The Tcpdump Group git mirrors - tcpdump/blob - instrument-functions.c

   1 /*
   2  * Redistribution and use in source and binary forms, with or without
   3  * modification, are permitted provided that: (1) source code
   4  * distributions retain the above copyright notice and this paragraph
   5  * in its entirety, and (2) distributions including binary code include
   6  * the above copyright notice and this paragraph in its entirety in
   7  * the documentation or other materials provided with the distribution.
   8  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND
   9  * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
  10  * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  11  * FOR A PARTICULAR PURPOSE.
  12  */
  13
  14 #include <stdio.h>
  15 #include <string.h>
  16 #include <stdlib.h>
  17 #include <unistd.h>
  18 #include <bfd.h>
  19
  20 /*
  21  * Generate instrumentation calls for entry and exit to functions.
  22  * Just after function entry and just before function exit, the
  23  * following profiling functions are called with the address of the
  24  * current function and its call site (currently not use).
  25  *
  26  * The attribute 'no_instrument_function' causes this instrumentation is
  27  * not done.
  28  *
  29  * These profiling functions call print_debug(). This function prints the
  30  * current function name with indentation and call level.
  31  * If entering in a function it prints also the calling function name with
  32  * file name and line number.
  33  *
  34  * If the environment variable INSTRUMENT is
  35  * unset or set to an empty string, print nothing, like with no instrumentation
  36  * set to "all" or "a", print all the functions names
  37  * set to "global" or "g", print only the global functions names
  38  */
  39
  40 #define ND_NO_INSTRUMENT __attribute__((no_instrument_function))
  41
  42 /* Store the function call level, used also in pretty_print_packet() */
  43 extern int profile_func_level;
  44 int profile_func_level = -1;
  45
  46 typedef enum {
  47         ENTER,
  48         EXIT
  49 } action_type;
  50
  51 void __cyg_profile_func_enter(void *this_fn, void *call_site) ND_NO_INSTRUMENT;
  52
  53 void __cyg_profile_func_exit(void *this_fn, void *call_site) ND_NO_INSTRUMENT;
  54
  55 static void print_debug(void *this_fn, void *call_site, action_type action)
  56         ND_NO_INSTRUMENT;
  57
  58 void
  59 __cyg_profile_func_enter(void *this_fn, void *call_site)
  60 {
  61         print_debug(this_fn, call_site, ENTER);
  62 }
  63
  64 void
  65 __cyg_profile_func_exit(void *this_fn, void *call_site)
  66 {
  67         print_debug(this_fn, call_site, EXIT);
  68 }
  69
  70 static void print_debug(void *this_fn, void *call_site, action_type action)
  71 {
  72         static bfd* abfd;
  73         static asymbol **symtab;
  74         static long symcount;
  75         static asection *text;
  76         static bfd_vma vma;
  77         static int instrument_set;
  78         static int instrument_off;
  79         static int instrument_global;
  80         int i;
  81
  82         if (!instrument_set) {
  83                 static char *instrument_type;
  84
  85                 /* Get the configuration environment variable INSTRUMENT value if any */
  86                 instrument_type = getenv("INSTRUMENT");
  87                 /* unset or set to an empty string ? */
  88                 if (instrument_type == NULL ||
  89                         !strncmp(instrument_type, "", sizeof(""))) {
  90                         instrument_off = 1;
  91                 } else {
  92                         /* set to "global" or "g" ? */
  93                         if (!strncmp(instrument_type, "global", sizeof("global")) ||
  94                                 !strncmp(instrument_type, "g", sizeof("g")))
  95                                 instrument_global = 1;
  96                         else if (strncmp(instrument_type, "all", sizeof("all")) &&
  97                                          strncmp(instrument_type, "a", sizeof("a"))) {
  98                                 fprintf(stderr, "INSTRUMENT can be only \"\", \"all\", \"a\", "
  99                                                 "\"global\" or \"g\".\n");
 100                                 exit(1);
 101                         }
 102                 }
 103                 instrument_set = 1;
 104         }
 105
 106         if (instrument_off)
 107                         return;
 108
 109         /* If no errors, this block should be executed one time */
 110         if (!abfd) {
 111                 char pgm_name[1024];
 112                 long symsize;
 113
 114                 ssize_t ret = readlink("/proc/self/exe", pgm_name, sizeof(pgm_name));
 115                 if (ret == -1) {
 116                         perror("failed to find executable");
 117                         return;
 118                 }
 119                 if (ret == sizeof(pgm_name)) {
 120                         /* no space for the '\0' */
 121                         printf("truncation may have occurred\n");
 122                         return;
 123                 }
 124                 pgm_name[ret] = '\0';
 125
 126                 bfd_init();
 127
 128                 abfd = bfd_openr(pgm_name, NULL);
 129                 if (!abfd) {
 130                         bfd_perror("bfd_openr");
 131                         return;
 132                 }
 133
 134                 if (!bfd_check_format(abfd, bfd_object)) {
 135                         bfd_perror("bfd_check_format");
 136                         return;
 137                 }
 138
 139                 if((symsize = bfd_get_symtab_upper_bound(abfd)) == -1) {
