Re: [PATCH perf/core 1/2] [BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no instance

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Jan 30, 2015 at 11:21:35AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Jan 30, 2015 at 06:37:44PM +0900, Masami Hiramatsu escreveu:
> > Fix to handle optimized no-inline functions which have
> > only function definition but no actual instance at
> > that point. To fix this problem, we need to find actual
> > instance of the function.
> > 
> > Without this patch:
> >   ----
> >   # perf probe -a __up
> >   Failed to get entry address of __up.
> >     Error: Failed to add events.
> >   # perf probe -L __up
> >   Specified source line is not found.
> >     Error: Failed to show lines.
> >   ----
> > 
> > With this patch:
> >   ----
> >   # perf probe -a __up
> >   Added new event:
> >     probe:__up           (on __up)
> > 
> >   You can now use it in all perf tools, such as:
> > 
> >           perf record -e probe:__up -aR sleep 1
> > 
> >   # perf probe -L __up
> >   <__up@/home/fedora/ksrc/linux-3/kernel/locking/semaphore.c:0>
> >         0  static noinline void __sched __up(struct semaphore *sem)
> >            {
> >                   struct semaphore_waiter *waiter = list_first_entry(&sem->wait_
> >                                                           struct semaphore_waite
> >         4         list_del(&waiter->list);
> >         5         waiter->up = true;
> >         6         wake_up_process(waiter->task);
> >         7  }
> >   ----
> 
> Since __up here was built in some other way, I looked for another

Nah, I saw you trying to add "perf probe -a __up" and stopped there,
hadn't seen that it fails _as well_ for just listing the source code...

Yes, I managed to reproduce the problem and test your fix, it works:

  [root@zoo ~]# perf probe --del __up
  Removed event: probe:__up
  [root@zoo ~]# perf probe -L __up
  Specified source line is not found.
    Error: Failed to show lines.

---->>>>>> APPLY THE PATCH, rebuild and try again:

  [root@zoo ~]# 
  [root@zoo ~]# perf probe -L __up
  <__up@/home/git/linux/kernel/locking/semaphore.c:0>
        0  static noinline void __sched __up(struct semaphore *sem)
           {
                  struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
                                                          struct semaphore_waiter, list);
        4         list_del(&waiter->list);
        5         waiter->up = true;
        6         wake_up_process(waiter->task);
        7  }
  [root@zoo ~]#

--------------------------------------------------------------

So its just this other case that fails, vmalloc_fault, can you check
this one? Does it happen in your machine as well?

Applying your patch, thanks,

- Arnaldo

> 'noinline' function to try, and it failed here:
> 
>   [root@zoo ~]# perf probe -L vmalloc_fault | head -5
>   <vmalloc_fault@/home/git/linux/arch/x86/mm/fault.c:0>
>         0  static noinline int vmalloc_fault(unsigned long address)
>         1  {
>            	pgd_t *pgd, *pgd_ref;
>            	pud_t *pud, *pud_ref;
>   [root@zoo ~]# perf probe vmalloc_fault
>   Added new event:
>   Failed to write event: Invalid argument
>     Error: Failed to add events.
> 
> ---->>>>>> APPLY THE PATCH, rebuild and try again:
> 
>   [root@zoo ~]# perf probe vmalloc_fault
>   Added new event:
>   Failed to write event: Invalid argument
>     Error: Failed to add events.
>   [root@zoo ~]# perf probe -v vmalloc_fault
>   probe-definition(0): vmalloc_fault 
>   symbol:vmalloc_fault file:(null) line:0 offset:0 return:0 lazy:(null)
>   0 arguments
>   Looking at the vmlinux_path (7 entries long)
>   Using /lib/modules/3.19.0-rc6+/build/vmlinux for symbols
>   Open Debuginfo file: /lib/modules/3.19.0-rc6+/build/vmlinux
>   Try to find probe point from debuginfo.
>   Probe point found: vmalloc_fault+0
>   Found 1 probe_trace_events.
>   Opening /sys/kernel/debug/tracing/kprobe_events write=1
>   Added new event:
>   Writing event: p:probe/vmalloc_fault _text+289600
>   Failed to write event: Invalid argument
>     Error: Failed to add events. Reason: Invalid argument (Code: -22)
>   [root@zoo ~]# grep -w vmalloc_fault /proc/kallsyms
>   ffffffff81046b40 t vmalloc_fault
>   [root@zoo ~]# grep -w _text /proc/kallsyms 
>   ffffffff81000000 T _text
>   [root@zoo ~]# python 
>   Python 2.7.5 (default, Nov  3 2014, 14:26:24) 
>   [GCC 4.8.3 20140911 (Red Hat 4.8.3-7)] on linux2
>   Type "help", "copyright", "credits" or "license" for more information.
>   >>> 0xffffffff81046b40 - 0xffffffff81000000
>   289600L
>   >>> 
>   [root@zoo ~]# readelf -s /lib/modules/3.19.0-rc6+/build/vmlinux | egrep -w _text\|vmalloc_fault
>     3499: ffffffff81046b40   410 FUNC    LOCAL  DEFAULT    1 vmalloc_fault
>    48873: ffffffff81000000     0 NOTYPE  GLOBAL DEFAULT    1 _text
>   [root@zoo ~]# 
> 
> ---------------------------------------------------------------------------
> 
> So perhaps I need a 'noinline' _and_ '__sched', so that I have a "optimized
> no-inline functions which have only function definition but no actual instance
> at that point"?
> 
> Looking for one, will post here after objdump -dS finishes...
> 
> - Arnaldo