kernel/trace/trace_printk.c

   1 /*
   2  * trace binary printk
   3  *
   4  * Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
   5  *
   6  */
   7 #include <linux/seq_file.h>
   8 #include <linux/debugfs.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/kernel.h>
  11 #include <linux/ftrace.h>
  12 #include <linux/string.h>
  13 #include <linux/module.h>
  14 #include <linux/mutex.h>
  15 #include <linux/ctype.h>
  16 #include <linux/list.h>
  17 #include <linux/slab.h>
  18 #include <linux/fs.h>
  19
  20 #include "trace.h"
  21
  22 #ifdef CONFIG_MODULES
  23
  24 /*
  25  * modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
  26  * which are queued on trace_bprintk_fmt_list.
  27  */
  28 static LIST_HEAD(trace_bprintk_fmt_list);
  29
  30 /* serialize accesses to trace_bprintk_fmt_list */
  31 static DEFINE_MUTEX(btrace_mutex);
  32
  33 struct trace_bprintk_fmt {
  34         struct list_head list;
  35         const char *fmt;
  36 };
  37
  38 static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
  39 {
  40         struct trace_bprintk_fmt *pos;
  41
  42         if (!fmt)
  43                 return ERR_PTR(-EINVAL);
  44
  45         list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
  46                 if (!strcmp(pos->fmt, fmt))
  47                         return pos;
  48         }
  49         return NULL;
  50 }
  51
  52 static
  53 void hold_module_trace_bprintk_format(const char **start, const char **end)
  54 {
  55         const char **iter;
  56         char *fmt;
  57
  58         /* allocate the trace_printk per cpu buffers */
  59         if (start != end)
  60                 trace_printk_init_buffers();
  61
  62         mutex_lock(&btrace_mutex);
  63         for (iter = start; iter < end; iter++) {
  64                 struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
  65                 if (tb_fmt) {
  66                         if (!IS_ERR(tb_fmt))
  67                                 *iter = tb_fmt->fmt;
  68                         continue;
  69                 }
  70
  71                 fmt = NULL;
  72                 tb_fmt = kmalloc(sizeof(*tb_fmt), GFP_KERNEL);
  73                 if (tb_fmt) {
  74                         fmt = kmalloc(strlen(*iter) + 1, GFP_KERNEL);
  75                         if (fmt) {
  76                                 list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
  77                                 strcpy(fmt, *iter);
  78                                 tb_fmt->fmt = fmt;
  79                         } else
  80                                 kfree(tb_fmt);
  81                 }
  82                 *iter = fmt;
  83
  84         }
  85         mutex_unlock(&btrace_mutex);
  86 }
  87
  88 static int module_trace_bprintk_format_notify(struct notifier_block *self,
  89                 unsigned long val, void *data)
  90 {
  91         struct module *mod = data;
  92         if (mod->num_trace_bprintk_fmt) {
  93                 const char **start = mod->trace_bprintk_fmt_start;
  94                 const char **end = start + mod->num_trace_bprintk_fmt;
  95
  96                 if (val == MODULE_STATE_COMING)
  97                         hold_module_trace_bprintk_format(start, end);
  98         }
  99         return 0;
 100 }
 101
 102 /*
 103  * The debugfs/tracing/printk_formats file maps the addresses with
 104  * the ASCII formats that are used in the bprintk events in the
 105  * buffer. For userspace tools to be able to decode the events from
 106  * the buffer, they need to be able to map the address with the format.
 107  *
 108  * The addresses of the bprintk formats are in their own section
 109  * __trace_printk_fmt. But for modules we copy them into a link list.
 110  * The code to print the formats and their addresses passes around the
 111  * address of the fmt string. If the fmt address passed into the seq
 112  * functions is within the kernel core __trace_printk_fmt section, then
 113  * it simply uses the next pointer in the list.
