Support for LLVM 13 fuzzing

[alexcrichton]

I got a notification that the flate2 project's coverage build is failing and has the error message:

Step #5: warning: /workspace/out/coverage/dumps/fuzz_gz_roundtrip.16218861006045500770_0.profraw: Unsupported instrumentation profile format version
Step #5: error: No profiles could be merged.

AFAIK nothing about flate2 itself has changed, but the most recent change I can think of is that the Rust compiler upgraded to LLVM 13 over the weekend. I suspect that the new LLVM version may have updated something about coverage instrumentation?

[alexcrichton]

Also we're seeing a different failure in wasmtime's normal fuzz builds which I believe is mixing C/Rust so I think that there's possibly another incompatibility with LLVM 13, which Rust is using, and the system C compiler perhaps?

[DavidKorczynski]

Can confirm Rust issues - I get build failures on many (all projects I am CCed on) Rust projects.

[alexcrichton]

I'm attempting to pin the Rust toolchain to a pre-LLVM-13 version in #6288 as a temporary fix for now.

[maflcko]

Is this still an issue?

[catenacyber]

@jonathanmetzman this is still an issue after rolling out clang 14

Reverting to clang13 makes suricata and rustls coverage builds succeed :

Patch is

diff --git a/infra/base-images/base-clang/checkout_build_install_llvm.sh b/infra/base-images/base-clang/checkout_build_install_llvm.sh
index a62b27cf..b4c00ad9 100755
--- a/infra/base-images/base-clang/checkout_build_install_llvm.sh
+++ b/infra/base-images/base-clang/checkout_build_install_llvm.sh
@@ -70,11 +70,11 @@ cd clang
 LLVM_SRC=$SRC/llvm-project
 
 # For manual bumping.
-OUR_LLVM_REVISION=llvmorg-12-init-17251-g6de48655
+OUR_LLVM_REVISION=llvmorg-13.0.0-rc1-gd6974c010878
 
 # To allow for manual downgrades. Set to 0 to use Chrome's clang version (i.e.
 # *not* force a manual downgrade). Set to 1 to force a manual downgrade.
-FORCE_OUR_REVISION=0
+FORCE_OUR_REVISION=1
 LLVM_REVISION=$(grep -Po "CLANG_REVISION = '\K([^']+)" scripts/update.py)
 
 clone_with_retries https://github.com/llvm/llvm-project.git $LLVM_SRC

Test is

python3 infra/helper.py build_image --no-pull base-builder
python3 infra/helper.py build_image --no-pull base-builder-rust
python3 infra/helper.py build_image --no-pull base-runner
python3 infra/helper.py build_image --no-pull suricata
python infra/helper.py build_fuzzers --sanitizer coverage suricata
python infra/helper.py coverage --no-corpus-download suricata

Right now, without this patch, we get malformed instrumentation profile data errors
Before rolling clang-14 we had Unsupported instrumentation profile format version (because rust compiler used clang13 profile format)

Before : https://oss-fuzz-build-logs.storage.googleapis.com/log-3022ca9e-fbae-44d7-ac43-1214b857004b.txt
After : https://oss-fuzz-build-logs.storage.googleapis.com/log-b7dd2a93-58b6-47d2-88ef-7e0c2ffb7bd9.txt

Should we revert to clang 13 ? Only for rust projects ?

[catenacyber]

llvmorg-14-init+ cherry-pick of a6c14fba70e170a279f7e77f068368f09d8c5eaf seems good to me

[catenacyber]

I found the culprit commit in llvm : https://reviews.llvm.org/D104556