fuzz: Add support for logging QTest commands

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20200529221450.26673-3-alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/qtest/fuzz/fuzz.c

@@ -94,7 +94,9 @@ static void usage(char *path)
     printf("Alternatively, add -target-FUZZ_TARGET to the executable name\n\n"
            "Set the environment variable FUZZ_SERIALIZE_QTEST=1 to serialize\n"
            "QTest commands into an ASCII protocol. Useful for building crash\n"
-           "reproducers, but slows down execution.\n");
+           "reproducers, but slows down execution.\n\n"
+           "Set the environment variable QTEST_LOG=1 to log all qtest commands"
+           "\n");
     exit(0);
 }
 
@@ -197,6 +199,11 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
 
     /* Run QEMU's softmmu main with the fuzz-target dependent arguments */
     const char *init_cmdline = fuzz_target->get_init_cmdline(fuzz_target);
+    init_cmdline = g_strdup_printf("%s -qtest /dev/null -qtest-log %s",
+                                   init_cmdline,
+                                   getenv("QTEST_LOG") ? "/dev/fd/2"
+                                                       : "/dev/null");
+
 
     /* Split the runcmd into an argv and argc */
     wordexp_t result;