 114  *
 115  * When the fmt pointer is outside the kernel core __trace_printk_fmt
 116  * section, then we need to read the link list pointers. The trick is
 117  * we pass the address of the string to the seq function just like
 118  * we do for the kernel core formats. To get back the structure that
 119  * holds the format, we simply use containerof() and then go to the
 120  * next format in the list.
 121  */
 122 static const char **
 123 find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
 124 {
 125         struct trace_bprintk_fmt *mod_fmt;
 126
 127         if (list_empty(&trace_bprintk_fmt_list))
 128                 return NULL;
 129
 130         /*
 131          * v will point to the address of the fmt record from t_next
 132          * v will be NULL from t_start.
 133          * If this is the first pointer or called from start
 134          * then we need to walk the list.
 135          */
 136         if (!v || start_index == *pos) {
 137                 struct trace_bprintk_fmt *p;
 138
 139                 /* search the module list */
 140                 list_for_each_entry(p, &trace_bprintk_fmt_list, list) {
 141                         if (start_index == *pos)
 142                                 return &p->fmt;
 143                         start_index++;
 144                 }
 145                 /* pos > index */
 146                 return NULL;
 147         }
 148
 149         /*
 150          * v points to the address of the fmt field in the mod list
 151          * structure that holds the module print format.
 152          */
 153         mod_fmt = container_of(v, typeof(*mod_fmt), fmt);
 154         if (mod_fmt->list.next == &trace_bprintk_fmt_list)
 155                 return NULL;
 156
 157         mod_fmt = container_of(mod_fmt->list.next, typeof(*mod_fmt), list);
 158
 159         return &mod_fmt->fmt;
 160 }
 161
 162 static void format_mod_start(void)
 163 {
 164         mutex_lock(&btrace_mutex);
 165 }
 166
 167 static void format_mod_stop(void)
 168 {
 169         mutex_unlock(&btrace_mutex);
 170 }
 171
 172 #else /* !CONFIG_MODULES */
 173 __init static int
 174 module_trace_bprintk_format_notify(struct notifier_block *self,
 175                 unsigned long val, void *data)
 176 {
 177         return 0;
 178 }
 179 static inline const char **
 180 find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
 181 {
 182         return NULL;
 183 }
 184 static inline void format_mod_start(void) { }
 185 static inline void format_mod_stop(void) { }
 186 #endif /* CONFIG_MODULES */
 187
 188
 189 __initdata_or_module static
 190 struct notifier_block module_trace_bprintk_format_nb = {
 191         .notifier_call = module_trace_bprintk_format_notify,
 192 };
 193
 194 int __trace_bprintk(unsigned long ip, const char *fmt, ...)
 195  {
 196         int ret;
 197         va_list ap;
 198
 199         if (unlikely(!fmt))
 200                 return 0;
 201
 202         if (!(trace_flags & TRACE_ITER_PRINTK))
 203                 return 0;
 204
 205         va_start(ap, fmt);
 206         ret = trace_vbprintk(ip, fmt, ap);
 207         va_end(ap);
 208         return ret;
 209 }
 210 EXPORT_SYMBOL_GPL(__trace_bprintk);
 211
 212 int __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap)
 213  {
 214         if (unlikely(!fmt))
 215                 return 0;
 216
 217         if (!(trace_flags & TRACE_ITER_PRINTK))
 218                 return 0;
 219
 220         return trace_vbprintk(ip, fmt, ap);
 221 }
 222 EXPORT_SYMBOL_GPL(__ftrace_vbprintk);
 223
 224 int __trace_printk(unsigned long ip, const char *fmt, ...)
