kernel/trace/trace_probe.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Common code for probe-based Dynamic events.
   4  *
   5  * This code was copied from kernel/trace/trace_kprobe.c written by
   6  * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
   7  *
   8  * Updates to make this generic:
   9  * Copyright (C) IBM Corporation, 2010-2011
  10  * Author:     Srikar Dronamraju
  11  */
  12 #define pr_fmt(fmt)     "trace_probe: " fmt
  13
  14 #include "trace_probe.h"
  15
  16 const char *reserved_field_names[] = {
  17         "common_type",
  18         "common_flags",
  19         "common_preempt_count",
  20         "common_pid",
  21         "common_tgid",
  22         FIELD_STRING_IP,
  23         FIELD_STRING_RETIP,
  24         FIELD_STRING_FUNC,
  25 };
  26
  27 /* Printing  in basic type function template */
  28 #define DEFINE_BASIC_PRINT_TYPE_FUNC(tname, type, fmt)                  \
  29 int PRINT_TYPE_FUNC_NAME(tname)(struct trace_seq *s, const char *name,  \
  30                                 void *data, void *ent)                  \
  31 {                                                                       \
  32         trace_seq_printf(s, " %s=" fmt, name, *(type *)data);           \
  33         return !trace_seq_has_overflowed(s);                            \
  34 }                                                                       \
  35 const char PRINT_TYPE_FMT_NAME(tname)[] = fmt;                          \
  36 NOKPROBE_SYMBOL(PRINT_TYPE_FUNC_NAME(tname));
  37
  38 DEFINE_BASIC_PRINT_TYPE_FUNC(u8,  u8,  "%u")
  39 DEFINE_BASIC_PRINT_TYPE_FUNC(u16, u16, "%u")
  40 DEFINE_BASIC_PRINT_TYPE_FUNC(u32, u32, "%u")
  41 DEFINE_BASIC_PRINT_TYPE_FUNC(u64, u64, "%Lu")
  42 DEFINE_BASIC_PRINT_TYPE_FUNC(s8,  s8,  "%d")
  43 DEFINE_BASIC_PRINT_TYPE_FUNC(s16, s16, "%d")
  44 DEFINE_BASIC_PRINT_TYPE_FUNC(s32, s32, "%d")
  45 DEFINE_BASIC_PRINT_TYPE_FUNC(s64, s64, "%Ld")
  46 DEFINE_BASIC_PRINT_TYPE_FUNC(x8,  u8,  "0x%x")
  47 DEFINE_BASIC_PRINT_TYPE_FUNC(x16, u16, "0x%x")
  48 DEFINE_BASIC_PRINT_TYPE_FUNC(x32, u32, "0x%x")
  49 DEFINE_BASIC_PRINT_TYPE_FUNC(x64, u64, "0x%Lx")
  50
  51 /* Print type function for string type */
  52 int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s, const char *name,
  53                                  void *data, void *ent)
  54 {
  55         int len = *(u32 *)data >> 16;
  56
  57         if (!len)
  58                 trace_seq_printf(s, " %s=(fault)", name);
  59         else
  60                 trace_seq_printf(s, " %s=\"%s\"", name,
  61                                  (const char *)get_loc_data(data, ent));
  62         return !trace_seq_has_overflowed(s);
  63 }
  64 NOKPROBE_SYMBOL(PRINT_TYPE_FUNC_NAME(string));
  65
  66 const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
  67
  68 #define CHECK_FETCH_FUNCS(method, fn)                   \
  69         (((FETCH_FUNC_NAME(method, u8) == fn) ||        \
  70           (FETCH_FUNC_NAME(method, u16) == fn) ||       \
  71           (FETCH_FUNC_NAME(method, u32) == fn) ||       \
  72           (FETCH_FUNC_NAME(method, u64) == fn) ||       \
  73           (FETCH_FUNC_NAME(method, string) == fn) ||    \
  74           (FETCH_FUNC_NAME(method, string_size) == fn)) \
  75          && (fn != NULL))
  76
  77 /* Data fetch function templates */
  78 #define DEFINE_FETCH_reg(type)                                          \
  79 void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs, void *offset, void *dest) \
  80 {                                                                       \
  81         *(type *)dest = (type)regs_get_register(regs,                   \
  82                                 (unsigned int)((unsigned long)offset)); \
  83 }                                                                       \
  84 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(reg, type));
  85 DEFINE_BASIC_FETCH_FUNCS(reg)
  86 /* No string on the register */
  87 #define fetch_reg_string        NULL
  88 #define fetch_reg_string_size   NULL
  89
  90 #define DEFINE_FETCH_retval(type)                                       \
  91 void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,                \
  92                                    void *dummy, void *dest)             \
  93 {                                                                       \
  94         *(type *)dest = (type)regs_return_value(regs);                  \
  95 }                                                                       \
  96 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(retval, type));
  97 DEFINE_BASIC_FETCH_FUNCS(retval)
  98 /* No string on the retval */
  99 #define fetch_retval_string             NULL
 100 #define fetch_retval_string_size        NULL
 101
 102 /* Dereference memory access function */
 103 struct deref_fetch_param {
 104         struct fetch_param      orig;
 105         long                    offset;
 106         fetch_func_t            fetch;
 107         fetch_func_t            fetch_size;
 108 };
 109
 110 #define DEFINE_FETCH_deref(type)                                        \
