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

[Taeung Song]

Hi, Steven

On 02/26/2016 12:47 AM, Steven Rostedt wrote:
On Fri, 26 Feb 2016 00:24:18 +0900
Taeung Song <treeze.tae...@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 <t...@linutronix.de>
Cc: Lai Jiangshan <jiangshan...@gmail.com>
Signed-off-by: Taeung Song <treeze.tae...@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);
  }