libust/serialize.c

   1 /*
   2  * LTTng serializing code.
   3  *
   4  * Copyright Mathieu Desnoyers, March 2007.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  19  *
  20  *
  21  * See this discussion about weirdness about passing va_list and then va_list to
  22  * functions. (related to array argument passing). va_list seems to be
  23  * implemented as an array on x86_64, but not on i386... This is why we pass a
  24  * va_list * to ltt_vtrace.
  25  */
  26
  27 #define _GNU_SOURCE
  28 #define _LGPL_SOURCE
  29 #include <unistd.h>
  30 #include <sys/syscall.h>
  31 #include <stdarg.h>
  32 #include <string.h>
  33 #include <stdint.h>
  34 #include <stdio.h>
  35
  36 #include <urcu-bp.h>
  37 #include <urcu/rculist.h>
  38
  39 #include <ust/core.h>
  40 #include <ust/clock.h>
  41 #include "buffers.h"
  42 #include "tracer.h"
  43 #include "usterr_signal_safe.h"
  44 #include "ust_snprintf.h"
  45
  46 /*
  47  * Because UST core defines a non-const PAGE_SIZE, define PAGE_SIZE_STATIC here.
  48  * It is just an approximation for the tracer stack.
  49  */
  50 #define PAGE_SIZE_STATIC        4096
  51
  52 enum ltt_type {
  53         LTT_TYPE_SIGNED_INT,
  54         LTT_TYPE_UNSIGNED_INT,
  55         LTT_TYPE_STRING,
  56         LTT_TYPE_NONE,
  57 };
  58
  59 /*
  60  * Special stack for the tracer. Keeps serialization offsets for each field.
  61  * Per-thread. Deals with reentrancy from signals by simply ensuring that
  62  * interrupting signals put the stack back to its original position.
  63  */
  64 #define TRACER_STACK_LEN        (PAGE_SIZE_STATIC / sizeof(unsigned long))
  65 static unsigned long __thread tracer_stack[TRACER_STACK_LEN];
  66
  67 static unsigned int __thread tracer_stack_pos;
  68
  69 #define LTT_ATTRIBUTE_NETWORK_BYTE_ORDER (1<<1)
  70
  71 /*
  72  * Inspired from vsnprintf
  73  *
  74  * The serialization format string supports the basic printf format strings.
  75  * In addition, it defines new formats that can be used to serialize more
  76  * complex/non portable data structures.
  77  *
  78  * Typical use:
  79  *
  80  * field_name %ctype
  81  * field_name #tracetype %ctype
  82  * field_name #tracetype %ctype1 %ctype2 ...
  83  *
  84  * A conversion is performed between format string types supported by GCC and
  85  * the trace type requested. GCC type is used to perform type checking on format
  86  * strings. Trace type is used to specify the exact binary representation
  87  * in the trace. A mapping is done between one or more GCC types to one trace
  88  * type. Sign extension, if required by the conversion, is performed following
  89  * the trace type.
  90  *
  91  * If a gcc format is not declared with a trace format, the gcc format is
  92  * also used as binary representation in the trace.
  93  *
  94  * Strings are supported with %s.
  95  * A single tracetype (sequence) can take multiple c types as parameter.
  96  *
  97  * c types:
  98  *
  99  * see printf(3).
 100  *
 101  * Note: to write a uint32_t in a trace, the following expression is recommended
 102  * si it can be portable:
 103  *
 104  * ("#4u%lu", (unsigned long)var)
 105  *
 106  * trace types:
 107  *
 108  * Serialization specific formats :
 109  *
 110  * Fixed size integers
 111  * #1u     writes uint8_t
 112  * #2u     writes uint16_t
 113  * #4u     writes uint32_t
 114  * #8u     writes uint64_t
 115  * #1d     writes int8_t
 116  * #2d     writes int16_t
 117  * #4d     writes int32_t
 118  * #8d     writes int64_t
 119  * i.e.:
 120  * #1u%lu #2u%lu #4d%lu #8d%lu #llu%hu #d%lu
 121  *
 122  * * Attributes:
 123  *
 124  * n:  (for network byte order)
 125  * #ntracetype%ctype
 126  *            is written in the trace in network byte order.
