refcnt;
+ int index;
+ int flags;
+};
+
+/*
+ * Stores per-file events references, as users register events
+ * within a file this structure is modified and freed via RCU.
+ * The lifetime of this struct is tied to the lifetime of the file.
+ * These are not shared and only accessible by the file that created it.
+ */
+struct user_event_refs {
+ struct rcu_head rcu;
+ int count;
+ struct user_event *events[];
+};
+
+typedef void (*user_event_func_t) (struct user_event *user,
+ void *data, u32 datalen,
+ void *tpdata);
+
+static int user_event_parse(char *name, char *args, char *flags,
+ struct user_event **newuser);
+
+static u32 user_event_key(char *name)
+{
+ return jhash(name, strlen(name), 0);
+}
+
+static struct list_head *user_event_get_fields(struct trace_event_call *call)
+{
+ struct user_event *user = (struct user_event *)call->data;
+
+ return &user->fields;
+}
+
+/*
+ * Parses a register command for user_events
+ * Format: event_name[:FLAG1[,FLAG2...]] [field1[;field2...]]
+ *
+ * Example event named test with a 20 char msg field with a unsigned int after:
+ * test char[20] msg;unsigned int id
+ *
+ * NOTE: Offsets are from the user data perspective, they are not from the
+ * trace_entry/buffer perspective. We automatically add the common properties
+ * sizes to the offset for the user.
+ */
+static int user_event_parse_cmd(char *raw_command, struct user_event **newuser)
+{
+ char *name = raw_command;
+ char *args = strpbrk(name, " ");
+ char *flags;
+
+ if (args)
+ *args++ = 0;
+
+ flags = strpbrk(name, ":");
+
+ if (flags)
+ *flags++ = 0;
+
+ return user_event_parse(name, args, flags, newuser);
+}
+
+static int user_field_array_size(const char *type)
+{
+ const char *start = strchr(type, '[');
+ char val[8];
+ int size = 0;
+
+ if (start == NULL)
+ return -EINVAL;
+
+ start++;
+
+ while (*start != ']' && size < (sizeof(val) - 1))
+ val[size++] = *start++;
+
+ if (*start != ']')
+ return -EINVAL;
+
+ val[size] = 0;
+
+ if (kstrtouint(val, 0, &size))
+ return -EINVAL;
+
+ if (size > MAX_FIELD_ARRAY_SIZE)
+ return -EINVAL;
+
+ return size;
+}
+
+static int user_field_size(const char *type)
+{
+ /* long is not allowed from a user, since it's ambigious in size */
+ if (strcmp(type, "s64") == 0)
+ return sizeof(s64);
+ if (strcmp(type, "u64") == 0)
+ return sizeof(u64);
+ if (strcmp(type, "s32") == 0)
+ return sizeof(s32);
+ if (strcmp(type, "u32") == 0)
+ return sizeof(u32);
+ if (strcmp(type, "int") == 0)
+ return sizeof(int);
+ if (strcmp(type, "unsigned int") == 0)
+ return sizeof(unsigned int);
+ if (strcmp(type, "s16") == 0)
+ return sizeof(s16);
+ if (strcmp(type, "u16") == 0)
+ return sizeof(u16);
+ if (strcmp(type, "short") == 0)
+ return sizeof(short);
+ if (strcmp(type, "unsigned short") == 0)
+ return sizeof(unsigned short);
+ if (strcmp(type, "s8") == 0)
+ return sizeof(s8);
+ if (strcmp(type, "u8") == 0)
+ return sizeof(u8);
+ if (strcmp(type, "char") == 0)
+ return sizeof(char);
+ if (strcmp(type, "unsigned char") == 0)
+ return sizeof(unsigned char);
+ if (str_has_prefix(type, "char["))
