好吧...抱歉耽搁了,但我不得不考虑一下...
我不确定您是否可以仅使用链接器脚本[完全]完成此操作。它might有可能,但我认为有一种更简单/更可靠的方法[需要一些额外的准备]
我以前使用过的一种方法是编译-S
得到一个.s
文件。改变/破坏它。然后,编译修改后的.s
请注意,您可能会遇到一些全局问题,例如:
int B;
这将转到一个.comm
asm 源代码中的部分。这可能并不理想。
对于初始化数据:
int B = 23;
您可能需要添加一个部分属性以将其强制到一个特殊部分。否则,它最终会变成一个.data
section
所以,我可能会避免.comm
and/or .bss
有利于的部分always使用初始化数据。那是因为.comm
有同样的问题.rodata
(即它最终成为一大团)。
无论如何,下面是一个逐步的过程。
我将部分名称宏放在一个公共文件中(例如)sctname.h
:
#define _SCTJOIN(_pre,_sct) _pre #_sct
#define _TXTSCT(_sct) __attribute__((section(_SCTJOIN(".txt",_sct))))
#define _DATSCT(_sct) __attribute__((section(_SCTJOIN(".dat",_sct))))
#ifdef SCTNO
#define TXTSCT _TXTSCT(SCTNO)
#define DATSCT _DATSCT(SCTNO)
#endif
这是您的稍作修改的版本.c
文件(例如module.c
):
#include <stdio.h>
#ifndef SCTNO
#define SCTNO 152
#endif
#include "sctname.h"
int B DATSCT = 23;
TXTSCT void
TestFunc(int A)
{
printf("%d Squared Is: %d\r\n", A, A * A * B);
}
要创建.s
文件,我们做:
cc -S -Wall -Werror -O2 module.c
实际的部分名称/编号可以在命令行上指定:
cc -S -Wall -Werror -O2 -DSCTNO=152 module.c
这给了我们一个module.s
:
.file "module.c"
.text
.section .rodata.str1.1,"aMS",@progbits,1
.LC0:
.string "%d Squared Is: %d\r\n"
.section .txt152,"ax",@progbits
.p2align 4,,15
.globl TestFunc
.type TestFunc, @function
TestFunc:
.LFB11:
.cfi_startproc
movl %edi, %edx
movl %edi, %esi
xorl %eax, %eax
imull %edi, %edx
movl $.LC0, %edi
imull B(%rip), %edx
jmp printf
.cfi_endproc
.LFE11:
.size TestFunc, .-TestFunc
.globl B
.section .dat152,"aw"
.align 4
.type B, @object
.size B, 4
B:
.long 23
.ident "GCC: (GNU) 8.3.1 20190223 (Red Hat 8.3.1-2)"
.section .note.GNU-stack,"",@progbits
现在,我们必须阅读.s
并修改它。我创建了一个 perl 脚本来执行此操作(例如rofix
):
#!/usr/bin/perl
master(@ARGV);
exit(0);
sub master
{
my(@argv) = @_;
$root = shift(@argv);
$root =~ s/[.][^.]+$//;
$sfile = "$root.s";
$ofile = "$root.TMP";
open($xfsrc,"<$sfile") or
die("rofix: unable to open '$sfile' -- $!\n");
open($xfdst,">$ofile") or
die("rofix: unable to open '$sfile' -- $!\n");
$txtpre = "^[.]txt";
$datpre = "^[.]dat";
# find the text and data sections
seek($xfsrc,0,0);
while ($bf = <$xfsrc>) {
chomp($bf);
if ($bf =~ /^\s*[.]section\s(\S+)/) {
$sctcur = $1;
sctget($txtpre);
sctget($datpre);
}
}
# modify the data sections
seek($xfsrc,0,0);
while ($bf = <$xfsrc>) {
chomp($bf);
if ($bf =~ /^\s*[.]section\s(\S+)/) {
$sctcur = $1;
sctfix();
print($xfdst $bf,"\n");
next;
}
print($xfdst $bf,"\n");
}
close($xfsrc);
close($xfdst);
system("diff -u $sfile $ofile");
rename($ofile,$sfile) or
die("rofix: unable to rename '$ofile' to '$sfile' -- $!\n");
}
sub sctget
{
my($pre) = @_;
my($sctname,@sct);
{
last unless (defined($pre));
@sct = split(",",$sctcur);
$sctname = shift(@sct);
last unless ($sctname =~ /$pre/);
printf("sctget: FOUND %s\n",$sctname);
$sct_lookup{$pre} = $sctname;
}
}
sub sctfix
{
my($sctname,@sct);
my($sctnew);
{
last unless ($sctcur =~ /^[.]rodata/);
$sctnew = $sct_lookup{$txtpre};
last unless (defined($sctnew));
@sct = split(",",$sctcur);
$sctname = shift(@sct);
$sctname .= $sctnew;
unshift(@sct,$sctname);
$sctname = join(",",@sct);
$bf = sprintf("\t.section\t%s",$sctname);
}
}
新旧的区别module.s
is:
sctget: FOUND .txt152
sctget: FOUND .dat152
--- module.s 2020-04-20 19:02:23.777302484 -0400
+++ module.TMP 2020-04-20 19:06:33.631926065 -0400
@@ -1,6 +1,6 @@
.file "module.c"
.text
- .section .rodata.str1.1,"aMS",@progbits,1
+ .section .rodata.txt152,"aMS",@progbits,1
.LC0:
.string "%d Squared Is: %d\r\n"
.section .txt152,"ax",@progbits
所以,现在,创建.o
with:
cc -c module.s
对于 makefile,它可能类似于[带有一些通配符]:
module.o: module.c
cc -S -Wall -Werror -O2 module.c
./rofix module.s
cc -c module.s
现在,您可以在链接器脚本中为[您的原始部分]添加适当的位置.txt152
和新的.rodata.txt152
.
