[PATCH] ARM: kprobes: fix test coverage missing failures

[Keun-O Park]

On Wed, Apr 3, 2013 at 6:11 PM, Jon Medhurst (Tixy) <tixy at linaro.org> wrote:
> On Wed, 2013-04-03 at 11:00 +0900, Keun-O Park wrote:
>> On Tue, Apr 2, 2013 at 11:19 PM, Jon Medhurst (Tixy) <tixy at linaro.org> wrote:
>> > On Tue, 2013-04-02 at 12:04 +0900, kpark3469 at gmail.com wrote:
>> >> From: Sahara <keun-o.park at windriver.com>
>> >>
>> >> If kprobe tests run on ARMv6k or ARMv6, there're a number of test
>> >> coverage missing failures like:
>> >
>> > The tests only fail (return an error code) for the coverage tests when
>> > compiled for ARMv7 because, obviously, that's the only architecture that
>> > can cover all the combinations of instructions. Perhaps we should just
>> > disabled the coverage tests pre-ARMv7 kernels to avoid the noisy output
>> > you see.
>> >
>> > I think the best way to look at it is that the coverage tests are test
>> > code for the test code, and should only be of concern to people updating
>> > the test code.
>> >
>> > If we go down the route that this patch follows of conditional
>> > compilation then we are making the main kernel code more messy in order
>> > to support test code and I'm not sure that is a good idea. It will be
>> > much worse should someone want to do the same for ARMv5.
>> >
>> > There is also the problem that once you #ifdef things for ARMv6 then you
>> > need an ARMv6 system to test that combination of data structures,
>> > whereas at the moment an ARMv7 board will cover everything.
>> >
>> > --
>> > Tixy
>>
>> Hi Jon,
>> I see. You're worried about the main kernel code being tainted by adding more
>> test code for test. To keep the clean decode table without #ifdef,
>> most modified codes in
>> arch/arm/kernel/kprobes-arm.c may be removed. architectures without
>> But, in order to keep consistency supporting 'nop', I think at least we still
>> need to add patches for 'nop' in arch/arm/kernel/kprobes-test.c and
>> kprobes-test.h.
>> It doesn't look good 'nop' is used by default like TEST_INSTRUCTION()
>> while TEST('nop') is
>> excluded in kprobe_arm_test_cases.
>
> I hate to sound overly awkward, but I'm not sure I agree with this
> either :-) When building for architectures without a proper NOP
> instructions the assembler will treat it as a pseudo-instruction
> equivalent to MOV R0,R0 in ARM code and MOV R8,R8 in Thumb code. So it
> doesn't seem worth adding an explicit macro to do this if the assembler
> already does it anyway.
>
> --
> Tixy
>

Ah.. I see. What I missed was whether the assembler treat nop as a
pseudo-instruction or not.
If so, it's ok with that. I agree with you.
Thanks.

-- Kpark


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