+ return user_field_array_size(type);
+ if (str_has_prefix(type, "unsigned char["))
+ return user_field_array_size(type);
+ if (str_has_prefix(type, "__data_loc "))
+ return sizeof(u32);
+ if (str_has_prefix(type, "__rel_loc "))
+ return sizeof(u32);
+
+ /* Uknown basic type, error */
+ return -EINVAL;
+}
+
+static void user_event_destroy_fields(struct user_event *user)
+{
+ struct ftrace_event_field *field, *next;
+ struct list_head *head = &user->fields;
+
+ list_for_each_entry_safe(field, next, head, link) {
+ list_del(&field->link);
+ kfree(field);
+ }
+}
+
+static int user_event_add_field(struct user_event *user, const char *type,
+ const char *name, int offset, int size,
+ int is_signed, int filter_type)
+{
+ struct ftrace_event_field *field;
+
+ field = kmalloc(sizeof(*field), GFP_KERNEL);
+
+ if (!field)
+ return -ENOMEM;
+
+ field->type = type;
+ field->name = name;
+ field->offset = offset;
+ field->size = size;
+ field->is_signed = is_signed;
+ field->filter_type = filter_type;
+
+ list_add(&field->link, &user->fields);
+
+ return 0;
+}
+
+/*
+ * Parses the values of a field within the description
+ * Format: type name [size]
+ */
+static int user_event_parse_field(char *field, struct user_event *user,
+ u32 *offset)
+{
+ char *part, *type, *name;
+ u32 depth = 0, saved_offset = *offset;
+ int len, size = -EINVAL;
+ bool is_struct = false;
+
+ field = skip_spaces(field);
+
+ if (*field == 0)
+ return 0;
+
+ /* Handle types that have a space within */
+ len = str_has_prefix(field, "unsigned ");
+ if (len)
+ goto skip_next;
+
+ len = str_has_prefix(field, "struct ");
+ if (len) {
+ is_struct = true;
+ goto skip_next;
+ }
+
+ len = str_has_prefix(field, "__data_loc unsigned ");
+ if (len)
+ goto skip_next;
+
+ len = str_has_prefix(field, "__data_loc ");
+ if (len)
+ goto skip_next;
+
+ len = str_has_prefix(field, "__rel_loc unsigned ");
+ if (len)
+ goto skip_next;
+
+ len = str_has_prefix(field, "__rel_loc ");
+ if (len)
+ goto skip_next;
+
+ goto parse;
+skip_next:
+ type = field;
+ field = strpbrk(field + len, " ");
+
+ if (field == NULL)
+ return -EINVAL;
+
+ *field++ = 0;
+ depth++;
+parse:
+ while ((part = strsep(&field, " ")) != NULL) {
+ switch (depth++) {
+ case FIELD_DEPTH_TYPE:
+ type = part;
+ break;
+ case FIELD_DEPTH_NAME:
+ name = part;
+ break;
+ case FIELD_DEPTH_SIZE:
+ if (!is_struct)
+ return -EINVAL;
+
+ if (kstrtou32(part, 10, &size))
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+ }
+
+ if (depth < FIELD_DEPTH_SIZE)
+ return -EINVAL;
+
+ if (depth == FIELD_DEPTH_SIZE)
+ size = user_field_size(type);
+
+ if (size == 0)
+ return -EINVAL;
+
+ if (size < 0)
+ return size;
+
+ *offset = saved_offset + size;
+
+ return user_event_add_field(user, type, name, saved_offset, size,
+ type[0] != 'u', FILTER_OTHER);
+}
+
+static void user_event_parse_flags(struct user_event *user, char *flags)
+{
+ char *flag;
+
+ if (flags == NULL)
+ return;
+
+ while ((flag = strsep(&flags, ",")) != NULL) {
+ if (strcmp(flag, "BPF_ITER") == 0)
+ user->flags |= FLAG_BPF_ITER;
+ }
+}
+