 140                         bfd_perror("bfd_get_symtab_upper_bound");
 141                         return;
 142                 }
 143
 144                 symtab = (asymbol **)malloc(symsize);
 145                 symcount = bfd_canonicalize_symtab(abfd, symtab);
 146                 if (symcount < 0) {
 147                         free(symtab);
 148                         bfd_perror("bfd_canonicalize_symtab");
 149                         return;
 150                 }
 151
 152                 if ((text = bfd_get_section_by_name(abfd, ".text")) == NULL) {
 153                         bfd_perror("bfd_get_section_by_name");
 154                         return;
 155                 }
 156                 vma = text->vma;
 157         }
 158
 159         if (instrument_global) {
 160                 symbol_info syminfo;
 161                 int found;
 162
 163                 i = 0;
 164                 found = 0;
 165                 while (i < symcount && !found) {
 166                         bfd_get_symbol_info(abfd, symtab[i], &syminfo);
 167                         if ((void *)syminfo.value == this_fn) {
 168                                 found = 1;
 169                         }
 170                         i++;
 171                 }
 172                 /* type == 'T' for a global function */
 173                 if (found == 1 && syminfo.type != 'T')
 174                         return;
 175         }
 176
 177         /* Current function */
 178         if ((bfd_vma)this_fn < vma) {
 179                 printf("[ERROR address this_fn]");
 180         } else {
 181                 const char *file;
 182                 const char *func;
 183                 unsigned int line;
 184
 185                 if (!bfd_find_nearest_line(abfd, text, symtab, (bfd_vma)this_fn - vma,
 186                                                                    &file, &func, &line)) {
 187                         printf("[ERROR bfd_find_nearest_line this_fn]");
 188                 } else {
 189                         if (action == ENTER)
 190                                 profile_func_level += 1;
 191                         /* Indentation */
 192                         for (i = 0 ; i < profile_func_level ; i++)
 193                                 putchar(' ');
 194                         if (action == ENTER)
 195                                 printf("[>> ");
 196                         else
 197                                 printf("[<< ");
 198                         /* Function name */
 199                         if (func == NULL || *func == '\0')
 200                                 printf("???");
 201                         else
 202                                 printf("%s", func);
 203                         printf(" (%d)", profile_func_level);
 204                         /* Print the "from" part except for the main function) */
 205                         if (action == ENTER && func != NULL &&
 206                                 strncmp(func, "main", sizeof("main"))) {
 207                                 /* Calling function */
 208                                 if ((bfd_vma)call_site < vma) {
 209                                         printf("[ERROR address call_site]");
 210                                 } else {
 211                                         if (!bfd_find_nearest_line(abfd, text, symtab,
 212                                                                                            (bfd_vma)call_site - vma, &file,
 213                                                                                            &func, &line)) {
 214                                                 printf("[ERROR bfd_find_nearest_line call_site]");
 215                                         } else {
 216                                                 printf(" from ");
 217                                                 /* Function name */
 218                                                 if (func == NULL || *func == '\0')
 219                                                         printf("???");
 220                                                 else
 221                                                         printf("%s", func);
 222                                                 /* File name */
 223                                                 if (file == NULL || *file == '\0')
 224                                                         printf(" ??:");
 225                                                 else {
 226                                                         char *slashp = strrchr(file, '/');
 227                                                         if (slashp != NULL)
 228                                                                 file = slashp + 1;
 229                                                         printf(" %s:", file);
 230                                                 }
 231                                                 /* Line number */
 232                                                 if (line == 0)
 233                                                         printf("?");
 234                                                 else
 235                                                         printf("%u", line);
 236                                                 printf("]");
 237                                         }
 238                                 }
 239                         }
 240                         putchar('\n');
 241                         if (action == EXIT)
 242                                 profile_func_level -= 1;
 243                 }
 244         }
 245         fflush(stdout);
 246 }
 247
 248 /* vi: set tabstop=4 softtabstop=0 shiftwidth=4 smarttab autoindent : */