Re: [PATCH RESEND 1/3] tracing/syscalls: Rename variable 'nr' to 'syscall_nr'

[Taeung Song <treeze.taeung@gmail.com>]

Hi, Steven

On 02/26/2016 12:47 AM, Steven Rostedt wrote:
> On Fri, 26 Feb 2016 00:24:18 +0900
> Taeung Song <treeze.taeung@gmail.com> wrote:
>
>> There is a problem about duplicated variable name
>> for system call number and a argument of some
>> system call. I found this problem when I tested
>> perf-script with python script as below.
>>
>>      # perf record -e syscalls:*
>>      # perf script -g python
>>      # perf script -s perf-script.py
>>        File "perf-script.py", line 8694
>>          def syscalls__sys_enter_io_getevents(event_name, context, common_cpu,
>>      SyntaxError: duplicate argument 'nr' in function definition
>>      Error running python script perf-script.py
>>
>> As above, problems about duplicated argument occurred
>> when processing sys_enter_io_getevent() and sys_enter_io_submit().
>> Because the two system calls have a argument 'nr' as below.
>>
>>      int io_getevents(aio_context_t ctx_id, long min_nr, long nr,
>>                       struct io_event *events, struct timespec *timeout);
>>
>>      int io_submit(aio_context_t ctx_id, long nr, struct iocb **iocbpp);
>>
>> So rename a variable 'nr' to 'syscall_nr' for system call number
>> in print_syscall_enter().
>
> WTF, how does changing the kernel fix a user space python generation
> bug?
>

The underlying cause of this problem is not because of
the python script. This problem have relevance to tracing/syscalls
as below.

# cat 
/sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format
name: sys_enter_io_getevents
ID: 739
format:
        field:unsigned short common_type; offset:0;size:2;signed:0;
        field:unsigned char common_flags; offset:2;size:1;signed:0;
        field:unsigned char common_preempt_count; offset:3;size:1;signed:0;
        field:int common_pid;             offset:4;size:4;signed:1;
        field:int nr;                     offset:8;size:4;signed:1;
        field:aio_context_t ctx_id;       offset:16;size:8;signed:0;
        field:long min_nr;                offset:24;size:8;signed:0;
        field:long nr;                    offset:32;size:8;signed:0;
        field:struct io_event * events;   offset:40;size:8;signed:0;
        field:struct timespec * timeout;  offset:48;size:8;signed:0;

print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: 0x%08lx, events: 
0x%08lx, timeout: 0x%08lx", ((unsigned long)(REC->ctx_id)), ((unsigned 
long)(REC->min_nr)), ((unsigned long)(REC->nr)), ((unsigned 
long)(REC->events)), ((unsigned long)(REC->timeout))


As you see, there are duplicated variable name among fields.
So I renamed the variable name 'nr' to 'syscall_nr' to avoid this
duplication. As you know 'nr' in print_syscall_enter() mean
system call number so, I changed 'nr' to 'syscall_nr'(IMHO).


Thanks,
Taeung

>>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
>> Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
>> ---
>>   kernel/trace/trace.h          |  4 ++--
>>   kernel/trace/trace_syscalls.c | 16 ++++++++--------
>>   2 files changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
>> index 8414fa4..beddeb1 100644
>> --- a/kernel/trace/trace.h
>> +++ b/kernel/trace/trace.h
>> @@ -88,13 +88,13 @@ enum trace_type {
>>    */
>>   struct syscall_trace_enter {
>>   	struct trace_entry	ent;
>> -	int			nr;
>> +	int			syscall_nr;
>>   	unsigned long		args[];
>>   };
>>
>>   struct syscall_trace_exit {
>>   	struct trace_entry	ent;
>> -	int			nr;
>> +	int			syscall_nr;
>>   	long			ret;
>>   };
>>
>> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
>> index 0655afb..956209f 100644
>> --- a/kernel/trace/trace_syscalls.c
>> +++ b/kernel/trace/trace_syscalls.c
>> @@ -118,7 +118,7 @@ print_syscall_enter(struct trace_iterator *iter, int flags,
>>   	int i, syscall;
>>
>>   	trace = (typeof(trace))ent;
>> -	syscall = trace->nr;
>> +	syscall = trace->syscall_nr;
>>   	entry = syscall_nr_to_meta(syscall);
>>
>>   	if (!entry)
>> @@ -164,7 +164,7 @@ print_syscall_exit(struct trace_iterator *iter, int flags,
>>   	struct syscall_metadata *entry;
>>
>>   	trace = (typeof(trace))ent;
>> -	syscall = trace->nr;
>> +	syscall = trace->syscall_nr;
>>   	entry = syscall_nr_to_meta(syscall);
>>
>>   	if (!entry) {
>> @@ -261,7 +261,7 @@ static int __init syscall_enter_define_fields(struct trace_event_call *call)
>>   	int i;
>>   	int offset = offsetof(typeof(trace), args);
>>
>> -	ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
>> +	ret = trace_define_field(call, SYSCALL_FIELD(int, syscall_nr), FILTER_OTHER);
>>   	if (ret)
>>   		return ret;
>>
>> @@ -281,7 +281,7 @@ static int __init syscall_exit_define_fields(struct trace_event_call *call)
>>   	struct syscall_trace_exit trace;
>>   	int ret;
>>
>> -	ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
>> +	ret = trace_define_field(call, SYSCALL_FIELD(int, syscall_nr), FILTER_OTHER);
>>   	if (ret)
>>   		return ret;
>>
>> @@ -332,7 +332,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
>>   		return;
>>
>>   	entry = ring_buffer_event_data(event);
>> -	entry->nr = syscall_nr;
>> +	entry->syscall_nr = syscall_nr;
>>   	syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
>>
>>   	event_trigger_unlock_commit(trace_file, buffer, event, entry,
>> @@ -378,7 +378,7 @@ static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
>>   		return;
>>
>>   	entry = ring_buffer_event_data(event);
>> -	entry->nr = syscall_nr;
>> +	entry->syscall_nr = syscall_nr;
>>   	entry->ret = syscall_get_return_value(current, regs);
>>
>>   	event_trigger_unlock_commit(trace_file, buffer, event, entry,
>> @@ -579,7 +579,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
>>   	if (!rec)
>>   		return;
>>
>> -	rec->nr = syscall_nr;
>> +	rec->syscall_nr = syscall_nr;
>>   	syscall_get_arguments(current, regs, 0, sys_data->nb_args,
>>   			       (unsigned long *)&rec->args);
>>   	perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
>> @@ -652,7 +652,7 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
>>   	if (!rec)
>>   		return;
>>
>> -	rec->nr = syscall_nr;
>> +	rec->syscall_nr = syscall_nr;
>>   	rec->ret = syscall_get_return_value(current, regs);
>>   	perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
>>   }
>