+static int user_event_parse_fields(struct user_event *user, char *args)
+{
+ char *field;
+ u32 offset = sizeof(struct trace_entry);
+ int ret = -EINVAL;
+
+ if (args == NULL)
+ return 0;
+
+ while ((field = strsep(&args, ";")) != NULL) {
+ ret = user_event_parse_field(field, user, &offset);
+
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+static struct trace_event_fields user_event_fields_array[1];
+
+static enum print_line_t user_event_print_trace(struct trace_iterator *iter,
+ int flags,
+ struct trace_event *event)
+{
+ /* Unsafe to try to decode user provided print_fmt, use hex */
+ trace_print_hex_dump_seq(&iter->seq, "", DUMP_PREFIX_OFFSET, 16,
+ 1, iter->ent, iter->ent_size, true);
+
+ return trace_handle_return(&iter->seq);
+}
+
+static struct trace_event_functions user_event_funcs = {
+ .trace = user_event_print_trace,
+};
+
+static int destroy_user_event(struct user_event *user)
+{
+ int ret = 0;
+
+ /* Must destroy fields before call removal */
+ user_event_destroy_fields(user);
+
+ ret = trace_remove_event_call(&user->call);
+
+ if (ret)
+ return ret;
+
+ dyn_event_remove(&user->devent);
+
+ register_page_data[user->index] = 0;
+ clear_bit(user->index, page_bitmap);
+ hash_del(&user->node);
+
+ kfree(EVENT_NAME(user));
+ kfree(user);
+
+ return ret;
+}
+
+static struct user_event *find_user_event(char *name, u32 *outkey)
+{
+ struct user_event *user;
+ u32 key = user_event_key(name);
+
+ *outkey = key;
+
+ hash_for_each_possible(register_table, user, node, key)
+ if (!strcmp(EVENT_NAME(user), name))
+ return user;
+
+ return NULL;
+}
+
+/*
+ * Writes the user supplied payload out to a trace file.
+ */
+static void user_event_ftrace(struct user_event *user, void *data, u32 datalen,
+ void *tpdata)
+{
+ struct trace_event_file *file;
+ struct trace_entry *entry;
+ struct trace_event_buffer event_buffer;
+
+ file = (struct trace_event_file *)tpdata;
+
+ if (!file ||
+ !(file->flags & EVENT_FILE_FL_ENABLED) ||
+ trace_trigger_soft_disabled(file))
+ return;
+
+ /* Allocates and fills trace_entry, + 1 of this is data payload */
+ entry = trace_event_buffer_reserve(&event_buffer, file,
+ sizeof(*entry) + datalen);
+
+ if (unlikely(!entry))
+ return;
+
+ memcpy(entry + 1, data, datalen);
+
+ trace_event_buffer_commit(&event_buffer);
+}
+
+/*
+ * Update the register page that is shared between user processes.
+ */
+static void update_reg_page_for(struct user_event *user)
+{
+ struct tracepoint *tp = &user->tracepoint;
+ char status = 0;
+
+ if (atomic_read(&tp->key.enabled) > 0) {
+ struct tracepoint_func *probe_func_ptr;
+ user_event_func_t probe_func;
+
+ rcu_read_lock_sched();
+
+ probe_func_ptr = rcu_dereference_sched(tp->funcs);
+
+ if (probe_func_ptr) {
+ do {
+ probe_func = probe_func_ptr->func;
+
+ if (probe_func == user_event_ftrace)
+ status |= EVENT_STATUS_FTRACE;
+ else
+ status |= EVENT_STATUS_OTHER;
+ } while ((++probe_func_ptr)->func);
+ }
+
+ rcu_read_unlock_sched();
+ }
+
+ register_page_data[user->index] = status;
+}
+
+/*
+ * Register callback for our events from tracing sub-systems.
