[resend] Re: handling overflow in sbrk.

[Carlos O'Donell]

Chris Demetriou wrote:
> I figured this wasn't reasonably testable on 64-bit systems (since I
> know none that support remotely close to 64 VA bits -- i.e., the
> kernel should ENOMEM before you get close enough to *try* to wrap
> around), so punted there.  It might not be harmful to allow the test
> to run normally on 64-bit, but while I'm comfortable w/ trying to
> allocate 4GB of virtual memory, I'm less comfortable about filling a
> 64-bit process's address space.  8-)

What does the test do when you run make -k check on an native 64-bit system?

> 2008-05-20  Chris Demetriou  <cgd@google.com>
> 
>         * misc/sbrk.c (__sbrk): If incrementing __curbrk by the requested
>         amount would cause it to overflow, return an error (ENOMEM).
>         * misc/tst-sbrk1.c: New test.
>         * misc/Makefile (tests): Add new test.
> 

I saw you posted this again to libc-alpha, I hope you put on asbestos 
underwear.

The patch makes the common case in sbrk slower, and the kernel (2.6.25) 
already has support checking this overflow?

~~~ mm/mmap.c (do_brk) ~~~
        if ((addr + len) > TASK_SIZE || (addr + len) < addr)
                 return -EINVAL;
~~~

Can you identify which kernels are broken?

Cheers,
Carlos.
-- 
Carlos O'Donell
CodeSourcery
carlos@codesourcery.com
(650) 331-3385 x716