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         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
  61 static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  62         .func   = pstore_ftrace_call,
  63 };
  64
  65 static DEFINE_MUTEX(pstore_ftrace_lock);
  66 static bool pstore_ftrace_enabled;
  67
  68 static 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;
  97 out:
  98         ret = count;
  99 err:
 100         mutex_unlock(&pstore_ftrace_lock);
 101
 102         return ret;
 103 }
 104
 105 static 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
 113 static 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
 119 static struct dentry *pstore_ftrace_dir;
 120
 121 void 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;
 142 err_file:
 143         debugfs_remove(pstore_ftrace_dir);
 144 }
 145
 146 void 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 }