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file: elf_copy.c


  1 /*
  2 * Copy an elf to an ELF object.
  3 * This is a demo program for libraries libelf and gelf. The resulting elf file
  4 * may not be loadable due to offset changes.
  5 * 2007.11.10 19:52:23 Emmanuel AZENCOT
  6 *   Creation
  7 * Sun Nov 22 20:33:20 CET 2009
  8 *   bug fix in error message \%s\"
  9 *
 10 * build : gcc -Wall -g -o elf_copy -lelf elf_copy.c
 11 * TODO
 12 *  output a working binary
 13 */

 14 #include <string.h>
 15 #include <stdio.h>
 16 #include <stdlib.h>
 17 #include <sysexits.h>
 18 #include <unistd.h>
 19 #include <fcntl.h>
 20 #include <errno.h>
 21
 22 #include <err.h>
 23 #include <gelf.h>
 24
 25 #define /*X*/ errx(code, fmt, args...) { \
 26   fprintf(stderr,#code ": error in file %s at line %d in function %s:", __FILE__,__LINE__,__FUNCTION__); \
 27   fprintf(stderr,fmt "\n", ##args); \
 28   exit(1); \
 29 }

 30 #define /*X*/ merrx(code, fmt, args...) { \
 31   fprintf(stderr,#code ": error in file %s at line %d in function %s:", __FILE__,__LINE__,__FUNCTION__); \
 32   fprintf(stderr,fmt "\n", ##args); \
 33   return 0; \
 34 }

