[CRIU] How to compile criu static binary

[Christopher Covington]

Hi John,

On 03/09/2015 08:56 AM, Pavel Emelyanov wrote:
> On 03/08/2015 02:31 PM, John Statham wrote:
>> Is it possible to compile any version of criu binary statically ?
> 
> We didn't try, but if the libraries we use allow for that, I see
> no reason why it shouldn't work :)
> 
>> If you have already tried this on any version of criu...could you
>> provide some relevant source code/ changes for same.

We've done it with older versions, but my vague recollection is that the
latest versions have problems in the test suite or libcriu or something like
that, which being nonessential you can just not specify for building (test
suite) or hack out of the makefiles (libcriu).

My personal preference is to use dynamic linking but set the
linker/loader/interpreter and library search path/rpath as needed for foreign
systems. For example if you wanted to target a Debian multiarch style layout
using a toolchain that doesn't default to that, you could pass (replacing the
AArch64 examples with whatever target architecture you care about)

USERCFLAGS="-Wl,-dynamic-linker=/lib/aarch64-linux-gnu/ld-linux-aarch64.so.1
-Wl,-rpath=/lib/aarch64-linux-gnu"

(Although in practice I use the more portable /lib/ld-linux-aarch64.so.1
linker/loader/interpreter path.)

Something similar should work for /data/local on Android or /tmp or /opt on
other Linux systems.

You can check that these flags correctly took effect, and also list out the
libraries you need to make sure exist in RPATH, with the following commands.

aarch64-linux-gnu-readelf -a criu | grep -Ei '(interpr|needed|rpath)'

If the interpreter is set wrong, you'll probably get a criu not found or does
not exist error (which at first I found confusing).

Alternatively, if you have an ELF that doesn't have INTERP and RPATH
customized, you can achieve pretty much the same effect with:

LD_LIBRARY_PATH=/path/to/my/libs /path/to/my/ld-linux.so /path/to/criu

Mildly interesting CRIU corner case: last time I tried to dump and restore a
process launched like this (such as `/lib64/ld-linux-x86-64.so.2 /bin/sleep
infinity`) it failed because of funky /proc/self/exe issues, but this style of
invocation is so obscure that I didn't know what the right way to fix it would
be so I just installed my linker/loader/interpreter and libraries into INTERP
and RPATH, respectively, and moved on.

Chris

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