[Bug pch/48004] New: doesn't work with randomize_va_space

[Bug pch/48004] New: doesn't work with randomize_va_space

[wbrana at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

           Summary: doesn't work with randomize_va_space
           Product: gcc
           Version: 4.5.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: pch
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: wbrana@gmail.com


If address space randomization is enabled
echo 1 > /proc/sys/kernel/randomize_va_space
pch isn't used - warning: had text segment at different address

[Bug pch/48004] doesn't work with randomize_va_space

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-03-06 21:07:04 UTC ---
Which host is this on?

[Bug pch/48004] doesn't work with randomize_va_space

[wbrana at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

wbrana <wbrana at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
               Host|                            |x86_64-pc-linux-gnu

--- Comment #2 from wbrana <wbrana at gmail dot com> 2011-03-06 21:11:50 UTC ---
x86_64-pc-linux-gnu

[Bug pch/48004] doesn't work with randomize_va_space

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2011.03.07 10:24:39
     Ever Confirmed|0                           |1

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-07 10:24:39 UTC ---
It should work, we use fixed mappings for this.

[Bug pch/48004] doesn't work with randomize_va_space

[wbrana at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

--- Comment #4 from wbrana <wbrana at gmail dot com> 2011-03-07 10:54:43 UTC ---
It is possible that this bug is related to PaX, which I'm using
http://bugs.gentoo.org/show_bug.cgi?id=301299#c31
I tried to disable PaX with "paxctl -pemrxs cc1plus", but warning disappear
only if randomize_va_space is 0

[Bug pch/48004] doesn't work with randomize_va_space

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW

--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-07 11:07:33 UTC ---
We can't simply use MAP_FIXED, as that will discard existing overlapping
mappings.

       MAP_FIXED
              Don't interpret addr as a hint: place  the  mapping  at  exactly
              that address.  addr must be a multiple of the page size.  If the
              memory region specified by addr and len overlaps  pages  of  any
              existing  mapping(s),  then  the overlapped part of the existing
              mapping(s) will be discarded.  If the specified  address  cannot
              be  used,  mmap()  will fail.  Because requiring a fixed address
              for a mapping is less portable, the use of this option  is  dis-
              couraged.

So we'd need to portably check for existing mappings in the range we want
to request.  I don't think that is desirable (if only from a performance
perspective).  The only way to do this that I can think of is parsing
/proc or installing a SIGSEGV/SIGBUS handler and poking every page ...

[Bug pch/48004] doesn't work with randomize_va_space

[wbrana at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

--- Comment #6 from wbrana <wbrana at gmail dot com> 2011-03-07 11:20:55 UTC ---
I can see warning also when PaX is disabled with kernel 2.6.37.2
randomize_va_space is 1 by default.

[Bug pch/48004] doesn't work with randomize_va_space

[wbrana at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

--- Comment #7 from wbrana <wbrana at gmail dot com> 2011-03-07 12:35:23 UTC ---
Parsing /proc doesn't have to work with PaX kernel. 
PaX removes some info from e.g. maps file.

[Bug pch/48004] doesn't work with randomize_va_space

[wbrana at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48004

wbrana <wbrana at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #8 from wbrana <wbrana at gmail dot com> 2012-07-19 18:57:26 UTC ---
I have tested GCC 4.5.4 and 4.7.1. It seems to be fixed.