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 int PRINT_TYPE_FUNC_NAME(type)(struct trace_seq *s, const char *name, \ 41 void *data, void *ent) \ 42 { \ 43 trace_seq_printf(s, " %s=" fmt, name, *(type *)data); \ 44 return !trace_seq_has_overflowed(s); \ 45 } \ 46 const char PRINT_TYPE_FMT_NAME(type)[] = fmt; \ 47 NOKPROBE_SYMBOL(PRINT_TYPE_FUNC_NAME(type)); 48 49 DEFINE_BASIC_PRINT_TYPE_FUNC(u8 , "0x%x") 50 DEFINE_BASIC_PRINT_TYPE_FUNC(u16, "0x%x") 51 DEFINE_BASIC_PRINT_TYPE_FUNC(u32, "0x%x") 52 DEFINE_BASIC_PRINT_TYPE_FUNC(u64, "0x%Lx") 53 DEFINE_BASIC_PRINT_TYPE_FUNC(s8, "%d") 54 DEFINE_BASIC_PRINT_TYPE_FUNC(s16, "%d") 55 DEFINE_BASIC_PRINT_TYPE_FUNC(s32, "%d") 56 DEFINE_BASIC_PRINT_TYPE_FUNC(s64, "%Ld") 57 58 /* Print type function for string type */ 59 int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s, const char *name, 60 void *data, void *ent) 61 { 62 int len = *(u32 *)data >> 16; 63 64 if (!len) 65 trace_seq_printf(s, " %s=(fault)", name); 66 else 67 trace_seq_printf(s, " %s=\"%s\"", name, 68 (const char *)get_loc_data(data, ent)); 69 return !trace_seq_has_overflowed(s); 70 } 71 NOKPROBE_SYMBOL(PRINT_TYPE_FUNC_NAME(string)); 72 73 const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\""; 74 75 #define CHECK_FETCH_FUNCS(method, fn) \ 76 (((FETCH_FUNC_NAME(method, u8) == fn) || \ 77 (FETCH_FUNC_NAME(method, u16) == fn) || \ 78 (FETCH_FUNC_NAME(method, u32) == fn) || \ 79 (FETCH_FUNC_NAME(method, u64) == fn) || \ 80 (FETCH_FUNC_NAME(method, string) == fn) || \ 81 (FETCH_FUNC_NAME(method, string_size) == fn)) \ 82 && (fn != NULL)) 83 84 /* Data fetch function templates */ 85 #define DEFINE_FETCH_reg(type) \ 86 void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs, void *offset, void *dest) \ 87 { \ 88 *(type *)dest = (type)regs_get_register(regs, \ 89 (unsigned int)((unsigned long)offset)); \ 90 } \ 91 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(reg, type)); 92 DEFINE_BASIC_FETCH_FUNCS(reg) 93 /* No string on the register */ 94 #define fetch_reg_string NULL 95 #define fetch_reg_string_size NULL 96 97 #define DEFINE_FETCH_retval(type) \ 98 void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs, \ 99 void *dummy, void *dest) \ 100 { \ 101 *(type *)dest = (type)regs_return_value(regs); \ 102 } \ 103 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(retval, type)); 104 DEFINE_BASIC_FETCH_FUNCS(retval) 105 /* No string on the retval */ 106 #define fetch_retval_string NULL 107 #define fetch_retval_string_size NULL 108 109 /* Dereference memory access function */ 110 struct deref_fetch_param { 111 struct fetch_param orig; 112 long offset; 113 fetch_func_t fetch; 114 fetch_func_t fetch_size; 115 }; 116 117 #define DEFINE_FETCH_deref(type) \ 118 void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs, \ 119 void *data, void *dest) \ 120 { \ 121 struct deref_fetch_param *dprm = data; \ 122 unsigned long addr; \ 123 call_fetch(&dprm->orig, regs, &addr); \ 124 if (addr) { \ 125 addr += dprm->offset; \ 126 dprm->fetch(regs, (void *)addr, dest); \ 127 } else \ 128 *(type *)dest = 0; \ 129 } \ 130 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, type)); 131 DEFINE_BASIC_FETCH_FUNCS(deref) 132 DEFINE_FETCH_deref(string) 133 134 void FETCH_FUNC_NAME(deref, string_size)(struct pt_regs *regs, 135 void *data, void *dest) 136 { 137 struct deref_fetch_param *dprm = data; 138 unsigned long addr; 139 140 call_fetch(&dprm->orig, regs, &addr); 141 if (addr && dprm->fetch_size) { 142 addr += dprm->offset; 143 dprm->fetch_size(regs, (void *)addr, dest); 144 } else 145 *(string_size *)dest = 0; 146 } 147 