On Mon, Jan 18, 2016 at 07:06:14PM +0100, Jérémy Bobbio wrote:
> Hi Mike!
>
> Mike Hommey:
> > When comparing large ELF binaries, some minor differences can end up hurting
> > the visibility of more important differences.
> >
> > Specifically, objdump --disassemble displays symbols+offsets for addresses
> > it derives from IP-relative addressing, like the following:
> >
> > 9d2be2: 48 8d 05 42 65 24 02 lea 0x2246542(%rip),%rax #
> > 2c1912b <_fini@@xul45a1+0x1d803>
>
> I would be grateful if you could try again using the master branch.
> Dhole made diffoscope compare ELF sections individually and I wonder how
> much it helped with this problem.
I don't think it changed anything.
> If it doesn't, would you be so kind to provide example binaries?
I can't find the differing binary anymore :( But that can be reproduced
with a small testcase:
$ cat <<EOF > test.c
extern const int qux;
int bar() {
#ifdef FOO
return qux * 2;
#else
return qux;
#endif
}
EOF
$ cat <<EOF > test2.c
const int qux = 2;
EOF
$ gcc -shared -o /tmp/test.so /tmp/test{,2}.c -fPIC
$ gcc -shared -o /tmp/test2.so /tmp/test{,2}.c -fPIC -DFOO
$ strip test{,2}.so
$ diffoscope --text - /tmp/test*.so
(...)
│ @@ -29,56 +29,57 @@
│ 5a2: 48 89 e5 mov %rsp,%rbp
│ 5a5: 48 c1 fe 03 sar $0x3,%rsi
│ 5a9: 48 89 f0 mov %rsi,%rax
│ 5ac: 48 c1 e8 3f shr $0x3f,%rax
│ 5b0: 48 01 c6 add %rax,%rsi
│ 5b3: 48 d1 fe sar %rsi
│ 5b6: 74 18 je 5d0 <_init@@Base+0xc8>
│ - 5b8: 48 8b 05 01 03 20 00 mov 0x200301(%rip),%rax #
2008c0 <qux@@Base+0x200254>
│ + 5b8: 48 8b 05 01 03 20 00 mov 0x200301(%rip),%rax #
2008c0 <qux@@Base+0x200250>
│ 5bf: 48 85 c0 test %rax,%rax
│ 5c2: 74 0c je 5d0 <_init@@Base+0xc8>
│ 5c4: 5d pop %rbp
│ 5c5: ff e0 jmpq *%rax
│ 5c7: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
│ 5ce: 00 00
│ 5d0: 5d pop %rbp
│ 5d1: c3 retq
│ 5d2: 0f 1f 40 00 nopl 0x0(%rax)
│ 5d6: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
│ 5dd: 00 00 00
│ 5e0: 80 3d 09 03 20 00 00 cmpb $0x0,0x200309(%rip) #
2008f0 <_edata@@Base>
│ 5e7: 75 27 jne 610 <_init@@Base+0x108>
│ - 5e9: 48 83 3d d7 02 20 00 cmpq $0x0,0x2002d7(%rip) #
2008c8 <qux@@Base+0x20025c>
│ + 5e9: 48 83 3d d7 02 20 00 cmpq $0x0,0x2002d7(%rip) #
2008c8 <qux@@Base+0x200258>
│ 5f0: 00
│ 5f1: 55 push %rbp
│ 5f2: 48 89 e5 mov %rsp,%rbp
│ 5f5: 74 0c je 603 <_init@@Base+0xfb>
│ - 5f7: 48 8b 3d ea 02 20 00 mov 0x2002ea(%rip),%rdi #
2008e8 <qux@@Base+0x20027c>
│ + 5f7: 48 8b 3d ea 02 20 00 mov 0x2002ea(%rip),%rdi #
2008e8 <qux@@Base+0x200278>
│ 5fe: e8 45 ff ff ff callq 548 <_init@@Base+0x40>
│ 603: e8 48 ff ff ff callq 550 <_init@@Base+0x48>
│ 608: 5d pop %rbp
│ 609: c6 05 e0 02 20 00 01 movb $0x1,0x2002e0(%rip) #
2008f0 <_edata@@Base>
│ 610: f3 c3 repz retq
│ 612: 0f 1f 40 00 nopl 0x0(%rax)
│ 616: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
│ 61d: 00 00 00
│ - 620: 48 8d 3d e1 00 20 00 lea 0x2000e1(%rip),%rdi #
200708 <qux@@Base+0x20009c>
│ + 620: 48 8d 3d e1 00 20 00 lea 0x2000e1(%rip),%rdi #
200708 <qux@@Base+0x200098>
│ 627: 48 83 3f 00 cmpq $0x0,(%rdi)
│ 62b: 75 0b jne 638 <_init@@Base+0x130>
│ 62d: e9 5e ff ff ff jmpq 590 <_init@@Base+0x88>
│ 632: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
│ - 638: 48 8b 05 79 02 20 00 mov 0x200279(%rip),%rax #
2008b8 <qux@@Base+0x20024c>
│ + 638: 48 8b 05 79 02 20 00 mov 0x200279(%rip),%rax #
2008b8 <qux@@Base+0x200248>
│ 63f: 48 85 c0 test %rax,%rax
│ 642: 74 e9 je 62d <_init@@Base+0x125>
│ 644: 55 push %rbp
│ 645: 48 89 e5 mov %rsp,%rbp
│ 648: ff d0 callq *%rax
│ 64a: 5d pop %rbp
│ 64b: e9 40 ff ff ff jmpq 590 <_init@@Base+0x88>
│
│ 0000000000000650 <bar@@Base>:
│ 650: 55 push %rbp
│ 651: 48 89 e5 mov %rsp,%rbp
│ - 654: 48 8b 05 4d 02 20 00 mov 0x20024d(%rip),%rax #
2008a8 <qux@@Base+0x20023c>
│ + 654: 48 8b 05 4d 02 20 00 mov 0x20024d(%rip),%rax #
2008a8 <qux@@Base+0x200238>
│ 65b: 8b 00 mov (%rax),%eax
│ - 65d: 5d pop %rbp
│ - 65e: c3 retq
│ + 65d: 01 c0 add %eax,%eax
│ + 65f: 5d pop %rbp
│ + 660: c3 retq
╵
Mike
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