Re: LuaJIT, pagezero_size, and valgrind

[Mike Pall <mikelu-1104@...>]

Douglas Creager wrote:
> The comments from the appropriate part of the valgrind source:
> 
>     // Don't honour the client's request to map PAGEZERO.  Why not?
>     // Because when the kernel loaded the valgrind tool executable,
>     // it will have mapped pagezero itself.  So further attempts
>     // to map it when loading the client are guaranteed to fail.

Umm, maybe the Valgrind binary itself can be relinked with the
-pagezero_size flag?

> So I'm at an impasse.  I'd love to be able to both (a) use
> LuaJIT in my app, and (b) run valgrind on it.  Any thoughts on
> how to proceed?

Either run the tests on a 32 bit binary or run the tests on
Linux/x64 (where Valgrind works just fine).

> How big of a change would it be to make LuaJIT's allocator not
> require pagesize_zero, or to have LuaJIT work with a custom
> allocator on x64?

No chance. The x64 port needs to allocate memory in the lowest 2GB
(that's why you are forced to use the built-in allocator). The
default 4GB pagezero blocks that memory range, so it needs to be
changed.

--Mike