[LTP] [PATCH v4] Add a test case for mmap MAP_GROWSDOWN flag

[Li Wang]

> +     child_pid = SAFE_FORK();
> > +     if (!child_pid)
> > +             grow_stack(stack, stack_size, stack - stack_size +
> UNITS(1));
>
> Why don't we allocate the stack here in the child process? That way we
> can also get rid of the cleanup() function.
>

Ok, that's no problem.


> Also when we are at it, can we also add a second test where we mmap() a
> page in the space the stack is supposed to grow into i.e. do
> allocate_stack() then mmap() a page in the free address space and check
> that the child is killed by a SIGSEGV?
>

Sure, it is a strict way to verify everything goes well with
MAP_GROWSDOWN:).
And to guarantee SIGSEGV, it needs mapping into the address higher than the
(void *)(stack - stack_size), because older kernel set 'stack_guard_gap' as
1 page.

I'll try this in V5 tomorrow.


>
> > +     SAFE_WAIT(&wstatus);
> > +     if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0)
> > +             tst_res(TPASS, "Stack grows in unmapped region");
> > +     else if (WIFSIGNALED(wstatus))
> > +             tst_res(TFAIL, "Child killed by %s",
> tst_strsig(WTERMSIG(wstatus)));
>
> There is no point in this else if and tst_res(), the tst_strstatus() will
> print that info
> for you.
>
Agree.

-- 
Regards,
Li Wang
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