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 static 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
  52 static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  53         .func   = pstore_ftrace_call,
  54 };
  55
  56 static DEFINE_MUTEX(pstore_ftrace_lock);
  57 static bool pstore_ftrace_enabled;
  58
  59 static 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;
  85 out:
  86         ret = count;
  87 err:
  88         mutex_unlock(&pstore_ftrace_lock);
  89
  90         return ret;
  91 }
  92
  93 static 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
 101 static 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
 107 void 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;
 129 err_file:
 130         debugfs_remove(dir);
 131 }