libinterfork/interfork.c

   1 /* Copyright (C) 2009  Pierre-Marc Fournier
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <dlfcn.h>
  20 #include <unistd.h>
  21 #include <stdio.h>
  22 #include <signal.h>
  23 #include "usterr.h"
  24
  25 extern void ust_fork(void);
  26 extern void ust_potential_exec(void);
  27
  28 pid_t fork(void)
  29 {
  30         static pid_t (*plibc_func)(void) = NULL;
  31
  32         pid_t retval;
  33
  34         int result;
  35         sigset_t all_sigs;
  36         sigset_t orig_sigs;
  37
  38         if(plibc_func == NULL) {
  39                 plibc_func = dlsym(RTLD_NEXT, "fork");
  40                 if(plibc_func == NULL) {
  41                         fprintf(stderr, "libcwrap: unable to find fork\n");
  42                         return -1;
  43                 }
  44         }
  45
  46         /* Disable interrupts. This is to avoid that the child
  47          * intervenes before it is properly setup for tracing. It is
  48          * safer to disable all signals, because then we know we are not
  49          * breaking anything by restoring the original mask.
  50          */
  51
  52         /* FIXME:
  53                 - only do this if tracing is active
  54         */
  55
  56         /* Disable signals */
  57         sigfillset(&all_sigs);
  58         result = sigprocmask(SIG_BLOCK, &all_sigs, &orig_sigs);
  59         if(result == -1) {
  60                 PERROR("sigprocmask");
  61                 return -1;
  62         }
  63
  64         /* Do the real fork */
  65         retval = plibc_func();
  66
  67         if(retval == 0) {
  68                 /* child */
  69                 ust_fork();
  70         }
  71
  72         /* Restore signals */
  73         result = sigprocmask(SIG_BLOCK, &orig_sigs, NULL);
  74         if(result == -1) {
  75                 PERROR("sigprocmask");
  76                 return -1;
  77         }
  78
  79         return retval;
  80 }
  81
  82 int execve(const char *filename, char *const argv[], char *const envp[])
  83 {
  84         static int (*plibc_func)(const char *filename, char *const argv[], char *const envp[]) = NULL;
  85
  86         pid_t retval;
  87
  88         if(plibc_func == NULL) {
  89                 plibc_func = dlsym(RTLD_NEXT, "execve");
  90                 if(plibc_func == NULL) {
  91                         fprintf(stderr, "libcwrap: unable to find execve\n");
  92                         return -1;
  93                 }
  94         }
  95
  96         ust_potential_exec();
  97
  98         retval = plibc_func(filename, argv, envp);
  99
 100         return retval;
 101 }