just some notes on my fuzzing FreeBSD fsck..

README.md

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+Fuzzing FreeBSD w/ AFL
+======================
+
+This project is used to store the various information and scripts that
+I have used in fuzzing FreeBSD.
+
+This project started when someone reported that fsck_ffs couldn't
+repair a file system they had, but as we all know, file systems are
+often large, and contain data the people don't want to share, making
+getting test cases more difficult than most.  I decided to see if
+fuzzing was able to reproduce their failure, and the very first
+failure was the reported, but it also managed to find some more.
+
+Building
+--------
+
+There is a script `build.sh` that will set the compiler correctly when
+building parts of the FreeBSD source tree.  You do have to be careful
+when doing this as there are sometimes dependencies that need to be
+built as well, e.g. `libufs` for `fsck_ffs`.

build.sh

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+CC=/usr/local/afl++-llvm/bin/afl-cc CXX=/usr/local/afl++-llvm/bin/afl-c++ make "$@"

fsck_ffs/README.md

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+fsck_ffs
+========
+
+Collect stack traces for examination:
+```
+for i in id:000*; do echo TEST CASE "$i"; (echo run -y $i; echo bt) | gdb /usr/obj/usr/src/arm64.aarch64/sbin/fsck_ffs/fsck_ffs; done > crashes.txt
+```

fsck_ffs/build.test.cases.sh

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+size=512kb
+
+for fstype in -O1 -O2; do
+	for secsize in -S512 -S4096; do
+		for blkfrag in "" "-b 4096 -f 512"; do
+			if [ ! -z "$blkfrag" ]; then
+				part=".b4096f512"
+			else
+				part=""
+			fi
+			fname="test.$fstype.$secsize$part.img"
+			truncate -s "$size" "$fname"
+			dev=$(mdconfig -f "$fname")
+			newfs $fstype $secsize $blkfrag "$dev"
+			mdconfig -d -u "$dev"
+		done
+	done
+done

fsck_ffs/run.main.sh

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+/usr/local/afl++-llvm/bin/afl-fuzz -i testcase_dir -o sync_dir -M fuzzer01 /usr/obj/usr/src/arm64.aarch64/sbin/fsck_ffs/fsck_ffs -y @@
+
+#secondaries:
+# /usr/local/afl++-llvm/bin/afl-fuzz -i testcase_dir -o sync_dir -S fuzzerXX /usr/obj/usr/src/arm64.aarch64/sbin/fsck_ffs/fsck_ffs -y @@