Pileus Git - ~andy/linux/blob - kernel/trace/trace_probe.c

   1 /*
   2  * Common code for probe-based Dynamic events.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   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  * You should have received a copy of the GNU General Public License
  14  * along with this program; if not, write to the Free Software
  15  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  16  *
  17  * This code was copied from kernel/trace/trace_kprobe.c written by
  18  * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
  19  *
  20  * Updates to make this generic:
  21  * Copyright (C) IBM Corporation, 2010-2011
  22  * Author:     Srikar Dronamraju
  23  */
  24
  25 #include "trace_probe.h"
  26
  27 const char *reserved_field_names[] = {
  28         "common_type",
  29         "common_flags",
  30         "common_preempt_count",
  31         "common_pid",
  32         "common_tgid",
  33         FIELD_STRING_IP,
  34         FIELD_STRING_RETIP,
  35         FIELD_STRING_FUNC,
  36 };
  37
  38 /* Printing  in basic type function template */
  39 #define DEFINE_BASIC_PRINT_TYPE_FUNC(type, fmt)                         \
  40 __kprobes int PRINT_TYPE_FUNC_NAME(type)(struct trace_seq *s,   \
  41                                                 const char *name,       \
  42                                                 void *data, void *ent)  \
  43 {                                                                       \
  44         return trace_seq_printf(s, " %s=" fmt, name, *(type *)data);    \
  45 }                                                                       \
  46 const char PRINT_TYPE_FMT_NAME(type)[] = fmt;
  47
  48 DEFINE_BASIC_PRINT_TYPE_FUNC(u8 , "0x%x")
  49 DEFINE_BASIC_PRINT_TYPE_FUNC(u16, "0x%x")
  50 DEFINE_BASIC_PRINT_TYPE_FUNC(u32, "0x%x")
  51 DEFINE_BASIC_PRINT_TYPE_FUNC(u64, "0x%Lx")
  52 DEFINE_BASIC_PRINT_TYPE_FUNC(s8,  "%d")
  53 DEFINE_BASIC_PRINT_TYPE_FUNC(s16, "%d")
  54 DEFINE_BASIC_PRINT_TYPE_FUNC(s32, "%d")
  55 DEFINE_BASIC_PRINT_TYPE_FUNC(s64, "%Ld")
  56
  57 /* Print type function for string type */
  58 __kprobes int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s,
  59                                                   const char *name,
  60                                                   void *data, void *ent)
  61 {
  62         int len = *(u32 *)data >> 16;
  63
  64         if (!len)
  65                 return trace_seq_printf(s, " %s=(fault)", name);
  66         else
  67                 return trace_seq_printf(s, " %s=\"%s\"", name,
  68                                         (const char *)get_loc_data(data, ent));
  69 }
  70
  71 const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
  72
  73 #define CHECK_FETCH_FUNCS(method, fn)                   \
  74         (((FETCH_FUNC_NAME(method, u8) == fn) ||        \
  75           (FETCH_FUNC_NAME(method, u16) == fn) ||       \
  76           (FETCH_FUNC_NAME(method, u32) == fn) ||       \
  77           (FETCH_FUNC_NAME(method, u64) == fn) ||       \
  78           (FETCH_FUNC_NAME(method, string) == fn) ||    \
  79           (FETCH_FUNC_NAME(method, string_size) == fn)) \
  80          && (fn != NULL))
  81
  82 /* Data fetch function templates */
  83 #define DEFINE_FETCH_reg(type)                                          \
  84 __kprobes void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs,         \
  85                                         void *offset, void *dest)       \
  86 {                                                                       \
  87         *(type *)dest = (type)regs_get_register(regs,                   \
  88                                 (unsigned int)((unsigned long)offset)); \
  89 }
  90 DEFINE_BASIC_FETCH_FUNCS(reg)
  91 /* No string on the register */
  92 #define fetch_reg_string        NULL
  93 #define fetch_reg_string_size   NULL
  94
  95 #define DEFINE_FETCH_retval(type)                                       \
  96 __kprobes void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,      \
  97                                           void *dummy, void *dest)      \
  98 {                                                                       \
  99         *(type *)dest = (type)regs_return_value(regs);                  \
 100 }
 101 DEFINE_BASIC_FETCH_FUNCS(retval)
 102 /* No string on the retval */
 103 #define fetch_retval_string             NULL
 104 #define fetch_retval_string_size        NULL
 105
 106 /* Dereference memory access function */
 107 struct deref_fetch_param {