+ */
+static int user_event_reg(struct trace_event_call *call,
+ enum trace_reg type,
+ void *data)
+{
+ struct user_event *user = (struct user_event *)call->data;
+ int ret = 0;
+
+ if (!user)
+ return -ENOENT;
+
+ switch (type) {
+ case TRACE_REG_REGISTER:
+ ret = tracepoint_probe_register(call->tp,
+ call->class->probe,
+ data);
+ if (!ret)
+ goto inc;
+ break;
+
+ case TRACE_REG_UNREGISTER:
+ tracepoint_probe_unregister(call->tp,
+ call->class->probe,
+ data);
+ goto dec;
+
+#ifdef CONFIG_PERF_EVENTS
+ case TRACE_REG_PERF_REGISTER:
+ case TRACE_REG_PERF_UNREGISTER:
+ case TRACE_REG_PERF_OPEN:
+ case TRACE_REG_PERF_CLOSE:
+ case TRACE_REG_PERF_ADD:
+ case TRACE_REG_PERF_DEL:
+ break;
+#endif
+ }
+
+ return ret;
+inc:
+ atomic_inc(&user->refcnt);
+ update_reg_page_for(user);
+ return 0;
+dec:
+ update_reg_page_for(user);
+ atomic_dec(&user->refcnt);
+ return 0;
+}
+
+static int user_event_create(const char *raw_command)
+{
+ struct user_event *user;
+ char *name;
+ int ret;
+
+ if (!str_has_prefix(raw_command, USER_EVENTS_PREFIX))
+ return -ECANCELED;
+
+ raw_command += USER_EVENTS_PREFIX_LEN;
+ raw_command = skip_spaces(raw_command);
+
+ name = kstrdup(raw_command, GFP_KERNEL);
+
+ if (!name)
+ return -ENOMEM;
+
+ mutex_lock(&reg_mutex);
+ ret = user_event_parse_cmd(name, &user);
+ mutex_unlock(&reg_mutex);
+
+ if (ret)
+ kfree(name);
+
+ return ret;
+}
+
+static int user_event_show(struct seq_file *m, struct dyn_event *ev)
+{
+ struct user_event *user = container_of(ev, struct user_event, devent);
+ struct ftrace_event_field *field, *next;
+ struct list_head *head;
+ int depth = 0;
+
+ seq_printf(m, "%s%s", USER_EVENTS_PREFIX, EVENT_NAME(user));
+
+ head = trace_get_fields(&user->call);
+
+ list_for_each_entry_safe_reverse(field, next, head, link) {
+ if (depth == 0)
+ seq_puts(m, " ");
+ else
+ seq_puts(m, "; ");
+ seq_printf(m, "%s %s", field->type, field->name);
+ depth++;
+ }
+
+ seq_puts(m, "\n");
+
+ return 0;
+}
+
+static bool user_event_is_busy(struct dyn_event *ev)
+{
+ struct user_event *user = container_of(ev, struct user_event, devent);
+
+ return atomic_read(&user->refcnt) != 0;
+}
+
+static int user_event_free(struct dyn_event *ev)
+{
+ struct user_event *user = container_of(ev, struct user_event, devent);
+
+ if (atomic_read(&user->refcnt) != 0)
+ return -EBUSY;
+
+ return destroy_user_event(user);
+}
+
+static bool user_event_match(const char *system, const char *event,
+ int argc, const char **argv, struct dyn_event *ev)
+{
+ struct user_event *user = container_of(ev, struct user_event, devent);
+
+ return strcmp(EVENT_NAME(user), event) == 0 &&
+ (!system || strcmp(system, USER_EVENTS_SYSTEM) == 0);
+}
+
+static struct dyn_event_operations user_event_dops = {
+ .create = user_event_create,
+ .show = user_event_show,
+ .is_busy = user_event_is_busy,
+ .free = user_event_free,
+ .match = user_event_match,
+};
+
+static int user_event_trace_register(struct user_event *user)
+{
+ int ret;
+
+ ret = register_trace_event(&user->call.event);
+
+ if (!ret)
+ return -ENODEV;
+
+ ret = trace_add_event_call(&user->call);
+
+ if (ret)
+ unregister_trace_event(&user->call.event);
+
+ return ret;
+}
+
+/*
+ * Parses the event name, arguments and flags then registers if successful.
