LXR linux/fs/pstore/ftrace.c

   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
  30/* This doesn't need to be atomic: speed is chosen over correctness here. */
  31static u64 pstore_ftrace_stamp;
  32
  33static void notrace pstore_ftrace_call(unsigned long ip,
  34                                       unsigned long parent_ip,
  35                                       struct ftrace_ops *op,
  36                                       struct pt_regs *regs)
  37{
  38        unsigned long flags;
  39        struct pstore_ftrace_record rec = {};
  40        struct pstore_record record = {
  41                .type = PSTORE_TYPE_FTRACE,
  42                .buf = (char *)&rec,
  43                .size = sizeof(rec),
  44                .psi = psinfo,
  45        };
  46
  47        if (unlikely(oops_in_progress))
  48                return;
  49
  50        local_irq_save(flags);
  51
  52        rec.ip = ip;
  53        rec.parent_ip = parent_ip;
  54        pstore_ftrace_write_timestamp(&rec, pstore_ftrace_stamp++);
  55        pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
  56        psinfo->write(&record);
  57
  58        local_irq_restore(flags);
  59}
  60
  61static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  62        .func   = pstore_ftrace_call,
  63};
  64
  65static DEFINE_MUTEX(pstore_ftrace_lock);
  66static bool pstore_ftrace_enabled;
  67
  68static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
  69                                        size_t count, loff_t *ppos)
  70{
  71        u8 on;
  72        ssize_t ret;
  73
  74        ret = kstrtou8_from_user(buf, count, 2, &on);
  75        if (ret)
  76                return ret;
  77
  78        mutex_lock(&pstore_ftrace_lock);
  79
  80        if (!on ^ pstore_ftrace_enabled)
  81                goto out;
  82
  83        if (on) {
  84                ftrace_ops_set_global_filter(&pstore_ftrace_ops);
  85                ret = register_ftrace_function(&pstore_ftrace_ops);
  86        } else {
  87                ret = unregister_ftrace_function(&pstore_ftrace_ops);
  88        }
  89
  90        if (ret) {
  91                pr_err("%s: unable to %sregister ftrace ops: %zd\n",
  92                       __func__, on ? "" : "un", ret);
  93                goto err;
  94        }
  95
  96        pstore_ftrace_enabled = on;
  97out:
  98        ret = count;
  99err:
 100        mutex_unlock(&pstore_ftrace_lock);
 101
 102        return ret;
 103}
 104
 105static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
 106                                       size_t count, loff_t *ppos)
 107{
 108        char val[] = { '0' + pstore_ftrace_enabled, '\n' };
 109
 110        return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
 111}
 112
 113static const struct file_operations pstore_knob_fops = {
 114        .open   = simple_open,
 115        .read   = pstore_ftrace_knob_read,
 116        .write  = pstore_ftrace_knob_write,
 117};
 118
 119static struct dentry *pstore_ftrace_dir;
 120
 121void pstore_register_ftrace(void)
 122{
 123        struct dentry *file;
 124
 125        if (!psinfo->write)
 126                return;
 127
 128        pstore_ftrace_dir = debugfs_create_dir("pstore", NULL);
 129        if (!pstore_ftrace_dir) {
 130                pr_err("%s: unable to create pstore directory\n", __func__);
 131                return;
 132        }
 133
 134        file = debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir,
 135                                   NULL, &pstore_knob_fops);
 136        if (!file) {
 137                pr_err("%s: unable to create record_ftrace file\n", __func__);
 138                goto err_file;
 139        }
 140
 141        return;
 142err_file:
 143        debugfs_remove(pstore_ftrace_dir);
 144}
 145
 146void pstore_unregister_ftrace(void)
 147{
 148        mutex_lock(&pstore_ftrace_lock);
 149        if (pstore_ftrace_enabled) {
 150                unregister_ftrace_function(&pstore_ftrace_ops);
 151                pstore_ftrace_enabled = 0;
 152        }
 153        mutex_unlock(&pstore_ftrace_lock);
 154
 155        debugfs_remove_recursive(pstore_ftrace_dir);
 156}
 157