Re: [Qemu-devel] [RFC PATCH v2 01/17] fuzz: Move initialization from main to qemu_init

[Paolo Bonzini <pbonzini@redhat.com>]

On 05/08/19 09:11, Oleinik, Alexander wrote:
> Using this, we avoid needing a special case to break out of main(),
> early, when initializing the fuzzer, as we can just call qemu_init.
> There is still a #define around main(), since it otherwise conflicts
> with the libfuzzer main().
> 
> Signed-off-by: Alexander Oleinik <alxndr@bu.edu>
> ---
>  include/sysemu/sysemu.h |  5 +++++
>  vl.c                    | 25 +++++++++++++++++++++++--
>  2 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 984c439ac9..a63d5ccce3 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -184,6 +184,8 @@ QemuOpts *qemu_get_machine_opts(void);
>  
>  bool defaults_enabled(void);
>  
> +int qemu_init(int argc, char **argv, char **envp);
> +
>  extern QemuOptsList qemu_legacy_drive_opts;
>  extern QemuOptsList qemu_common_drive_opts;
>  extern QemuOptsList qemu_drive_opts;
> @@ -197,4 +199,7 @@ extern QemuOptsList qemu_global_opts;
>  extern QemuOptsList qemu_mon_opts;
>  extern QemuOptsList qemu_semihosting_config_opts;
>  
> +#ifdef CONFIG_FUZZ
> +int real_main(int argc, char **argv, char **envp);
> +#endif
>  #endif
> diff --git a/vl.c b/vl.c
> index 130a389712..914bb9b2de 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -130,6 +130,10 @@ int main(int argc, char **argv)
>  #include "sysemu/iothread.h"
>  #include "qemu/guest-random.h"
>  
> +#ifdef CONFIG_FUZZ
> +#include "tests/libqtest.h"
> +#endif

Why is this #include needed?

If you leave out the changes to introduce real_main, the patch can be
committed independent of the rest.  Those can be introduced in patch 2
or even 12 ("Add fuzzer skeleton").

Paolo

>  #define MAX_VIRTIO_CONSOLES 1
>  
>  static const char *data_dir[16];
> @@ -2854,7 +2858,7 @@ static void user_register_global_props(void)
>                        global_init_func, NULL, NULL);
>  }
>  
> -int main(int argc, char **argv, char **envp)
> +int qemu_init(int argc, char **argv, char **envp)
>  {
>      int i;
>      int snapshot, linux_boot;
> @@ -4453,7 +4457,7 @@ int main(int argc, char **argv, char **envp)
>      if (vmstate_dump_file) {
>          /* dump and exit */
>          dump_vmstate_json_to_file(vmstate_dump_file);
> -        return 0;
> +        exit(0);
>      }
>  
>      if (incoming) {
> @@ -4470,6 +4474,23 @@ int main(int argc, char **argv, char **envp)
>      accel_setup_post(current_machine);
>      os_setup_post();
>  
> +    return 0;
> +}
> +#ifdef CONFIG_FUZZ
> +/*
> + * Without this, the compiler complains about all of the unused
> + * cleanup and shutdown() functions
> + */
> +int real_main(int argc, char **argv, char **envp)
> +#else
> +int main(int argc, char **argv, char **envp)
> +#endif
> +{
> +    int ret = qemu_init(argc, argv, envp);
> +    if (ret != 0) {
> +        return ret;
> +    }
> +
>      main_loop();
>  
>      gdbserver_cleanup();
>