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. */
  31 static u64 pstore_ftrace_stamp;
  32
  33 static 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
  41         if (unlikely(oops_in_progress))
  42                 return;
  43
  44         local_irq_save(flags);
  45
  46         rec.ip = ip;
  47         rec.parent_ip = parent_ip;
  48         pstore_ftrace_write_timestamp(&rec, pstore_ftrace_stamp++);
  49         pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
  50         psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
  51                           0, sizeof(rec), psinfo);
  52
  53         local_irq_restore(flags);
  54 }
  55
  56 static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  57         .func   = pstore_ftrace_call,
  58 };
  59
  60 static DEFINE_MUTEX(pstore_ftrace_lock);
  61 static bool pstore_ftrace_enabled;
  62
  63 static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
  64                                         size_t count, loff_t *ppos)
  65 {
  66         u8 on;
  67         ssize_t ret;
  68
  69         ret = kstrtou8_from_user(buf, count, 2, &on);
  70         if (ret)
  71                 return ret;
  72
  73         mutex_lock(&pstore_ftrace_lock);
  74
  75         if (!on ^ pstore_ftrace_enabled)
  76                 goto out;
  77
  78         if (on) {
  79                 ftrace_ops_set_global_filter(&pstore_ftrace_ops);
  80                 ret = register_ftrace_function(&pstore_ftrace_ops);
  81         } else {
  82                 ret = unregister_ftrace_function(&pstore_ftrace_ops);
  83         }
  84
  85         if (ret) {
  86                 pr_err("%s: unable to %sregister ftrace ops: %zd\n",
  87                        __func__, on ? "" : "un", ret);
  88                 goto err;
  89         }
  90
  91         pstore_ftrace_enabled = on;
  92 out:
  93         ret = count;
  94 err:
  95         mutex_unlock(&pstore_ftrace_lock);
  96
  97         return ret;
  98 }
  99
 100 static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
 101                                        size_t count, loff_t *ppos)
 102 {
 103         char val[] = { '0' + pstore_ftrace_enabled, '\n' };
 104
 105         return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
 106 }
 107
 108 static const struct file_operations pstore_knob_fops = {
 109         .open   = simple_open,
 110         .read   = pstore_ftrace_knob_read,
 111         .write  = pstore_ftrace_knob_write,
 112 };
 113
 114 static struct dentry *pstore_ftrace_dir;
 115
 116 void pstore_register_ftrace(void)
 117 {
 118         struct dentry *file;
 119
 120         if (!psinfo->write_buf)
 121                 return;
 122
 123         pstore_ftrace_dir = debugfs_create_dir("pstore", NULL);
 124         if (!pstore_ftrace_dir) {
 125                 pr_err("%s: unable to create pstore directory\n", __func__);
 126                 return;
 127         }
 128
 129         file = debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir,
 130                                    NULL, &pstore_knob_fops);
 131         if (!file) {
 132                 pr_err("%s: unable to create record_ftrace file\n", __func__);
 133                 goto err_file;
 134         }
 135
 136         return;
 137 err_file:
 138         debugfs_remove(pstore_ftrace_dir);
 139 }
 140
 141 void pstore_unregister_ftrace(void)
 142 {
 143         mutex_lock(&pstore_ftrace_lock);
 144         if (pstore_ftrace_enabled) {
 145                 unregister_ftrace_function(&pstore_ftrace_ops);
 146                 pstore_ftrace_enabled = 0;
 147         }
 148         mutex_unlock(&pstore_ftrace_lock);
 149
 150         debugfs_remove_recursive(pstore_ftrace_dir);
 151 }