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, string_size)); 148 149 static void update_deref_fetch_param(struct deref_fetch_param *data) 150 { 151 if (CHECK_FETCH_FUNCS(deref, data->orig.fn)) 152 update_deref_fetch_param(data->orig.data); 153 else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn)) 154 update_symbol_cache(data->orig.data); 155 } 156 NOKPROBE_SYMBOL(update_deref_fetch_param); 157 158 static void free_deref_fetch_param(struct deref_fetch_param *data) 159 { 160 if (CHECK_FETCH_FUNCS(deref, data->orig.fn)) 161 free_deref_fetch_param(data->orig.data); 162 else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn)) 163 free_symbol_cache(data->orig.data); 164 kfree(data); 165 } 166 NOKPROBE_SYMBOL(free_deref_fetch_param); 167 168 /* Bitfield fetch function */ 169 struct bitfield_fetch_param { 170 struct fetch_param orig; 171 unsigned char hi_shift; 172 unsigned char low_shift; 173 }; 174 175 #define DEFINE_FETCH_bitfield(type) \ 176 void FETCH_FUNC_NAME(bitfield, type)(struct pt_regs *regs, \ 177 void *data, void *dest) \ 178 { \ 179 struct bitfield_fetch_param *bprm = data; \ 180 type buf = 0; \ 181 call_fetch(&bprm->orig, regs, &buf); \ 182 if (buf) { \ 183 buf <<= bprm->hi_shift; \ 184 buf >>= bprm->low_shift; \ 185 } \ 186 *(type *)dest = buf; \ 187 } \ 188 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(bitfield, type)); 189 DEFINE_BASIC_FETCH_FUNCS(bitfield) 190 #define fetch_bitfield_string NULL 191 #define fetch_bitfield_string_size NULL 192 193 static void 194 update_bitfield_fetch_param(struct bitfield_fetch_param *data) 195 { 196 /* 197 * Don't check the bitfield itself, because this must be the 198 * last fetch function. 199 */ 200 if (CHECK_FETCH_FUNCS(deref, data->orig.fn)) 201 update_deref_fetch_param(data->orig.data); 202 else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn)) 203 update_symbol_cache(data->orig.data); 204 } 205 206 static void 207 free_bitfield_fetch_param(struct bitfield_fetch_param *data) 208 { 209 /* 210 * Don't check the bitfield itself, because this must be the 211 * last fetch function. 212 */ 213 if (CHECK_FETCH_FUNCS(deref, data->orig.fn)) 214 free_deref_fetch_param(data->orig.data); 215 else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn)) 216 free_symbol_cache(data->orig.data); 217 218 kfree(data); 219 } 220 221 static const struct fetch_type *find_fetch_type(const char *type, 222 const struct fetch_type *ftbl) 223 { 224 int i; 225 226 if (!type) 227 type = DEFAULT_FETCH_TYPE_STR; 228 229 /* Special case: bitfield */ 230 if (*type == 'b') { 231 unsigned long bs; 232 233 type = strchr(type, '/'); 234 if (!type) 235 goto fail; 236 237 type++; 238 if (kstrtoul(type, 0, &bs)) 239 goto fail; 240 241 switch (bs) { 242 case 8: 243 return find_fetch_type("u8", ftbl); 244 case 16: 245 return find_fetch_type("u16", ftbl); 246 case 32: 247 return find_fetch_type("u32", ftbl); 248 case 64: 249 return find_fetch_type("u64", ftbl); 250 default: 251 goto fail; 252 } 253 } 254 255 for (i = 0; ftbl[i].name; i++) { 256 if (strcmp(type, ftbl[i].name) == 0) 257 return &ftbl[i]; 258 } 259 260 fail: 261 return NULL; 262 } 263 264 /* Special function : only accept unsigned long */ 265 static void fetch_kernel_stack_address(struct pt_regs *regs, void *dummy, void *dest) 266 { 267 *(unsigned long *)dest = kernel_stack_pointer(regs); 268 } 269 NOKPROBE_SYMBOL(fetch_kernel_stack_address); 270 271 static void fetch_user_stack_address(struct pt_regs *regs, void *dummy, void *dest) 272 { 273 *(unsigned long *)dest = user_stack_pointer(regs); 274 } 275 NOKPROBE_SYMBOL(fetch_user_stack_address); 276 277 static fetch_func_t