Support for musl library

[MartinNowack]

Initial support for executing KLEE using musl library.
Similar to uclibc (--libc=uclib), use --libc=musllibc.

To be able to use it, put a link to the musllibc bc file into your Release+Asserts/lib directory.
This will be automated soon.

@mdimjasevic This should get you going. Please try it out.
If you see any issues, let me know.

[MartinNowack]

Replace the code with: mainModule = linkWithMusllibc(mainModule, LibraryDir); to use musllibc instead of uclibc for testing.

[MartinNowack]

Here is the repository for the musl libc: https://github.com/MartinNowack/klee-musl
You find the build instructions here: https://github.com/MartinNowack/klee-musl/blob/klee_support/README.klee.md

By the way, test suite should pass if musl is selected as default library (See code comment).

[ccadar]

Thanks, @MartinNowack ! @mdimjasevic, is this in line with what you were trying?

[andreamattavelli]

I guess you should guard it with "#ifndef SUPPORT_KLEE_UCLIBC"

[mdimjasevic]

@ccadar : I believe it's very close, much closer than I managed to get it on my own!

However, I believe there are more changes to be done to KLEE to support Musl. You can see I make changes to more files than @MartinNowack in this pull request: mdimjasevic@367543b

This includes changes to configuration files in KLEE. I believe it's better to have them and not pretend Musl is KLEE-uClibc with a different location on the file system.

That being said, with a manual tweak or two after compiling this, I am able to run KLEE on the hostname utility. I wanted to confirm I can get rid of an earlier false bug due to a missing function implementation in KLEE-uClibc:

$ ~/research/klee-mnowack-support-for-musl/Release+Asserts/bin/klee -libc=musllibc -posix-runtime hostname -A
KLEE: NOTE: Using klee-musllibc : /home/marko/research/klee-mnowack-support-for-musl/Release+Asserts/lib/musllibc.bca
KLEE: NOTE: Using model: /home/marko/research/klee-mnowack-support-for-musl/Release+Asserts/lib/libkleeRuntimePOSIX.bca
KLEE: output directory is "/home/marko/research/klee/examples/hostname-3.18/hostname-3.18/klee-out-25"
Using STP solver backend
KLEE: WARNING ONCE: function "qsort" has inline asm
KLEE: WARNING ONCE: function "trinkle" has inline asm
KLEE: WARNING ONCE: function "__init_libc" has inline asm
KLEE: WARNING ONCE: function "cgt_init" has inline asm
KLEE: WARNING ONCE: function "__lockfile" has inline asm
KLEE: WARNING ONCE: function "__unlockfile" has inline asm
KLEE: WARNING ONCE: function "static_init_tls" has inline asm
KLEE: WARNING ONCE: function "__wait" has inline asm
KLEE: WARNING ONCE: function "__lock" has inline asm
KLEE: WARNING ONCE: function "__unlock" has inline asm
KLEE: WARNING ONCE: function "__do_orphaned_stdio_locks" has inline asm
KLEE: WARNING ONCE: function "ftrylockfile" has inline asm
KLEE: WARNING: undefined reference to function: endutent
KLEE: WARNING: undefined reference to function: getutent
KLEE: WARNING: undefined reference to function: klee_posix_prefer_cex
KLEE: WARNING: undefined reference to function: printf
KLEE: WARNING: undefined reference to function: realpath
KLEE: WARNING: undefined reference to function: setutent
KLEE: WARNING: undefined reference to function: utmpname
KLEE: WARNING ONCE: calling external: syscall(218, 44423024)
KLEE: WARNING ONCE: calling __user_main with extra arguments.
KLEE: ERROR: /home/marko/research/klee-musl-mnowack/./arch/x86_64/atomic_arch.h:13: inline assembly is unsupported
KLEE: NOTE: now ignoring this error at this location

KLEE: done: total instructions = 316958
KLEE: done: completed paths = 1
KLEE: done: generated tests = 1

Therefore, I can get this running. I guess the particular error reported by KLEE is to say we'd need to do more massaging of KLEE-Musl by @MartinNowack.

[MartinNowack]

@mdimjasevic I know, the configuration are still missing. But it is trivial to add. This patch is just a WIP.
You got me wrong with uclibc = musllibc, I wanted to say, it is already working as a drop-in replacement for uclibc if you replace manually the code, you see that the test suite successfully runs.
Another question, did you use the klee_support branch?

[mdimjasevic]

@MartinNowack , yes, I used the klee_support branch.

[ccadar]

Given the age of the PR, I will close it, but place it in the Extensions project at https://github.com/klee/klee/projects/4, so that others can build up on it if there is interest.