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 <sys/types.h>
  18 #include <sys/stat.h>
  19 #include <unistd.h>
  20 #include <bfd.h>
  21
  22 /*
  23  * Generate instrumentation calls for entry and exit to functions.
  24  * Just after function entry and just before function exit, the
  25  * following profiling functions are called with the address of the
  26  * current function and its call site (currently not use).
  27  *
  28  * The attribute 'no_instrument_function' causes this instrumentation is
  29  * not done.
  30  *
  31  * These profiling functions call print_debug(). This function prints the
  32  * current function name with indentation and call level.
  33  * If entering in a function it prints also the calling function name with
  34  * file name and line number.
  35  *
  36  * To configure the printing of only the global functions names:
  37  * $ make instrument_global
  38  *
  39  * To go back to print all the functions names:
  40  * $ make instrument_all
  41  *
  42  * To print nothing, like with no instrumentation:
  43  * $ make instrument_off
  44  */
  45
  46 #define ND_NO_INSTRUMENT __attribute__((no_instrument_function))
  47
  48 /* Store the function call level, used also in pretty_print_packet() */
  49 extern int profile_func_level;
  50 int profile_func_level = -1;
  51
  52 typedef enum {
  53         ENTER,
  54         EXIT
  55 } action_type;
  56
  57 void __cyg_profile_func_enter(void *this_fn, void *call_site) ND_NO_INSTRUMENT;
  58
  59 void __cyg_profile_func_exit(void *this_fn, void *call_site) ND_NO_INSTRUMENT;
  60
  61 static void print_debug(void *this_fn, void *call_site, action_type action)
  62         ND_NO_INSTRUMENT;
  63
  64 void
  65 __cyg_profile_func_enter(void *this_fn, void *call_site)
  66 {
  67         print_debug(this_fn, call_site, ENTER);
  68 }
  69
  70 void
  71 __cyg_profile_func_exit(void *this_fn, void *call_site)
  72 {
  73         print_debug(this_fn, call_site, EXIT);
  74 }
  75
  76 /* If this file exists, print only the global functions */
  77 #define ND_FILE_FLAG_GLOBAL "tcpdump_instrument_functions_global.devel"
  78
  79 /* If this file exists, print nothing, like with no instrumentation */
  80 #define ND_FILE_FLAG_OFF "tcpdump_instrument_functions_off.devel"
  81
  82 static void print_debug(void *this_fn, void *call_site, action_type action)
  83 {
  84         static bfd* abfd;
  85         static asymbol **symtab;
  86         static long symcount;
  87         static asection *text;
  88         static bfd_vma vma;
  89         static int print_only_global;
  90         symbol_info syminfo;
  91         struct stat statbuf;
  92         int i, found;
  93
  94         if (!stat(ND_FILE_FLAG_OFF, &statbuf))
  95                 return;
  96
  97         /* If no errors, this block should be executed one time */
  98         if (!abfd) {
  99                 char pgm_name[1024];
 100                 long symsize;
 101
 102                 if (!stat(ND_FILE_FLAG_GLOBAL, &statbuf))
 103                         print_only_global = 1;
 104
 105                 ssize_t ret = readlink("/proc/self/exe", pgm_name, sizeof(pgm_name));
 106                 if (ret == -1) {
 107                         perror("failed to find executable\n");
 108                         return;
 109                 }
 110                 pgm_name[ret] = 0;
 111
 112                 bfd_init();
 113
 114                 abfd = bfd_openr(pgm_name, NULL);
 115                 if (!abfd) {
 116                         bfd_perror("bfd_openr");
 117                         return;
 118                 }
 119
 120                 if (!bfd_check_format(abfd, bfd_object)) {
 121                         bfd_perror("bfd_check_format");
 122                         return;
 123                 }
 124
 125                 if((symsize = bfd_get_symtab_upper_bound(abfd)) == -1) {
 126                         bfd_perror("bfd_get_symtab_upper_bound");
 127                         return;
 128                 }
 129
 130                 symtab = (asymbol **)malloc(symsize);
 131                 symcount = bfd_canonicalize_symtab(abfd, symtab);
 132                 if (symcount < 0) {
 133                         free (symtab);
 134                         bfd_perror ("bfd_canonicalize_symtab");
 135                         return;
 136                 }
 137
 138                 if ((text = bfd_get_section_by_name(abfd, ".text")) == NULL) {
 139                         bfd_perror("bfd_get_section_by_name");
 140                         return;
 141                 }
 142                 vma = text->vma;
 143         }
 144
 145         if (print_only_global) {
 146                 i = 0;
 147                 found = 0;
 148                 while (i < symcount && !found) {
 149                         bfd_get_symbol_info(abfd, symtab[i], &syminfo);
 150                         if ((void *)syminfo.value == this_fn) {
 151                                 found = 1;
 152                         }
 153                         i++;
 154                 }
 155                 /* type == 'T' for a global function */
 156                 if (found == 1 && syminfo.type != 'T')
 157                         return;
 158         }
 159
 160         /* Current function */
 161         if ((bfd_vma)this_fn < vma) {
 162                 printf("[ERROR address this_fn]");
 163         } else {
 164                 const char *file;
 165                 const char *func;
 166                 unsigned int line;
 167
 168                 if (!bfd_find_nearest_line(abfd, text, symtab, (bfd_vma)this_fn - vma,
 169                                                                    &file, &func, &line)) {
 170                         printf("[ERROR bfd_find_nearest_line this_fn]");
 171                 } else {
 172                         if (action == ENTER)
 173                                 profile_func_level += 1;
 174                         /* Indentation */
 175                         for (i = 0 ; i < profile_func_level ; i++)
 176                                 putchar(' ');
 177                         if (action == ENTER)
 178                                 printf("[>> ");
 179                         else
 180                                 printf("[<< ");
 181                         /* Function name */
 182                         if (func == NULL || *func == '\0')
 183                                 printf("???");
 184                         else
 185                                 printf("%s", func);
 186                         printf(" (%d)", profile_func_level);
 187                         /* Print the "from" part except for the main function) */
 188                         if (action == ENTER && strncmp(func, "main", sizeof("main"))) {
 189                                 /* Calling function */
 190                                 if ((bfd_vma)call_site < vma) {
 191                                         printf("[ERROR address call_site]");
 192                                 } else {
 193                                         if (!bfd_find_nearest_line(abfd, text, symtab,
 194                                                                                            (bfd_vma)call_site - vma, &file,
 195                                                                                            &func, &line)) {
 196                                                 printf("[ERROR bfd_find_nearest_line call_site]");
 197                                         } else {
 198                                                 printf(" from ");
 199                                                 /* Function name */
 200                                                 if (func == NULL || *func == '\0')
 201                                                         printf("???");
 202                                                 else
 203                                                         printf("%s", func);
 204                                                 /* File name */
 205                                                 if (file == NULL || *file == '\0')
 206                                                         printf(" ??:");
 207                                                 else {
 208                                                         char *slashp = strrchr(file, '/');
 209                                                         if (slashp != NULL)
 210                                                                 file = slashp + 1;
 211                                                         printf(" %s:", file);
 212                                                 }
 213                                                 /* Line number */
 214                                                 if (line == 0)
 215                                                         printf("?");
 216                                                 else
 217                                                         printf("%u", line);
 218                                                 printf("]");
 219                                         }
 220                                 }
 221                         }
 222                         putchar('\n');
 223                         if (action == EXIT)
 224                                 profile_func_level -= 1;
 225                 }
 226         }
 227         fflush(stdout);
 228 }
 229
 230 /* vi: set tabstop=4 softtabstop=0 shiftwidth=4 smarttab autoindent : */