[GHC] #7500: GHC: internal error: getMBlock: mmap: Operation not permitted

[GHC]

#7500: GHC: internal error: getMBlock: mmap: Operation not permitted
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        Reporter:  guest          |            Owner:
            Type:  bug            |           Status:  patch
        Priority:  normal         |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.4.1
      Resolution:                 |         Keywords:
Operating System:  Linux          |     Architecture:  Unknown/Multiple
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:                 |       Blocked By:
        Blocking:                 |  Related Tickets:
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Changes (by rwbarton):

 * status:  new => patch


Comment:

 I dug into this some more.  In the kernel I have installed (Debian
 2.6.32-5-686), mmap selects an address for the new mapping based on the
 hint address and the process's current mappings, but without regard to
 `mmap_min_addr`.  Then, if the address selected was less than
 `mmap_min_addr`, mmap may return EPERM, depending on the SELinux
 configuration.  I believe the same applies to at least all 32-bit x86
 Linux versions.

 In my kernel, it doesn't seem that trying to mmap again with no hint
 address can ever help Linux find the unmapped areas above `mmap_min_addr`.
 I'm not sure whether this holds in modern Linux, which has an entirely new
 algorithm for finding unmapped areas.  But in any case, it is easy enough
 to try a second mmap with no hint address.

 I've attached a patch which, on Linux, tries to do a second mmap if it
 receives EPERM, and treats EPERM as an out-of-memory condition.  With the
 patch, the example program allocates 2929 MB and then exits with the
 message

 {{{
 part.hs: out of memory (requested 1048576 bytes)
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7500#comment:6>
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