[GHC] #6059: FFI: segfault when jumping to code buffer (under certain conditions)

[GHC]

#6059: FFI: segfault when jumping to code buffer (under certain conditions)
-----------------------------+----------------------------------------------
  Reporter:  guest           |          Owner:              
      Type:  bug             |         Status:  closed      
  Priority:  normal          |      Milestone:  7.6.1       
 Component:  Compiler (FFI)  |        Version:  7.4.1       
Resolution:  invalid         |       Keywords:  segfault ffi
        Os:  Linux           |   Architecture:  x86         
   Failure:  Runtime crash   |     Difficulty:  Unknown     
  Testcase:                  |      Blockedby:              
  Blocking:                  |        Related:              
-----------------------------+----------------------------------------------
Changes (by guest):

  * status:  new => closed
  * resolution:  => invalid


Comment:

 Well, as I said, it's reproducible (at least on my system). Within `make`
 it works as desired, but calling it from shell, it doesn't.

 I looked at the implementation of `mallocBytes`. It's just calling
 `malloc`, so a came up with this code:
 {{{
 #!C
 #include <stdio.h>
 #include <stdlib.h>

 int main(void)
 {
         unsigned short *ptr = (unsigned short*) malloc(2);
         *ptr = 0xc390;
         printf("entry point: 0x%08x\n", (unsigned short) ptr);
         ((void (*)()) ptr) ();
         printf("welcome back\n");
 }
 }}}
 Same behaviour: Calling it from `make`, everything is fine. Calling it
 from shell, segfault.
 So I guess it isn't GHC related at all. Sorry :-/ I think this ticket can
 be closed.


 The solution for my project was, allocate memory and mark it as executable
 with `mprotect`.


 Thanks,
 bernhard

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6059#comment:3>
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