[LTP] LTP release

[Li Wang]

On Tue, Sep 8, 2020 at 11:36 PM Cyril Hrubis <chrubis@suse.cz> wrote:

> Hi!
> > And I'd like to add the MAP_GROWSDOWN test too, but I haven't come up
> with
> > a way to solve the segment fault on s390x.
> > http://lists.linux.it/pipermail/ltp/2020-August/018416.html
>
> Maybe we end up allocating a mapping that is too close to something
> else, see:
>
>
> https://stackoverflow.com/questions/56888725/why-is-map-growsdown-mapping-does-not-grow
>
> I guess that we should make the initial mmap in find_free_range() larger
> and return and adress that is quaranteed not to have a mapping that is
> closer than 256 pages in the direction we want to grow.
>

Sounds reasonable. I tried to reserve more space for the mapping grows, and
that works for me:).

static void *find_free_range(size_t size)
{
    void *mem;

    /*
    * To avoid the mapping grows to within a page of the high end of
    * the next lower mapping, which might result in a SIGSEGV signal.
    * Here reserve twifold memory spaces for growing, especially for s390x.
    */
    mem = SAFE_MMAP(NULL, size * 2, PROT_READ | PROT_WRITE,
    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    SAFE_MUNMAP(mem, size * 2);

    return mem;
}

-- 
Regards,
Li Wang
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