fs/pstore/ftrace.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2012  Google, Inc.
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/compiler.h>
   8 #include <linux/irqflags.h>
   9 #include <linux/percpu.h>
  10 #include <linux/smp.h>
  11 #include <linux/atomic.h>
  12 #include <linux/types.h>
  13 #include <linux/mutex.h>
  14 #include <linux/ftrace.h>
  15 #include <linux/fs.h>
  16 #include <linux/debugfs.h>
  17 #include <linux/err.h>
  18 #include <linux/cache.h>
  19 #include <linux/slab.h>
  20 #include <asm/barrier.h>
  21 #include "internal.h"
  22
  23 /* This doesn't need to be atomic: speed is chosen over correctness here. */
  24 static u64 pstore_ftrace_stamp;
  25
  26 static void notrace pstore_ftrace_call(unsigned long ip,
  27                                        unsigned long parent_ip,
  28                                        struct ftrace_ops *op,
  29                                        struct ftrace_regs *fregs)
  30 {
  31         int bit;
  32         unsigned long flags;
  33         struct pstore_ftrace_record rec = {};
  34         struct pstore_record record = {
  35                 .type = PSTORE_TYPE_FTRACE,
  36                 .buf = (char *)&rec,
  37                 .size = sizeof(rec),
  38                 .psi = psinfo,
  39         };
  40
  41         if (unlikely(oops_in_progress))
  42                 return;
  43
  44         bit = ftrace_test_recursion_trylock(ip, parent_ip);
  45         if (bit < 0)
  46                 return;
  47
  48         local_irq_save(flags);
  49
  50         rec.ip = ip;
  51         rec.parent_ip = parent_ip;
  52         pstore_ftrace_write_timestamp(&rec, pstore_ftrace_stamp++);
  53         pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
  54         psinfo->write(&record);
  55
  56         local_irq_restore(flags);
  57         ftrace_test_recursion_unlock(bit);
  58 }
  59
  60 static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
  61         .func   = pstore_ftrace_call,
  62 };
  63
  64 static DEFINE_MUTEX(pstore_ftrace_lock);
  65 static bool pstore_ftrace_enabled;
  66
  67 static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
  68                                         size_t count, loff_t *ppos)
  69 {
  70         u8 on;
  71         ssize_t ret;
  72
  73         ret = kstrtou8_from_user(buf, count, 2, &on);
  74         if (ret)
  75                 return ret;
  76
  77         mutex_lock(&pstore_ftrace_lock);
  78
  79         if (!on ^ pstore_ftrace_enabled)
  80                 goto out;
  81
  82         if (on) {
  83                 ftrace_ops_set_global_filter(&pstore_ftrace_ops);
  84                 ret = register_ftrace_function(&pstore_ftrace_ops);
  85         } else {
  86                 ret = unregister_ftrace_function(&pstore_ftrace_ops);
  87         }
  88
  89         if (ret) {
  90                 pr_err("%s: unable to %sregister ftrace ops: %zd\n",
  91                        __func__, on ? "" : "un", ret);
  92                 goto err;
  93         }
  94
  95         pstore_ftrace_enabled = on;
  96 out:
  97         ret = count;
  98 err:
  99         mutex_unlock(&pstore_ftrace_lock);
 100
 101         return ret;
 102 }
 103
 104 static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
 105                                        size_t count, loff_t *ppos)
 106 {
 107         char val[] = { '0' + pstore_ftrace_enabled, '\n' };
 108
 109         return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
 110 }
 111
 112 static const struct file_operations pstore_knob_fops = {
 113         .open   = simple_open,
 114         .read   = pstore_ftrace_knob_read,
 115         .write  = pstore_ftrace_knob_write,
 116 };
 117
 118 static struct dentry *pstore_ftrace_dir;
 119
 120 void pstore_register_ftrace(void)
 121 {
 122         if (!psinfo->write)
 123                 return;
 124
 125         pstore_ftrace_dir = debugfs_create_dir("pstore", NULL);
 126
 127         debugfs_create_file("record_ftrace", 0600, pstore_ftrace_dir, NULL,
 128                             &pstore_knob_fops);
 129 }
 130
 131 void pstore_unregister_ftrace(void)
 132 {
 133         mutex_lock(&pstore_ftrace_lock);
 134         if (pstore_ftrace_enabled) {
 135                 unregister_ftrace_function(&pstore_ftrace_ops);
 136                 pstore_ftrace_enabled = false;
 137         }
 138         mutex_unlock(&pstore_ftrace_lock);
 139
 140         debugfs_remove_recursive(pstore_ftrace_dir);
 141 }
 142
 143 ssize_t pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
 144                                   const char *src_log, size_t src_log_size)
 145 {
 146         size_t dest_size, src_size, total, dest_off, src_off;
 147         size_t dest_idx = 0, src_idx = 0, merged_idx = 0;
 148         void *merged_buf;
 149         struct pstore_ftrace_record *drec, *srec, *mrec;
 150         size_t record_size = sizeof(struct pstore_ftrace_record);
 151
 152         dest_off = *dest_log_size % record_size;
 153         dest_size = *dest_log_size - dest_off;
 154
 155         src_off = src_log_size % record_size;
 156         src_size = src_log_size - src_off;
 157
 158         total = dest_size + src_size;
 159         merged_buf = kmalloc(total, GFP_KERNEL);
 160         if (!merged_buf)
 161                 return -ENOMEM;
 162
 163         drec = (struct pstore_ftrace_record *)(*dest_log + dest_off);
 164         srec = (struct pstore_ftrace_record *)(src_log + src_off);
 165         mrec = (struct pstore_ftrace_record *)(merged_buf);
 166
 167         while (dest_size > 0 && src_size > 0) {
 168                 if (pstore_ftrace_read_timestamp(&drec[dest_idx]) <
 169                     pstore_ftrace_read_timestamp(&srec[src_idx])) {
 170                         mrec[merged_idx++] = drec[dest_idx++];
 171                         dest_size -= record_size;
 172                 } else {
 173                         mrec[merged_idx++] = srec[src_idx++];
 174                         src_size -= record_size;
 175                 }
 176         }
 177
 178         while (dest_size > 0) {
 179                 mrec[merged_idx++] = drec[dest_idx++];
 180                 dest_size -= record_size;
 181         }
 182
 183         while (src_size > 0) {
 184                 mrec[merged_idx++] = srec[src_idx++];
 185                 src_size -= record_size;
 186         }
 187
 188         kfree(*dest_log);
 189         *dest_log = merged_buf;
 190         *dest_log_size = total;
 191
 192         return 0;
 193 }
 194 EXPORT_SYMBOL_GPL(pstore_ftrace_combine_log);