知识大全 Linux汇编指南

Posted 2022-07-16 指南

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　　摘要:The following is designed to be a Linux equivalent to Developing Assembly Language Programs on a PC by Douglas V Hall This tutorial requires the following: 　　Introduction 　　　　　　The following is designed to be a Linux equivalent to Developing Assembly Language Programs on a PC by Douglas V Hall This tutorial requires the following: 　　　　　　an i family PC running Linux 　　　　　　as the GNU assembler (included with any gcc installation) ld the GNU linker (also included with gcc) gdb the GNU debugger The tutorial was developed on a Redhat Linux installation running a version kernel and the version and C language libraries with ELF file format But I have tried to make the tutorial as general possible with respect to Linux systems I highly remend working through this tutorial with as and gdb documentation close at hand 　　　　　　Overview 　　　　　　The process of developing an assembly program under linux is somewhat different from development under NT In order to acmodate object oriented languages which require the piler to create constructor and destructor methods which execute before and after the execution of main the GNU development model embeds user code within a wrapper of system code In other words the user s main is treated as a function call An advantage of this is that user is not required to initialize segment registers though user code must obey some function requirements 　　　　　　The Code 　　　　　　The following is the Linux version of the average temperature program It will be referred to as average s Note: Assembly language programs should use the s suffix 　　　　/* linux version of AVTEMP ASM CS fall */　　 data /* beginning of data segment */　　/* hi_temp data item */　　 type hi_temp @object /* declare as data object */　　 size hi_temp /* declare size in bytes */　　hi_temp:　　 byte x /* set value */　　/* lo_temp data item */　　 type lo_temp @object　　 size lo_temp 　　lo_temp:　　 byte x 　　/* av_temp data item */　　 type av_temp @object　　 size av_temp 　　av_temp:　　 byte 　　/* segment registers set up by linked code */　　/* beginning of text(code) segment */　　 text　　 align /* set double word alignment */　　 globl main /* make main global for linker */　　 type main @function /* declare main as a function */　　main:　　 pushl %ebp /* function requirement */　　 movl %esp %ebp /* function requirement */　　 movb hi_temp %al　　 addb lo_temp %al　　 movb $ %ah　　 adcb $ %ah　　 movb $ %bl　　 idivb %bl　　 movb %al av_temp　　 leave /* function requirement */　　 ret /* function requirement */　　　　　　assembly instructions　　　　　　This code may be assembled with the following mand: 　　　　as a gstabs o average o average s 　　　　　　The a option prints a memory listing during assembly This output gives the location variables and code with respect to the beginnings of the data and code segments gstabs places debugging information in the executable (used by gdb) o specifies average o as the output file name (the default is a out which is confusing since the file is not executable ) 　　　　　　The object file (average o) can then be linked to the Linux wrapper code in order to create an executable These files are crt o crti o and crtn o crt o and crti o provide initialization code and crtn o does cleanup These should all be located in /usr/lib be may be elsewere on some systems They and their source might be located by executing the following find mand: 　　　　　　find / name crt* print 　　　　　　The link mand is the following: 　　　　ld m elf_i static /usr/lib/crt o /usr/lib/crti o 　　 lc average o /usr/lib/crtn o 　　　　　　 m elf_i instructs the linker to use the ELF file format static cause static rather than dynamic linking to occur And lc links in the standard c libraries (libc a) It might be necessary to include I/libdirectory in the invocation for ld to find the c library 　　　　　　It will be necessary to change the mode of the resulting object file with chmod +x /a out 　　　　　　It should now be possible to execute the file But of course there will be no output 　　　　　　I remend placing the above mands in a makefile 　　　　　　debugging 　　　　　　The gstabs option given to the assembler allows the assembly program to be debugged under gdb The first step is to invoke gdb: 　　　　　　gdb /a out 　　　　　　gdb should start with the following message: 　　　　[bjorn@pomade src]$ gdb /a out　　　　　　GNU gdb 　　　　　　Copyright Free Sofare Foundation Inc GDB is free sofare covered by the GNU General Public License and you are　　　　　　wele to change it and/or distribute copies of it under certain conditions Type show copying to see the conditions 　　　　　　There is absolutely no warranty for GDB Type show warranty for details 　　　　　　This GDB was configured as i redhat linux 　　　　　　(gdb) 　　　　　　The l mand will list the program sourcecode 　　　　　　(gdb) l　　　　 /* linux version of AVTEMP ASM CS fall */　　 data /* beginning of data segment */　　　　 /* hi_temp data item */　　 type hi_temp @object /* declare as data object */　　 size hi_temp /* declare size in bytes */　　 hi_temp:　　 byte x /* set value */　　　　 /* lo_temp data item */　　(gdb) 　　　　　　The first thing to do is set a breakpoint so it will be possible to step through the code 　　　　(gdb) break main　　Breakpoint at x f 　　(gdb) 　　　　　　This sets a breakpoint at the beginning of main Now run the program 　　　　(gdb) run　　Starting program: /home/bjorn/src/ /a out 　　Breakpoint main () at average s: 　　 movb hi_temp %al　　Current language: auto; currently asm　　(gdb) 　　　　　　values in registers can be checked with either info registers 　　　　(gdb) info registers　　eax x 　　ecx xbffffd 　　edx x 　　ebx x bf 　　esp xbffffdd xbffffdd 　　ebp xbffffdd xbffffdd 　　esi x 　　edi x 　　eip x f x f 　　eflags x 　　cs x 　　ss x b 　　ds x b 　　es x b 　　fs x b 　　gs x b 　　(gdb) 　　　　　　 or p/x $eax which prints the value in the EAX register in hex The e in front of the register name indicates a bit register The Intel x family has included extended bit registers since the These E registers are to the X registers as the L and H are to the X registers Linux also uses a flat and protected memory model rather that segmentation thus the EIP stores the entire current address 　　　　(gdb cha138/Article/program/Oracle/201311/16623