linux/fs/pstore/ftrace.c
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   1/*
   2 * Copyright 2012  Google, Inc.
   3 *
   4 * This software is licensed under the terms of the GNU General Public
   5 * License version 2, as published by the Free Software Foundation, and
   6 * may be copied, distributed, and modified under those terms.
   7 *
   8 * This program is distributed in the hope that it will be useful,
   9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 * GNU General Public License for more details.
  12 */
  13
  14#include <linux/kernel.h>
  15#include <linux/compiler.h>
  16#include <linux/irqflags.h>
  17#include <linux/percpu.h>
  18#include <linux/smp.h>
  19#include <linux/atomic.h>
  20#include <linux/types.h>
  21#include <linux/mutex.h>
  22#include <linux/ftrace.h>
  23#include <linux/fs.h>
  24#include <linux/debugfs.h>
  25#include <linux/err.h>
  26#include <linux/cache.h>
  27#include <asm/barrier.h>
  28#include "internal.h"
  29
  30static void notrace pstore_ftrace_call(unsigned long ip,
  31                                       unsigned long parent_ip)
  32{
  33        unsigned long flags;
  34        struct pstore_ftrace_record rec = {};
  35
  36        if (unlikely(oops_in_progress))
  37                return;
  38
  39        local_irq_save(flags);
  40
  41        rec.ip = ip;
  42        rec.parent_ip = parent_ip;
  43        pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
  44        psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
  45                          sizeof(rec), psinfo);
  46
  47        local_irq_restore(flags);
  48}
  49
  50static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  51        .func   = pstore_ftrace_call,
  52};
  53
  54static DEFINE_MUTEX(pstore_ftrace_lock);
  55static bool pstore_ftrace_enabled;
  56
  57static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
  58                                        size_t count, loff_t *ppos)
  59{
  60        u8 on;
  61        ssize_t ret;
  62
  63        ret = kstrtou8_from_user(buf, count, 2, &on);
  64        if (ret)
  65                return ret;
  66
  67        mutex_lock(&pstore_ftrace_lock);
  68
  69        if (!on ^ pstore_ftrace_enabled)
  70                goto out;
  71
  72        if (on)
  73                ret = register_ftrace_function(&pstore_ftrace_ops);
  74        else
  75                ret = unregister_ftrace_function(&pstore_ftrace_ops);
  76        if (ret) {
  77                pr_err("%s: unable to %sregister ftrace ops: %zd\n",
  78                       __func__, on ? "" : "un", ret);
  79                goto err;
  80        }
  81
  82        pstore_ftrace_enabled = on;
  83out:
  84        ret = count;
  85err:
  86        mutex_unlock(&pstore_ftrace_lock);
  87
  88        return ret;
  89}
  90
  91static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
  92                                       size_t count, loff_t *ppos)
  93{
  94        char val[] = { '0' + pstore_ftrace_enabled, '\n' };
  95
  96        return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
  97}
  98
  99static const struct file_operations pstore_knob_fops = {
 100        .open   = simple_open,
 101        .read   = pstore_ftrace_knob_read,
 102        .write  = pstore_ftrace_knob_write,
 103};
 104
 105void pstore_register_ftrace(void)
 106{
 107        struct dentry *dir;
 108        struct dentry *file;
 109
 110        if (!psinfo->write_buf)
 111                return;
 112
 113        dir = debugfs_create_dir("pstore", NULL);
 114        if (!dir) {
 115                pr_err("%s: unable to create pstore directory\n", __func__);
 116                return;
 117        }
 118
 119        file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
 120                                   &pstore_knob_fops);
 121        if (!file) {
 122                pr_err("%s: unable to create record_ftrace file\n", __func__);
 123                goto err_file;
 124        }
 125
 126        return;
 127err_file:
 128        debugfs_remove(dir);
 129}
 130
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