To get me unlocked, I added this rule to the makefile, on which fill-kfs
depends.
If we want to change it later on, thats fine.
create-build-file:
ifneq ($(INVARIANT_BUILD),1)
@echo "Kernel: $(abspath $(KERNEL_OBJ))" > kern/kfs/etc/build.info
endif
On Sun, Dec 13, 2015 at 10:39 AM, Davide Libenzi <[email protected]>
wrote:
> Also, KFS uses CPIO, which in turn embeds file metadata (time as well).
> So our builds will have to either point to an invariant KFS, or not have
> it at all.
>
>
> On Sun, Dec 13, 2015 at 10:37 AM, Davide Libenzi <[email protected]>
> wrote:
>
>> If this will ever be an issue, we can have a build option which does not
>> include neither KFS (because the same invariant will have to apply to its
>> populated ELF files as well), nor other build dependent information.
>> Without that, you will not be able to use perf to generate traces though.
>>
>>
>> On Sun, Dec 13, 2015 at 10:31 AM, ron minnich <[email protected]> wrote:
>>
>>> It's true that that non-reproducible bits are typically embedded in a
>>> linux kernel at present. That may change.
>>>
>>> But debian and coreboot at least are looking at the problem.
>>>
>>> We can try to get it right from the start.
>>>
>>> ron
>>>
>>> On Sun, Dec 13, 2015 at 9:58 AM 'Davide Libenzi' via Akaros <
>>> [email protected]> wrote:
>>>
>>>> Now our KFS image is stuck in an ELF section as well.
>>>> The typical kernel uname info is generally generated (at least the time
>>>> part) and compile time as well.
>>>>
>>>>
>>>> On Sun, Dec 13, 2015 at 9:52 AM, ron minnich <[email protected]>
>>>> wrote:
>>>>
>>>>> Sorry, what I mean is we have to be careful what we put into the
>>>>> kernel image, so that different people can build kernels
>>>>> that are byte for byte the same given a git ref. This reproducible
>>>>> build stuff is all the rage now.
>>>>>
>>>>> I think putting stuff like paths in the kernel binary will defeat
>>>>> reproducible builds.
>>>>>
>>>>> ron
>>>>>
>>>>> On Sun, Dec 13, 2015 at 9:50 AM 'Davide Libenzi' via Akaros <
>>>>> [email protected]> wrote:
>>>>>
>>>>>> Did not parse that ☺
>>>>>>
>>>>>>
>>>>>> On Sun, Dec 13, 2015 at 9:48 AM, ron minnich <[email protected]>
>>>>>> wrote:
>>>>>>
>>>>>>> One thing is it would be nice if however we do this, we can make
>>>>>>> sure we have reproducible builds, which the
>>>>>>> ELF approach might cause trouble with.
>>>>>>>
>>>>>>> ron
>>>>>>>
>>>>>>> On Sun, Dec 13, 2015 at 9:43 AM 'Davide Libenzi' via Akaros <
>>>>>>> [email protected]> wrote:
>>>>>>>
>>>>>>>> There is a way, and Linux perf has an ID for every trace, ID which
>>>>>>>> you can bind to any event string you can push into the perf file.
>>>>>>>> But, in order to do that, I will need to add libpfm4 dependency to
>>>>>>>> kprof2perf, which is not worth it.
>>>>>>>> Instead I will go ahead to move the akaros to linux perf
>>>>>>>> conversion, to the akaros perf tool (which already has the libpfm4
>>>>>>>> dependency), and drop the kprof2perf tool altogether.
>>>>>>>> In order to do that though, I will need to know, on the Akaros
>>>>>>>> side, the full path within the build directory, of the akaros kernel
>>>>>>>> ELF
>>>>>>>> file.
>>>>>>>> A couple of solutions which come to my mind:
>>>>>>>>
>>>>>>>> 1) Build system create a magic build info file into KFS
>>>>>>>> 2) Build info are stuck in a kernel ELF section, retrievable via
>>>>>>>> system call or #some-dev-file
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Sat, Dec 12, 2015 at 4:53 PM, Davide Libenzi <
>>>>>>>> [email protected]> wrote:
>>>>>>>>
>>>>>>>>> On Fri, Dec 11, 2015 at 12:09 PM, Davide Libenzi <
>>>>>>>>> [email protected]> wrote:
>>>>>>>>>
>>>>>>>>>> > +void perfmon_interrupt(struct hw_trapframe *hw_tf, void *data)
>>>>>>>>>>> > +{
>>>>>>>>>>> > + int i;
>>>>>>>>>>> > + struct perfmon_cpu_context *cctx =
>>>>>>>>>>> PERCPU_VARPTR(counters_env);
>>>>>>>>>>> > + uint64_t gctrl, status;
>>>>>>>>>>> > +
>>>>>>>>>>> > + profiler_add_hw_sample(hw_tf);
>>>>>>>>>>>
>>>>>>>>>>> So it looks like we generate a trace whenever any of the
>>>>>>>>>>> counters overflow, but
>>>>>>>>>>> we lose track of which one overflowed. I guess that's what
>>>>>>>>>>> userland perf
>>>>>>>>>>> expects?
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I need to add an "ID", and figure out how to pass that to
>>>>>>>>>> userland perf.
>>>>>>>>>> Will do in follow up CL.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Actually, doing it in this stream, as tail commits.
>>>>>>>>> I already added an "info" field containing the event coordinates.
>>>>>>>>> Need to figure out how to translate it for Linux perf now ...
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
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