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