 35
 36 int /*X*/ melf_cpy_scn (Elf *elf_out, Elf_Scn  *scn_out, Elf *elf_in, Elf_Scn *scn_in) {
 37   Elf_Data *data_in, *data_out;
 38   GElf_Shdr shdr_in, shdr_out;
 39   size_t n;
 40
 41   if (gelf_getshdr(scn_in, &shdr_in) != &shdr_in)
 42      merrx(EX_SOFTWARE, "getshdr() failed: %s.", elf_errmsg(-1));
 43
 44   data_in = NULL; n = 0;
 45   while (n < shdr_in.sh_size && (data_in = elf_getdata(scn_in, data_in)) != NULL) {
 46      if ((data_out = elf_newdata(scn_out)) == NULL)
 47         merrx(EX_SOFTWARE, "elf_newdata() failed: %s.", elf_errmsg(-1));
 48      *data_out = *data_in;
 49   }
 50
 51   if ( gelf_getshdr(scn_out, &shdr_out) != &shdr_out)
 52      merrx(EX_SOFTWARE, "gelf_getshdr() failed: %s.", elf_errmsg(-1));
 53
 54   shdr_out = shdr_in;
 55
 56   if ( gelf_update_shdr (scn_out, &shdr_out) == 0)
 57      merrx(EX_SOFTWARE, "gelf_update_shdr() failed: %s.", elf_errmsg(-1));
 58
 59   return 1;
 60 }
 61 int /*X*/ main(int argc, char *argv[]) {
 62   int fd_in = -1, fd_out = -1;
 63   Elf *elf_in = 0, *elf_out = 0;
 64
 65   Elf_Scn *scn_in, *scn_out;
 66   GElf_Ehdr ehdr_in, ehdr_out;
 67
 68   size_t shstrndx;
 69
 70   int scn_index = 0;
 71
 72   if (argc != 3)
 73      errx(EX_USAGE, "USAGE: %s in-file-name out-file-name", argv[0]);
 74
 75   if (elf_version(EV_CURRENT) == EV_NONE)
 76      errx(EX_SOFTWARE, "ELF library initialization failed: %s", elf_errmsg(-1));
 77
 78   if ((fd_in = open(argv[1], O_RDONLY, 0)) < 0)
 79      err(EX_NOINPUT, "open \"%s\" failed", argv[1]);
 80
 81   if ((elf_in = elf_begin(fd_in, ELF_C_READ, NULL)) == NULL)
 82      errx(EX_SOFTWARE, "elf_begin() failed: %s.", elf_errmsg(-1));
 83
 84   if (gelf_getehdr(elf_in, &ehdr_in) != &ehdr_in)
 85      errx(EX_SOFTWARE, "gelf_getehdr() failed: %s.", elf_errmsg(-1));
 86
 87   /* get string section index for section names */
 88   if (elf_getshstrndx(elf_in, &shstrndx) != 0)
 89       errx(EX_SOFTWARE, "getshstrndx() failed: %s, %d.", elf_errmsg(-1), shstrndx);
 90
 91   /* Checks and warns */
 92   if ( elf_kind(elf_in) != ELF_K_ELF ) {
 93      fprintf(stderr, "%s : %s must be an ELF file.\n", argv[0], argv[1]);
 94      exit(1);
 95   }
 96
 97   printf("Elf %s have %d sections\n", argv[1], ehdr_in.e_shnum);
 98   /* opent output elf */
 99   if ((fd_out = open(argv[2], O_WRONLY|O_CREAT, 0777)) < 0)
100      errx(EX_OSERR, "open \"%s\" failed", argv[2]);
101
102   if ((elf_out = elf_begin(fd_out, ELF_C_WRITE, NULL)) == NULL)
103      errx(EX_SOFTWARE, "elf_begin() failed: %s.", elf_errmsg(-1));
104
105   /* create new elf header */
106   if ( gelf_newehdr(elf_out, ehdr_in.e_ident[EI_CLASS]) == 0)
107      errx(EX_SOFTWARE, "gelf_newehdr() failed: %s.", elf_errmsg(-1));
108   if ( gelf_getehdr(elf_out, &ehdr_out) != &ehdr_out)
109      errx(EX_SOFTWARE, "gelf_getehdr() failed: %s.", elf_errmsg(-1));
110   ehdr_out = ehdr_in;
111   ehdr_out.e_ehsize = 0;
112   ehdr_out.e_phentsize = 0;
113   ehdr_out.e_phnum = 0;
114   ehdr_out.e_shentsize = 0;
115   ehdr_out.e_shnum = 0;
116   if ( gelf_update_ehdr (elf_out, &ehdr_out) == 0)
117      errx(EX_SOFTWARE, "gelf_update_ehdr() failed: %s.", elf_errmsg(-1));
118
119   {
120      GElf_Phdr phdr_in, phdr_out;
121      int ph_ndx;
122
123      if ( ehdr_in.e_phnum && gelf_newphdr (elf_out, ehdr_in.e_phnum) == 0 )
124         errx(EX_SOFTWARE, "gelf_newphdr() failed: %s.", elf_errmsg(-1));
125
126      for ( ph_ndx = 0; ph_ndx < ehdr_in.e_phnum; ++ph_ndx ) {
127         printf("Copying prog header %d\n", ph_ndx);
128
129         if ( gelf_getphdr (elf_in, ph_ndx, &phdr_in) != &phdr_in )
130            errx(EX_SOFTWARE, "gelf_getphdr() failed: %s.", elf_errmsg(-1));
131
132         if ( gelf_getphdr (elf_out, ph_ndx, &phdr_out) != &phdr_out )
133            errx(EX_SOFTWARE, "gelf_getphdr() failed: %s.", elf_errmsg(-1));
134         phdr_out = phdr_in;
135
136         if ( gelf_update_phdr (elf_out, ph_ndx, &phdr_out) == 0)
137            errx(EX_SOFTWARE, "gelf_update_phdr() failed: %s.", elf_errmsg(-1));
138      }
139   }
140   /* copy sections to new elf */
141   for ( scn_index = 1; scn_index < ehdr_in.e_shnum; scn_index++ ) {
142      if ( (scn_in = elf_getscn(elf_in, scn_index)) == NULL)
143         errx(EX_SOFTWARE, "getshdr() failed: %s.", elf_errmsg(-1));
144      if ((scn_out = elf_newscn(elf_out)) == NULL)
145         errx(EX_SOFTWARE, "elf_newscn() failed: %s.", elf_errmsg(-1));
146      if ( melf_cpy_scn (elf_out, scn_out, elf_in, scn_in) == 0 )
147         errx(EX_SOFTWARE, "melf_cpy_scn() failed: %s.", elf_errmsg(-1));
148   }
149   /* Adjust section offset in Phrs */
150   {
151      GElf_Phdr phdr_in, phdr_out;
152      int ph_ndx;
153
154      if ( ehdr_in.e_phnum && gelf_newphdr (elf_out, ehdr_in.e_phnum) == 0 )
155         errx(EX_SOFTWARE, "gelf_newphdr() failed: %s.", elf_errmsg(-1));
156
157      for ( ph_ndx = 0; ph_ndx < ehdr_in.e_phnum; ++ph_ndx ) {
158         GElf_Shdr shdr_out;
159         if ( gelf_getphdr (elf_in, ph_ndx, &phdr_in) != &phdr_in )
160            errx(EX_SOFTWARE, "gelf_getphdr() failed: %s.", elf_errmsg(-1));
161
162         if ( gelf_getphdr (elf_out, ph_ndx, &phdr_out) != &phdr_out )
163            errx(EX_SOFTWARE, "gelf_getphdr() failed: %s.", elf_errmsg(-1));
164
165         if ( !phdr_in.p_offset || phdr_in.p_type == PT_PHDR ) continue;
166         /* Get section offset from input phdr */
167         if ( (scn_in = gelf_offscn (elf_in, phdr_in.p_offset )) == NULL)
168            errx(EX_SOFTWARE, "gelf_offscn() failed: %s.", elf_errmsg(-1));
169         /* Convert to section index */
170         if ( (scn_index = elf_ndxscn (scn_in)) == 0)
171            fprintf(stderr, "elf_ndxscn() failed for phdr %d : %s.", ph_ndx, elf_errmsg(-1));
172         /* get out section at same index from out elf */
173         if ( (scn_out   = elf_getscn(elf_out, scn_index)) == NULL)
174            errx(EX_SOFTWARE, "getshdr() failed: %s.", elf_errmsg(-1));
175         /* get out section offset from section header */
176         if ( gelf_getshdr(scn_out, &shdr_out) != &shdr_out)
177            merrx(EX_SOFTWARE, "gelf_getshdr() failed: %s.", elf_errmsg(-1));
178
179         phdr_out.p_offset = shdr_out.sh_offset;
180
181         if ( gelf_update_phdr (elf_out, ph_ndx, &phdr_out) == 0)
182            errx(EX_SOFTWARE, "gelf_update_phdr() failed: %s.", elf_errmsg(-1));
183      }
184   }
185   if (elf_update(elf_out, ELF_C_WRITE) < 0)
186      errx(EX_SOFTWARE, "elf_update() failed: %s.", elf_errmsg(-1));
187
188   elf_end(elf_out);
189   close(fd_out);
190   elf_end(elf_in);
191   close(fd_in);
192
193   exit(EX_OK);
194 }
195


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Hosted by the courtesy of  
http://www.webou.net/communaute/Themes/dilbermc/images/lightblue/logo.jpg 
The stars ASAP english francais spanish
Durée du voyage intersidéral francais
Résolutions de l'ONU en HTML francais
Bussard Ramjet english francais
DWARF : dwarf2xml english
ELF : libelf examples english
Code presentation : ctoohtml english