/*
 * trace event based perf event profiling/tracing
 *
 * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
 * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
 */

#include <linux/module.h>
#include <linux/kprobes.h>
#include "trace.h"

static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];

/*
 * Force it to be aligned to unsigned long to avoid misaligned accesses
 * suprises
 */
typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
        perf_trace_t;

/* Count the events in use (per event id, not per instance) */
static int      total_ref_count;

static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
                                 struct perf_event *p_event)
{
        /* No tracing, just counting, so no obvious leak */
        if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
                return 0;

        /* Some events are ok to be traced by non-root users... */
        if (p_event->attach_state == PERF_ATTACH_TASK) {
                if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
                        return 0;
        }

        /*
         * ...otherwise raw tracepoint data can be a severe data leak,
         * only allow root to have these.
         */
        if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
                return -EPERM;

        return 0;
}

static int perf_trace_event_init(struct ftrace_event_call *tp_event,
                                 struct perf_event *p_event)
{
        struct hlist_head __percpu *list;
        int ret;
        int cpu;

        ret = perf_trace_event_perm(tp_event, p_event);
        if (ret)
                return ret;

        p_event->tp_event = tp_event;
        if (tp_event->perf_refcount++ > 0)
                return 0;

        ret = -ENOMEM;

        list = alloc_percpu(struct hlist_head);
        if (!list)
                goto fail;

        for_each_possible_cpu(cpu)
                INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));

        tp_event->perf_events = list;

        if (!total_ref_count) {
                char __percpu *buf;
                int i;

                for (i = 0; i < PERF_NR_CONTEXTS; i++) {
                        buf = (char __percpu *)alloc_percpu(perf_trace_t);
                        if (!buf)
                                goto fail;

                        perf_trace_buf[i] = buf;
                }
        }

        ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);
        if (ret)
                goto fail;

        total_ref_count++;
        return 0;

fail:
        if (!total_ref_count) {
                int i;

                for (i = 0; i < PERF_NR_CONTEXTS; i++) {
                        free_percpu(perf_trace_buf[i]);
                        perf_trace_buf[i] = NULL;
                }
        }

        if (!--tp_event->perf_refcount) {
                free_percpu(tp_event->perf_events);
                tp_event->perf_events = NULL;
        }

        return ret;
}

int perf_trace_init(struct perf_event *p_event)
{
        struct ftrace_event_call *tp_event;
        int event_id = p_event->attr.config;
        int ret = -EINVAL;

        mutex_lock(&event_mutex);
        list_for_each_entry(tp_event, &ftrace_events, list) {
                if (tp_event->event.type == event_id &&
                    tp_event->class && tp_event->class->reg &&
                    try_module_get(tp_event->mod)) {
                        ret = perf_trace_event_init(tp_event, p_event);
                        if (ret)
                                module_put(tp_event->mod);
                        break;
                }
        }
        mutex_unlock(&event_mutex);

        return ret;
}

int perf_trace_add(struct perf_event *p_event, int flags)
{
        struct ftrace_event_call *tp_event = p_event->tp_event;
        struct hlist_head __percpu *pcpu_list;
        struct hlist_head *list;

        pcpu_list = tp_event->perf_events;
        if (WARN_ON_ONCE(!pcpu_list))
                return -EINVAL;

        if (!(flags & PERF_EF_START))
                p_event->hw.state = PERF_HES_STOPPED;

        list = this_cpu_ptr(pcpu_list);
        hlist_add_head_rcu(&p_event->hlist_entry, list);

        return 0;
}

void perf_trace_del(struct perf_event *p_event, int flags)
{
        hlist_del_rcu(&p_event->hlist_entry);
}

void perf_trace_destroy(struct perf_event *p_event)
{
        struct ftrace_event_call *tp_event = p_event->tp_event;
        int i;

        mutex_lock(&event_mutex);
        if (--tp_event->perf_refcount > 0)
                goto out;

        tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);

        /*
         * Ensure our callback won't be called anymore. The buffers
         * will be freed after that.
         */
        tracepoint_synchronize_unregister();

        free_percpu(tp_event->perf_events);
        tp_event->perf_events = NULL;

        if (!--total_ref_count) {
                for (i = 0; i < PERF_NR_CONTEXTS; i++) {
                        free_percpu(perf_trace_buf[i]);
                        perf_trace_buf[i] = NULL;
                }
        }
out:
        module_put(tp_event->mod);
        mutex_unlock(&event_mutex);
}

__kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
                                       struct pt_regs *regs, int *rctxp)
{
        struct trace_entry *entry;
        unsigned long flags;
        char *raw_data;
        int pc;

        BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));

        pc = preempt_count();

        *rctxp = perf_swevent_get_recursion_context();
        if (*rctxp < 0)
                return NULL;

        raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);

        /* zero the dead bytes from align to not leak stack to user */
        memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));

        entry = (struct trace_entry *)raw_data;
        local_save_flags(flags);
        tracing_generic_entry_update(entry, flags, pc);
        entry->type = type;

        return raw_data;
}
EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);