 108         struct fetch_param      orig;
 109         long                    offset;
 110         fetch_func_t            fetch;
 111         fetch_func_t            fetch_size;
 112 };
 113
 114 #define DEFINE_FETCH_deref(type)                                        \
 115 __kprobes void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs,       \
 116                                             void *data, void *dest)     \
 117 {                                                                       \
 118         struct deref_fetch_param *dprm = data;                          \
 119         unsigned long addr;                                             \
 120         call_fetch(&dprm->orig, regs, &addr);                           \
 121         if (addr) {                                                     \
 122                 addr += dprm->offset;                                   \
 123                 dprm->fetch(regs, (void *)addr, dest);                  \
 124         } else                                                          \
 125                 *(type *)dest = 0;                                      \
 126 }
 127 DEFINE_BASIC_FETCH_FUNCS(deref)
 128 DEFINE_FETCH_deref(string)
 129
 130 __kprobes void FETCH_FUNC_NAME(deref, string_size)(struct pt_regs *regs,
 131                                                    void *data, void *dest)
 132 {
 133         struct deref_fetch_param *dprm = data;
 134         unsigned long addr;
 135
 136         call_fetch(&dprm->orig, regs, &addr);
 137         if (addr && dprm->fetch_size) {
 138                 addr += dprm->offset;
 139                 dprm->fetch_size(regs, (void *)addr, dest);
 140         } else
 141                 *(string_size *)dest = 0;
 142 }
 143
 144 static __kprobes void update_deref_fetch_param(struct deref_fetch_param *data)
 145 {
 146         if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 147                 update_deref_fetch_param(data->orig.data);
 148         else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 149                 update_symbol_cache(data->orig.data);
 150 }
 151
 152 static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
 153 {
 154         if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 155                 free_deref_fetch_param(data->orig.data);
 156         else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 157                 free_symbol_cache(data->orig.data);
 158         kfree(data);
 159 }
 160
 161 /* Bitfield fetch function */
 162 struct bitfield_fetch_param {
 163         struct fetch_param      orig;
 164         unsigned char           hi_shift;
 165         unsigned char           low_shift;
 166 };
 167
 168 #define DEFINE_FETCH_bitfield(type)                                     \
 169 __kprobes void FETCH_FUNC_NAME(bitfield, type)(struct pt_regs *regs,    \
 170                                             void *data, void *dest)     \
 171 {                                                                       \
 172         struct bitfield_fetch_param *bprm = data;                       \
 173         type buf = 0;                                                   \
 174         call_fetch(&bprm->orig, regs, &buf);                            \
 175         if (buf) {                                                      \
 176                 buf <<= bprm->hi_shift;                                 \
 177                 buf >>= bprm->low_shift;                                \
 178         }                                                               \
 179         *(type *)dest = buf;                                            \
 180 }
 181
 182 DEFINE_BASIC_FETCH_FUNCS(bitfield)
 183 #define fetch_bitfield_string           NULL
 184 #define fetch_bitfield_string_size      NULL
 185
 186 static __kprobes void
 187 update_bitfield_fetch_param(struct bitfield_fetch_param *data)
 188 {
 189         /*
 190          * Don't check the bitfield itself, because this must be the
 191          * last fetch function.
 192          */
 193         if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 194                 update_deref_fetch_param(data->orig.data);
 195         else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 196                 update_symbol_cache(data->orig.data);
 197 }
 198
 199 static __kprobes void
 200 free_bitfield_fetch_param(struct bitfield_fetch_param *data)
 201 {
 202         /*
 203          * Don't check the bitfield itself, because this must be the
 204          * last fetch function.
