pdns/binpatch.cc

   1 /*
   2     PowerDNS Versatile Database Driven Nameserver
   3     Copyright (C) 2002  PowerDNS.COM BV
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License
  16     along with this program; if not, write to the Free Software
  17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 */
  19 #include <iostream>
  20 #include <cstdio>
  21 #include <cstring>
  22 #include <cstdlib>
  23 #include <unistd.h>
  24 #include <errno.h>
  25 #include <climits>
  26 #include <string>
  27 #include <map>
  28 #include <sys/mman.h>
  29 #include <fcntl.h>
  30 #include <sys/types.h>
  31
  32 #include <sys/stat.h>
  33
  34
  35 using namespace std;
  36
  37 static void imbue(char *pname, const char *search, const string &replace);
  38 static string stringerror();
  39 static off_t filesize(int fd);
  40
  41 int main(int argc, char **argv)
  42 {
  43   if(argc!=3) {
  44     cerr<<"Syntax: binpatch binary configuration-directory"<<endl;
  45     exit(0);
  46   }
  47
  48   imbue(argv[1],"!@@SYSCONFDIR@@:",argv[2]);
  49 }
  50
  51 static void imbue(char *pname, const char *search, const string &replace)
  52 {
  53   int fd=open(pname, O_RDWR);
  54   if(fd<0) {
  55     cerr<<"Unable to open executable read/write for imbuing: "<<stringerror()<<endl;
  56     exit(1);
  57   }
  58   int fs=filesize(fd);
  59   void *ptr=mmap(0,fs,PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  60   if(ptr==(caddr_t)-1) {
  61     cerr<<"Unable to mmap executable read/write for imbuing: "<<stringerror()<<endl;
  62     exit(1);
  63   }
  64
  65   char *p=(char *)ptr;
  66   char *end=p+fs;
  67   for(;p<end;++p)
  68     if(*p==*search && *(p+1)==*(search+1) && !memcmp(p,search,strlen(search)))
  69       break;
  70
  71   if(p==end) {
  72     cerr<<"Cannot find marker in binary, not imbueing"<<endl;
  73     exit(1);
  74   }
  75   strcpy(p+strlen(search),replace.c_str());
  76   munmap(ptr,filesize(fd));
  77   close(fd);
  78   cerr<<"Imbued configuration location '"<<replace<<"'"<<endl;
  79   return;
  80 }
  81
  82 static off_t filesize(int fd)
  83 {
  84   struct stat buf;
  85   fstat(fd, &buf);
  86   return buf.st_size;
  87 }
  88 static string stringerror()
  89 {
  90   return strerror(errno);
  91 }