+ * The name buffer lifetime is owned by this method for success cases only.
+ */
+static int user_event_parse(char *name, char *args, char *flags,
+ struct user_event **newuser)
+{
+ int ret;
+ int index;
+ u32 key;
+ struct user_event *user = find_user_event(name, &key);
+
+ if (user) {
+ *newuser = user;
+ /*
+ * Name is allocated by caller, free it since it already exists.
+ * Caller only worries about failure cases for freeing.
+ */
+ kfree(name);
+ return 0;
+ }
+
+ index = find_first_zero_bit(page_bitmap, MAX_EVENTS);
+
+ if (index == MAX_EVENTS)
+ return -EMFILE;
+
+ user = kzalloc(sizeof(*user), GFP_KERNEL);
+
+ if (!user)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&user->class.fields);
+ INIT_LIST_HEAD(&user->fields);
+
+ user->tracepoint.name = name;
+
+ user_event_parse_flags(user, flags);
+
+ ret = user_event_parse_fields(user, args);
+
+ if (ret)
+ goto put_user;
+
+ /* Minimal print format */
+ user->call.print_fmt = "\"\"";
+
+ user->call.data = user;
+ user->call.class = &user->class;
+ user->call.name = name;
+ user->call.flags = TRACE_EVENT_FL_TRACEPOINT;
+ user->call.tp = &user->tracepoint;
+ user->call.event.funcs = &user_event_funcs;
+
+ user->class.system = USER_EVENTS_SYSTEM;
+ user->class.fields_array = user_event_fields_array;
+ user->class.get_fields = user_event_get_fields;
+ user->class.reg = user_event_reg;
+ user->class.probe = user_event_ftrace;
+
+ mutex_lock(&event_mutex);
+ ret = user_event_trace_register(user);
+ mutex_unlock(&event_mutex);
+
+ if (ret)
+ goto put_user;
+
+ user->index = index;
+ dyn_event_init(&user->devent, &user_event_dops);
+ dyn_event_add(&user->devent, &user->call);
+ set_bit(user->index, page_bitmap);
+ hash_add(register_table, &user->node, key);
+
+ *newuser = user;
+ return 0;
+put_user:
+ user_event_destroy_fields(user);
+ kfree(user);
+ return ret;
+}
+
+/*
+ * Deletes a previously created event if it is no longer being used.
+ */
+static int delete_user_event(char *name)
+{
+ u32 key;
+ int ret;
+ struct user_event *user = find_user_event(name, &key);
+
+ if (!user)
+ return -ENOENT;
+
+ if (atomic_read(&user->refcnt) != 0)
+ return -EBUSY;
+
+ mutex_lock(&event_mutex);
+ ret = destroy_user_event(user);
+ mutex_unlock(&event_mutex);
+
+ return ret;
+}
+
+/*
+ * Validates the user payload and writes via iterator.
+ */
+static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
+{
+ struct user_event_refs *refs;
+ struct user_event *user = NULL;
+ struct tracepoint *tp;
+ ssize_t ret = i->count;
+ int idx;
+
+ if (unlikely(copy_from_iter(&idx, sizeof(idx), i) != sizeof(idx)))
+ return -EFAULT;
+
+ rcu_read_lock_sched();
+
+ refs = rcu_dereference_sched(file->private_data);
+
+ /*
+ * The refs->events array is protected by RCU, and new items may be
+ * added. But the user retrieved from indexing into the events array
+ * shall be immutable while the file is opened.
