tools/lib/traceevent/trace-seq.c

   1 // SPDX-License-Identifier: LGPL-2.1
   2 /*
   3  * Copyright (C) 2009 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
   4  *
   5  */
   6 #include "trace-seq.h"
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <stdarg.h>
  12
  13 #include <asm/bug.h>
  14 #include "event-parse.h"
  15 #include "event-utils.h"
  16
  17 /*
  18  * The TRACE_SEQ_POISON is to catch the use of using
  19  * a trace_seq structure after it was destroyed.
  20  */
  21 #define TRACE_SEQ_POISON        ((void *)0xdeadbeef)
  22 #define TRACE_SEQ_CHECK(s)                                              \
  23 do {                                                                    \
  24         if (WARN_ONCE((s)->buffer == TRACE_SEQ_POISON,                  \
  25                       "Usage of trace_seq after it was destroyed"))     \
  26                 (s)->state = TRACE_SEQ__BUFFER_POISONED;                \
  27 } while (0)
  28
  29 #define TRACE_SEQ_CHECK_RET_N(s, n)             \
  30 do {                                            \
  31         TRACE_SEQ_CHECK(s);                     \
  32         if ((s)->state != TRACE_SEQ__GOOD)      \
  33                 return n;                       \
  34 } while (0)
  35
  36 #define TRACE_SEQ_CHECK_RET(s)   TRACE_SEQ_CHECK_RET_N(s, )
  37 #define TRACE_SEQ_CHECK_RET0(s)  TRACE_SEQ_CHECK_RET_N(s, 0)
  38
  39 /**
  40  * trace_seq_init - initialize the trace_seq structure
  41  * @s: a pointer to the trace_seq structure to initialize
  42  */
  43 void trace_seq_init(struct trace_seq *s)
  44 {
  45         s->len = 0;
  46         s->readpos = 0;
  47         s->buffer_size = TRACE_SEQ_BUF_SIZE;
  48         s->buffer = malloc(s->buffer_size);
  49         if (s->buffer != NULL)
  50                 s->state = TRACE_SEQ__GOOD;
  51         else
  52                 s->state = TRACE_SEQ__MEM_ALLOC_FAILED;
  53 }
  54
  55 /**
  56  * trace_seq_reset - re-initialize the trace_seq structure
  57  * @s: a pointer to the trace_seq structure to reset
  58  */
  59 void trace_seq_reset(struct trace_seq *s)
  60 {
  61         if (!s)
  62                 return;
  63         TRACE_SEQ_CHECK(s);
  64         s->len = 0;
  65         s->readpos = 0;
  66 }
  67
  68 /**
  69  * trace_seq_destroy - free up memory of a trace_seq
  70  * @s: a pointer to the trace_seq to free the buffer
  71  *
  72  * Only frees the buffer, not the trace_seq struct itself.
  73  */
  74 void trace_seq_destroy(struct trace_seq *s)
  75 {
  76         if (!s)
  77                 return;
  78         TRACE_SEQ_CHECK_RET(s);
  79         free(s->buffer);
  80         s->buffer = TRACE_SEQ_POISON;
  81 }
  82
  83 static void expand_buffer(struct trace_seq *s)
  84 {
  85         char *buf;
  86
  87         buf = realloc(s->buffer, s->buffer_size + TRACE_SEQ_BUF_SIZE);
  88         if (WARN_ONCE(!buf, "Can't allocate trace_seq buffer memory")) {
  89                 s->state = TRACE_SEQ__MEM_ALLOC_FAILED;
  90                 return;
  91         }
  92
  93         s->buffer = buf;
  94         s->buffer_size += TRACE_SEQ_BUF_SIZE;
  95 }
  96
  97 /**
  98  * trace_seq_printf - sequence printing of trace information
  99  * @s: trace sequence descriptor
 100  * @fmt: printf format string
 101  *
 102  * It returns 0 if the trace oversizes the buffer's free
 103  * space, the number of characters printed, or a negative
 104  * value in case of an error.
 105  *
 106  * The tracer may use either sequence operations or its own
 107  * copy to user routines. To simplify formating of a trace
 108  * trace_seq_printf is used to store strings into a special
 109  * buffer (@s). Then the output may be either used by
 110  * the sequencer or pulled into another buffer.
