ftrace.c

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/*
 * Copyright 2012  Google, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/kernel.h>
#include <linux/compiler.h>
#include <linux/irqflags.h>
#include <linux/percpu.h>
#include <linux/smp.h>
#include <linux/atomic.h>
#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/ftrace.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/err.h>
#include <linux/cache.h>
#include <asm/barrier.h>
#include "internal.h"

static void notrace pstore_ftrace_call(unsigned long ip,
                       unsigned long parent_ip)
{
    unsigned long flags;
    struct pstore_ftrace_record rec = {};

    if (unlikely(oops_in_progress))
        return;

    local_irq_save(flags);

    rec.ip = ip;
    rec.parent_ip = parent_ip;
    pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
    psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
              sizeof(rec), psinfo);

    local_irq_restore(flags);
}

static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
    .func   = pstore_ftrace_call,
};

static DEFINE_MUTEX(pstore_ftrace_lock);
static bool pstore_ftrace_enabled;

static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
                    size_t count, loff_t *ppos)
{
    u8 on;
    ssize_t ret;

    ret = kstrtou8_from_user(buf, count, 2, &on);
    if (ret)
        return ret;

    mutex_lock(&pstore_ftrace_lock);

    if (!on ^ pstore_ftrace_enabled)
        goto out;

    if (on)
        ret = register_ftrace_function(&pstore_ftrace_ops);
    else
        ret = unregister_ftrace_function(&pstore_ftrace_ops);
    if (ret) {
        pr_err("%s: unable to %sregister ftrace ops: %zd\n",
               __func__, on ? "" : "un", ret);
        goto err;
    }

    pstore_ftrace_enabled = on;
out:
    ret = count;
err:
    mutex_unlock(&pstore_ftrace_lock);

    return ret;
}

static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
                       size_t count, loff_t *ppos)
{
    char val[] = { '0' + pstore_ftrace_enabled, '\n' };

    return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
}

static const struct file_operations pstore_knob_fops = {
    .open   = simple_open,
    .read   = pstore_ftrace_knob_read,
    .write  = pstore_ftrace_knob_write,
};

void pstore_register_ftrace(void)
{
    struct dentry *dir;
    struct dentry *file;

    if (!psinfo->write_buf)
        return;

    dir = debugfs_create_dir("pstore", NULL);
    if (!dir) {
        pr_err("%s: unable to create pstore directory\n", __func__);
        return;
    }

    file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
                   &pstore_knob_fops);
    if (!file) {
        pr_err("%s: unable to create record_ftrace file\n", __func__);
        goto err_file;
    }

    return;
err_file:
    debugfs_remove(dir);
}