 127  *
 128  * i.e.: #bn4u%lu, #n%lu, #b%u
 129  *
 130  * TODO (eventually)
 131  * Variable length sequence
 132  * #a #tracetype1 #tracetype2 %array_ptr %elem_size %num_elems
 133  *            In the trace:
 134  *            #a specifies that this is a sequence
 135  *            #tracetype1 is the type of elements in the sequence
 136  *            #tracetype2 is the type of the element count
 137  *            GCC input:
 138  *            array_ptr is a pointer to an array that contains members of size
 139  *            elem_size.
 140  *            num_elems is the number of elements in the array.
 141  * i.e.: #a #lu #lu %p %lu %u
 142  *
 143  * Callback
 144  * #k         callback (taken from the probe data)
 145  *            The following % arguments are exepected by the callback
 146  *
 147  * i.e.: #a #lu #lu #k %p
 148  *
 149  * Note: No conversion is done from floats to integers, nor from integers to
 150  * floats between c types and trace types. float conversion from double to float
 151  * or from float to double is also not supported.
 152  *
 153  * REMOVE
 154  * %*b     expects sizeof(data), data
 155  *         where sizeof(data) is 1, 2, 4 or 8
 156  *
 157  * Fixed length struct, union or array.
 158  * FIXME: unable to extract those sizes statically.
 159  * %*r     expects sizeof(*ptr), ptr
 160  * %*.*r   expects sizeof(*ptr), __alignof__(*ptr), ptr
 161  * struct and unions removed.
 162  * Fixed length array:
 163  * [%p]#a[len #tracetype]
 164  * i.e.: [%p]#a[12 #lu]
 165  *
 166  * Variable length sequence
 167  * %*.*:*v expects sizeof(*ptr), __alignof__(*ptr), elem_num, ptr
 168  *         where elem_num is the number of elements in the sequence
 169  */
 170 static inline const char *parse_trace_type(const char *fmt,
 171                 char *trace_size, enum ltt_type *trace_type,
 172                 unsigned long *attributes)
 173 {
 174         int qualifier;          /* 'h', 'l', or 'L' for integer fields */
 175                                 /* 'z' support added 23/7/1999 S.H.    */
 176                                 /* 'z' changed to 'Z' --davidm 1/25/99 */
 177                                 /* 't' added for ptrdiff_t */
 178
 179         /* parse attributes. */
 180 repeat:
 181         switch (*fmt) {
 182         case 'n':
 183                 *attributes |= LTT_ATTRIBUTE_NETWORK_BYTE_ORDER;
 184                 ++fmt;
 185                 goto repeat;
 186         }
 187
 188         /* get the conversion qualifier */
 189         qualifier = -1;
 190         if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' ||
 191             *fmt == 'Z' || *fmt == 'z' || *fmt == 't' ||
 192             *fmt == 'S' || *fmt == '1' || *fmt == '2' ||
 193             *fmt == '4' || *fmt == 8) {
 194                 qualifier = *fmt;
 195                 ++fmt;
 196                 if (qualifier == 'l' && *fmt == 'l') {
 197                         qualifier = 'L';
 198                         ++fmt;
 199                 }
 200         }
 201
 202         switch (*fmt) {
 203         case 'c':
 204                 *trace_type = LTT_TYPE_UNSIGNED_INT;
 205                 *trace_size = sizeof(unsigned char);
 206                 goto parse_end;
 207         case 's':
 208                 *trace_type = LTT_TYPE_STRING;
 209                 goto parse_end;
 210         case 'p':
 211                 *trace_type = LTT_TYPE_UNSIGNED_INT;
 212                 *trace_size = sizeof(void *);
 213                 goto parse_end;
 214         case 'd':
 215         case 'i':
 216                 *trace_type = LTT_TYPE_SIGNED_INT;
 217                 break;
 218         case 'o':
 219         case 'u':
 220         case 'x':
 221         case 'X':
 222                 *trace_type = LTT_TYPE_UNSIGNED_INT;
 223                 break;
 224         default:
 225                 if (!*fmt)
 226                         --fmt;
 227                 goto parse_end;
 228         }
 229         switch (qualifier) {
 230         case 'L':
 231                 *trace_size = sizeof(long long);
