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|ID||Project||Category||View Status||Date Submitted||Last Update|
|0006167||OCaml||OCaml backend (code generation)||public||2013-09-10 16:20||2013-09-11 22:07|
|Assigned To|| |
|Product Version||4.01.0+beta/+rc|| |
|Target Version||Fixed in Version|| |
|Summary||0006167: OCAMLPARAM Support for Disabling Position-Independent Code (PIC) Generation|
|Description||Add support for disabling Position-Independent Code (PIC) generation through the OCAMLPARAM environment variable. This change would make it possible to specify a "nopic" token which, when set, instructs the native code generator to emit position-dependent code independently of what was requested at the command line.|
The rationale of this option is similar to the other flags already supported by OCAMLPARAM: Allow the user to force generation of position-dependent code without the need for modifying build system files or sources.
This patch was directly motivated by the need for making cross-compilation possible of the Mirage unikernel  to the "kFreeBSD" backend. This backend basically compiles Mirage (OCaml) programs into FreeBSD kernel modules, where certain expectations must be satisfied. One of those expectations is that the generated code must not be position-independent as the FreeBSD kernel dynamic loader (kld(4)) does not support ELF relocations of that type. Hence PIC generation has to be disabled globally for all the compiled code, regardless what the original upstream packages were instructed for. The "nodynlink" flag is also used in this case.
The attached patch implements this functionality by moving the `pic_code` variable to the `Clflags` module for both the AMD64 and the ARM native code generator backends, while it retains the default settings for both. I have tested it on FreeBSD/amd64, but it should work on the ARM platform and on other operating systems.
 http://openmirage.org/ [^]
|Attached Files|| nopic.diff [^] (8,737 bytes) 2013-09-10 16:20 [Show Content]