svn commit: r320430 - head/sys/vm

[Shawn Webb]

On Wed, Jun 28, 2017 at 04:02:37AM +0000, Konstantin Belousov wrote:
> Author: kib
> Date: Wed Jun 28 04:02:36 2017
> New Revision: 320430
> URL: https://svnweb.freebsd.org/changeset/base/320430
> 
> Log:
>   Treat the addr argument for mmap(2) request without MAP_FIXED flag as
>   a hint.
>   
>   Right now, for non-fixed mmap(2) calls, addr is de-facto interpreted
>   as the absolute minimal address of the range where the mapping is
>   created.  The VA allocator only allocates in the range [addr,
>   VM_MAXUSER_ADDRESS].  This is too restrictive, the mmap(2) call might
>   unduly fail if there is no free addresses above addr but a lot of
>   usable space below it.
>   
>   Lift this implementation limitation by allocating VA in two passes.
>   First, try to allocate above addr, as before.  If that fails, do the
>   second pass with less restrictive constraints for the start of
>   allocation by specifying minimal allocation address at the max bss
>   end, if this limit is less than addr.
>   
>   One important case where this change makes a difference is the
>   allocation of the stacks for new threads in libthr.  Under some
>   configuration conditions, libthr tries to hint kernel to reuse the
>   main thread stack grow area for the new stacks.  This cannot work by
>   design now after grow area is converted to stack, and there is no
>   unallocated VA above the main stack.  Interpreting requested stack
>   base address as the hint provides compatibility with old libthr and
>   with (mis-)configured current libthr.
>   
>   Reviewed by:	alc
>   Tested by:	dim (previous version)
>   Sponsored by:	The FreeBSD Foundation
>   MFC after:	1 week
> 
> Modified:
>   head/sys/vm/vm_map.c
>   head/sys/vm/vm_map.h
>   head/sys/vm/vm_mmap.c

Hey Kostik,

This commit breaks both xorg and shutting down/rebooting. Reverting this
commit makes my laptop happy again.

Thanks,

-- 
Shawn Webb
Cofounder and Security Engineer
HardenedBSD

GPG Key ID:          0x6A84658F52456EEE
GPG Key Fingerprint: 2ABA B6BD EF6A F486 BE89  3D9E 6A84 658F 5245 6EEE
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