 111 void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs,                 \
 112                                   void *data, void *dest)               \
 113 {                                                                       \
 114         struct deref_fetch_param *dprm = data;                          \
 115         unsigned long addr;                                             \
 116         call_fetch(&dprm->orig, regs, &addr);                           \
 117         if (addr) {                                                     \
 118                 addr += dprm->offset;                                   \
 119                 dprm->fetch(regs, (void *)addr, dest);                  \
 120         } else                                                          \
 121                 *(type *)dest = 0;                                      \
 122 }                                                                       \
 123 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, type));
 124 DEFINE_BASIC_FETCH_FUNCS(deref)
 125 DEFINE_FETCH_deref(string)
 126
 127 void FETCH_FUNC_NAME(deref, string_size)(struct pt_regs *regs,
 128                                          void *data, void *dest)
 129 {
 130         struct deref_fetch_param *dprm = data;
 131         unsigned long addr;
 132
 133         call_fetch(&dprm->orig, regs, &addr);
 134         if (addr && dprm->fetch_size) {
 135                 addr += dprm->offset;
 136                 dprm->fetch_size(regs, (void *)addr, dest);
 137         } else
 138                 *(string_size *)dest = 0;
 139 }
 140 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, string_size));
 141
 142 static void update_deref_fetch_param(struct deref_fetch_param *data)
 143 {
 144         if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 145                 update_deref_fetch_param(data->orig.data);
 146         else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 147                 update_symbol_cache(data->orig.data);
 148 }
 149 NOKPROBE_SYMBOL(update_deref_fetch_param);
 150
 151 static void free_deref_fetch_param(struct deref_fetch_param *data)
 152 {
 153         if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 154                 free_deref_fetch_param(data->orig.data);
 155         else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 156                 free_symbol_cache(data->orig.data);
 157         kfree(data);
 158 }
 159 NOKPROBE_SYMBOL(free_deref_fetch_param);
 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 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 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(bitfield, type));
 182 DEFINE_BASIC_FETCH_FUNCS(bitfield)
 183 #define fetch_bitfield_string           NULL
 184 #define fetch_bitfield_string_size      NULL
 185
 186 static 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 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 void FETCH_FUNC_NAME(comm, string)(struct pt_regs *regs,
 215                                           void *data, void *dest)
 216 {
 217         int maxlen = get_rloc_len(*(u32 *)dest);
 218         u8 *dst = get_rloc_data(dest);
 219         long ret;
 220
 221         if (!maxlen)
 222                 return;
 223
 224         ret = strlcpy(dst, current->comm, maxlen);
 225         *(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
 226 }
 227 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(comm, string));
 228
 229 void FETCH_FUNC_NAME(comm, string_size)(struct pt_regs *regs,
 230                                                void *data, void *dest)
 231 {
 232         *(u32 *)dest = strlen(current->comm) + 1;
 233 }
 234 NOKPROBE_SYMBOL(FETCH_FUNC_NAME(comm, string_size));
 235
 236 static const struct fetch_type *find_fetch_type(const char *type,
 237                                                 const struct fetch_type *ftbl)
 238 {
 239         int i;
 240
 241         if (!type)
 242                 type = DEFAULT_FETCH_TYPE_STR;
 243
 244         /* Special case: bitfield */
 245         if (*type == 'b') {
 246                 unsigned long bs;
 247
 248                 type = strchr(type, '/');
 249                 if (!type)
 250                         goto fail;
 251
 252                 type++;
 253                 if (kstrtoul(type, 0, &bs))
 254                         goto fail;
 255
 256                 switch (bs) {
 257                 case 8:
 258                         return find_fetch_type("u8", ftbl);
 259                 case 16:
 260                         return find_fetch_type("u16", ftbl);
 261                 case 32:
 262                         return find_fetch_type("u32", ftbl);
 263                 case 64:
 264                         return find_fetch_type("u64", ftbl);
 265                 default:
 266                         goto fail;
 267                 }
 268         }
 269
 270         for (i = 0; ftbl[i].name; i++) {
 271                 if (strcmp(type, ftbl[i].name) == 0)
 272                         return &ftbl[i];
 273         }
 274
 275 fail:
 276         return NULL;
 277 }
 278
 279 /* Special function : only accept unsigned long */
