[Bug binutils/970] New: objcopy COFF/Pe-coff -> ELF relocation translations wrong?

[vamiot at ameritege dot com]

Converting COFF objects to ELF with objcopy seems to generate wrong ELF
relocations, introducing a 4-byte offset systematically
$ ld -v
GNU ld version 2.15.94 20041229
(reworked ld/configure.tgt to add extra_emuls
 
i[3-7]86-*-cygwin*)     targ_emul=i386pe ;
                        targ_extra_ofiles="deffilep.o pe-dll.o"
                        targ_extra_emuls="elf_i386 i386coff i386msdos"
)
See example below
 
 
________________________________
# get COFF objects
gcc  -c x.s y.s
# get ELF copies
objcopy x.o x.obj -O elf32-i386
objcopy y.o y.obj -O elf32-i386
# link / locate program
$ ./ld x.obj y.obj -m elf_i386 --oformat elf32-i386 -o z.x -Map z.map
./ld: warning: cannot find entry symbol _start; defaulting to 08048080
 
________________________________
X:
________________________________
.xref y
.globl x
.text
x:
        call y
________________________________
Y:
________________________________
.global y
.text
y:
        ret
________________________________
Relocation is off by 4 bytes!
________________________________
$ ./objdump -rS z.x
 
z.x:     file format elf32-i386
 
Disassembly of section .text:
 
08048080 <x>:
 8048080:       e8 0f 00 00 00          call   8048094 <y+0x4> ; HUUUUUH ????
 8048085:       90                      nop
 8048086:       90                      nop
 8048087:       90                      nop
 8048088:       90                      nop
 8048089:       90                      nop
 804808a:       90                      nop
 804808b:       90                      nop
 804808c:       90                      nop
 804808d:       90                      nop
 804808e:       90                      nop
 804808f:       90                      nop
 
08048090 <y>:
 8048090:       c3                      ret
 
________________________________
$ objdump -rS x.obj
 
x.obj:     file format elf32-i386
 
Disassembly of section .text:
 
00000000 <x>:
   0:   e8 00 00 00 00          call   5 <x+0x5>
                        1: R_386_PC32   y
   5:   90                      nop
________________________________
$ objdump -rS x.o
 
x.o:     file format pe-i386
 
Disassembly of section .text:
 
00000000 <x>:
   0:   e8 00 00 00 00          call   5 <x+0x5>
                        1: DISP32       y
   5:   90                      nop
 
BUT
When linking the original objects NOT ELF-ized 
 
$ objdump -rS x.o
 
x.o:     file format pe-i386
 
Disassembly of section .text:
 
00000000 <x>:
   0:   e8 00 00 00 00          call   5 <x+0x5>
                        1: DISP32       y
   5:   90                      nop
 
$ ./ld x.o y.o -m elf_i386 --oformat elf32-i386 -o z.x -Map z.map
./ld: warning: cannot find entry symbol _start; defaulting to 08048080
 
$ objdump -rS z.x
 
z.x:     file format elf32-i386
 
Disassembly of section .text:
 
08048080 <x>:
 8048080:       e8 0b 00 00 00          call   8048090 <y> ; OK THIS TIME
 8048085:       90                      nop
 8048086:       90                      nop
 8048087:       90                      nop
 8048088:       90                      nop
 8048089:       90                      nop
 804808a:       90                      nop
 804808b:       90                      nop
 804808c:       90                      nop
 804808d:       90                      nop
 804808e:       90                      nop
 804808f:       90                      nop
 
08048090 <y>:
 8048090:       c3                      ret
 8048091:       90                      nop

-- 
           Summary: objcopy COFF/Pe-coff -> ELF relocation translations
                    wrong?
           Product: binutils
           Version: 2.17 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
        AssignedTo: unassigned at sources dot redhat dot com
        ReportedBy: vamiot at ameritege dot com
                CC: bug-binutils at gnu dot org
 GCC build triplet: i686-pc-cygwin
  GCC host triplet: i686-pc-cygwin
GCC target triplet: i686-pc-cygwin


http://sources.redhat.com/bugzilla/show_bug.cgi?id=970

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