[GHC] #14081: 8.2.1 runghc from Windows x32 segfaults an all programs

[GHC]

#14081: 8.2.1 runghc from Windows x32 segfaults an all programs
----------------------------------+------------------------------
        Reporter:  sergv          |                Owner:  (none)
            Type:  bug            |               Status:  new
        Priority:  highest        |            Milestone:  8.2.2
       Component:  Compiler       |              Version:  8.2.1
      Resolution:                 |             Keywords:
Operating System:  Windows        |         Architecture:  x86
 Type of failure:  Runtime crash  |            Test Case:
      Blocked By:                 |             Blocking:
 Related Tickets:                 |  Differential Rev(s):
       Wiki Page:                 |
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Comment (by sergv):

 I still wasn't able to use gdb to any good, but I think I found out the
 problem. The tl;dr version is: `addDLLHandle` assumes that import table is
 always present and it is not the case for 32-bit `ntdll.dll`.

 The long version is:
 I have stumbled upon some code for reading import table -
 https://stackoverflow.com/questions/15960437/how-to-read-import-directory-
 table-in-c#17457077. The GHC currently uses somewhat different but simpler
 approach. In particular it doesn't use anything resembling `Rva2Offset`
 function. I tried to use `Rva2Offset` and friends from the post but it
 didn't work. I didn't manage to debug it, but while trying to I noticed
 that post's code explicitly checks for the case when dll has no import
 table. I added this check to ghc and it seems that was enough to get `ghc
 --interactive` working. The check is:

 {{{
 diff --git i/rts/linker/PEi386.c w/rts/linker/PEi386.c
 index 42e700805e..011b0a8314 100644
 --- i/rts/linker/PEi386.c
 +++ w/rts/linker/PEi386.c
 @@ -240,6 +240,13 @@ static void addDLLHandle(pathchar* dll_name,
 HINSTANCE instance) {
          (PIMAGE_IMPORT_DESCRIPTOR)((BYTE *)instance + header->
 OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);

 +    bool importTableMissing =
 +
 header->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].Size ==
 0;
 +
 +    if (importTableMissing) {
 +        return;
 +    }
 +
      /* Ignore these compatibility shims.  */
      const pathchar* ms_dll = WSTR("api-ms-win-");
      const int len = wcslen(ms_dll);
 }}}

 @Phyx- is the fix sensible? Should we try to merge it in?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14081#comment:20>
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