 280 static void fetch_kernel_stack_address(struct pt_regs *regs, void *dummy, void *dest)
 281 {
 282         *(unsigned long *)dest = kernel_stack_pointer(regs);
 283 }
 284 NOKPROBE_SYMBOL(fetch_kernel_stack_address);
 285
 286 static void fetch_user_stack_address(struct pt_regs *regs, void *dummy, void *dest)
 287 {
 288         *(unsigned long *)dest = user_stack_pointer(regs);
 289 }
 290 NOKPROBE_SYMBOL(fetch_user_stack_address);
 291
 292 static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
 293                                             fetch_func_t orig_fn,
 294                                             const struct fetch_type *ftbl)
 295 {
 296         int i;
 297
 298         if (type != &ftbl[FETCH_TYPE_STRING])
 299                 return NULL;    /* Only string type needs size function */
 300
 301         for (i = 0; i < FETCH_MTD_END; i++)
 302                 if (type->fetch[i] == orig_fn)
 303                         return ftbl[FETCH_TYPE_STRSIZE].fetch[i];
 304
 305         WARN_ON(1);     /* This should not happen */
 306
 307         return NULL;
 308 }
 309
 310 /* Split symbol and offset. */
 311 int traceprobe_split_symbol_offset(char *symbol, long *offset)
 312 {
 313         char *tmp;
 314         int ret;
 315
 316         if (!offset)
 317                 return -EINVAL;
 318
 319         tmp = strpbrk(symbol, "+-");
 320         if (tmp) {
 321                 ret = kstrtol(tmp, 0, offset);
 322                 if (ret)
 323                         return ret;
 324                 *tmp = '\0';
 325         } else
 326                 *offset = 0;
 327
 328         return 0;
 329 }
 330
 331 #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
 332
 333 static int parse_probe_vars(char *arg, const struct fetch_type *t,
 334                             struct fetch_param *f, bool is_return,
 335                             bool is_kprobe)
 336 {
 337         int ret = 0;
 338         unsigned long param;
 339
 340         if (strcmp(arg, "retval") == 0) {
 341                 if (is_return)
 342                         f->fn = t->fetch[FETCH_MTD_retval];
 343                 else
 344                         ret = -EINVAL;
 345         } else if (strncmp(arg, "stack", 5) == 0) {
 346                 if (arg[5] == '\0') {
 347                         if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR))
 348                                 return -EINVAL;
 349
 350                         if (is_kprobe)
 351                                 f->fn = fetch_kernel_stack_address;
 352                         else
 353                                 f->fn = fetch_user_stack_address;
 354                 } else if (isdigit(arg[5])) {
 355                         ret = kstrtoul(arg + 5, 10, &param);
 356                         if (ret || (is_kprobe && param > PARAM_MAX_STACK))
 357                                 ret = -EINVAL;
 358                         else {
 359                                 f->fn = t->fetch[FETCH_MTD_stack];
 360                                 f->data = (void *)param;
 361                         }
 362                 } else
 363                         ret = -EINVAL;
 364         } else if (strcmp(arg, "comm") == 0) {
 365                 if (strcmp(t->name, "string") != 0 &&
 366                     strcmp(t->name, "string_size") != 0)
 367                         return -EINVAL;
 368                 f->fn = t->fetch[FETCH_MTD_comm];
 369         } else
 370                 ret = -EINVAL;
 371
 372         return ret;
 373 }
 374
 375 /* Recursive argument parser */
 376 static int parse_probe_arg(char *arg, const struct fetch_type *t,
 377                      struct fetch_param *f, bool is_return, bool is_kprobe,
 378                      const struct fetch_type *ftbl)
 379 {
 380         unsigned long param;
 381         long offset;
 382         char *tmp;
 383         int ret = 0;
 384
 385         switch (arg[0]) {
 386         case '$':
 387                 ret = parse_probe_vars(arg + 1, t, f, is_return, is_kprobe);
 388                 break;
 389
 390         case '%':       /* named register */
 391                 ret = regs_query_register_offset(arg + 1);
 392                 if (ret >= 0) {
 393                         f->fn = t->fetch[FETCH_MTD_reg];
 394                         f->data = (void *)(unsigned long)ret;
 395                         ret = 0;
 396                 }
 397                 break;
 398
 399         case '@':       /* memory, file-offset or symbol */
 400                 if (isdigit(arg[1])) {
 401                         ret = kstrtoul(arg + 1, 0, &param);
 402                         if (ret)
 403                                 break;
 404
 405                         f->fn = t->fetch[FETCH_MTD_memory];
 406                         f->data = (void *)param;
 407                 } else if (arg[1] == '+') {
 408                         /* kprobes don't support file offsets */
 409                         if (is_kprobe)
 410                                 return -EINVAL;
 411
 412                         ret = kstrtol(arg + 2, 0, &offset);
