Re: Limiting malloc to the low 2GB?

[RVP <rvp%SDF.ORG@localhost>]

On Mon, 28 Nov 2022, Valery Ushakov wrote:

> Do we have a way to tell malloc on a 32-bit system to allocate memory
> only below the 2GB boundary (on i386, including when run under amd64)?
> I'm trying to port a(n old) program that wants to use the sign bit for
> its internal purposes.  I guess one option would be to prevent malloc
> from using mmap (and disable alsr?) so that only sbrk (in the low 2GB)
> is used.

The standard jemalloc in the system has a compile-time flag to do this
`--with-lg-vaddr=31'. No run-time setting possible from what I can see.
Or, you could compile the program against the old `src/lib/libbsdmalloc'
which only uses sbrk().

-RVP