Messages in this thread | | | Date | Tue, 03 Aug 2010 11:12:15 +0200 | From | Peter Oberparleiter <> | Subject | Re: GCOV doesn't seem to work on ARM with kernel 2.6.35-rc6 |
| |
On 03.08.2010 07:20, George G. Davis wrote: > On Thu, Jul 29, 2010 at 06:25:35PM +0200, Karol Lewandowski wrote: >> On 07/28/2010 05:57 PM, Peter Oberparleiter wrote: >>> On 28.07.2010 15:44, Karol Lewandowski wrote: >>>> On 07/28/2010 03:12 PM, Peter Oberparleiter wrote: >>>>> On 27.07.2010 09:35, Karol Lewandowski wrote: >>>>>> On 07/26/2010 06:57 PM, Peter Oberparleiter wrote: >>>>>>> Karol Lewandowski wrote: >>>>>>>> On 07/26/2010 12:32 PM, Karol Lewandowski wrote: >>>>>>>>> I'm trying to use code coverage measurements with mainline Linux >>>>>>>>> kernel >>>>>>>>> 2.6.35-rc6 on ARM platform (specifically on Samsung's S5PC110 >>>>>>>>> board). >>>>>> ... >>>>>>> I just tested gcov support for 2.6.35-rc6 on s390 and it works without >>>>>>> a problem. My assumption would be that you are using an EABI-GCC to >>>>>>> compile your kernel. Those compilers name their constructor symbols >>>>>> >>>>>> Exactly. >>>>>> >>>>>>> differently than the vanilla GCC so that the whole constructor calling >>>>>>> mechanism on which the gcov support relies, will fail. If that is >>>>>>> indeed the case, the following testing patch should solve your >>>>>>> problem: >>>>>> >>>>>> Yes, that was the case and your patch indeed solved my problem. >>>>> >>>>> Excellent. I could imagine that other ARM users might also benefit from >>>>> this patch. Before I submit it for integration though, I need to make >>>>> sure that it also works for kernel modules. Could you enable profiling >>>>> for a kernel module and verify that you are seeing files in >>>>> /sys/kernel/debug/gcov belonging to that module?? >>>> >>>> That does work too. >>>> >>>> However, having seen this[x] patch I would ask if constructor name might >>>> be dynamically selected via user-(in)visible Kconfig option (like in >>>> that patch?) I've tested it and it does seem to work too. >>>> >>>> [x] >>>> http://groups.google.com/group/linux.kernel/browse_thread/thread/84439151c5386e0f/d7dbec62b9d7989f?show_docid=d7dbec62b9d7989f >>>> >>>> >>>> >>>> I've copy pasted interesting parts from that patch below - I'm sure you >>>> get the idea. >>>> >>>> Thanks. >>>> >>>> --- a/include/asm-generic/vmlinux.lds.h >>>> +++ b/include/asm-generic/vmlinux.lds.h >>>> @@ -442,7 +442,7 @@ >>>> #ifdef CONFIG_CONSTRUCTORS >>>> #define KERNEL_CTORS() . = ALIGN(8); \ >>>> VMLINUX_SYMBOL(__ctors_start) = .; \ >>>> - *(.ctors) \ >>>> + *(CONFIG_GCOV_CTORS) \ >>> >>> This should be named differently - gcov uses constructors but this >>> doesn't mean that constructors rely on gcov at all. > > I actually changed that patch [x] long ago relative to the above but > haven't gotten around to following up with a new version and no one > has been anxious to reply about it since anyway. ; )
I wasn't aware of the patch until now or I would have replied.
> The original > version of [x] had a GCOV_CTORS depends on GCOV_KERNEL bug where > GCOV_KERNEL could be disabled resulting in a CONSTRUCTORS build > error due to undefined GCOV_CTORS. A new version of [x] is > attached below. > >>> >>>> --- a/kernel/gcov/Kconfig >>>> +++ b/kernel/gcov/Kconfig >>>> +config GCOV_CTORS >>>> + string >>>> + depends on GCOV_KERNEL >>>> + default ".init_array" if ARM&& AEABI >>>> + default ".ctors" >>> >>> Is it guaranteed that gcc will only create EABI compliant object files >>> if CONFIG_AEABI is defined? I don't have personal experience with arm so >>> my previous assumption was that if you're using an EABI gcc, you would >>> always get EABI object code, no matter what the compiler options were. >> >> Honestly - I don't know. Maybe George - author of cited patch could >> explain this? (CC added). > > Yes that is correct.
Ok, that makes things easier. Your patch looks good to me, but it needs to be split into two parts: 1. kernel: constructor support for ARM EABI compilers 2. gcov: enable GCOV_PROFILE_ALL for arm
For both, it would be great if you could provide a good explanation of what the changes do and why they are needed for arm. For 1, it's obvious, but the author of the original arm-hack patches wasn't too clear about those points for 2.
Also, when you re-post these patches, please add the following people to cc (in addition to the current cc list):
1. For the constructor change: Rusty Russell <rusty@rustcorp.com.au> (for module comments) Sam Ravnborg <sam@ravnborg.org> (for kbuild comnents) Michal Marek <mmarek@suse.cz> (for kbuild comments) Andrew Morton <akpm@linux-foundation.org> (hopefully for integration)
2. For the gcov-arm change: Andrew Morton <akpm@linux-foundation.org>
Regards, Peter
| |