 232                 break;
 233         case 'l':
 234                 *trace_size = sizeof(long);
 235                 break;
 236         case 'Z':
 237         case 'z':
 238                 *trace_size = sizeof(size_t);
 239                 break;
 240 //ust// case 't':
 241 //ust//         *trace_size = sizeof(ptrdiff_t);
 242 //ust//         break;
 243         case 'h':
 244                 *trace_size = sizeof(short);
 245                 break;
 246         case '1':
 247                 *trace_size = sizeof(uint8_t);
 248                 break;
 249         case '2':
 250                 *trace_size = sizeof(uint16_t);
 251                 break;
 252         case '4':
 253                 *trace_size = sizeof(uint32_t);
 254                 break;
 255         case '8':
 256                 *trace_size = sizeof(uint64_t);
 257                 break;
 258         default:
 259                 *trace_size = sizeof(int);
 260         }
 261
 262 parse_end:
 263         return fmt;
 264 }
 265
 266 /*
 267  * Restrictions:
 268  * Field width and precision are *not* supported.
 269  * %n not supported.
 270  */
 271 static inline
 272 const char *parse_c_type(const char *fmt, char *c_size, enum ltt_type *c_type,
 273                          char *outfmt)
 274 {
 275         int qualifier;          /* 'h', 'l', or 'L' for integer fields */
 276                                 /* 'z' support added 23/7/1999 S.H.    */
 277                                 /* 'z' changed to 'Z' --davidm 1/25/99 */
 278                                 /* 't' added for ptrdiff_t */
 279
 280         /* process flags : ignore standard print formats for now. */
 281 repeat:
 282         switch (*fmt) {
 283         case '-':
 284         case '+':
 285         case ' ':
 286         case '#':
 287         case '0':
 288                 ++fmt;
 289                 goto repeat;
 290         }
 291
 292         /* get the conversion qualifier */
 293         qualifier = -1;
 294         if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L' ||
 295             *fmt == 'Z' || *fmt == 'z' || *fmt == 't' ||
 296             *fmt == 'S') {
 297                 qualifier = *fmt;
 298                 ++fmt;
 299                 if (qualifier == 'l' && *fmt == 'l') {
 300                         qualifier = 'L';
 301                         ++fmt;
 302                 }
 303         }
 304
 305         if (outfmt) {
 306                 if (qualifier != -1)
 307                         *outfmt++ = (char)qualifier;
 308                 *outfmt++ = *fmt;
 309                 *outfmt = 0;
 310         }
 311
 312         switch (*fmt) {
 313         case 'c':
 314                 *c_type = LTT_TYPE_UNSIGNED_INT;
 315                 *c_size = sizeof(unsigned char);
 316                 goto parse_end;
 317         case 's':
 318                 *c_type = LTT_TYPE_STRING;
 319                 goto parse_end;
 320         case 'p':
 321                 *c_type = LTT_TYPE_UNSIGNED_INT;
 322                 *c_size = sizeof(void *);
 323                 goto parse_end;
 324         case 'd':
 325         case 'i':
 326                 *c_type = LTT_TYPE_SIGNED_INT;
 327                 break;
 328         case 'o':
 329         case 'u':
 330         case 'x':
 331         case 'X':
 332                 *c_type = LTT_TYPE_UNSIGNED_INT;
 333                 break;
 334         default:
 335                 if (!*fmt)
 336                         --fmt;
 337                 goto parse_end;
 338         }
 339         switch (qualifier) {
 340         case 'L':
 341                 *c_size = sizeof(long long);
 342                 break;
 343         case 'l':
 344                 *c_size = sizeof(long);
 345                 break;
 346         case 'Z':
 347         case 'z':
 348                 *c_size = sizeof(size_t);
 349                 break;
 350 //ust// case 't':
 351 //ust//         *c_size = sizeof(ptrdiff_t);
 352 //ust//         break;
 353         case 'h':
 354                 *c_size = sizeof(short);
 355                 break;
 356         default:
 357                 *c_size = sizeof(int);
 358         }
 359
 360 parse_end:
 361         return fmt;
 362 }
 363
 364 static inline size_t serialize_trace_data(struct ust_buffer *buf,
 365                 size_t buf_offset,
 366                 char trace_size, enum ltt_type trace_type,
 367                 char c_size, enum ltt_type c_type,
 368                 unsigned int *stack_pos_ctx,
 369                 int *largest_align,
 370                 va_list *args)
 371 {
 372         union {
 373                 unsigned long v_ulong;
 374                 uint64_t v_uint64;
 375                 struct {
 376                         const char *s;
 377                         size_t len;
 378                 } v_string;
 379         } tmp;
 380
 381         /*
 382          * Be careful about sign extension here.
 383          * Sign extension is done with the destination (trace) type.
 384          */
 385         switch (trace_type) {
 386         case LTT_TYPE_SIGNED_INT:
 387                 switch (c_size) {
 388                 case 1:
 389                         tmp.v_ulong = (long)(int8_t)va_arg(*args, int);
 390                         break;
 391                 case 2:
 392                         tmp.v_ulong = (long)(int16_t)va_arg(*args, int);
 393                         break;
 394                 case 4:
 395                         tmp.v_ulong = (long)(int32_t)va_arg(*args, int);
 396                         break;
 397                 case 8:
 398                         tmp.v_uint64 = va_arg(*args, int64_t);
 399                         break;
 400                 default:
 401                         BUG();
 402                 }
 403                 break;
 404         case LTT_TYPE_UNSIGNED_INT:
 405                 switch (c_size) {
 406                 case 1:
 407                         tmp.v_ulong = (unsigned long)(uint8_t)va_arg(*args, unsigned int);
 408                         break;
 409                 case 2:
 410                         tmp.v_ulong = (unsigned long)(uint16_t)va_arg(*args, unsigned int);
 411                         break;
 412                 case 4:
 413                         tmp.v_ulong = (unsigned long)(uint32_t)va_arg(*args, unsigned int);
 414                         break;
 415                 case 8:
 416                         tmp.v_uint64 = va_arg(*args, uint64_t);
 417                         break;
 418                 default:
 419                         BUG();
 420                 }
 421                 break;
 422         case LTT_TYPE_STRING:
 423                 tmp.v_string.s = va_arg(*args, const char *);
 424                 if ((unsigned long)tmp.v_string.s < PAGE_SIZE)
 425                         tmp.v_string.s = "<NULL>";
 426                 if (!buf) {
 427                         /*
 428                          * Reserve tracer stack entry.
 429                          */
 430                         tracer_stack_pos++;
 431                         assert(tracer_stack_pos <= TRACER_STACK_LEN);
 432                         cmm_barrier();
 433                         tracer_stack[*stack_pos_ctx] =
 434                                         strlen(tmp.v_string.s) + 1;
 435                 }
 436                 tmp.v_string.len = tracer_stack[(*stack_pos_ctx)++];
 437                 if (buf)
 438                         ust_buffers_strncpy(buf, buf_offset, tmp.v_string.s,
 439                                             tmp.v_string.len);
 440                 buf_offset += tmp.v_string.len;
 441                 goto copydone;
 442         default:
 443                 BUG();
 444         }
 445
 446         /*
 447          * If trace_size is lower or equal to 4 bytes, there is no sign
 448          * extension to do because we are already encoded in a long. Therefore,
 449          * we can combine signed and unsigned ops. 4 bytes float also works
 450          * with this, because we do a simple copy of 4 bytes into 4 bytes
 451          * without manipulation (and we do not support conversion from integers
 452          * to floats).