 205          */
 206         if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 207                 free_deref_fetch_param(data->orig.data);
 208         else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 209                 free_symbol_cache(data->orig.data);
 210
 211         kfree(data);
 212 }
 213
 214 static const struct fetch_type *find_fetch_type(const char *type,
 215                                                 const struct fetch_type *ftbl)
 216 {
 217         int i;
 218
 219         if (!type)
 220                 type = DEFAULT_FETCH_TYPE_STR;
 221
 222         /* Special case: bitfield */
 223         if (*type == 'b') {
 224                 unsigned long bs;
 225
 226                 type = strchr(type, '/');
 227                 if (!type)
 228                         goto fail;
 229
 230                 type++;
 231                 if (kstrtoul(type, 0, &bs))
 232                         goto fail;
 233
 234                 switch (bs) {
 235                 case 8:
 236                         return find_fetch_type("u8", ftbl);
 237                 case 16:
 238                         return find_fetch_type("u16", ftbl);
 239                 case 32:
 240                         return find_fetch_type("u32", ftbl);
 241                 case 64:
 242                         return find_fetch_type("u64", ftbl);
 243                 default:
 244                         goto fail;
 245                 }
 246         }
 247
 248         for (i = 0; ftbl[i].name; i++) {
 249                 if (strcmp(type, ftbl[i].name) == 0)
 250                         return &ftbl[i];
 251         }
 252
 253 fail:
 254         return NULL;
 255 }
 256
 257 /* Special function : only accept unsigned long */
 258 static __kprobes void fetch_stack_address(struct pt_regs *regs,
 259                                         void *dummy, void *dest)
 260 {
 261         *(unsigned long *)dest = kernel_stack_pointer(regs);
 262 }
 263
 264 static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
 265                                             fetch_func_t orig_fn,
 266                                             const struct fetch_type *ftbl)
 267 {
 268         int i;
 269
 270         if (type != &ftbl[FETCH_TYPE_STRING])
 271                 return NULL;    /* Only string type needs size function */
 272
 273         for (i = 0; i < FETCH_MTD_END; i++)
 274                 if (type->fetch[i] == orig_fn)
 275                         return ftbl[FETCH_TYPE_STRSIZE].fetch[i];
 276
 277         WARN_ON(1);     /* This should not happen */
 278
 279         return NULL;
 280 }
 281
 282 /* Split symbol and offset. */
 283 int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
 284 {
 285         char *tmp;
 286         int ret;
 287
 288         if (!offset)
 289                 return -EINVAL;
 290
 291         tmp = strchr(symbol, '+');
 292         if (tmp) {
 293                 /* skip sign because kstrtoul doesn't accept '+' */
 294                 ret = kstrtoul(tmp + 1, 0, offset);
 295                 if (ret)
 296                         return ret;
 297
 298                 *tmp = '\0';
 299         } else
 300                 *offset = 0;
 301
 302         return 0;
 303 }
 304
 305 #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
 306
 307 static int parse_probe_vars(char *arg, const struct fetch_type *t,
 308                             struct fetch_param *f, bool is_return)
 309 {
 310         int ret = 0;
 311         unsigned long param;
 312
 313         if (strcmp(arg, "retval") == 0) {
 314                 if (is_return)
 315                         f->fn = t->fetch[FETCH_MTD_retval];
 316                 else
 317                         ret = -EINVAL;
 318         } else if (strncmp(arg, "stack", 5) == 0) {
 319                 if (arg[5] == '\0') {
 320                         if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR) == 0)
 321                                 f->fn = fetch_stack_address;
 322                         else
 323                                 ret = -EINVAL;
 324                 } else if (isdigit(arg[5])) {
 325                         ret = kstrtoul(arg + 5, 10, &param);
 326                         if (ret || param > PARAM_MAX_STACK)
 327                                 ret = -EINVAL;
 328                         else {
 329                                 f->fn = t->fetch[FETCH_MTD_stack];
 330                                 f->data = (void *)param;