 413                         if (ret)
 414                                 break;
 415
 416                         f->fn = t->fetch[FETCH_MTD_file_offset];
 417                         f->data = (void *)offset;
 418                 } else {
 419                         /* uprobes don't support symbols */
 420                         if (!is_kprobe)
 421                                 return -EINVAL;
 422
 423                         ret = traceprobe_split_symbol_offset(arg + 1, &offset);
 424                         if (ret)
 425                                 break;
 426
 427                         f->data = alloc_symbol_cache(arg + 1, offset);
 428                         if (f->data)
 429                                 f->fn = t->fetch[FETCH_MTD_symbol];
 430                 }
 431                 break;
 432
 433         case '+':       /* deref memory */
 434                 arg++;  /* Skip '+', because kstrtol() rejects it. */
 435         case '-':
 436                 tmp = strchr(arg, '(');
 437                 if (!tmp)
 438                         break;
 439
 440                 *tmp = '\0';
 441                 ret = kstrtol(arg, 0, &offset);
 442
 443                 if (ret)
 444                         break;
 445
 446                 arg = tmp + 1;
 447                 tmp = strrchr(arg, ')');
 448
 449                 if (tmp) {
 450                         struct deref_fetch_param        *dprm;
 451                         const struct fetch_type         *t2;
 452
 453                         t2 = find_fetch_type(NULL, ftbl);
 454                         *tmp = '\0';
 455                         dprm = kzalloc(sizeof(struct deref_fetch_param), GFP_KERNEL);
 456
 457                         if (!dprm)
 458                                 return -ENOMEM;
 459
 460                         dprm->offset = offset;
 461                         dprm->fetch = t->fetch[FETCH_MTD_memory];
 462                         dprm->fetch_size = get_fetch_size_function(t,
 463                                                         dprm->fetch, ftbl);
 464                         ret = parse_probe_arg(arg, t2, &dprm->orig, is_return,
 465                                                         is_kprobe, ftbl);
 466                         if (ret)
 467                                 kfree(dprm);
 468                         else {
 469                                 f->fn = t->fetch[FETCH_MTD_deref];
 470                                 f->data = (void *)dprm;
 471                         }
 472                 }
 473                 break;
 474         }
 475         if (!ret && !f->fn) {   /* Parsed, but do not find fetch method */
 476                 pr_info("%s type has no corresponding fetch method.\n", t->name);
 477                 ret = -EINVAL;
 478         }
 479
 480         return ret;
 481 }
 482
 483 #define BYTES_TO_BITS(nb)       ((BITS_PER_LONG * (nb)) / sizeof(long))
 484
 485 /* Bitfield type needs to be parsed into a fetch function */
 486 static int __parse_bitfield_probe_arg(const char *bf,
 487                                       const struct fetch_type *t,
 488                                       struct fetch_param *f)
 489 {
 490         struct bitfield_fetch_param *bprm;
 491         unsigned long bw, bo;
 492         char *tail;
 493
 494         if (*bf != 'b')
 495                 return 0;
 496
 497         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
 498         if (!bprm)
 499                 return -ENOMEM;
 500
 501         bprm->orig = *f;
 502         f->fn = t->fetch[FETCH_MTD_bitfield];
 503         f->data = (void *)bprm;
 504         bw = simple_strtoul(bf + 1, &tail, 0);  /* Use simple one */
 505
 506         if (bw == 0 || *tail != '@')
 507                 return -EINVAL;
 508
 509         bf = tail + 1;
 510         bo = simple_strtoul(bf, &tail, 0);
 511
 512         if (tail == bf || *tail != '/')
 513                 return -EINVAL;
 514
 515         bprm->hi_shift = BYTES_TO_BITS(t->size) - (bw + bo);
 516         bprm->low_shift = bprm->hi_shift + bo;
 517
 518         return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
 519 }
 520
 521 /* String length checking wrapper */
 522 int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
 523                 struct probe_arg *parg, bool is_return, bool is_kprobe,
 524                 const struct fetch_type *ftbl)
 525 {
 526         const char *t;
 527         int ret;
 528
 529         if (strlen(arg) > MAX_ARGSTR_LEN) {
 530                 pr_info("Argument is too long.: %s\n",  arg);
 531                 return -ENOSPC;
 532         }
 533         parg->comm = kstrdup(arg, GFP_KERNEL);
 534         if (!parg->comm) {
 535                 pr_info("Failed to allocate memory for command '%s'.\n", arg);
 536                 return -ENOMEM;
 537         }
 538         t = strchr(parg->comm, ':');
 539         if (t) {
 540                 arg[t - parg->comm] = '\0';
 541                 t++;
 542         }
 543         /*
 544          * The default type of $comm should be "string", and it can't be
 545          * dereferenced.
