QEMU mode for different architectures does not work!!

[sadulla...@gmail.com]

Hi,

I started playing with afl last week and it seems pretty useful. Thanks for this great tool. I am able to configure qemu for x86_64 architecture by just running the build_qemu_support.sh script without specifying target architecture. However, If I set target architecture, for instance if I set CPU_TARGET as i386, and runs the build_qemu_support.sh, it returns me:

......

[+] Successfully created '../afl-qemu-trace'.

[*] Testing the build...

[-] Error: afl-qemu-trace instrumentation doesn't seem to work!

All I did was to add one line into your script that specify cpu target, i.e. CPU_TARGET=i386

My uname -a results:

Linux ubuntu 4.8.0-54-generic #57~16.04.1-Ubuntu SMP  x86_64 GNU/Linux

Am I missing something? I looked for different questions in group but none of them actually solved my problem. 

Thanks in advance

Sadullah

[sadulla...@gmail.com]

Hi again, 

I actually noticed my fault. I was setting CPU_TARGET too late in the script which leads me this error. Currently, I am getting:

......

[+] Successfully created '../afl-qemu-trace'.

[!] Note: can't test instrumentation when CPU_TARGET set.

[+] All set, you can now (hopefully) use the -Q mode in afl-fuzz!

The problem is that I am not able to use -Q mode in afl-fuzz. It returns this error:

[-] PROGRAM ABORT : Fork server handshake failed

         Location : init_forkserver(), afl-fuzz.c:2251

I again checked the group posts, here are some the tricks that I tried to run in Q mode:

setting AFL_NO_FORKSRV=1

running afl-fuzz with -m none

running afl-showmap to get detailed error which returns me:

-- Program output begins -- Unable to reserve 0xf7000000 bytes of virtual address space for use as guest address space (check your virtual memory ulimit setting or reserve less using -R option) -- Program output ends -- [-] PROGRAM ABORT : No instrumentation detected Location : main(), afl-showmap.c:755

I also fine tune -m option to run my program. I tried bunch of different parameters, none of them seemed to work.

By the way, I configured QEMU for i386 and compiled my simple c program using  gcc -m32 -static command.

Thanks,

Sadullah

[Michal Zalewski]

> running afl-showmap to get detailed error which returns me:
>
> -- Program output begins -- Unable to reserve 0xf7000000 bytes of virtual
> address space for use as guest address space (check your virtual memory
> ulimit setting or reserve less using -R option) -- Program output ends --
> [-] PROGRAM ABORT : No instrumentation detected Location : main(),
> afl-showmap.c:755

Try afl-showmap -m none (and then the remaining parameters, including -Q).

/mz

[sadulla...@gmail.com]

Thanks a lot. It worked successfully after using -m none at the beginning.

Sadullah