并且,初始化的数据部分.dat152
请注意,实际的命名约定是任意的。如果你想改变它们,只需修改rofix
[和链接描述文件]适当地
这是readelf -a
输出为module.o
:
请注意,还有一个.rela.txt152
部分!?!?
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: REL (Relocatable file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x0
Start of program headers: 0 (bytes into file)
Start of section headers: 808 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 0 (bytes)
Number of program headers: 0
Size of section headers: 64 (bytes)
Number of section headers: 15
Section header string table index: 14
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS 0000000000000000 00000040
0000000000000000 0000000000000000 AX 0 0 1
[ 2] .data PROGBITS 0000000000000000 00000040
0000000000000000 0000000000000000 WA 0 0 1
[ 3] .bss NOBITS 0000000000000000 00000040
0000000000000000 0000000000000000 WA 0 0 1
[ 4] .rodata.txt152 PROGBITS 0000000000000000 00000040
0000000000000014 0000000000000001 AMS 0 0 1
[ 5] .txt152 PROGBITS 0000000000000000 00000060
000000000000001a 0000000000000000 AX 0 0 16
[ 6] .rela.txt152 RELA 0000000000000000 00000250
0000000000000048 0000000000000018 I 12 5 8
[ 7] .dat152 PROGBITS 0000000000000000 0000007c
0000000000000004 0000000000000000 WA 0 0 4
[ 8] .comment PROGBITS 0000000000000000 00000080
000000000000002d 0000000000000001 MS 0 0 1
[ 9] .note.GNU-stack PROGBITS 0000000000000000 000000ad
0000000000000000 0000000000000000 0 0 1
[10] .eh_frame PROGBITS 0000000000000000 000000b0
0000000000000030 0000000000000000 A 0 0 8
[11] .rela.eh_frame RELA 0000000000000000 00000298
0000000000000018 0000000000000018 I 12 10 8
[12] .symtab SYMTAB 0000000000000000 000000e0
0000000000000150 0000000000000018 13 11 8
[13] .strtab STRTAB 0000000000000000 00000230
000000000000001c 0000000000000000 0 0 1
[14] .shstrtab STRTAB 0000000000000000 000002b0
0000000000000078 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
l (large), p (processor specific)
There are no section groups in this file.
There are no program headers in this file.
There is no dynamic section in this file.
Relocation section '.rela.txt152' at offset 0x250 contains 3 entries:
Offset Info Type Sym. Value Sym. Name + Addend
00000000000a 00050000000a R_X86_64_32 0000000000000000 .rodata.txt152 + 0
000000000011 000c00000002 R_X86_64_PC32 0000000000000000 B - 4
000000000016 000d00000004 R_X86_64_PLT32 0000000000000000 printf - 4
Relocation section '.rela.eh_frame' at offset 0x298 contains 1 entry:
Offset Info Type Sym. Value Sym. Name + Addend
000000000020 000600000002 R_X86_64_PC32 0000000000000000 .txt152 + 0
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.symtab' contains 14 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 FILE LOCAL DEFAULT ABS module.c
2: 0000000000000000 0 SECTION LOCAL DEFAULT 1
3: 0000000000000000 0 SECTION LOCAL DEFAULT 2
4: 0000000000000000 0 SECTION LOCAL DEFAULT 3
5: 0000000000000000 0 SECTION LOCAL DEFAULT 4
6: 0000000000000000 0 SECTION LOCAL DEFAULT 5
7: 0000000000000000 0 SECTION LOCAL DEFAULT 7
8: 0000000000000000 0 SECTION LOCAL DEFAULT 9
9: 0000000000000000 0 SECTION LOCAL DEFAULT 10
10: 0000000000000000 0 SECTION LOCAL DEFAULT 8
11: 0000000000000000 26 FUNC GLOBAL DEFAULT 5 TestFunc
12: 0000000000000000 4 OBJECT GLOBAL DEFAULT 7 B
13: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND printf
No version information found in this file.