+ */
+ if (likely(refs && idx < refs->count))
+ user = refs->events[idx];
+
+ rcu_read_unlock_sched();
+
+ if (unlikely(user == NULL))
+ return -ENOENT;
+
+ tp = &user->tracepoint;
+
+ /*
+ * It's possible key.enabled disables after this check, however
+ * we don't mind if a few events are included in this condition.
+ */
+ if (likely(atomic_read(&tp->key.enabled) > 0)) {
+ struct tracepoint_func *probe_func_ptr;
+ user_event_func_t probe_func;
+ void *tpdata;
+ void *kdata;
+ u32 datalen;
+
+ kdata = kmalloc(i->count, GFP_KERNEL);
+
+ if (unlikely(!kdata))
+ return -ENOMEM;
+
+ datalen = copy_from_iter(kdata, i->count, i);
+
+ rcu_read_lock_sched();
+
+ probe_func_ptr = rcu_dereference_sched(tp->funcs);
+
+ if (probe_func_ptr) {
+ do {
+ probe_func = probe_func_ptr->func;
+ tpdata = probe_func_ptr->data;
+ probe_func(user, kdata, datalen, tpdata);
+ } while ((++probe_func_ptr)->func);
+ }
+
+ rcu_read_unlock_sched();
+
+ kfree(kdata);
+ }
+
+ return ret;
+}
+
+static ssize_t user_events_write(struct file *file, const char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ struct iovec iov;
+ struct iov_iter i;
+
+ if (unlikely(*ppos != 0))
+ return -EFAULT;
+
+ if (unlikely(import_single_range(READ, (char *)ubuf, count, &iov, &i)))
+ return -EFAULT;
+
+ return user_events_write_core(file, &i);
+}
+
+static ssize_t user_events_write_iter(struct kiocb *kp, struct iov_iter *i)
+{
+ return user_events_write_core(kp->ki_filp, i);
+}
+
+static int user_events_ref_add(struct file *file, struct user_event *user)
+{
+ struct user_event_refs *refs, *new_refs;
+ int i, size, count = 0;
+
+ refs = rcu_dereference_protected(file->private_data,
+ lockdep_is_held(&reg_mutex));
+
+ if (refs) {
+ count = refs->count;
+
+ for (i = 0; i < count; ++i)
+ if (refs->events[i] == user)
+ return i;
+ }
+
+ size = struct_size(refs, events, count + 1);
+
+ new_refs = kzalloc(size, GFP_KERNEL);
+
+ if (!new_refs)
+ return -ENOMEM;
+
+ new_refs->count = count + 1;
+
+ for (i = 0; i < count; ++i)
+ new_refs->events[i] = refs->events[i];
+
+ new_refs->events[i] = user;
+
+ atomic_inc(&user->refcnt);
+
+ rcu_assign_pointer(file->private_data, new_refs);
+
+ if (refs)
+ kfree_rcu(refs, rcu);
+
+ return i;
+}
+
+static long user_reg_get(struct user_reg __user *ureg, struct user_reg *kreg)
+{
+ u32 size;
+ long ret;
+
+ ret = get_user(size, &ureg->size);
+
+ if (ret)
+ return ret;
+
+ if (size > PAGE_SIZE)
+ return -E2BIG;
+
+ return copy_struct_from_user(kreg, sizeof(*kreg), ureg, size);
+}
+
+/*
+ * Registers a user_event on behalf of a user process.
+ */
+static long user_events_ioctl_reg(struct file *file, unsigned long uarg)
+{
+ struct user_reg __user *ureg = (struct user_reg __user *)uarg;
+ struct user_reg reg;
+ struct user_event *user;
+ char *name;
+ long ret;
+
+ ret = user_reg_get(ureg, &reg);
+
+ if (ret)
+ return ret;
+
+ name = strndup_user((const char __user *)(uintptr_t)reg.name_args,
+ MAX_EVENT_DESC);
+
+ if (IS_ERR(name)) {
+ ret = PTR_ERR(name);
+ return ret;
+ }
+
+ ret = user_event_parse_cmd(name, &user);
+
+ if (ret) {
+ kfree(name);
+ return ret;
+ }
+
+ ret = user_events_ref_add(file, user);
+
+ /* Positive number is index and valid */
+ if (ret < 0)
+ return ret;
+
+ put_user((u32)ret, &ureg->write_index);
+ put_user(user->index, &ureg->status_index);
+
+ return 0;
+}
+
+/*
+ * Deletes a user_event on behalf of a user process.