get_fetch_size_function(const struct fetch_type *type, 278 fetch_func_t orig_fn, 279 const struct fetch_type *ftbl) 280 { 281 int i; 282 283 if (type != &ftbl[FETCH_TYPE_STRING]) 284 return NULL; /* Only string type needs size function */ 285 286 for (i = 0; i < FETCH_MTD_END; i++) 287 if (type->fetch[i] == orig_fn) 288 return ftbl[FETCH_TYPE_STRSIZE].fetch[i]; 289 290 WARN_ON(1); /* This should not happen */ 291 292 return NULL; 293 } 294 295 /* Split symbol and offset. */ 296 int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset) 297 { 298 char *tmp; 299 int ret; 300 301 if (!offset) 302 return -EINVAL; 303 304 tmp = strchr(symbol, '+'); 305 if (tmp) { 306 /* skip sign because kstrtoul doesn't accept '+' */ 307 ret = kstrtoul(tmp + 1, 0, offset); 308 if (ret) 309 return ret; 310 311 *tmp = '\0'; 312 } else 313 *offset = 0; 314 315 return 0; 316 } 317 318 #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long)) 319 320 static int parse_probe_vars(char *arg, const struct fetch_type *t, 321 struct fetch_param *f, bool is_return, 322 bool is_kprobe) 323 { 324 int ret = 0; 325 unsigned long param; 326 327 if (strcmp(arg, "retval") == 0) { 328 if (is_return) 329 f->fn = t->fetch[FETCH_MTD_retval]; 330 else 331 ret = -EINVAL; 332 } else if (strncmp(arg, "stack", 5) == 0) { 333 if (arg[5] == '\0') { 334 if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR)) 335 return -EINVAL; 336 337 if (is_kprobe) 338 f->fn = fetch_kernel_stack_address; 339 else 340 f->fn = fetch_user_stack_address; 341 } else if (isdigit(arg[5])) { 342 ret = kstrtoul(arg + 5, 10, ¶m); 343 if (ret || (is_kprobe && param > PARAM_MAX_STACK)) 344 ret = -EINVAL; 345 else { 346 f->fn = t->fetch[FETCH_MTD_stack]; 347 f->data = (void *)param; 348 } 349 } else 350 ret = -EINVAL; 351 } else 352 ret = -EINVAL; 353 354 return ret; 355 } 356 357 /* Recursive argument parser */ 358 static int parse_probe_arg(char *arg, const struct fetch_type *t, 359 struct fetch_param *f, bool is_return, bool is_kprobe, 360 const struct fetch_type *ftbl) 361 { 362 unsigned long param; 363 long offset; 364 char *tmp; 365 int ret = 0; 366 367 switch (arg[0]) { 368 case '$': 369 ret = parse_probe_vars(arg + 1, t, f, is_return, is_kprobe); 370 break; 371 372 case '%': /* named register */ 373 ret = regs_query_register_offset(arg + 1); 374 if (ret >= 0) { 375 f->fn = t->fetch[FETCH_MTD_reg]; 376 f->data = (void *)(unsigned long)ret; 377 ret = 0; 378 } 379 break; 380 381 case '@': /* memory, file-offset or symbol */ 382 if (isdigit(arg[1])) { 383 ret = kstrtoul(arg + 1, 0, ¶m); 384 if (ret) 385 break; 386 387 f->fn = t->fetch[FETCH_MTD_memory]; 388 f->data = (void *)param; 389 } else if (arg[1] == '+') { 390 /* kprobes don't support file offsets */ 391 if (is_kprobe) 392 return -EINVAL; 393 394 ret = kstrtol(arg + 2, 0, &offset); 395 if (ret) 396 break; 397 398 f->fn = t->fetch[FETCH_MTD_file_offset]; 399 f->data = (void *)offset; 400 } else { 401 /* uprobes don't support symbols */ 402 if (!is_kprobe) 403 return -EINVAL; 404 405 ret = traceprobe_split_symbol_offset(arg + 1, &offset); 406 if (ret) 407 break; 408 409 f->data = alloc_symbol_cache(arg + 1, offset); 410 if (f->data) 411 f->fn = t->fetch[FETCH_MTD_symbol]; 412 } 413 break; 414 415 case '+': /* deref memory */ 416 arg++; /* Skip '+', because kstrtol() rejects it. */ 417 case '-': 418 tmp = strchr(arg, '('); 419 if (!tmp) 420 break; 421 422 *tmp = '\0'; 423 ret = kstrtol(arg, 0, &offset); 424 425 if (ret) 426 break; 427 428 arg = tmp + 1; 429 tmp = strrchr(arg, ')'); 430 431 if (tmp) { 432 struct deref_fetch_param *dprm; 433 const struct fetch_type *t2; 434 435 