 225 {
 226         int ret;
 227         va_list ap;
 228
 229         if (!(trace_flags & TRACE_ITER_PRINTK))
 230                 return 0;
 231
 232         va_start(ap, fmt);
 233         ret = trace_vprintk(ip, fmt, ap);
 234         va_end(ap);
 235         return ret;
 236 }
 237 EXPORT_SYMBOL_GPL(__trace_printk);
 238
 239 int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
 240 {
 241         if (!(trace_flags & TRACE_ITER_PRINTK))
 242                 return 0;
 243
 244         return trace_vprintk(ip, fmt, ap);
 245 }
 246 EXPORT_SYMBOL_GPL(__ftrace_vprintk);
 247
 248 static const char **find_next(void *v, loff_t *pos)
 249 {
 250         const char **fmt = v;
 251         int start_index;
 252         int last_index;
 253
 254         start_index = __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt;
 255
 256         if (*pos < start_index)
 257                 return __start___trace_bprintk_fmt + *pos;
 258
 259         /*
 260          * The __tracepoint_str section is treated the same as the
 261          * __trace_printk_fmt section. The difference is that the
 262          * __trace_printk_fmt section should only be used by trace_printk()
 263          * in a debugging environment, as if anything exists in that section
 264          * the trace_prink() helper buffers are allocated, which would just
 265          * waste space in a production environment.
 266          *
 267          * The __tracepoint_str sections on the other hand are used by
 268          * tracepoints which need to map pointers to their strings to
 269          * the ASCII text for userspace.
 270          */
 271         last_index = start_index;
 272         start_index = __stop___tracepoint_str - __start___tracepoint_str;
 273
 274         if (*pos < last_index + start_index)
 275                 return __start___tracepoint_str + (*pos - last_index);
 276
 277         return find_next_mod_format(start_index, v, fmt, pos);
 278 }
 279
 280 static void *
 281 t_start(struct seq_file *m, loff_t *pos)
 282 {
 283         format_mod_start();
 284         return find_next(NULL, pos);
 285 }
 286
 287 static void *t_next(struct seq_file *m, void * v, loff_t *pos)
 288 {
 289         (*pos)++;
 290         return find_next(v, pos);
 291 }
 292
 293 static int t_show(struct seq_file *m, void *v)
 294 {
 295         const char **fmt = v;
 296         const char *str = *fmt;
 297         int i;
 298
 299         if (!*fmt)
 300                 return 0;
 301
 302         seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt);
 303
 304         /*
 305          * Tabs and new lines need to be converted.
 306          */
 307         for (i = 0; str[i]; i++) {
 308                 switch (str[i]) {
 309                 case '\n':
 310                         seq_puts(m, "\\n");
 311                         break;
 312                 case '\t':
 313                         seq_puts(m, "\\t");
 314                         break;
 315                 case '\\':
 316                         seq_puts(m, "\\");
 317                         break;
 318                 case '"':
 319                         seq_puts(m, "\\\"");
 320                         break;
 321                 default:
 322                         seq_putc(m, str[i]);
 323                 }
 324         }
 325         seq_puts(m, "\"\n");
 326
 327         return 0;
 328 }
 329
 330 static void t_stop(struct seq_file *m, void *p)
 331 {
 332         format_mod_stop();
 333 }
 334
 335 static const struct seq_operations show_format_seq_ops = {
 336         .start = t_start,
 337         .next = t_next,
 338         .show = t_show,
 339         .stop = t_stop,
 340 };
 341
 342 static int
 343 ftrace_formats_open(struct inode *inode, struct file *file)
 344 {
 345         return seq_open(file, &show_format_seq_ops);
 346 }
 347
 348 static const struct file_operations ftrace_formats_fops = {
 349         .open = ftrace_formats_open,
 350         .read = seq_read,
 351         .llseek = seq_lseek,
 352         .release = seq_release,
 353 };
 354
 355 static __init int init_trace_printk_function_export(void)
 356 {
 357         struct dentry *d_tracer;
 358
 359         d_tracer = tracing_init_dentry();
 360         if (!d_tracer)
 361                 return 0;
 362
 363         trace_create_file("printk_formats", 0444, d_tracer,
 364                                     NULL, &ftrace_formats_fops);
 365
 366         return 0;
 367 }
 368
 369 fs_initcall(init_trace_printk_function_export);
 370
 371 static __init int init_trace_printk(void)
 372 {
 373         return register_module_notifier(&module_trace_bprintk_format_nb);
 374 }
 375
 376 early_initcall(init_trace_printk);