"warning: Linking two modules of different target triples" when using KLEE via Docker with the `--libc=uclibc` option

[Yike Zhou]

Description

I'm using KLEE 3.0 via Docker. I came across lots of unexpected warning messages like this:

warning: Linking two modules of different target triples: 'get_sign.bc' is 'x86_64-unknown-linux-gnu' whereas '__uClibc_main.os' is 'x86_64-pc-linux-gnu'

Manually specifying the target triple may solve this problem. I wonder if this could be fixed globally in the construction of a Docker image.

Steps to reproduce

First, pull the docker image down and start a fresh container.

$ docker pull klee/klee:3.0
$ docker run --rm -ti --ulimit='stack=-1:-1' klee/klee:3.0

Then we need to find some input for KLEE.
The program doesn't matter here. So I choose get_sign.c as an example.

$ cd ~/klee_src/examples/get_sign/
$ clang -I ../../include -emit-llvm -c -g -O0 -Xclang -disable-O0-optnone get_sign.c

Now we have the .bc file. We can invoke KLEE with the following command-line.

$ klee --libc=uclibc get_sign.bc

Note: I'm aware that the --libc=uclibc option is unnecessary here.
It is only used to illustrate the warnings caused by this option.

KLEE complains about the mismatching targets.

KLEE: NOTE: Using klee-uclibc : /tmp/klee_build130stp_z3/runtime/lib/klee-uclibc.bca
KLEE: output directory is "/home/klee/klee_src/examples/get_sign/klee-out-0"
KLEE: Using STP solver backend
KLEE: SAT solver: MiniSat
warning: Linking two modules of different target triples: 'get_sign.bc' is 'x86_64-unknown-linux-gnu' whereas '__uClibc_main.os' is 'x86_64-pc-linux-gnu'

warning: Linking two modules of different target triples: 'klee_overshift_check64_Debug+Asserts.bc' is 'x86_64-unknown-linux-gnu' whereas '__uClibc_main.os' is 'x86_64-pc-linux-gnu'

KLEE: WARNING: undefined reference to function: __syscall_rt_sigaction
KLEE: WARNING: undefined reference to function: fcntl
KLEE: WARNING: undefined reference to function: fstat
KLEE: WARNING: undefined reference to function: ioctl
KLEE: WARNING: undefined reference to function: open
KLEE: WARNING: undefined reference to function: write
KLEE: WARNING: undefined reference to function: kill (UNSAFE)!
KLEE: WARNING ONCE: calling external: ioctl(0, 21505, 94527241372272) at libc/termios/tcgetattr.c:43 12
KLEE: WARNING ONCE: calling __user_main with extra arguments.

KLEE: done: total instructions = 11973
KLEE: done: completed paths = 3
KLEE: done: partially completed paths = 0
KLEE: done: generated tests = 3

Platform

I'm running Docker (with the WSL 2 backend) on a Windows PC.

[MartinNowack]

This is unfortunately a result of building uclibc (building with wllvm) differently than KLEE's bitcode files (building with clang directly).
As a result, the target triplets are slightly different:
'x86_64-unknown-linux-gnu' vs. 'x86_64-pc-linux-gnu'
In this case, they are compatible.

But it becomes a problem if bitcode files of different platforms/architectures are mixed that's why KLEE is warning about it.

@YikeZhou I'll close this issue but feel free to re-open it with related follow-up questions.

[Cristian Cadar]

I think it would be an improvement in terms of usability to remove such warnings when they don't matter, but this is something that LLVM rather than KLEE warns about.

[Frank Busse]

I think you might get a fitting target triple when building klee-uclibc with:

$ make -j2 KLEE_CFLAGS="--target=x86_64-unknown-linux-gnu" 

[Cristian Cadar]

That would be nice to try. Let's reopen this until we try.