 331                         }
 332                 } else
 333                         ret = -EINVAL;
 334         } else
 335                 ret = -EINVAL;
 336
 337         return ret;
 338 }
 339
 340 /* Recursive argument parser */
 341 static int parse_probe_arg(char *arg, const struct fetch_type *t,
 342                      struct fetch_param *f, bool is_return, bool is_kprobe)
 343 {
 344         const struct fetch_type *ftbl;
 345         unsigned long param;
 346         long offset;
 347         char *tmp;
 348         int ret = 0;
 349
 350         ftbl = is_kprobe ? kprobes_fetch_type_table : uprobes_fetch_type_table;
 351         BUG_ON(ftbl == NULL);
 352
 353         /* Until uprobe_events supports only reg arguments */
 354         if (!is_kprobe && arg[0] != '%')
 355                 return -EINVAL;
 356
 357         switch (arg[0]) {
 358         case '$':
 359                 ret = parse_probe_vars(arg + 1, t, f, is_return);
 360                 break;
 361
 362         case '%':       /* named register */
 363                 ret = regs_query_register_offset(arg + 1);
 364                 if (ret >= 0) {
 365                         f->fn = t->fetch[FETCH_MTD_reg];
 366                         f->data = (void *)(unsigned long)ret;
 367                         ret = 0;
 368                 }
 369                 break;
 370
 371         case '@':       /* memory or symbol */
 372                 if (isdigit(arg[1])) {
 373                         ret = kstrtoul(arg + 1, 0, &param);
 374                         if (ret)
 375                                 break;
 376
 377                         f->fn = t->fetch[FETCH_MTD_memory];
 378                         f->data = (void *)param;
 379                 } else {
 380                         ret = traceprobe_split_symbol_offset(arg + 1, &offset);
 381                         if (ret)
 382                                 break;
 383
 384                         f->data = alloc_symbol_cache(arg + 1, offset);
 385                         if (f->data)
 386                                 f->fn = t->fetch[FETCH_MTD_symbol];
 387                 }
 388                 break;
 389
 390         case '+':       /* deref memory */
 391                 arg++;  /* Skip '+', because kstrtol() rejects it. */
 392         case '-':
 393                 tmp = strchr(arg, '(');
 394                 if (!tmp)
 395                         break;
 396
 397                 *tmp = '\0';
 398                 ret = kstrtol(arg, 0, &offset);
 399
 400                 if (ret)
 401                         break;
 402
 403                 arg = tmp + 1;
 404                 tmp = strrchr(arg, ')');
 405
 406                 if (tmp) {
 407                         struct deref_fetch_param        *dprm;
 408                         const struct fetch_type         *t2;
 409
 410                         t2 = find_fetch_type(NULL, ftbl);
 411                         *tmp = '\0';
 412                         dprm = kzalloc(sizeof(struct deref_fetch_param), GFP_KERNEL);
 413
 414                         if (!dprm)
 415                                 return -ENOMEM;
 416
 417                         dprm->offset = offset;
 418                         dprm->fetch = t->fetch[FETCH_MTD_memory];
 419                         dprm->fetch_size = get_fetch_size_function(t,
 420                                                         dprm->fetch, ftbl);
 421                         ret = parse_probe_arg(arg, t2, &dprm->orig, is_return,
 422                                                         is_kprobe);
 423                         if (ret)
 424                                 kfree(dprm);
 425                         else {
 426                                 f->fn = t->fetch[FETCH_MTD_deref];
 427                                 f->data = (void *)dprm;
 428                         }
 429                 }
 430                 break;
 431         }
 432         if (!ret && !f->fn) {   /* Parsed, but do not find fetch method */
 433                 pr_info("%s type has no corresponding fetch method.\n", t->name);
 434                 ret = -EINVAL;
 435         }
 436
 437         return ret;
 438 }
 439
 440 #define BYTES_TO_BITS(nb)       ((BITS_PER_LONG * (nb)) / sizeof(long))
 441
 442 /* Bitfield type needs to be parsed into a fetch function */
 443 static int __parse_bitfield_probe_arg(const char *bf,
 444                                       const struct fetch_type *t,
