[GHC] #10375: arm: ghci hits an illegal instruction

[GHC]

#10375: arm: ghci hits an illegal instruction
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        Reporter:  erikd             |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.10.3
       Component:  Runtime System    |                 Version:  7.10.1
  (Linker)                           |
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:  arm
 Type of failure:  GHCi crash        |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by erikd):

 On irc, @bgamari suggested that this problem may just be a failure to
 flush the instruction caches. On inspecting the code and adding debug
 printf statements, found that the instruction cache is indeed being
 flushed.

 Futhermore cache flushing on arm/linux only works if it was allocated
 using `mmap()` with the `PROT_EXEC` flag set. I have also confirmed that
 this is case.

 Since this issue of a `SIGILL` in seemingly correct and valid code only
 happens when I try to break on `watch $lr == 0x70000000` I'm going to
 chalk this up to an GDB related Heisenburg-like interaction between GDB
 and the debug target.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10375#comment:59>
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