Update CI fuzzing to use hard-coded full_stack seeds

This should materially improve our fuzzing coverage in CI.

Author: TheBlueMatt

.github/workflows/build.yml

@@ -262,11 +262,12 @@ jobs:
           sudo apt-get -y install build-essential binutils-dev libunwind-dev
       - name: Pin the regex dependency
         run: |
-          cd fuzz && cargo update -p regex --precise "1.9.6" --verbose && cd ..
+          cd fuzz && cargo update -p regex --precise "1.9.6" --verbose
+          cd write-seeds && cargo update -p regex --precise "1.9.6" --verbose
       - name: Sanity check fuzz targets on Rust ${{ env.TOOLCHAIN }}
         run: |
           cd fuzz
-          RUSTFLAGS="--cfg=fuzzing --cfg=secp256k1_fuzz --cfg=hashes_fuzz" cargo test --verbose --color always
+          RUSTFLAGS="--cfg=fuzzing --cfg=secp256k1_fuzz --cfg=hashes_fuzz" cargo test --verbose --color always --lib --bins
           cargo clean
       - name: Run fuzzers
         run: cd fuzz && ./ci-fuzz.sh && cd ..

fuzz/ci-fuzz.sh

@@ -13,10 +13,17 @@ rm *_target.rs
 [ "$(git diff)" != "" ] && exit 1
 popd
 
+export RUSTFLAGS="--cfg=secp256k1_fuzz --cfg=hashes_fuzz"
+
+mkdir -p hfuzz_workspace/full_stack_target/input
+pushd write-seeds
+RUSTFLAGS="$RUSTFLAGS --cfg=fuzzing" cargo run ../hfuzz_workspace/full_stack_target/input
+popd
+
 cargo install --color always --force honggfuzz --no-default-features
 sed -i 's/lto = true//' Cargo.toml
+sed -i 's/codegen-units = 1//' Cargo.toml
 
-export RUSTFLAGS="--cfg=secp256k1_fuzz --cfg=hashes_fuzz"
 export HFUZZ_BUILD_ARGS="--features honggfuzz_fuzz"
 
 cargo --color always hfuzz build