Changes

== Summary ==

== Summary ==

There are two moments of time when criu runs in somewhat strange environment

There are two moments in time where criu runs in a somewhat strange environment

* [[Parasite code]] execution

* [[Parasite code]] execution

== Building PIE code blobs for criu ==

== Building PIE code blobs for criu ==

Parasite code executes in dumpee process context thus it needs to be [http://en.wikipedia.org/wiki/Position-independent_code PIE]

Parasite code executes in the dumpee process context thus it needs to be [http://en.wikipedia.org/wiki/Position-independent_code PIE]

compiled and to have own stack. The same applies to restorer code, which takes place at the very end of restore procedure.

compiled and to have own stack. The same applies to restorer code, which takes place at the very end of restore procedure.

Thus we need to reserve stack place statically somewhere in criu and use it at dump/checkpoint stages. To achieve

Thus we need to reserve stack, place it statically somewhere in criu and use it at dump/checkpoint stages. To achieve

this (and still have some human way to edit source code) we do the following tricks

this (and still have some human way to edit source code) we use the following tricks

* Parasite code has own bootstrap code laid in pure assembler file (parasite_head.S)

* Parasite code has own bootstrap code laid in a pure assembler file (parasite_head.S)

* Restorer bootstrap code is done a bit simplier in restorer.c file.  

* Restorer bootstrap code is done in a simpler way in restorer.c.  

For both cases we generate headers files which consist of

For both cases we generate header files which consist of

* Functions offsets for export

* Functions offsets for export

  };

  };

These headers we include in criu compiled file and then use for checkpoint/restore.

These headers we include in the criu compiled file and then use them for checkpoint/restore.

Generation of this files is done in several steps

Generation of these files is done in several steps

* All object files needed by are linked into 'built-in.o'

* All object files needed by are linked into 'built-in.o'