t2 = find_fetch_type(NULL, ftbl); 436 *tmp = '\0'; 437 dprm = kzalloc(sizeof(struct deref_fetch_param), GFP_KERNEL); 438 439 if (!dprm) 440 return -ENOMEM; 441 442 dprm->offset = offset; 443 dprm->fetch = t->fetch[FETCH_MTD_memory]; 444 dprm->fetch_size = get_fetch_size_function(t, 445 dprm->fetch, ftbl); 446 ret = parse_probe_arg(arg, t2, &dprm->orig, is_return, 447 is_kprobe, ftbl); 448 if (ret) 449 kfree(dprm); 450 else { 451 f->fn = t->fetch[FETCH_MTD_deref]; 452 f->data = (void *)dprm; 453 } 454 } 455 break; 456 } 457 if (!ret && !f->fn) { /* Parsed, but do not find fetch method */ 458 pr_info("%s type has no corresponding fetch method.\n", t->name); 459 ret = -EINVAL; 460 } 461 462 return ret; 463 } 464 465 #define BYTES_TO_BITS(nb) ((BITS_PER_LONG * (nb)) / sizeof(long)) 466 467 /* Bitfield type needs to be parsed into a fetch function */ 468 static int __parse_bitfield_probe_arg(const char *bf, 469 const struct fetch_type *t, 470 struct fetch_param *f) 471 { 472 struct bitfield_fetch_param *bprm; 473 unsigned long bw, bo; 474 char *tail; 475 476 if (*bf != 'b') 477 return 0; 478 479 bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); 480 if (!bprm) 481 return -ENOMEM; 482 483 bprm->orig = *f; 484 f->fn = t->fetch[FETCH_MTD_bitfield]; 485 f->data = (void *)bprm; 486 bw = simple_strtoul(bf + 1, &tail, 0); /* Use simple one */ 487 488 if (bw == 0 || *tail != '@') 489 return -EINVAL; 490 491 bf = tail + 1; 492 bo = simple_strtoul(bf, &tail, 0); 493 494 if (tail == bf || *tail != '/') 495 return -EINVAL; 496 497 bprm->hi_shift = BYTES_TO_BITS(t->size) - (bw + bo); 498 bprm->low_shift = bprm->hi_shift + bo; 499 500 return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0; 501 } 502 503 /* String length checking wrapper */ 504 int traceprobe_parse_probe_arg(char *arg, ssize_t *size, 505 struct probe_arg *parg, bool is_return, bool is_kprobe, 506 const struct fetch_type *ftbl) 507 { 508 const char *t; 509 int ret; 510 511 if (strlen(arg) > MAX_ARGSTR_LEN) { 512 pr_info("Argument is too long.: %s\n", arg); 513 return -ENOSPC; 514 } 515 parg->comm = kstrdup(arg, GFP_KERNEL); 516 if (!parg->comm) { 517 pr_info("Failed to allocate memory for command '%s'.\n", arg); 518 return -ENOMEM; 519 } 520 t = strchr(parg->comm, ':'); 521 if (t) { 522 arg[t - parg->comm] = '\0'; 523 t++; 524 } 525 parg->type = find_fetch_type(t, ftbl); 526 if (!parg->type) { 527 pr_info("Unsupported type: %s\n", t); 528 return -EINVAL; 529 } 530 parg->offset = *size; 531 *size += parg->type->size; 532 ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return, 533 is_kprobe, ftbl); 534 535 if (ret >= 0 && t != NULL) 536 ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch); 537 538 if (ret >= 0) { 539 parg->fetch_size.fn = get_fetch_size_function(parg->type, 540 parg->fetch.fn, 541 ftbl); 542 parg->fetch_size.data = parg->fetch.data; 543 } 544 545 return ret; 546 } 547 548 /* Return 1 if name is reserved or already used by another argument */ 549 int traceprobe_conflict_field_name(const char *name, 550 struct probe_arg *args, int narg) 551 { 552 int i; 553 554 for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++) 555 if (strcmp(reserved_field_names[i], name) == 0) 556 return 1; 557 558 for (i = 0; i < narg; i++) 559 if (strcmp(args[i].name, name) == 0) 560 return 1; 561 562 return 0; 563 } 564 565 void traceprobe_update_arg(struct probe_arg *arg) 566 { 567 if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn)) 568 update_bitfield_fetch_param(arg->fetch.data); 569 else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn)) 570 update_deref_fetch_param(arg->fetch.data); 