Re: [Xen-devel] [PATCH] xen/console: Fix build when CONFIG_DEBUG_TRACE=y

[Julien Grall <julien.grall@arm.com>]

Hi,

On 20/08/2019 14:12, Andrew Cooper wrote:
> On 19/08/2019 19:37, Julien Grall wrote:
>> Hi Andrew,
>>
>> On 8/19/19 7:04 PM, Andrew Cooper wrote:
>>> On 19/08/2019 19:01, Julien Grall wrote:
>>>> Commit b5e6e1ee8da "xen/console: Don't treat NUL character as the end
>>>> of the buffer" extended sercon_puts to take the number of character
>>>> to print in argument.
>>>>
>>>> Sadly, a couple of couple of the callers in debugtrace_dump_worker()
>>>> were not converted. This result to a build failure when enabling
>>>> CONFIG_DEBUG_TRACE.
>>>>
>>>> Spotted by Travis using randconfig
>>>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>>> ---
>>>>    xen/drivers/char/console.c | 5 +++--
>>>>    1 file changed, 3 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
>>>> index 2c14c2ca73..924d4971ca 100644
>>>> --- a/xen/drivers/char/console.c
>>>> +++ b/xen/drivers/char/console.c
>>>> @@ -1185,11 +1185,12 @@ static void debugtrace_dump_worker(void)
>>>>          /* Print oldest portion of the ring. */
>>>>        ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
>>>> -    sercon_puts(&debugtrace_buf[debugtrace_prd]);
>>>> +    sercon_puts(&debugtrace_buf[debugtrace_prd],
>>>> +                strlen(&debugtrace_buf[debugtrace_prd]));
>>>
>>> Isn't this just debugtrace_bytes - debugtrace_prd - 1 ?
>>
>> I tried and it resulted to print a lot of @^ on the console. This is
>> because the ring may not be full.
>>
>> So the portion between debugtrace_prd and debugtrace_bytes will be
>> full of zero.
>>
>> Looking at the code again, I think this portion and either be full of
>> zero character or full of non-zero character. In other word, a mix
>> would not be possible. So how about:
>>
>> if ( debugtrace_buf[debugtrace_prd] != '\0' )
>>    sercon_puts(&debugtrace_buf[debugtrace_prd],
>>                debugtrace_bytes - debugtrace_prd - 1);
> 
> LGTM.  Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

Thank you! I will update the patch and commit it.

Cheers,

-- 
Julien Grall

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