[Pharo-project] [Vm-dev] Re: SystemTracer

Guillermo Polito guillermopolito at gmail.com
Thu Mar 15 15:26:54 EDT 2012


On Thu, Mar 15, 2012 at 1:58 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:

>
> Hi Guillermo,
>
> On Wed, Mar 14, 2012 at 12:48 PM, Guillermo Polito <
> guillermopolito at gmail.com> wrote:
>
>> Hi Eliot,
>>
>> do you have a pointer of where can I see the differences between the old
>> Squeak format and the cog image format, so I can make SystemTracer work on
>> Cog vms?
>>
>
> So the image format differences are
> - floats are in platform order, not necessarily in big-endian order
> - the layout of the specialObjectsArray is slightly different (documented
> in recreateSpecialObjectsArray)
> - there are more words in the header, see
> StackInterpreter>writeImageFileIO:, i.e.
>
> in Cog:
> self putLong: self imageFormatVersion toFile: f.
> self putLong: headerSize toFile: f.
>  self putLong: imageBytes toFile: f.
> self putLong: objectMemory startOfMemory toFile: f.
>  self putLong: objectMemory specialObjectsOop toFile: f.
> self putLong: objectMemory newObjectHash toFile: f.
>  self putLong: self ioScreenSize toFile: f.
> self putLong: self getImageHeaderFlags toFile: f.
>  self putLong: extraVMMemory toFile: f.
> self putShort: desiredNumStackPages toFile: f.
>  self putShort: self unknownShortOrCodeSizeInKs toFile: f.
> self putLong: desiredEdenBytes toFile: f.
>  self putShort: (maxExtSemTabSizeSet ifTrue: [self
> ioGetMaxExtSemTableSize] ifFalse: [0]) toFile: f.
> self putShort: 0 toFile: f.
>  1 to: 4 do: [:i | self putLong: 0 toFile: f].  "fill remaining header
> words with zeros"
>
> in Interpreter:
>  self putLong: (self imageFormatVersion) toFile: f.
> self putLong: headerSize toFile: f.
>  self putLong: imageBytes toFile: f.
> self putLong: (self startOfMemory) toFile: f.
>  self putLong: specialObjectsOop toFile: f.
> self putLong: lastHash toFile: f.
>  self putLong: (self ioScreenSize) toFile: f.
> self putLong: fullScreenFlag toFile: f.
>  self putLong: extraVMMemory toFile: f.
> 1 to: 7 do: [:i | self putLong: 0 toFile: f].  "fill remaining header
> words with zeros"
>
> Then
>
> getImageHeaderFlags
> "Answer the flags that are contained in the 7th long of the image header."
>  ^fullScreenFlag "0 or 1"
> + (VMBIGENDIAN ifTrue: [0] ifFalse: [2]) "this is the
> imageFloatsLittleEndian flag"
>  + (processHasThreadId ifTrue: [4] ifFalse: [0])
> + (flagInterpretedMethods ifTrue: [8] ifFalse: [0])
>  + (preemptionYields ifTrue: [0] ifFalse: [16])
> + (noThreadingOfGUIThread ifTrue: [32] ifFalse: [0])
>  + (imageHeaderFlags bitAnd: 63 bitInvert32) "these are any flags we do
> not recognize"
>
> Now most of the information in the flags is accessible from vmParameterAt:
> (or some convenience methods).  e.g. vm parameter 49 is the max external
> semaphore table size, and vm parameter 48 is the following flags:
>
> getCogVMFlags
> "Answer an array of flags indicating various properties of the Cog VM.
>  Bit 0: implies the image's Process class has threadId as its 3rd inst var
> (zero relative)
>  Bit 1: if set, methods that are interpreted will have the flag bit set
> in their header
>  Bit 2: if set, implies preempting a process does not put it to the back
> of its run queue"
>  ^objectMemory integerObjectOf: (processHasThreadId ifTrue: [1] ifFalse:
> [0])
> + (flagInterpretedMethods ifTrue: [2] ifFalse: [0])
>  + (preemptionYields ifTrue: [0] ifFalse: [4])
> + (noThreadingOfGUIThread ifTrue: [8] ifFalse: [0])
>

Hehe, in pharo the comment reaches up to 41 :).  I'll look at squeak to
update it.


>
> Read the comment for vmParameterAt: to get things like num stack pages and
> cog code size.
>
> Is this OK?  I know it's a bit of a mess. If you or I (we?) write it up
> where should we put the info?
>
>>
>> Thanks,
>> Guille
>>
>> On Thu, Jan 27, 2011 at 6:36 PM, Levente Uzonyi <leves at elte.hu> wrote:
>>
>>> On Thu, 27 Jan 2011, Benjamin wrote:
>>>
>>>  It works for  PharoCore-1.1-11196-UNSTABLE.1 but it seems to be the
>>>> only version where it works :S
>>>>
>>>> Does someone know why ?
>>>>
>>>
>>> It doesn't support Cog's image format. Try an image with the original
>>> Squeak format. You can convert your image with the latest SqueakVM. Only
>>> the unix VM was released with this feature yet, so you can use that
>>> http://squeakvm.org/unix/ or build a VM for your favorite platform.
>>>
>>>
>>> Levente
>>>
>>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>> Ben
>>>>
>>>> On Jan 27, 2011, at 3:36 PM, Benjamin wrote:
>>>>
>>>>  Hello guys,
>>>>>
>>>>> for one of my projects, I'm trying to use SystemTracer to create  anew
>>>>> image, but it appears that it doesn't work on Pharo ...
>>>>> I can create a new image, but I can't open it. I've tried with an
>>>>> older VM (Squeak 3.8.18beta1U), but it's the same ...
>>>>>
>>>>>
>>>>> Did someone already have this problem ? Does someone have a solution ?
>>>>>
>>>>>
>>>>>
>>>>> Thanks in advance,
>>>>>
>>>>> Ben
>>>>>
>>>>
>>>>
>>>>
>>>
>>
>
>
> --
> best,
> Eliot
>
>
>
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