From: Philip Prindeville <philipp_subx@redfish-solutions.com>
To: Simon Richter <Simon.Richter@hogyros.de>
Cc: binutils@sourceware.org
Subject: Re: Comparing binaries automatically
Date: Wed, 20 Dec 2017 01:15:00 -0000 [thread overview]
Message-ID: <A9D02ED3-9490-446D-82F8-4B6A7B1351FB@redfish-solutions.com> (raw)
In-Reply-To: <01D91EFE-2DCE-4E48-A22F-B876E2AD3C35@redfish-solutions.com>
[-- Attachment #1: Type: text/plain, Size: 2690 bytes --]
> On Dec 19, 2017, at 12:09 PM, Philip Prindeville <philipp_subx@redfish-solutions.com> wrote:
>
>
>
>> On Dec 19, 2017, at 6:06 AM, Simon Richter <Simon.Richter@hogyros.de> wrote:
>>
>> Hi,
>>
>> On 19.12.2017 05:48, Philip Prindeville wrote:
>>
>>> Anyone know of a way to do a “smart” comparison of executables (or relocatable objections, or shared libraries, or…)?
>>
>> The Debian Reproducible Builds project has a tool called "diffoscope",
>> as well as a few years experience reproducing compilation results, so
>> this may be a good starting point:
>>
>> https://wiki.debian.org/ReproducibleBuilds
>>
>> They don't have a good solution for __DATE__ yet though, unless you
>> consider a compiler flag warning about its use a solution.
>>
>> Simon
>>
>
>
> Yeah, I’ve seen a variety of approaches to the __DATE__/__TIME__/__TIMESTEMP__ problem, including setting SOURCE_DATE_EPOCH to the mtime of the youngest file in the tarball or the timestamp of the most recent git commit, etc. (although squashing/rebasing commits tends to screw up their timestamp in that the code might be changed/updated but the timestamp remains that of the original commit not the rebased once).
>
> No perfect solution.
>
> Will have a look at diffoscope, thanks.
>
>
> -Philip
>
Hi all,
I tried doing the following:
#define __Variant __attribute__((section(“.variant”)))
…
const char __revision[] __Variant = REVISION; /* defined by CPPFLAGS on command-line */
and then substituting out occurrences (there was just one) of REVISION for __revision, and recompiling.
The tried the following steps:
% mips-openwrt-linux-uclibc-objcopy -R .variant dnssec_test dnssec_test.stripped
% mips-openwrt-linux-uclibc-objdump -D dnssec_test > dnssec_test.lst
% mips-openwrt-linux-uclibc-objdump -D dnssec_test.stripped > dnssec_test.stripped.lst
% diff -u dnssec_test.lst dnssec_test.stripped.lstt > dnssec_test.diff
The result is attached.
The differences in the filenames I expected. The missing .variant section was of course the desired effect.
But what I don’t get is why the symbol names for the subsequent addresses (00414010, 0041443c, 00414440, 004144f0, and 0000000) ended up disagreeing.
In the future, when comparing two different compiles, I’ll be deleting the .variant section from both of them, so the offsets should be affected similarly, and there won’t be disagreement.
But here on the same file before and after deletion, there was. It shouldn’t be a problem but it is curious and I’d like to understand it and if possible, find a workaround.
Thanks,
-Philip
[-- Attachment #2: dnssec_test.diff --]
[-- Type: application/octet-stream, Size: 1583 bytes --]
--- dnssec_test.lst 2017-12-19 23:23:10.041489211 +0000
+++ dnssec_test.stripped.lst 2017-12-19 23:23:12.973515877 +0000
@@ -1,5 +1,5 @@
-dnssec_test: file format elf32-tradbigmips
+dnssec_test.stripped: file format elf32-tradbigmips
Disassembly of section .interp:
@@ -4686,18 +4686,6 @@
403ae0: 00403690 0x403690
403ae4: 0040369c 0x40369c
-Disassembly of section .variant:
-
-00403ae8 <.variant>:
- 403ae8: 616e6472 0x616e6472
- 403aec: 6f69642d 0x6f69642d
- 403af0: 32303137 andi s0,s1,0x3137
- 403af4: 2d30392d sltiu s0,t1,14637
- 403af8: 7263322d 0x7263322d
- 403afc: 372d6763 ori t5,t9,0x6763
- 403b00: 64313538 0x64313538
- 403b04: 36350000 ori s5,s1,0x0
-
Disassembly of section .eh_frame:
00403b08 <.eh_frame>:
@@ -4717,7 +4705,7 @@
Disassembly of section .data:
-00414010 <_fdata>:
+00414010 <.data>:
414010: 59000000 blezl t0,414014 <_fdata+0x4>
414014: 46000000 add.s $f0,$f0,$f0
414018: 46000000 add.s $f0,$f0,$f0
@@ -4732,12 +4720,12 @@
Disassembly of section .rld_map:
-0041443c <__RLD_MAP>:
+0041443c <_fdata+0x42c>:
41443c: 00000000 nop
Disassembly of section .got.plt:
-00414440 <.got.plt>:
+00414440 <__RLD_MAP+0x4>:
...
414448: 00400a20 0x400a20
41444c: 00400a20 0x400a20
@@ -4784,12 +4772,12 @@
Disassembly of section .bss:
-004144f0 <stderr>:
+004144f0 <.bss>:
...
Disassembly of section .comment:
-00000000 <.comment>:
+00000000 <stderr-0x4144f0>:
0: 4743433a c1 0x143433a
4: 2028474e addi t0,at,18254
8: 55292033 bnel t1,t1,80d8 <_init-0x3f88e8>
prev parent reply other threads:[~2017-12-20 1:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-19 4:48 Philip Prindeville
2017-12-19 13:06 ` Simon Richter
2017-12-19 19:09 ` Philip Prindeville
2017-12-20 1:15 ` Philip Prindeville [this message]
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