+ */
+static long user_events_ioctl_del(struct file *file, unsigned long uarg)
+{
+ void __user *ubuf = (void __user *)uarg;
+ char *name;
+ long ret;
+
+ name = strndup_user(ubuf, MAX_EVENT_DESC);
+
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ ret = delete_user_event(name);
+
+ kfree(name);
+
+ return ret;
+}
+
+/*
+ * Handles the ioctl from user mode to register or alter operations.
+ */
+static long user_events_ioctl(struct file *file, unsigned int cmd,
+ unsigned long uarg)
+{
+ long ret = -ENOTTY;
+
+ switch (cmd) {
+ case DIAG_IOCSREG:
+ mutex_lock(&reg_mutex);
+ ret = user_events_ioctl_reg(file, uarg);
+ mutex_unlock(&reg_mutex);
+ break;
+
+ case DIAG_IOCSDEL:
+ mutex_lock(&reg_mutex);
+ ret = user_events_ioctl_del(file, uarg);
+ mutex_unlock(&reg_mutex);
+ break;
+ }
+
+ return ret;
+}
+
+/*
+ * Handles the final close of the file from user mode.
+ */
+static int user_events_release(struct inode *node, struct file *file)
+{
+ struct user_event_refs *refs;
+ struct user_event *user;
+ int i;
+
+ /*
+ * Ensure refs cannot change under any situation by taking the
+ * register mutex during the final freeing of the references.
+ */
+ mutex_lock(&reg_mutex);
+
+ refs = file->private_data;
+
+ if (!refs)
+ goto out;
+
+ /*
+ * The lifetime of refs has reached an end, it's tied to this file.
+ * The underlying user_events are ref counted, and cannot be freed.
+ * After this decrement, the user_events may be freed elsewhere.
+ */
+ for (i = 0; i < refs->count; ++i) {
+ user = refs->events[i];
+
+ if (user)
+ atomic_dec(&user->refcnt);
+ }
+out:
+ file->private_data = NULL;
+
+ mutex_unlock(&reg_mutex);
+
+ kfree(refs);
+
+ return 0;
+}
+
+static const struct file_operations user_data_fops = {
+ .write = user_events_write,
+ .write_iter = user_events_write_iter,
+ .unlocked_ioctl = user_events_ioctl,
+ .release = user_events_release,
+};
+
+/*
+ * Maps the shared page into the user process for checking if event is enabled.
+ */
+static int user_status_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ unsigned long size = vma->vm_end - vma->vm_start;
+
+ if (size != MAX_EVENTS)
+ return -EINVAL;
+
+ return remap_pfn_range(vma, vma->vm_start,
+ virt_to_phys(register_page_data) >> PAGE_SHIFT,
+ size, vm_get_page_prot(VM_READ));
+}
+
+static int user_status_show(struct seq_file *m, void *p)
+{
+ struct user_event *user;
+ char status;
+ int i, active = 0, busy = 0, flags;
+
+ mutex_lock(&reg_mutex);
+
+ hash_for_each(register_table, i, user, node) {
+ status = register_page_data[user->index];
+ flags = user->flags;
+
+ seq_printf(m, "%d:%s", user->index, EVENT_NAME(user));
+
+ if (flags != 0 || status != 0)
+ seq_puts(m, " #");
+
+ if (status != 0) {
+ seq_puts(m, " Used by");
+ if (status & EVENT_STATUS_FTRACE)
+ seq_puts(m, " ftrace");
+ if (status & EVENT_STATUS_PERF)
+ seq_puts(m, " perf");
+ if (status & EVENT_STATUS_OTHER)
+ seq_puts(m, " other");
+ busy++;
+ }
+
+ if (flags & FLAG_BPF_ITER)
+ seq_puts(m, " FLAG:BPF_ITER");
+
+ seq_puts(m, "\n");
+ active++;
+ }
+
+ mutex_unlock(&reg_mutex);
+
+ seq_puts(m, "\n");
+ seq_printf(m, "Active: %d\n", active);
+ seq_printf(m, "Busy: %d\n", busy);
+ seq_printf(m, "Max: %ld\n", MAX_EVENTS);
+
+ return 0;
+}
+
+static ssize_t user_status_read(struct file *file, char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ /*
+ * Delay allocation of seq data until requested, most callers
+ * will never read the status file. They will only mmap.
