linux-kernel - Re: [PATCH] tracing: Fix event filters and triggers to handle negative numbers

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Message-ID: <f0929165-bc75-c13a-7a20-43262ef8a496@virtuozzo.com>
Date:   Thu, 28 Feb 2019 09:11:37 +0000
From:   Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     Ingo Molnar <mingo@...hat.com>, Al Viro <viro@...IV.linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: Fix event filters and triggers to handle
 negative numbers

ping, looks like the patch was lost

On 8/24/18 3:48 AM, Steven Rostedt wrote:
> On Thu, 23 Aug 2018 13:25:34 +0300
> Pavel Tikhomirov <ptikhomirov@...tuozzo.com> wrote:
> 
>> Then tracing syscall exit event it is extremely useful to filter exit
>> codes equal to some negative value, to react only to required errors.
>> But negative numbers does not work:
>>
>> [root@...rch sys_exit_read]# echo "ret == -1" > filter
>> bash: echo: write error: Invalid argument
>> [root@...rch sys_exit_read]# cat filter
>> ret == -1
>>          ^
>> parse_error: Invalid value (did you forget quotes)?
> 
> Thanks for the patch. I'll apply it and then start testing it!
> 
> -- Steve
> 
>>
>> Similar thing happens when setting triggers.
>>
>> These is a regression in v4.17 introduced by the commit mentioned below,
>> testing without these commit shows no problem with negative numbers.
>>
>> Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster")
>> Signed-off-by: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
>> ---
>>   kernel/trace/trace_events_filter.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
>> index 84a65173b1e9..2ba449292561 100644
>> --- a/kernel/trace/trace_events_filter.c
>> +++ b/kernel/trace/trace_events_filter.c
>> @@ -1299,7 +1299,7 @@ static int parse_pred(const char *str, void *data,
>>   		/* go past the last quote */
>>   		i++;
>>   
>> -	} else if (isdigit(str[i])) {
>> +	} else if (isdigit(str[i]) || str[i] == '-') {
>>   
>>   		/* Make sure the field is not a string */
>>   		if (is_string_field(field)) {
>> @@ -1312,6 +1312,9 @@ static int parse_pred(const char *str, void *data,
>>   			goto err_free;
>>   		}
>>   
>> +		if (str[i] == '-')
>> +			i++;
>> +
>>   		/* We allow 0xDEADBEEF */
>>   		while (isalnum(str[i]))
>>   			i++;
> 

-- 
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.