 453          * It is also the case if c_size is 8 bytes, which is the largest
 454          * possible integer.
 455          */
 456         if (ltt_get_alignment()) {
 457                 buf_offset += ltt_align(buf_offset, trace_size);
 458                 if (largest_align)
 459                         *largest_align = max_t(int, *largest_align, trace_size);
 460         }
 461         if (trace_size <= 4 || c_size == 8) {
 462                 if (buf) {
 463                         switch (trace_size) {
 464                         case 1:
 465                                 if (c_size == 8)
 466                                         ust_buffers_write(buf, buf_offset,
 467                                         (uint8_t[]){ (uint8_t)tmp.v_uint64 },
 468                                         sizeof(uint8_t));
 469                                 else
 470                                         ust_buffers_write(buf, buf_offset,
 471                                         (uint8_t[]){ (uint8_t)tmp.v_ulong },
 472                                         sizeof(uint8_t));
 473                                 break;
 474                         case 2:
 475                                 if (c_size == 8)
 476                                         ust_buffers_write(buf, buf_offset,
 477                                         (uint16_t[]){ (uint16_t)tmp.v_uint64 },
 478                                         sizeof(uint16_t));
 479                                 else
 480                                         ust_buffers_write(buf, buf_offset,
 481                                         (uint16_t[]){ (uint16_t)tmp.v_ulong },
 482                                         sizeof(uint16_t));
 483                                 break;
 484                         case 4:
 485                                 if (c_size == 8)
 486                                         ust_buffers_write(buf, buf_offset,
 487                                         (uint32_t[]){ (uint32_t)tmp.v_uint64 },
 488                                         sizeof(uint32_t));
 489                                 else
 490                                         ust_buffers_write(buf, buf_offset,
 491                                         (uint32_t[]){ (uint32_t)tmp.v_ulong },
 492                                         sizeof(uint32_t));
 493                                 break;
 494                         case 8:
 495                                 /*
 496                                  * c_size cannot be other than 8 here because
 497                                  * trace_size > 4.
 498                                  */
 499                                 ust_buffers_write(buf, buf_offset,
 500                                 (uint64_t[]){ (uint64_t)tmp.v_uint64 },
 501                                 sizeof(uint64_t));
 502                                 break;
 503                         default:
 504                                 BUG();
 505                         }
 506                 }
 507                 buf_offset += trace_size;
 508                 goto copydone;
 509         } else {
 510                 /*
 511                  * Perform sign extension.
 512                  */
 513                 if (buf) {
 514                         switch (trace_type) {
 515                         case LTT_TYPE_SIGNED_INT:
 516                                 ust_buffers_write(buf, buf_offset,
 517                                         (int64_t[]){ (int64_t)tmp.v_ulong },
 518                                         sizeof(int64_t));
 519                                 break;
 520                         case LTT_TYPE_UNSIGNED_INT:
 521                                 ust_buffers_write(buf, buf_offset,
 522                                         (uint64_t[]){ (uint64_t)tmp.v_ulong },
 523                                         sizeof(uint64_t));
 524                                 break;
 525                         default:
 526                                 BUG();
 527                         }
 528                 }
 529                 buf_offset += trace_size;
 530                 goto copydone;
 531         }
 532
 533 copydone:
 534         return buf_offset;
 535 }
 536
 537 notrace size_t ltt_serialize_data(struct ust_buffer *buf, size_t buf_offset,
 538                         struct ltt_serialize_closure *closure,
 539                         void *serialize_private,
 540                         unsigned int stack_pos_ctx,
 541                         int *largest_align,
 542                         const char *fmt, va_list *args)
 543 {
 544         char trace_size = 0, c_size = 0;        /*
 545                                                  * 0 (unset), 1, 2, 4, 8 bytes.
