问题描述
我们正在努力复制与参考相同的.elf文件。我们几乎在那儿，文件是相同的，但是注释部分的地址相同（其余都是二进制方式100％相同）。
使用readelf -e转储一个.elf文件的方法如下（目标是powerpc，但我认为这并不重要）：
ELF Header:
Magic: 7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement,big endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: PowerPC
Version: 0x1
Entry point address: 0x1800f88
Start of program headers: 52 (bytes into file)
Start of section headers: 1367724 (bytes into file)
Flags: 0x0
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 5
Size of section headers: 40 (bytes)
Number of section headers: 20
Section header string table index: 19
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .interp PROGBITS 018000f4 0000f4 000011 00 A 0 0 1
[ 2] .hash HASH 01800108 000108 000248 04 A 3 0 4
[ 3] .dynsym DYNSYM 01800350 000350 0004d0 10 A 4 1 4
[ 4] .dynstr STRTAB 01800820 000820 000473 00 A 0 0 1
[ 5] .rela.plt RELA 01800c94 000c94 0002dc 0c A 3 16 4
[ 6] .rela.sbss RELA 01800f70 000f70 000018 0c A 3 15 4
[ 7] .text PROGBITS 01800f88 000f88 0e4f78 00 AX 0 0 4
[ 8] .rodata PROGBITS 018e5f00 0e5f00 064708 00 A 0 0 8
[ 9] .sdata2 PROGBITS 0194a608 14a608 000000 00 A 0 0 4
[10] .data PROGBITS 0198a608 14a608 000b5c 00 WA 0 0 8
[11] .dynamic DYNAMIC 0198b164 14b164 000090 08 WA 4 0 4
[12] .got2 PROGBITS 0198b1f4 14b1f4 000024 00 WA 0 0 1
[13] .got PROGBITS 0198b218 14b218 000010 04 WA 0 0 4
[14] .sdata PROGBITS 0198b228 14b228 001814 00 WA 0 0 8
[15] .sbss NOBITS 0198ca40 14ca40 00064c 00 WA 0 0 8
[16] .plt NOBITS 0198d08c 14ca40 000324 00 WAX 0 0 4
[17] .bss NOBITS 0198d3b0 14ca40 223920 00 WA 0 0 16
[18] .comment PROGBITS 0026a8bd 14ca40 0013cb 00 0 0 1
[19] .shstrtab STRTAB 00000000 14de0b 00009e 00 0 0 1
地址为0的部分是有意义的：在加载程序时，这些部分未映射。其他0x18xxxxx值由链接器规范文件指定。
但是为什么注释部分有一个非零的地址（其中包含诸如编译器版本和执行平台之类的详细信息），链中的哪一部分使用了它（调试器？），以及链接程序如何确定放置在何处它吗？
链接描述文件甚至没有提到.comment部分：
OUTPUT_FORMAT("elf32-powerpc","elf32-powerpc","elf32-powerpc")
OUTPUT_ARCH(powerpc)
ENTRY(_start)
SEARCH_DIR(/opt/gnu/powerpc-wrs-vxworks/lib);
/* Do we need any of these for elf?
__DYNAMIC = 0; */
PROVIDE (__stack = 0);
SECTIONS
{
/* Read-only sections,merged into text segment: */
. = 0x01800000 + SIZEOF_HEADERS;
.interp : { *(.interp) }
.hash : { *(.hash) }
.dynsym : { *(.dynsym) }
.dynstr : { *(.dynstr) }
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.rela.text :
{ *(.rela.text) *(.rela.gnu.linkonce.t*) }
.rela.data :
{ *(.rela.data) *(.rela.gnu.linkonce.d*) }
.rela.rodata :
{ *(.rela.rodata) *(.rela.gnu.linkonce.r*) }
.rela.got : { *(.rela.got) }
.rela.got1 : { *(.rela.got1) }
.rela.got2 : { *(.rela.got2) }
.rela.ctors : { *(.rela.ctors) }
.rela.dtors : { *(.rela.dtors) }
.rela.init : { *(.rela.init) }
.rela.fini : { *(.rela.fini) }
.rela.bss : { *(.rela.bss) }
.rela.plt : { *(.rela.plt) }
.rela.sdata : { *(.rela.sdata) }
.rela.sbss : { *(.rela.sbss) }
.rela.sdata2 : { *(.rela.sdata2) }
.rela.sbss2 : { *(.rela.sbss2) }
.text :
{
*(.text)
/* .gnu.warning sections are handled specially by elf32.em. */
*(.gnu.warning)
*(.gnu.linkonce.t*)
} =0
.init : { *(.init) } =0
.fini : { *(.fini) } =0
.rodata : { *(.rodata) *(.gnu.linkonce.r*) }
.rodata1 : { *(.rodata1) }
_etext = .;
PROVIDE (etext = .);
.sdata2 : { *(.sdata2) }
.sbss2 : { *(.sbss2) }
/* Adjust the address for the data segment. We want to adjust up to
the same address within the page on the next page up. It would
be more correct to do this:
. = ALIGN(0x40000) + (ALIGN(8) & (0x40000 - 1));
The current expression does not correctly handle the case of a
text segment ending precisely at the end of a page; it causes the
data segment to skip a page. The above expression does not have
this problem,but it will currently (2/95) cause BFD to allocate
a single segment,combining both text and data,for this case.