 546          */
 547         if (!t && strcmp(arg, "$comm") == 0)
 548                 t = "string";
 549         parg->type = find_fetch_type(t, ftbl);
 550         if (!parg->type) {
 551                 pr_info("Unsupported type: %s\n", t);
 552                 return -EINVAL;
 553         }
 554         parg->offset = *size;
 555         *size += parg->type->size;
 556         ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return,
 557                               is_kprobe, ftbl);
 558
 559         if (ret >= 0 && t != NULL)
 560                 ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch);
 561
 562         if (ret >= 0) {
 563                 parg->fetch_size.fn = get_fetch_size_function(parg->type,
 564                                                               parg->fetch.fn,
 565                                                               ftbl);
 566                 parg->fetch_size.data = parg->fetch.data;
 567         }
 568
 569         return ret;
 570 }
 571
 572 /* Return 1 if name is reserved or already used by another argument */
 573 int traceprobe_conflict_field_name(const char *name,
 574                                struct probe_arg *args, int narg)
 575 {
 576         int i;
 577
 578         for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
 579                 if (strcmp(reserved_field_names[i], name) == 0)
 580                         return 1;
 581
 582         for (i = 0; i < narg; i++)
 583                 if (strcmp(args[i].name, name) == 0)
 584                         return 1;
 585
 586         return 0;
 587 }
 588
 589 void traceprobe_update_arg(struct probe_arg *arg)
 590 {
 591         if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
 592                 update_bitfield_fetch_param(arg->fetch.data);
 593         else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
 594                 update_deref_fetch_param(arg->fetch.data);
 595         else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
 596                 update_symbol_cache(arg->fetch.data);
 597 }
 598
 599 void traceprobe_free_probe_arg(struct probe_arg *arg)
 600 {
 601         if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
 602                 free_bitfield_fetch_param(arg->fetch.data);
 603         else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
 604                 free_deref_fetch_param(arg->fetch.data);
 605         else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
 606                 free_symbol_cache(arg->fetch.data);
 607
 608         kfree(arg->name);
 609         kfree(arg->comm);
 610 }
 611
 612 static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 613                            bool is_return)
 614 {
 615         int i;
 616         int pos = 0;
 617
 618         const char *fmt, *arg;
 619
 620         if (!is_return) {
 621                 fmt = "(%lx)";
 622                 arg = "REC->" FIELD_STRING_IP;
 623         } else {
 624                 fmt = "(%lx <- %lx)";
 625                 arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
 626         }
 627
 628         /* When len=0, we just calculate the needed length */
 629 #define LEN_OR_ZERO (len ? len - pos : 0)
 630
 631         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);
 632
 633         for (i = 0; i < tp->nr_args; i++) {
 634                 pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
 635                                 tp->args[i].name, tp->args[i].type->fmt);
 636         }
 637
 638         pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
 639
 640         for (i = 0; i < tp->nr_args; i++) {
 641                 if (strcmp(tp->args[i].type->name, "string") == 0)
 642                         pos += snprintf(buf + pos, LEN_OR_ZERO,
 643                                         ", __get_str(%s)",
 644                                         tp->args[i].name);
 645                 else
 646                         pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
 647                                         tp->args[i].name);
 648         }
 649
 650 #undef LEN_OR_ZERO
 651
 652         /* return the length of print_fmt */
 653         return pos;
 654 }
 655
 656 int set_print_fmt(struct trace_probe *tp, bool is_return)
 657 {
 658         int len;
 659         char *print_fmt;
 660
 661         /* First: called with 0 length to calculate the needed length */
 662         len = __set_print_fmt(tp, NULL, 0, is_return);
 663         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 664         if (!print_fmt)
 665                 return -ENOMEM;
 666
 667         /* Second: actually write the @print_fmt */
 668         __set_print_fmt(tp, print_fmt, len + 1, is_return);
 669         tp->call.print_fmt = print_fmt;
 670
 671         return 0;
 672 }