[Bug 216316] objcopy (elfcopy) in 11 appears to have a regression compared to the version in 10

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216316

Mitchell horne <mhorne063 at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |mhorne063 at gmail.com

--- Comment #3 from Mitchell horne <mhorne063 at gmail.com> ---
(In reply to pete from comment #2)

Here's the readelf section information on the file you provided:

$ readelf --sections ipxe.pxe.tmp

File: ipxe.pxe.tmp
There are 20 section headers, starting at offset 0x702650:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf
Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0 
0
  [ 1] .prefix           PROGBITS        00000000 000134 000cb1 00 WAX  0   0 
1
  [ 2] .text16.early     PROGBITS        00000000 000df0 0000ee 00 WAX  0   0 
2
  [ 3] .text16.late      PROGBITS        000000f0 000ee0 0007f2 00 WAX  0   0
16
  [ 4] .data16           PROGBITS        00000000 0016e0 000150 00  WA  0   0
16
  [ 5] .bss.data16       NOBITS          00000150 0cb780 003040 00  WA  0   0
16
  [ 6] .textdata         PROGBITS        00000000 001830 0c9ec8 00 WAX  0   0 
4
  [ 7] .bss.textdata     NOBITS          000c9f00 0cb780 0a5580 00  WA  0   0
128
  [ 8] .zinfo            PROGBITS        00000000 0cb6f8 000080 00   A  0   0 
1
  [ 9] .debug_info       PROGBITS        00000000 0cb778 398f31 00      0   0 
1
  [10] .debug_abbrev     PROGBITS        00000000 4646a9 054828 00      0   0 
1
  [11] .debug_aranges    PROGBITS        00000000 4b8ed1 008e50 00      0   0 
1
  [12] .debug_line       PROGBITS        00000000 4c1d21 059425 00      0   0 
1
  [13] .debug_str        PROGBITS        00000000 51b146 05a0b9 01  MS  0   0 
1
  [14] .debug_frame      PROGBITS        00000000 575200 02ec7c 00      0   0 
4
  [15] .debug_loc        PROGBITS        00000000 5a3e7c 15183d 00      0   0 
1
  [16] .debug_ranges     PROGBITS        00000000 6f56b9 00ced0 00      0   0 
1
  [17] .shstrtab         STRTAB          00000000 702589 0000c5 00      0   0 
1
  [18] .symtab           SYMTAB          00000000 702970 01af40 10     19 4079 
4
  [19] .strtab           STRTAB          00000000 71d8b0 01ebe8 00      0   0 
1

It appears that .bss.data16 and .bss.textdata overlap with .debug_info and this
is causing
them to be moved. According to the ELF specification, "Sections in a file may
not overlap.  
No byte in a file resides in more than one section" [1]. So whatever program is
generating
your ELF file is doing so incorrectly. Although GNU objcopy is able to ignore
this when
generating a binary file, it will adjust the section offsets similar to
elftoolchain objcopy
when performing other operations (e.g. objcopy -R .zinfo ipxe.pxe.tmp).

However, I'm not sure why this would be causing you problems either way. When
converting an
ELF file to binary, sections with NOBITS type are ignored since they take up no
actual space
in the file itself. This is the case regardless of which implementation of
objcopy you use. 
Perhaps elftoolchain has a different bug in the binary creation procedure, but
to find that 
you would need to provide additional info on how the binary output file is
unusable.

The simplest workaround (if you still need it at this point) is to use the GNU
version of
objcopy provided in the binutils package.

[1] http://www.skyfree.org/linux/references/ELF_Format.pdf

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