 445                                       struct fetch_param *f)
 446 {
 447         struct bitfield_fetch_param *bprm;
 448         unsigned long bw, bo;
 449         char *tail;
 450
 451         if (*bf != 'b')
 452                 return 0;
 453
 454         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
 455         if (!bprm)
 456                 return -ENOMEM;
 457
 458         bprm->orig = *f;
 459         f->fn = t->fetch[FETCH_MTD_bitfield];
 460         f->data = (void *)bprm;
 461         bw = simple_strtoul(bf + 1, &tail, 0);  /* Use simple one */
 462
 463         if (bw == 0 || *tail != '@')
 464                 return -EINVAL;
 465
 466         bf = tail + 1;
 467         bo = simple_strtoul(bf, &tail, 0);
 468
 469         if (tail == bf || *tail != '/')
 470                 return -EINVAL;
 471
 472         bprm->hi_shift = BYTES_TO_BITS(t->size) - (bw + bo);
 473         bprm->low_shift = bprm->hi_shift + bo;
 474
 475         return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
 476 }
 477
 478 /* String length checking wrapper */
 479 int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
 480                 struct probe_arg *parg, bool is_return, bool is_kprobe)
 481 {
 482         const struct fetch_type *ftbl;
 483         const char *t;
 484         int ret;
 485
 486         ftbl = is_kprobe ? kprobes_fetch_type_table : uprobes_fetch_type_table;
 487         BUG_ON(ftbl == NULL);
 488
 489         if (strlen(arg) > MAX_ARGSTR_LEN) {
 490                 pr_info("Argument is too long.: %s\n",  arg);
 491                 return -ENOSPC;
 492         }
 493         parg->comm = kstrdup(arg, GFP_KERNEL);
 494         if (!parg->comm) {
 495                 pr_info("Failed to allocate memory for command '%s'.\n", arg);
 496                 return -ENOMEM;
 497         }
 498         t = strchr(parg->comm, ':');
 499         if (t) {
 500                 arg[t - parg->comm] = '\0';
 501                 t++;
 502         }
 503         parg->type = find_fetch_type(t, ftbl);
 504         if (!parg->type) {
 505                 pr_info("Unsupported type: %s\n", t);
 506                 return -EINVAL;
 507         }
 508         parg->offset = *size;
 509         *size += parg->type->size;
 510         ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return, is_kprobe);
 511
 512         if (ret >= 0 && t != NULL)
 513                 ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch);
 514
 515         if (ret >= 0) {
 516                 parg->fetch_size.fn = get_fetch_size_function(parg->type,
 517                                                               parg->fetch.fn,
 518                                                               ftbl);
 519                 parg->fetch_size.data = parg->fetch.data;
 520         }
 521
 522         return ret;
 523 }
 524
 525 /* Return 1 if name is reserved or already used by another argument */
 526 int traceprobe_conflict_field_name(const char *name,
 527                                struct probe_arg *args, int narg)
 528 {
 529         int i;
 530
 531         for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
 532                 if (strcmp(reserved_field_names[i], name) == 0)
 533                         return 1;
 534
 535         for (i = 0; i < narg; i++)
 536                 if (strcmp(args[i].name, name) == 0)
 537                         return 1;
 538
 539         return 0;
 540 }
 541
 542 void traceprobe_update_arg(struct probe_arg *arg)
 543 {
 544         if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
 545                 update_bitfield_fetch_param(arg->fetch.data);
 546         else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
 547                 update_deref_fetch_param(arg->fetch.data);
 548         else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
 549                 update_symbol_cache(arg->fetch.data);
 550 }
 551
 552 void traceprobe_free_probe_arg(struct probe_arg *arg)
 553 {
 554         if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
 555                 free_bitfield_fetch_param(arg->fetch.data);
 556         else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
 557                 free_deref_fetch_param(arg->fetch.data);
 558         else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
 559                 free_symbol_cache(arg->fetch.data);
 560
 561         kfree(arg->name);
 562         kfree(arg->comm);
 563 }
 564
