fuzz: add a script to build reproducers

Currently, bash and C crash reproducers are be built manually. This is a
problem, as we want to integrate reproducers into the tree, for
regression testing. This patch adds a script that converts a sequence of
QTest commands into a pasteable Bash reproducer, or a libqtest-based C
program. This will try to wrap pasteable reproducers to 72 chars, but
the generated C code will not have nice formatting. Therefore, the C
output of this script should be piped through an auto-formatter, such as
clang-format

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/oss-fuzz/output_reproducer.py

@@ -0,0 +1,160 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Convert plain qtest traces to C or Bash reproducers
+
+Use this to help build bug-reports or create in-tree reproducers for bugs.
+Note: This will not format C code for you. Pipe the output through
+clang-format -style="{BasedOnStyle: llvm, IndentWidth: 4, ColumnLimit: 90}"
+or similar
+"""
+
+import sys
+import os
+import argparse
+import textwrap
+from datetime import date
+
+__author__     = "Alexander Bulekov <alxndr@bu.edu>"
+__copyright__  = "Copyright (C) 2021, Red Hat, Inc."
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Alexander Bulekov"
+__email__      = "alxndr@bu.edu"
+
+
+def c_header(owner):
+    return """/*
+ * Autogenerated Fuzzer Test Case
+ *
+ * Copyright (c) {date} {owner}
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "libqos/libqtest.h"
+
+    """.format(date=date.today().year, owner=owner)
+
+def c_comment(s):
+    """ Return a multi-line C comment. Assume the text is already wrapped """
+    return "/*\n * " + "\n * ".join(s.splitlines()) + "\n*/"
+
+def print_c_function(s):
+    print("/* ")
+    for l in s.splitlines():
+        print(" * {}".format(l))
+
+def bash_reproducer(path, args, trace):
+    result = '\\\n'.join(textwrap.wrap("cat << EOF | {} {}".format(path, args),
+                                       72, break_on_hyphens=False,
+                                       drop_whitespace=False))
+    for l in trace.splitlines():
+        result += "\n" + '\\\n'.join(textwrap.wrap(l,72,drop_whitespace=False))
+    result += "\nEOF"
+    return result
+
+def c_reproducer(name, args, trace):
+    result = []
+    result.append("""static void {}(void)\n{{""".format(name))
+
+    # libqtest will add its own qtest args, so get rid of them
+    args = args.replace("-accel qtest","")
+    args = args.replace(",accel=qtest","")
+    args = args.replace("-machine accel=qtest","")
+    args = args.replace("-qtest stdio","")
+    result.append("""QTestState *s = qtest_init("{}");""".format(args))
+    for l in trace.splitlines():
+        param = l.split()
+        cmd = param[0]
+        if cmd == "write":
+            buf = param[3][2:] #Get the 0x... buffer and trim the "0x"
+            assert len(buf)%2 == 0
+            bufbytes = [buf[i:i+2] for i in range(0, len(buf), 2)]
+            bufstring = '\\x'+'\\x'.join(bufbytes)
+            addr = param[1]
+            size = param[2]
+            result.append("""qtest_bufwrite(s, {}, "{}", {});""".format(
+                          addr, bufstring, size))
+        elif cmd.startswith("in") or cmd.startswith("read"):
+            result.append("qtest_{}(s, {});".format(
+                          cmd, param[1]))
+        elif cmd.startswith("out") or cmd.startswith("write"):
+            result.append("qtest_{}(s, {}, {});".format(
+                          cmd, param[1], param[2]))
+        elif cmd == "clock_step":
+            if len(param) ==1:
+                result.append("qtest_clock_step_next(s);")
+            else:
+                result.append("qtest_clock_step(s, {});".format(param[1]))
+    result.append("qtest_quit(s);\n}")
+    return "\n".join(result)
+
+def c_main(name, arch):
+    return """int main(int argc, char **argv)
+{{
+    const char *arch = qtest_get_arch();
+
+    g_test_init(&argc, &argv, NULL);
+
+   if (strcmp(arch, "{arch}") == 0) {{
+        qtest_add_func("fuzz/{name}",{name});
+   }}
+
+   return g_test_run();
+}}""".format(name=name, arch=arch)
+
+def main():
+    parser = argparse.ArgumentParser()
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument("-bash", help="Only output a copy-pastable bash command",
+                        action="store_true")
+    group.add_argument("-c", help="Only output a c function",
+                        action="store_true")
+    parser.add_argument('-owner', help="If generating complete C source code, \
+                        this specifies the Copyright owner",
+                        nargs='?', default="<name of author>")
+    parser.add_argument("-no_comment", help="Don't include a bash reproducer \
+                        as a comment in the C reproducers",
+                        action="store_true")
+    parser.add_argument('-name', help="The name of the c function",
+                        nargs='?', default="test_fuzz")
+    parser.add_argument('input_trace', help="input QTest command sequence \
+                        (stdin by default)",
+                        nargs='?', type=argparse.FileType('r'),
+                        default=sys.stdin)
+    args = parser.parse_args()
+
+    qemu_path = os.getenv("QEMU_PATH")
+    qemu_args = os.getenv("QEMU_ARGS")
+    if not qemu_args or not qemu_path:
+        print("Please set QEMU_PATH and QEMU_ARGS environment variables")
+        sys.exit(1)
+
+    bash_args = qemu_args
+    if " -qtest stdio" not in  qemu_args:
+        bash_args += " -qtest stdio"
+
+    arch = qemu_path.split("-")[-1]
+    trace = args.input_trace.read().strip()
+
+    if args.bash :
+        print(bash_reproducer(qemu_path, bash_args, trace))
+    else:
+        output = ""
+        if not args.c:
+            output += c_header(args.owner) + "\n"
+        if not args.no_comment:
+            output += c_comment(bash_reproducer(qemu_path, bash_args, trace))
+        output += c_reproducer(args.name, qemu_args, trace)
+        if not args.c:
+            output += c_main(args.name, arch)
+        print(output)
+
+
+if __name__ == '__main__':
+    main()