 546                                                  */
 547         enum ltt_type trace_type = LTT_TYPE_NONE, c_type = LTT_TYPE_NONE;
 548         unsigned long attributes = 0;
 549
 550         for (; *fmt ; ++fmt) {
 551                 switch (*fmt) {
 552                 case '#':
 553                         /* tracetypes (#) */
 554                         ++fmt;                  /* skip first '#' */
 555                         if (*fmt == '#')        /* Escaped ## */
 556                                 break;
 557                         attributes = 0;
 558                         fmt = parse_trace_type(fmt, &trace_size, &trace_type,
 559                                 &attributes);
 560                         break;
 561                 case '%':
 562                         /* c types (%) */
 563                         ++fmt;                  /* skip first '%' */
 564                         if (*fmt == '%')        /* Escaped %% */
 565                                 break;
 566                         fmt = parse_c_type(fmt, &c_size, &c_type, NULL);
 567                         /*
 568                          * Output c types if no trace types has been
 569                          * specified.
 570                          */
 571                         if (!trace_size)
 572                                 trace_size = c_size;
 573                         if (trace_type == LTT_TYPE_NONE)
 574                                 trace_type = c_type;
 575                         if (c_type == LTT_TYPE_STRING)
 576                                 trace_type = LTT_TYPE_STRING;
 577                         /* perform trace write */
 578                         buf_offset = serialize_trace_data(buf,
 579                                                 buf_offset, trace_size,
 580                                                 trace_type, c_size, c_type,
 581                                                 &stack_pos_ctx,
 582                                                 largest_align,
 583                                                 args);
 584                         trace_size = 0;
 585                         c_size = 0;
 586                         trace_type = LTT_TYPE_NONE;
 587                         c_size = LTT_TYPE_NONE;
 588                         attributes = 0;
 589                         break;
 590                         /* default is to skip the text, doing nothing */
 591                 }
 592         }
 593         return buf_offset;
 594 }
 595
 596 /*
 597  * Calculate data size
 598  * Assume that the padding for alignment starts at a sizeof(void *) address.
 599  */
 600 static notrace size_t ltt_get_data_size(struct ltt_serialize_closure *closure,
 601                                 void *serialize_private,
 602                                 unsigned int stack_pos_ctx, int *largest_align,
 603                                 const char *fmt, va_list *args)
 604 {
 605         ltt_serialize_cb cb = closure->callbacks[0];
 606         closure->cb_idx = 0;
 607         return (size_t)cb(NULL, 0, closure, serialize_private,
 608                           stack_pos_ctx, largest_align, fmt, args);
 609 }
 610
 611 static notrace
 612 void ltt_write_event_data(struct ust_buffer *buf, size_t buf_offset,
 613                                 struct ltt_serialize_closure *closure,
 614                                 void *serialize_private,
 615                                 unsigned int stack_pos_ctx,
 616                                 int largest_align,
 617                                 const char *fmt, va_list *args)
 618 {
 619         ltt_serialize_cb cb = closure->callbacks[0];
 620         closure->cb_idx = 0;
 621         buf_offset += ltt_align(buf_offset, largest_align);
 622         cb(buf, buf_offset, closure, serialize_private, stack_pos_ctx, NULL,
 623            fmt, args);
 624 }
 625
 626
 627 notrace void ltt_vtrace(const struct ust_marker *mdata, void *probe_data,
 628                         void *call_data,
 629                         const char *fmt, va_list *args)
 630 {
 631         int largest_align, ret;
 632         struct ltt_active_ust_marker *pdata;
 633         uint16_t eID;
 634         size_t data_size, slot_size;
 635         unsigned int chan_index;
 636         struct ust_channel *channel;
 637         struct ust_trace *trace, *dest_trace = NULL;
 638         struct ust_buffer *buf;
 639         u64 tsc;
 640         long buf_offset;
 641         va_list args_copy;
 642         struct ltt_serialize_closure closure;
 643         struct ltt_probe_private_data *private_data = call_data;
 644         void *serialize_private = NULL;
 645         int cpu;
 646         unsigned int rflags;
 647         unsigned int stack_pos_ctx;
 648
 649         /*
 650          * This test is useful for quickly exiting static tracing when no trace
 651          * is active. We expect to have an active trace when we get here.
