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                                       struct ftrace_ops *op,
  33                                       struct pt_regs *regs)
  34{
  35        unsigned long flags;
  36        struct pstore_ftrace_record rec = {};
  37
  38        if (unlikely(oops_in_progress))
  39                return;
  40
  41        local_irq_save(flags);
  42
  43        rec.ip = ip;
  44        rec.parent_ip = parent_ip;
  45        pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
  46        psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
  47                          sizeof(rec), psinfo);
  48
  49        local_irq_restore(flags);
  50}
  51
  52static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  53        .func   = pstore_ftrace_call,
  54};
  55
  56static DEFINE_MUTEX(pstore_ftrace_lock);
  57static bool pstore_ftrace_enabled;
  58
  59static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
  60                                        size_t count, loff_t *ppos)
  61{
  62        u8 on;
  63        ssize_t ret;
  64
  65        ret = kstrtou8_from_user(buf, count, 2, &on);
  66        if (ret)
  67                return ret;
  68
  69        mutex_lock(&pstore_ftrace_lock);
  70
  71        if (!on ^ pstore_ftrace_enabled)
  72                goto out;
  73
  74        if (on)
  75                ret = register_ftrace_function(&pstore_ftrace_ops);
  76        else
  77                ret = unregister_ftrace_function(&pstore_ftrace_ops);
  78        if (ret) {
  79                pr_err("%s: unable to %sregister ftrace ops: %zd\n",
  80                       __func__, on ? "" : "un", ret);
  81                goto err;
  82        }
  83
  84        pstore_ftrace_enabled = on;
  85out:
  86        ret = count;
  87err:
  88        mutex_unlock(&pstore_ftrace_lock);
  89
  90        return ret;
  91}
  92
  93static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
  94                                       size_t count, loff_t *ppos)
  95{
  96        char val[] = { '0' + pstore_ftrace_enabled, '\n' };
  97
  98        return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
  99}
 100
 101static const struct file_operations pstore_knob_fops = {
 102        .open   = simple_open,
 103        .read   = pstore_ftrace_knob_read,
 104        .write  = pstore_ftrace_knob_write,
 105};
 106
 107void pstore_register_ftrace(void)
 108{
 109        struct dentry *dir;
 110        struct dentry *file;
 111
 112        if (!psinfo->write_buf)
 113                return;
 114
 115        dir = debugfs_create_dir("pstore", NULL);
 116        if (!dir) {
 117                pr_err("%s: unable to create pstore directory\n", __func__);
 118                return;
 119        }
 120
 121        file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
 122                                   &pstore_knob_fops);
 123        if (!file) {
 124                pr_err("%s: unable to create record_ftrace file\n", __func__);
 125                goto err_file;
 126        }
 127
 128        return;
 129err_file:
 130        debugfs_remove(dir);
 131}
 132
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