Re: [PATCH] hw/display/omap_dss: Replace fprintf() call by qemu_log_mask(LOG_UNIMP)

[Philippe Mathieu-Daudé]

On 5/24/20 2:41 PM, Alexander Bulekov wrote:
> On 200524 1238, Philippe Mathieu-Daudé wrote:
>> Replace fprintf() call by qemu_log_mask(LOG_UNIMP), which is
>> disabled by default. This avoid flooding the terminal when
>> fuzzing the device.
>>
> Hi Philippe,
> libfuzzer also lets you pass -close_fd_mask=[1,2,3] to close stdout,
> stderr or both. As a side-effect, In this mode, libfuzzer will write the
> crashing stacktraces to individual files ./.$PID, instead of to the
> terminal's output.

Thanks, good to know.

This information is worth adding in docs/devel/fuzzing.txt :P

> As far as I know, closing the FDs doesn't bypass all
> of printf's allocation/formatting code, so getting rid of calls can
> still be a good idea for performance, sometimes.

Certainly.

> -Alex
> 
>> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
>> ---
>>  hw/display/omap_dss.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/display/omap_dss.c b/hw/display/omap_dss.c
>> index 32dc0d6aa7..21fde58a26 100644
>> --- a/hw/display/omap_dss.c
>> +++ b/hw/display/omap_dss.c
>> @@ -619,7 +619,7 @@ static void omap_rfbi_transfer_start(struct omap_dss_s 
>> *s)
>>      if (s->rfbi.control & (1 << 1)) {                               /* 
>> BYPASS */
>>          /* TODO: in non-Bypass mode we probably need to just assert the
>>           * DRQ and wait for DMA to write the pixels.  */
>> -        fprintf(stderr, "%s: Bypass mode unimplemented\n", __func__);
>> +        qemu_log_mask(LOG_UNIMP, "%s: Bypass mode unimplemented\n", 
>> __func__);
>>          return;
>>      }
>>  
>> -- 
>> 2.21.3
>>
>