tools/lib/traceevent/trace-seq.c

   1 /*
   2  * Copyright (C) 2009 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
   3  *
   4  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation;
   8  * version 2.1 of the License (not later!)
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this program; if not,  see <http://www.gnu.org/licenses>
  17  *
  18  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  19  */
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <stdarg.h>
  24
  25 #include <asm/bug.h>
  26 #include "event-parse.h"
  27 #include "event-utils.h"
  28
  29 /*
  30  * The TRACE_SEQ_POISON is to catch the use of using
  31  * a trace_seq structure after it was destroyed.
  32  */
  33 #define TRACE_SEQ_POISON        ((void *)0xdeadbeef)
  34 #define TRACE_SEQ_CHECK(s)                                              \
  35 do {                                                                    \
  36         if (WARN_ONCE((s)->buffer == TRACE_SEQ_POISON,                  \
  37                       "Usage of trace_seq after it was destroyed"))     \
  38                 (s)->state = TRACE_SEQ__BUFFER_POISONED;                \
  39 } while (0)
  40
  41 #define TRACE_SEQ_CHECK_RET_N(s, n)             \
  42 do {                                            \
  43         TRACE_SEQ_CHECK(s);                     \
  44         if ((s)->state != TRACE_SEQ__GOOD)      \
  45                 return n;                       \
  46 } while (0)
  47
  48 #define TRACE_SEQ_CHECK_RET(s)   TRACE_SEQ_CHECK_RET_N(s, )
  49 #define TRACE_SEQ_CHECK_RET0(s)  TRACE_SEQ_CHECK_RET_N(s, 0)
  50
  51 /**
  52  * trace_seq_init - initialize the trace_seq structure
  53  * @s: a pointer to the trace_seq structure to initialize
  54  */
  55 void trace_seq_init(struct trace_seq *s)
  56 {
  57         s->len = 0;
  58         s->readpos = 0;
  59         s->buffer_size = TRACE_SEQ_BUF_SIZE;
  60         s->buffer = malloc(s->buffer_size);
  61         if (s->buffer != NULL)
  62                 s->state = TRACE_SEQ__GOOD;
  63         else
  64                 s->state = TRACE_SEQ__MEM_ALLOC_FAILED;
  65 }
  66
  67 /**
  68  * trace_seq_reset - re-initialize the trace_seq structure
  69  * @s: a pointer to the trace_seq structure to reset
  70  */
  71 void trace_seq_reset(struct trace_seq *s)
  72 {
  73         if (!s)
  74                 return;
  75         TRACE_SEQ_CHECK(s);
  76         s->len = 0;
  77         s->readpos = 0;
  78 }
  79
  80 /**
  81  * trace_seq_destroy - free up memory of a trace_seq
  82  * @s: a pointer to the trace_seq to free the buffer
  83  *
  84  * Only frees the buffer, not the trace_seq struct itself.
  85  */
  86 void trace_seq_destroy(struct trace_seq *s)
  87 {
  88         if (!s)
  89                 return;
  90         TRACE_SEQ_CHECK_RET(s);
  91         free(s->buffer);
  92         s->buffer = TRACE_SEQ_POISON;
  93 }
  94
  95 static void expand_buffer(struct trace_seq *s)
  96 {
  97         char *buf;
  98
  99         buf = realloc(s->buffer, s->buffer_size + TRACE_SEQ_BUF_SIZE);
 100         if (WARN_ONCE(!buf, "Can't allocate trace_seq buffer memory")) {
 101                 s->state = TRACE_SEQ__MEM_ALLOC_FAILED;
 102                 return;
 103         }
 104
 105         s->buffer = buf;
 106         s->buffer_size += TRACE_SEQ_BUF_SIZE;
 107 }
 108
 109 /**
 110  * trace_seq_printf - sequence printing of trace information
 111  * @s: trace sequence descriptor
 112  * @fmt: printf format string
 113  *
 114  * It returns 0 if the trace oversizes the buffer's free
 115  * space, 1 otherwise.
