Re: [PATCH v3 11/16] scripts/oss-fuzz: Add general-fuzzer build script

[Alexander Bulekov <alxndr@bu.edu>]

On 201008 0935, Paolo Bonzini wrote:
> On 21/09/20 04:25, Alexander Bulekov wrote:
> > This parses a yaml file containing general-fuzzer configs and builds a
> > separate oss-fuzz wrapper binary for each one, changing some
> > preprocessor macros for each configuration. To avoid dealing with
> > escaping and stringifying, convert each string into a byte-array
> > representation
> > 
> > Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
> > ---
> >  scripts/oss-fuzz/build_general_fuzzers.py | 69 +++++++++++++++++++++++
> >  1 file changed, 69 insertions(+)
> >  create mode 100755 scripts/oss-fuzz/build_general_fuzzers.py
> > 
> > diff --git a/scripts/oss-fuzz/build_general_fuzzers.py b/scripts/oss-fuzz/build_general_fuzzers.py
> > new file mode 100755
> > index 0000000000..918f1143a5
> > --- /dev/null
> > +++ b/scripts/oss-fuzz/build_general_fuzzers.py
> > @@ -0,0 +1,69 @@
> > +#!/usr/bin/env python3
> > +# -*- coding: utf-8 -*-
> > +
> > +"""
> > +This script creates wrapper binaries that invoke the general-device-fuzzer with
> > +configurations specified in a yaml config file.
> > +"""
> > +import sys
> > +import os
> > +import yaml
> > +import tempfile
> > +
> > +CC = ""
> > +TEMPLATE_FILENAME = "target_template.c"
> > +TEMPLATE_PATH = ""
> > +
> > +
> > +def usage():
> > +    print("Usage: CC=COMPILER {} CONFIG_PATH \
> > +OUTPUT_PATH_PREFIX".format(sys.argv[0]))
> > +    sys.exit(0)
> > +
> > +
> > +def str_to_c_byte_array(s):
> > +    """
> > +    Convert strings to byte-arrays so we don't worry about formatting
> > +    strings to play nicely with cc -DQEMU_FUZZARGS etc
> > +    """
> > +    return ','.join('0x{:02x}'.format(ord(x)) for x in s)
> > +
> > +
> > +def compile_wrapper(cfg, path):
> > +    os.system('$CC -DQEMU_FUZZ_ARGS="{fuzz_args}" \
> > +               -DQEMU_FUZZ_OBJECTS="{fuzz_objs}" \
> > +               {wrapper_template} -o {output_bin}'.format(
> > +                   fuzz_args=str_to_c_byte_array(cfg["args"].replace("\n", " ")),
> > +                   fuzz_objs=str_to_c_byte_array(cfg["objects"].replace("\n", " ")),
> > +                   wrapper_template=TEMPLATE_PATH,
> > +                   output_bin=path))
> > +
> > +
> > +def main():
> > +    global CC
> > +    global TEMPLATE_PATH
> > +    global OUTPUT_BIN_NAME
> > +
> > +    if len(sys.argv) != 3:
> > +        usage()
> > +
> > +    cfg_path = sys.argv[1]
> > +    out_path = sys.argv[2]
> > +
> > +    CC = os.getenv("CC", default="cc")
> > +    TEMPLATE_PATH = os.path.join(os.path.dirname(__file__), TEMPLATE_FILENAME)
> > +    if not os.path.exists(TEMPLATE_PATH):
> > +        print("Error {} doesn't exist".format(TEMPLATE_PATH))
> > +        sys.exit(1)
> > +
> > +    with open(cfg_path, "r") as f:
> > +        configs = yaml.load(f)["configs"]
> > +    for cfg in configs:
> > +        assert "name" in cfg
> > +        assert "args" in cfg
> > +        assert "objects" in cfg
> > +        compile_wrapper(cfg, out_path + cfg["name"])
> > +
> > +
> > +if __name__ == '__main__':
> > +    main()
> > 
> 
> Can you instead write an array of
> 
> struct {
>     const char *name, *args, *objects;
> }
> 
> and use it in the normal argv0-based selection?  The advantage would be
> that you can do the whole build within tests/qtest/fuzz/meson.build
> instead of having yet another undocumented shell script (cue all the
> mess I made when trying to modify scripts/oss-fuzz/build.sh).
> 
> Paolo

Thanks for the suggestion. I did this in v4, and I think it is much
nicer. No more python script, c template, and preprocessor hacking. I
don't think the way I defined the configs is ideal, however I think it
is already a better solution.
-Alex

>