[PATCH] tracing: Fix event filters and triggers to handle negative numbers

[PATCH] tracing: Fix event filters and triggers to handle negative numbers

[Pavel Tikhomirov]

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@snorch sys_exit_read]# echo "ret == -1" > filter
bash: echo: write error: Invalid argument
[root@snorch sys_exit_read]# cat filter
ret == -1
        ^
parse_error: Invalid value (did you forget quotes)?

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@virtuozzo.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++;
-- 
2.17.1

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

[Steven Rostedt]

On Thu, 23 Aug 2018 13:25:34 +0300
Pavel Tikhomirov <ptikhomirov@virtuozzo.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@snorch sys_exit_read]# echo "ret == -1" > filter
> bash: echo: write error: Invalid argument
> [root@snorch 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@virtuozzo.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++;

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

[Pavel Tikhomirov]

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@virtuozzo.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@snorch sys_exit_read]# echo "ret == -1" > filter
>> bash: echo: write error: Invalid argument
>> [root@snorch 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@virtuozzo.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.

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

[Steven Rostedt]

On Thu, 28 Feb 2019 09:11:37 +0000
Pavel Tikhomirov <ptikhomirov@virtuozzo.com> wrote:

> 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@virtuozzo.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@snorch sys_exit_read]# echo "ret == -1" > filter
> >> bash: echo: write error: Invalid argument
> >> [root@snorch 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!

?!?

I remember applying this to my git queue (I don't reply like this
before doing so). Not sure how it got lost. All I can think of is that
it might have been added with commits that ended up failing the tests,
and got reverted with that code :-/

I'm currently traveling. Hopefully I remember tomorrow to add this.
Thanks for pointing this out, and I need to be a bit more careful when
reverting failed commits :-p

-- Steve