 565 int traceprobe_command(const char *buf, int (*createfn)(int, char **))
 566 {
 567         char **argv;
 568         int argc, ret;
 569
 570         argc = 0;
 571         ret = 0;
 572         argv = argv_split(GFP_KERNEL, buf, &argc);
 573         if (!argv)
 574                 return -ENOMEM;
 575
 576         if (argc)
 577                 ret = createfn(argc, argv);
 578
 579         argv_free(argv);
 580
 581         return ret;
 582 }
 583
 584 #define WRITE_BUFSIZE  4096
 585
 586 ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
 587                                 size_t count, loff_t *ppos,
 588                                 int (*createfn)(int, char **))
 589 {
 590         char *kbuf, *tmp;
 591         int ret = 0;
 592         size_t done = 0;
 593         size_t size;
 594
 595         kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
 596         if (!kbuf)
 597                 return -ENOMEM;
 598
 599         while (done < count) {
 600                 size = count - done;
 601
 602                 if (size >= WRITE_BUFSIZE)
 603                         size = WRITE_BUFSIZE - 1;
 604
 605                 if (copy_from_user(kbuf, buffer + done, size)) {
 606                         ret = -EFAULT;
 607                         goto out;
 608                 }
 609                 kbuf[size] = '\0';
 610                 tmp = strchr(kbuf, '\n');
 611
 612                 if (tmp) {
 613                         *tmp = '\0';
 614                         size = tmp - kbuf + 1;
 615                 } else if (done + size < count) {
 616                         pr_warning("Line length is too long: "
 617                                    "Should be less than %d.", WRITE_BUFSIZE);
 618                         ret = -EINVAL;
 619                         goto out;
 620                 }
 621                 done += size;
 622                 /* Remove comments */
 623                 tmp = strchr(kbuf, '#');
 624
 625                 if (tmp)
 626                         *tmp = '\0';
 627
 628                 ret = traceprobe_command(kbuf, createfn);
 629                 if (ret)
 630                         goto out;
 631         }
 632         ret = done;
 633
 634 out:
 635         kfree(kbuf);
 636
 637         return ret;
 638 }
 639
 640 static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 641                            bool is_return)
 642 {
 643         int i;
 644         int pos = 0;
 645
 646         const char *fmt, *arg;
 647
 648         if (!is_return) {
 649                 fmt = "(%lx)";
 650                 arg = "REC->" FIELD_STRING_IP;
 651         } else {
 652                 fmt = "(%lx <- %lx)";
 653                 arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
 654         }
 655
 656         /* When len=0, we just calculate the needed length */
 657 #define LEN_OR_ZERO (len ? len - pos : 0)
 658
 659         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);
 660
 661         for (i = 0; i < tp->nr_args; i++) {
 662                 pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
 663                                 tp->args[i].name, tp->args[i].type->fmt);
 664         }
 665
 666         pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
 667
 668         for (i = 0; i < tp->nr_args; i++) {
 669                 if (strcmp(tp->args[i].type->name, "string") == 0)
 670                         pos += snprintf(buf + pos, LEN_OR_ZERO,
 671                                         ", __get_str(%s)",
 672                                         tp->args[i].name);
 673                 else
 674                         pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
 675                                         tp->args[i].name);
 676         }
 677
 678 #undef LEN_OR_ZERO
 679
 680         /* return the length of print_fmt */
 681         return pos;
 682 }
 683
 684 int set_print_fmt(struct trace_probe *tp, bool is_return)
 685 {
 686         int len;
 687         char *print_fmt;
 688
 689         /* First: called with 0 length to calculate the needed length */
 690         len = __set_print_fmt(tp, NULL, 0, is_return);
 691         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 692         if (!print_fmt)
 693                 return -ENOMEM;
 694
 695         /* Second: actually write the @print_fmt */
 696         __set_print_fmt(tp, print_fmt, len + 1, is_return);
 697         tp->call.print_fmt = print_fmt;
 698
 699         return 0;
 700 }