 652          */
 653         if (unlikely(ltt_traces.num_active_traces == 0))
 654                 return;
 655
 656         rcu_read_lock();
 657         cpu = ust_get_cpu();
 658
 659         /* Force volatile access. */
 660         CMM_STORE_SHARED(ltt_nesting, CMM_LOAD_SHARED(ltt_nesting) + 1);
 661         stack_pos_ctx = tracer_stack_pos;
 662         cmm_barrier();
 663
 664         pdata = (struct ltt_active_ust_marker *)probe_data;
 665         eID = mdata->event_id;
 666         chan_index = mdata->channel_id;
 667         closure.callbacks = pdata->probe->callbacks;
 668
 669         if (unlikely(private_data)) {
 670                 dest_trace = private_data->trace;
 671                 if (private_data->serializer)
 672                         closure.callbacks = &private_data->serializer;
 673                 serialize_private = private_data->serialize_private;
 674         }
 675
 676         va_copy(args_copy, *args);
 677         /*
 678          * Assumes event payload to start on largest_align alignment.
 679          */
 680         largest_align = 1;      /* must be non-zero for ltt_align */
 681         data_size = ltt_get_data_size(&closure, serialize_private,
 682                                       stack_pos_ctx, &largest_align,
 683                                       fmt, &args_copy);
 684         largest_align = min_t(int, largest_align, sizeof(void *));
 685         va_end(args_copy);
 686
 687         /* Iterate on each trace */
 688         cds_list_for_each_entry_rcu(trace, &ltt_traces.head, list) {
 689                 /*
 690                  * Expect the filter to filter out events. If we get here,
 691                  * we went through tracepoint activation as a first step.
 692                  */
 693                 if (unlikely(dest_trace && trace != dest_trace))
 694                         continue;
 695                 if (unlikely(!trace->active))
 696                         continue;
 697                 if (unlikely(!ltt_run_filter(trace, eID)))
 698                         continue;
 699 #ifdef CONFIG_LTT_DEBUG_EVENT_SIZE
 700                 rflags = LTT_RFLAG_ID_SIZE;
 701 #else
 702                 if (unlikely(eID >= LTT_FREE_EVENTS))
 703                         rflags = LTT_RFLAG_ID;
 704                 else
 705                         rflags = 0;
 706 #endif
 707                 /*
 708                  * Skip channels added after trace creation.
 709                  */
 710                 if (unlikely(chan_index >= trace->nr_channels))
 711                         continue;
 712                 channel = &trace->channels[chan_index];
 713                 if (!channel->active)
 714                         continue;
 715
 716                 /*
 717                  * If a new cpu was plugged since the trace was started, we did
 718                  * not add it to the trace, and therefore we write the event to
 719                  * cpu 0.
 720                  */
 721                 if (cpu >= channel->n_cpus) {
 722                         cpu = 0;
 723                 }
 724
 725                 /* reserve space : header and data */
 726                 ret = ltt_reserve_slot(channel, trace, data_size, largest_align,
 727                                         cpu, &buf, &slot_size, &buf_offset,
 728                                         &tsc, &rflags);
 729                 if (unlikely(ret < 0))
 730                         continue; /* buffer full */
 731
 732                 va_copy(args_copy, *args);
 733                 /* FIXME : could probably encapsulate transport better. */
 734                 buf = channel->buf[cpu];
 735                 /* Out-of-order write : header and data */
 736                 buf_offset = ltt_write_event_header(channel, buf, buf_offset,
 737                                         eID, data_size, tsc, rflags);
 738                 ltt_write_event_data(buf, buf_offset, &closure,
 739                                      serialize_private,
 740                                      stack_pos_ctx, largest_align,
 741                                      fmt, &args_copy);
 742                 va_end(args_copy);
 743                 /* Out-of-order commit */
 744                 ltt_commit_slot(channel, buf, buf_offset, data_size, slot_size);
 745                 DBG("just commited event (%s/%s) at offset %ld and size %zd", mdata->channel, mdata->name, buf_offset, slot_size);
 746         }
 747
 748         cmm_barrier();
 749         tracer_stack_pos = stack_pos_ctx;
 750         CMM_STORE_SHARED(ltt_nesting, CMM_LOAD_SHARED(ltt_nesting) - 1);
 751
 752         rcu_read_unlock();
 753 }
 754
 755 notrace void ltt_trace(const struct ust_marker *mdata, void *probe_data,
 756                        void *call_data,
 757                        const char *fmt, ...)