571 else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn)) 572 update_symbol_cache(arg->fetch.data); 573 } 574 575 void traceprobe_free_probe_arg(struct probe_arg *arg) 576 { 577 if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn)) 578 free_bitfield_fetch_param(arg->fetch.data); 579 else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn)) 580 free_deref_fetch_param(arg->fetch.data); 581 else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn)) 582 free_symbol_cache(arg->fetch.data); 583 584 kfree(arg->name); 585 kfree(arg->comm); 586 } 587 588 int traceprobe_command(const char *buf, int (*createfn)(int, char **)) 589 { 590 char **argv; 591 int argc, ret; 592 593 argc = 0; 594 ret = 0; 595 argv = argv_split(GFP_KERNEL, buf, &argc); 596 if (!argv) 597 return -ENOMEM; 598 599 if (argc) 600 ret = createfn(argc, argv); 601 602 argv_free(argv); 603 604 return ret; 605 } 606 607 #define WRITE_BUFSIZE 4096 608 609 ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer, 610 size_t count, loff_t *ppos, 611 int (*createfn)(int, char **)) 612 { 613 char *kbuf, *tmp; 614 int ret = 0; 615 size_t done = 0; 616 size_t size; 617 618 kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL); 619 if (!kbuf) 620 return -ENOMEM; 621 622 while (done < count) { 623 size = count - done; 624 625 if (size >= WRITE_BUFSIZE) 626 size = WRITE_BUFSIZE - 1; 627 628 if (copy_from_user(kbuf, buffer + done, size)) { 629 ret = -EFAULT; 630 goto out; 631 } 632 kbuf[size] = '\0'; 633 tmp = strchr(kbuf, '\n'); 634 635 if (tmp) { 636 *tmp = '\0'; 637 size = tmp - kbuf + 1; 638 } else if (done + size < count) { 639 pr_warn("Line length is too long: Should be less than %d\n", 640 WRITE_BUFSIZE); 641 ret = -EINVAL; 642 goto out; 643 } 644 done += size; 645 /* Remove comments */ 646 tmp = strchr(kbuf, '#'); 647 648 if (tmp) 649 *tmp = '\0'; 650 651 ret = traceprobe_command(kbuf, createfn); 652 if (ret) 653 goto out; 654 } 655 ret = done; 656 657 out: 658 kfree(kbuf); 659 660 return ret; 661 } 662 663 static int __set_print_fmt(struct trace_probe *tp, char *buf, int len, 664 bool is_return) 665 { 666 int i; 667 int pos = 0; 668 669 const char *fmt, *arg; 670 671 if (!is_return) { 672 fmt = "(%lx)"; 673 arg = "REC->" FIELD_STRING_IP; 674 } else { 675 fmt = "(%lx <- %lx)"; 676 arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP; 677 } 678 679 /* When len=0, we just calculate the needed length */ 680 #define LEN_OR_ZERO (len ? len - pos : 0) 681 682 pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt); 683 684 for (i = 0; i < tp->nr_args; i++) { 685 pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s", 686 tp->args[i].name, tp->args[i].type->fmt); 687 } 688 689 pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg); 690 691 for (i = 0; i < tp->nr_args; i++) { 692 if (strcmp(tp->args[i].type->name, "string") == 0) 693 pos += snprintf(buf + pos, LEN_OR_ZERO, 694 ", __get_str(%s)", 695 tp->args[i].name); 696 else 697 pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s", 698 tp->args[i].name); 699 } 700 701 #undef LEN_OR_ZERO 702 703 /* return the length of print_fmt */ 704 return pos; 705 } 706 707 int set_print_fmt(struct trace_probe *tp, bool is_return) 708 { 709 int len; 710 char *print_fmt; 711 712 /* First: called with 0 length to calculate the needed length */ 713 len = __set_print_fmt(tp, NULL, 0, is_return); 714 print_fmt = kmalloc(len + 1, GFP_KERNEL); 715 if (!print_fmt) 716 return -ENOMEM; 717 718 /* Second: actually write the @print_fmt */ 719 __set_print_fmt(tp, print_fmt, len + 1, is_return); 720 tp->call.print_fmt = print_fmt; 721 722 return 0; 723 } 724