Re: [Qemu-devel] [PATCH 1/3] linux-user: Don't use MAP_FIXED in do_brk()

[Peter Maydell <peter.maydell@linaro.org>]

On 18 April 2011 16:34, Peter Maydell <peter.maydell@linaro.org> wrote:
> Since mmap() with MAP_FIXED will map over the top of existing mappings,
> it's a bad idea to use it to implement brk(), because brk() with a
> large size is likely to overwrite important things like qemu itself
> or the host libc. So we drop MAP_FIXED and handle "mapped but at
> different address" as an error case instead.

I've had a report from Martin Mohring that this patch breaks some
programs which previously worked in linux-user mode (one wonders if
they were overwriting some chunk of memory that they happened not
to be using for anything important...)

Anyway, probably better to hold off on applying this patch pending
further investigation. Patches 2/3 and 3/3 in this set should still
be fine to apply though.

-- PMM