 758 {
 759         va_list args;
 760
 761         va_start(args, fmt);
 762         ltt_vtrace(mdata, probe_data, call_data, fmt, &args);
 763         va_end(args);
 764 }
 765
 766 static notrace void skip_space(const char **ps)
 767 {
 768         while(**ps == ' ')
 769                 (*ps)++;
 770 }
 771
 772 static notrace void copy_token(char **out, const char **in)
 773 {
 774         while (**in != ' ' && **in != '\0') {
 775                 **out = **in;
 776                 (*out)++;
 777                 (*in)++;
 778         }
 779 }
 780
 781 /* serialize_to_text
 782  *
 783  * Given a format string and a va_list of arguments, convert them to a
 784  * human-readable string.
 785  *
 786  * @outbuf: the buffer to output the string to
 787  * @bufsize: the max size that can be used in outbuf
 788  * @fmt: the marker format string
 789  * @ap: a va_list that contains the arguments corresponding to fmt
 790  *
 791  * Return value: the number of chars that have been put in outbuf, excluding
 792  * the final \0, or, if the buffer was too small, the number of chars that
 793  * would have been written in outbuf if it had been large enough.
 794  *
 795  * outbuf may be NULL. The return value may then be used be allocate an
 796  * appropriate outbuf.
 797  *
 798  */
 799
 800 notrace
 801 int serialize_to_text(char *outbuf, int bufsize, const char *fmt, va_list ap)
 802 {
 803         int fmt_len = strlen(fmt);
 804         char *new_fmt = alloca(fmt_len + 1);
 805         const char *orig_fmt_p = fmt;
 806         char *new_fmt_p = new_fmt;
 807         char false_buf;
 808         int result;
 809         enum { none, cfmt, tracefmt, argname } prev_token = none;
 810
 811         while (*orig_fmt_p != '\0') {
 812                 if (*orig_fmt_p == '%') {
 813                         prev_token = cfmt;
 814                         copy_token(&new_fmt_p, &orig_fmt_p);
 815                 }
 816                 else if (*orig_fmt_p == '#') {
 817                         prev_token = tracefmt;
 818                         do {
 819                                 orig_fmt_p++;
 820                         } while (*orig_fmt_p != ' ' && *orig_fmt_p != '\0');
 821                 }
 822                 else if (*orig_fmt_p == ' ') {
 823                         if (prev_token == argname) {
 824                                 *new_fmt_p = '=';
 825                                 new_fmt_p++;
 826                         }
 827                         else if (prev_token == cfmt) {
 828                                 *new_fmt_p = ' ';
 829                                 new_fmt_p++;
 830                         }
 831
 832                         skip_space(&orig_fmt_p);
 833                 }
 834                 else {
 835                         prev_token = argname;
 836                         copy_token(&new_fmt_p, &orig_fmt_p);
 837                 }
 838         }
 839
 840         *new_fmt_p = '\0';
 841
 842         if (outbuf == NULL) {
 843                 /* use this false_buffer for compatibility with pre-C99 */
 844                 outbuf = &false_buf;
 845                 bufsize = 1;
 846         }
 847         result = ust_safe_vsnprintf(outbuf, bufsize, new_fmt, ap);
 848
 849         return result;
 850 }