Add a script for running multiple fuzzing sessions on multiple cores

doc/HACKING/Fuzzing.md

@@ -42,6 +42,7 @@ To Run:
   ../afl/afl-fuzz -i src/test/fuzz/fuzz_dir_testcase -o src/test/fuzz/fuzz_dir_findings -m <asan-memory-limit> -- src/test/fuzz_dir
 
 AFL has a multi-core mode, check the documentation for details.
+You might find the included fuzz-multi.sh script useful for this.
 
 macOS (OS X) requires slightly more preparation, including:
 * using afl-clang (or afl-clang-fast from the llvm directory)

src/test/fuzz_multi.sh

@@ -0,0 +1,34 @@
+MEMLIMIT_BYTES=21990500990976
+
+N_CPUS=1
+if [ $# -ge 1 ]; then
+    N_CPUS="$1"
+    shift
+fi
+
+FILTER=echo
+
+for i in `seq -w "$N_CPUS"`; do
+    if [ "$i" -eq 1 ]; then
+        if [ "$N_CPUS" -eq 1 ]; then
+            INSTANCE=""
+            NUMBER=""
+        else
+            INSTANCE="-M"
+            NUMBER="$i"
+        fi
+    else
+        INSTANCE="-S"
+        NUMBER="$i"
+    fi
+    # use whatever remains on the command-line to prefix the fuzzer command
+    # you have to copy and paste and run these commands yourself
+    "$FILTER" "$@" \
+        ../afl/afl-fuzz \
+        -i src/test/fuzz/fuzz_dir_testcase \
+        -o src/test/fuzz/fuzz_dir_findings \
+        -x src/test/fuzz/fuzz_dir_dictionary/fuzz_dir_http_header.dct \
+        -m "$MEMLIMIT_BYTES" \
+        "$INSTANCE" "$NUMBER" \
+        -- src/test/fuzz_dir
+done