+ */
+ if (file->private_data == NULL) {
+ int ret;
+
+ if (*ppos != 0)
+ return -EINVAL;
+
+ ret = single_open(file, user_status_show, NULL);
+
+ if (ret)
+ return ret;
+ }
+
+ return seq_read(file, ubuf, count, ppos);
+}
+
+static loff_t user_status_seek(struct file *file, loff_t offset, int whence)
+{
+ if (file->private_data == NULL)
+ return 0;
+
+ return seq_lseek(file, offset, whence);
+}
+
+static int user_status_release(struct inode *node, struct file *file)
+{
+ if (file->private_data == NULL)
+ return 0;
+
+ return single_release(node, file);
+}
+
+static const struct file_operations user_status_fops = {
+ .mmap = user_status_mmap,
+ .read = user_status_read,
+ .llseek = user_status_seek,
+ .release = user_status_release,
+};
+
+/*
+ * Creates a set of tracefs files to allow user mode interactions.
+ */
+static int create_user_tracefs(void)
+{
+ struct dentry *edata, *emmap;
+
+ edata = tracefs_create_file("user_events_data", TRACE_MODE_WRITE,
+ NULL, NULL, &user_data_fops);
+
+ if (!edata) {
+ pr_warn("Could not create tracefs 'user_events_data' entry\n");
+ goto err;
+ }
+
+ /* mmap with MAP_SHARED requires writable fd */
+ emmap = tracefs_create_file("user_events_status", TRACE_MODE_WRITE,
+ NULL, NULL, &user_status_fops);
+
+ if (!emmap) {
+ tracefs_remove(edata);
+ pr_warn("Could not create tracefs 'user_events_mmap' entry\n");
+ goto err;
+ }
+
+ return 0;
+err:
+ return -ENODEV;
+}
+
+static void set_page_reservations(bool set)
+{
+ int page;
+
+ for (page = 0; page < MAX_PAGES; ++page) {
+ void *addr = register_page_data + (PAGE_SIZE * page);
+
+ if (set)
+ SetPageReserved(virt_to_page(addr));
+ else
+ ClearPageReserved(virt_to_page(addr));
+ }
+}
+
+static int __init trace_events_user_init(void)
+{
+ int ret;
+
+ /* Zero all bits beside 0 (which is reserved for failures) */
+ bitmap_zero(page_bitmap, MAX_EVENTS);
+ set_bit(0, page_bitmap);
+
+ register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL);
+
+ if (!register_page_data)
+ return -ENOMEM;
+
+ set_page_reservations(true);
+
+ ret = create_user_tracefs();
+
+ if (ret) {
+ pr_warn("user_events could not register with tracefs\n");
+ set_page_reservations(false);
+ kfree(register_page_data);
+ return ret;
+ }
+
+ if (dyn_event_register(&user_event_dops))
+ pr_warn("user_events could not register with dyn_events\n");
+
+ return 0;
+}
+
+fs_initcall(trace_events_user_init);
--
2.17.1