This will prevent the text segment from being shared among
multiple executions of the program; I think that is more
important than losing a page of the virtual address space (note
that no actual memory is lost; the page which is skipped can not
be referenced). */
. = ALIGN(8) + 0x40000;
.data :
{
*(.data)
*(.gnu.linkonce.d*)
CONSTRUCTORS
}
.data1 : { *(.data1) }
.got1 : { *(.got1) }
.dynamic : { *(.dynamic) }
/* Put .ctors and .dtors next to the .got2 section,so that the pointers
get relocated with -mrelocatable. Also put in the .fixup pointers.
The current compiler no longer needs this,but keep it around for 2.7.2 */
PROVIDE (_GOT2_START_ = .);
.got2 : { *(.got2) }
PROVIDE (__CTOR_LIST__ = .);
.ctors : { *(.ctors) }
PROVIDE (__CTOR_END__ = .);
PROVIDE (__DTOR_LIST__ = .);
.dtors : { *(.dtors) }
PROVIDE (__DTOR_END__ = .);
PROVIDE (_FIXUP_START_ = .);
.fixup : { *(.fixup) }
PROVIDE (_FIXUP_END_ = .);
PROVIDE (_GOT2_END_ = .);
PROVIDE (_GOT_START_ = .);
.got : { *(.got) }
.got.plt : { *(.got.plt) }
PROVIDE (_GOT_END_ = .);
/* We want the small data sections together,so single-instruction offsets
can access them all,and initialized data all before uninitialized,so
we can shorten the on-disk segment size. */
.sdata : { *(.sdata) }
_edata = .;
PROVIDE (edata = .);
.sbss :
{
PROVIDE (__sbss_start = .);
*(.sbss)
*(.scommon)
*(.dynsbss)
PROVIDE (__sbss_end = .);
}
.plt : { *(.plt) }
.bss :
{
PROVIDE (__bss_start = .);
*(.dynbss)
*(.bss)
*(COMMON)
}
_end = . ;
PROVIDE (end = .);
/* These are needed for ELF backends which have not yet been
converted to the new style linker. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
/* DWARF debug sections.
Symbols in the DWARF debugging sections are relative to the beginning
of the section so we begin them at 0. */
/* DWARF 1 */
.debug 0 : { *(.debug) }
.line 0 : { *(.line) }
/* GNU DWARF 1 extensions */
.debug_srcinfo 0 : { *(.debug_srcinfo) }
.debug_sfnames 0 : { *(.debug_sfnames) }
/* DWARF 1.1 and DWARF 2 */
.debug_aranges 0 : { *(.debug_aranges) }
.debug_pubnames 0 : { *(.debug_pubnames) }
/* DWARF 2 */
.debug_info 0 : { *(.debug_info) }
.debug_abbrev 0 : { *(.debug_abbrev) }
.debug_line 0 : { *(.debug_line) }
.debug_frame 0 : { *(.debug_frame) }
.debug_str 0 : { *(.debug_str) }
.debug_loc 0 : { *(.debug_loc) }
.debug_macinfo 0 : { *(.debug_macinfo) }
/* SGI/MIPS DWARF 2 extensions */
.debug_weaknames 0 : { *(.debug_weaknames) }
.debug_funcnames 0 : { *(.debug_funcnames) }
.debug_typenames 0 : { *(.debug_typenames) }
.debug_varnames 0 : { *(.debug_varnames) }
/* These must appear regardless of . */
}
链接器版本也很旧（是的，我知道...）：
GNU ld 2.9.1
Copyright 1997 Free Software Foundation,Inc.
解决方法
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