 111  */
 112 int
 113 trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 114 {
 115         va_list ap;
 116         int len;
 117         int ret;
 118
 119  try_again:
 120         TRACE_SEQ_CHECK_RET0(s);
 121
 122         len = (s->buffer_size - 1) - s->len;
 123
 124         va_start(ap, fmt);
 125         ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
 126         va_end(ap);
 127
 128         if (ret >= len) {
 129                 expand_buffer(s);
 130                 goto try_again;
 131         }
 132
 133         if (ret > 0)
 134                 s->len += ret;
 135
 136         return ret;
 137 }
 138
 139 /**
 140  * trace_seq_vprintf - sequence printing of trace information
 141  * @s: trace sequence descriptor
 142  * @fmt: printf format string
 143  *
 144  * It returns 0 if the trace oversizes the buffer's free
 145  * space, the number of characters printed, or a negative
 146  * value in case of an error.
 147  * *
 148  * The tracer may use either sequence operations or its own
 149  * copy to user routines. To simplify formating of a trace
 150  * trace_seq_printf is used to store strings into a special
 151  * buffer (@s). Then the output may be either used by
 152  * the sequencer or pulled into another buffer.
 153  */
 154 int
 155 trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
 156 {
 157         int len;
 158         int ret;
 159
 160  try_again:
 161         TRACE_SEQ_CHECK_RET0(s);
 162
 163         len = (s->buffer_size - 1) - s->len;
 164
 165         ret = vsnprintf(s->buffer + s->len, len, fmt, args);
 166
 167         if (ret >= len) {
 168                 expand_buffer(s);
 169                 goto try_again;
 170         }
 171
 172         if (ret > 0)
 173                 s->len += ret;
 174
 175         return ret;
 176 }
 177
 178 /**
 179  * trace_seq_puts - trace sequence printing of simple string
 180  * @s: trace sequence descriptor
 181  * @str: simple string to record
 182  *
 183  * The tracer may use either the sequence operations or its own
 184  * copy to user routines. This function records a simple string
 185  * into a special buffer (@s) for later retrieval by a sequencer
 186  * or other mechanism.
 187  */
 188 int trace_seq_puts(struct trace_seq *s, const char *str)
 189 {
 190         int len;
 191
 192         TRACE_SEQ_CHECK_RET0(s);
 193
 194         len = strlen(str);
 195
 196         while (len > ((s->buffer_size - 1) - s->len))
 197                 expand_buffer(s);
 198
 199         TRACE_SEQ_CHECK_RET0(s);
 200
 201         memcpy(s->buffer + s->len, str, len);
 202         s->len += len;
 203
 204         return len;
 205 }
 206
 207 int trace_seq_putc(struct trace_seq *s, unsigned char c)
 208 {
 209         TRACE_SEQ_CHECK_RET0(s);
 210
 211         while (s->len >= (s->buffer_size - 1))
 212                 expand_buffer(s);
 213
 214         TRACE_SEQ_CHECK_RET0(s);
 215
 216         s->buffer[s->len++] = c;
 217
 218         return 1;
 219 }
 220
 221 void trace_seq_terminate(struct trace_seq *s)
 222 {
 223         TRACE_SEQ_CHECK_RET(s);
 224
 225         /* There's always one character left on the buffer */
 226         s->buffer[s->len] = 0;
 227 }
 228
 229 int trace_seq_do_fprintf(struct trace_seq *s, FILE *fp)
 230 {
 231         TRACE_SEQ_CHECK(s);
 232
 233         switch (s->state) {
 234         case TRACE_SEQ__GOOD:
 235                 return fprintf(fp, "%.*s", s->len, s->buffer);
 236         case TRACE_SEQ__BUFFER_POISONED:
 237                 fprintf(fp, "%s\n", "Usage of trace_seq after it was destroyed");
 238                 break;
 239         case TRACE_SEQ__MEM_ALLOC_FAILED:
 240                 fprintf(fp, "%s\n", "Can't allocate trace_seq buffer memory");
 241                 break;
 242         }
 243         return -1;
 244 }
 245
 246 int trace_seq_do_printf(struct trace_seq *s)
 247 {
 248         return trace_seq_do_fprintf(s, stdout);
 249 }