 116  *
 117  * The tracer may use either sequence operations or its own
 118  * copy to user routines. To simplify formating of a trace
 119  * trace_seq_printf is used to store strings into a special
 120  * buffer (@s). Then the output may be either used by
 121  * the sequencer or pulled into another buffer.
 122  */
 123 int
 124 trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 125 {
 126         va_list ap;
 127         int len;
 128         int ret;
 129
 130  try_again:
 131         TRACE_SEQ_CHECK_RET0(s);
 132
 133         len = (s->buffer_size - 1) - s->len;
 134
 135         va_start(ap, fmt);
 136         ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
 137         va_end(ap);
 138
 139         if (ret >= len) {
 140                 expand_buffer(s);
 141                 goto try_again;
 142         }
 143
 144         s->len += ret;
 145
 146         return 1;
 147 }
 148
 149 /**
 150  * trace_seq_vprintf - sequence printing of trace information
 151  * @s: trace sequence descriptor
 152  * @fmt: printf format string
 153  *
 154  * The tracer may use either sequence operations or its own
 155  * copy to user routines. To simplify formating of a trace
 156  * trace_seq_printf is used to store strings into a special
 157  * buffer (@s). Then the output may be either used by
 158  * the sequencer or pulled into another buffer.
 159  */
 160 int
 161 trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
 162 {
 163         int len;
 164         int ret;
 165
 166  try_again:
 167         TRACE_SEQ_CHECK_RET0(s);
 168
 169         len = (s->buffer_size - 1) - s->len;
 170
 171         ret = vsnprintf(s->buffer + s->len, len, fmt, args);
 172
 173         if (ret >= len) {
 174                 expand_buffer(s);
 175                 goto try_again;
 176         }
 177
 178         s->len += ret;
 179
 180         return len;
 181 }
 182
 183 /**
 184  * trace_seq_puts - trace sequence printing of simple string
 185  * @s: trace sequence descriptor
 186  * @str: simple string to record
 187  *
 188  * The tracer may use either the sequence operations or its own
 189  * copy to user routines. This function records a simple string
 190  * into a special buffer (@s) for later retrieval by a sequencer
 191  * or other mechanism.
 192  */
 193 int trace_seq_puts(struct trace_seq *s, const char *str)
 194 {
 195         int len;
 196
 197         TRACE_SEQ_CHECK_RET0(s);
 198
 199         len = strlen(str);
 200
 201         while (len > ((s->buffer_size - 1) - s->len))
 202                 expand_buffer(s);
 203
 204         TRACE_SEQ_CHECK_RET0(s);
 205
 206         memcpy(s->buffer + s->len, str, len);
 207         s->len += len;
 208
 209         return len;
 210 }
 211
 212 int trace_seq_putc(struct trace_seq *s, unsigned char c)
 213 {
 214         TRACE_SEQ_CHECK_RET0(s);
 215
 216         while (s->len >= (s->buffer_size - 1))
 217                 expand_buffer(s);
 218
 219         TRACE_SEQ_CHECK_RET0(s);
 220
 221         s->buffer[s->len++] = c;
 222
 223         return 1;
 224 }
 225
 226 void trace_seq_terminate(struct trace_seq *s)
 227 {
 228         TRACE_SEQ_CHECK_RET(s);
 229
 230         /* There's always one character left on the buffer */
 231         s->buffer[s->len] = 0;
 232 }
 233
 234 int trace_seq_do_printf(struct trace_seq *s)
 235 {
 236         TRACE_SEQ_CHECK(s);
 237
 238         switch (s->state) {
 239         case TRACE_SEQ__GOOD:
 240                 return printf("%.*s", s->len, s->buffer);
 241         case TRACE_SEQ__BUFFER_POISONED:
 242                 puts("Usage of trace_seq after it was destroyed");
 243                 break;
 244         case TRACE_SEQ__MEM_ALLOC_FAILED:
 245                 puts("Can't allocate trace_seq buffer memory");
 246                 break;
 247         }
 248         return -1;
 249 }