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 char *instrument_type;
  78         static int instrument_set;
  79         static int instrument_off;
  80         static int instrument_global;
  81         int i;
  82
  83         if (!instrument_set) {
  84                 /* Get the configuration environment variable INSTRUMENT value if any */
  85                 instrument_type = getenv("INSTRUMENT");
  86                 /* unset or set to an empty string ? */
  87                 if (instrument_type == NULL ||
  88                         !strncmp(instrument_type, "", sizeof(""))) {
  89                         instrument_off = 1;
  90                 } else {
  91                         /* set to "global" or "g" ? */
  92                         if (!strncmp(instrument_type, "global", sizeof("global")) ||
  93                                 !strncmp(instrument_type, "g", sizeof("g")))
  94                                 instrument_global = 1;
  95                         else if (strncmp(instrument_type, "all", sizeof("all")) &&
  96                                          strncmp(instrument_type, "a", sizeof("a"))) {
  97                                 fprintf(stderr, "INSTRUMENT can be only \"\", \"all\", \"a\", "
  98                                                 "\"global\" or \"g\".\n");
  99                                 exit(1);
 100                         }
 101                 }
 102                 instrument_set = 1;
 103         }
 104
 105         if (instrument_off)
 106                         return;
 107
 108         /* If no errors, this block should be executed one time */
 109         if (!abfd) {
 110                 char pgm_name[1024];
 111                 long symsize;
 112
 113                 ssize_t ret = readlink("/proc/self/exe", pgm_name, sizeof(pgm_name));
 114                 if (ret == -1) {
 115                         perror("failed to find executable");
 116                         return;
 117                 }
 118                 if (ret == sizeof(pgm_name)) {
 119                         /* no space for the '\0' */
 120                         printf("truncation may have occurred\n");
 121                         return;
 122                 }
 123                 pgm_name[ret] = '\0';
 124
 125                 bfd_init();
 126
 127                 abfd = bfd_openr(pgm_name, NULL);
 128                 if (!abfd) {
 129                         bfd_perror("bfd_openr");
 130                         return;
 131                 }
 132
 133                 if (!bfd_check_format(abfd, bfd_object)) {
 134                         bfd_perror("bfd_check_format");
 135                         return;
 136                 }
 137
 138                 if((symsize = bfd_get_symtab_upper_bound(abfd)) == -1) {
 139                         bfd_perror("bfd_get_symtab_upper_bound");
 140                         return;
 141                 }
 142
 143                 symtab = (asymbol **)malloc(symsize);
 144                 symcount = bfd_canonicalize_symtab(abfd, symtab);
 145                 if (symcount < 0) {
 146                         free(symtab);
 147                         bfd_perror("bfd_canonicalize_symtab");
 148                         return;
 149                 }
 150
 151                 if ((text = bfd_get_section_by_name(abfd, ".text")) == NULL) {
 152                         bfd_perror("bfd_get_section_by_name");
 153                         return;
 154                 }
 155                 vma = text->vma;
 156         }
 157
 158         if (instrument_global) {
 159                 symbol_info syminfo;
 160                 int found;
 161
 162                 i = 0;
 163                 found = 0;
 164                 while (i < symcount && !found) {
 165                         bfd_get_symbol_info(abfd, symtab[i], &syminfo);
 166                         if ((void *)syminfo.value == this_fn) {
 167                                 found = 1;
 168                         }
 169                         i++;
 170                 }
 171                 /* type == 'T' for a global function */
 172                 if (found == 1 && syminfo.type != 'T')
 173                         return;
 174         }
 175
 176         /* Current function */
 177         if ((bfd_vma)this_fn < vma) {
 178                 printf("[ERROR address this_fn]");
 179         } else {
 180                 const char *file;
 181                 const char *func;
 182                 unsigned int line;
 183
 184                 if (!bfd_find_nearest_line(abfd, text, symtab, (bfd_vma)this_fn - vma,
 185                                                                    &file, &func, &line)) {
 186                         printf("[ERROR bfd_find_nearest_line this_fn]");
 187                 } else {
 188                         if (action == ENTER)
 189                                 profile_func_level += 1;
 190                         /* Indentation */
 191                         for (i = 0 ; i < profile_func_level ; i++)
 192                                 putchar(' ');
 193                         if (action == ENTER)
 194                                 printf("[>> ");
 195                         else
 196                                 printf("[<< ");
 197                         /* Function name */
 198                         if (func == NULL || *func == '\0')
 199                                 printf("???");
 200                         else
 201                                 printf("%s", func);
 202                         printf(" (%d)", profile_func_level);
 203                         /* Print the "from" part except for the main function) */
 204                         if (action == ENTER && func != NULL &&
 205                                 strncmp(func, "main", sizeof("main"))) {
 206                                 /* Calling function */
 207                                 if ((bfd_vma)call_site < vma) {
 208                                         printf("[ERROR address call_site]");
 209                                 } else {
 210                                         if (!bfd_find_nearest_line(abfd, text, symtab,
 211                                                                                            (bfd_vma)call_site - vma, &file,
 212                                                                                            &func, &line)) {
 213                                                 printf("[ERROR bfd_find_nearest_line call_site]");
 214                                         } else {
 215                                                 printf(" from ");
 216                                                 /* Function name */
 217                                                 if (func == NULL || *func == '\0')
 218                                                         printf("???");
 219                                                 else
 220                                                         printf("%s", func);
 221                                                 /* File name */
 222                                                 if (file == NULL || *file == '\0')
 223                                                         printf(" ??:");
 224                                                 else {
 225                                                         char *slashp = strrchr(file, '/');
 226                                                         if (slashp != NULL)
 227                                                                 file = slashp + 1;
 228                                                         printf(" %s:", file);
 229                                                 }
 230                                                 /* Line number */
 231                                                 if (line == 0)
 232                                                         printf("?");
 233                                                 else
 234                                                         printf("%u", line);
 235                                                 printf("]");
 236                                         }
 237                                 }
 238                         }
 239                         putchar('\n');
 240                         if (action == EXIT)
 241                                 profile_func_level -= 1;
 242                 }
 243         }
 244         fflush(stdout);
 245 }
 246
 247 /* vi: set tabstop=4 softtabstop=0 shiftwidth=4 smarttab autoindent : */